CSF-to-blood toxins clearance is modulated by breathing through cranio-spinal CSF oscillation

Clearance of brain toxins occurs during sleep, although the mechanism remains unknown. Previous studies implied that the intracranial aqueductal cerebrospinal fluid (CSF) oscillations are involved, but no mechanism was suggested. The rationale for focusing on the aqueductal CSF oscillations is unclear. This study focuses on the cranio-spinal CSF oscillation and the factors that modulate this flow. We propose a mechanism where increased cranio-spinal CSF movements enhance CSF-to-blood metabolic waste clearance through the spinal CSF re-absorption sites. A recent study demonstrating that disturbed sleep impairs CSF-to-blood but not brain-to-CSF clearance, supports the fundamentals of our proposed mechanism. Eight healthy subjects underwent phase-contrast magnetic resonance imaging to quantify the effect of respiration on the cranio-spinal CSF oscillations. Maximal CSF volume displaced from the cranium to the spinal canal during each respiration and cardiac cycle were derived as measures of cranio-spinal CSF mixing level. Transition from normal to slow and abdominal breathing resulted in a 56% increase in the maximal displaced CSF volume. Maximal change in the arterial-venous blood volume, which is the driving force of the CSF oscillations, was increased by 41% during slow abdominal breathing. Cranio-spinal CSF oscillations are driven by the momentary difference between arterial inflow and venous outflow. Breathing modulates the CSF oscillation through changes in the venous outflow. The amount of toxins being transferred to the spinal canal during each respiratory cycle is significantly increased during slow and deeper abdominal breathing, which explains enhanced CSF-to-blood toxins clearance during slow-wave sleep and poor clearance during disrupted sleep.

Current Understanding of the Anatomy, Physiology, and Magnetic Resonance Imaging of Neurofluids: Update From the 2022 "ISMRM Imaging Neurofluids Study group" Workshop in Rome

Neurofluids is a term introduced to define all fluids in the brain and spine such as blood, cerebrospinal fluid, and interstitial fluid. Neuroscientists in the past millennium have steadily identified the several different fluid environments in the brain and spine that interact in a synchronized harmonious manner to assure a healthy microenvironment required for optimal neuroglial function. Neuroanatomists and biochemists have provided an incredible wealth of evidence revealing the anatomy of perivascular spaces, meninges and glia and their role in drainage of neuronal waste products. Human studies have been limited due to the restricted availability of noninvasive imaging modalities that can provide a high spatiotemporal depiction of the brain neurofluids. Therefore, animal studies have been key in advancing our knowledge of the temporal and spatial dynamics of fluids, for example, by injecting tracers with different molecular weights. Such studies have sparked interest to identify possible disruptions to neurofluids dynamics in human diseases such as small vessel disease, cerebral amyloid angiopathy, and dementia. However, key differences between rodent and human physiology should be considered when extrapolating these findings to understand the human brain. An increasing armamentarium of noninvasive MRI techniques is being built to identify markers of altered drainage pathways. During the three-day workshop organized by the International Society of Magnetic Resonance in Medicine that was held in Rome in September 2022, several of these concepts were discussed by a distinguished international faculty to lay the basis of what is known and where we still lack evidence. We envision that in the next decade, MRI will allow imaging of the physiology of neurofluid dynamics and drainage pathways in the human brain to identify true pathological processes underlying disease and to discover new avenues for early diagnoses and treatments including drug delivery. Evidence level: 1 Technical Efficacy: Stage 3.

Early Amnestic Mild Cognitive Impairment Is Associated with Reduced Total Cerebral Blood Flow with no Brain Tissue Loss

BACKGROUND

Lower cerebral blood flow (CBF) and excessive brain atrophy are linked to Alzheimer's disease (AD). It is still undetermined whether reduced CBF precedes or follows brain tissue loss.

OBJECTIVE

We compared total CBF (tCBF), global cerebral perfusion (GCP), and volumes of AD-prone regions between cognitively normal (CN) and early amnestic mild cognitive impairment (aMCI) and tested their associations with cognitive performance to assess their predictive value for differentiation between CN and early aMCI.

METHODS

A total of 74 participants (mean age 69.9±6.2 years, 47 females) were classified into two groups: 50 CN and 24 aMCI, of whom 88% were early aMCI. tCBF, GCP, and global and regional brain volumetry were measured using phase-contrast and T1-weighted MRI. Neuropsychological tests tapping global cognition and four cognitive domains (memory, executive function, language, and visuospatial) were administered. Comparisons and associations were investigated using analyses of covariance (ANCOVA) and linear regression analyses, respectively.

RESULTS

Women had significantly higher GCP than men. Both, tCBF and GCP were significantly reduced in aMCI compared with CN, while differences in volumes of cerebral gray matter, white matter, and AD-prone regions were not significant. tCBF and GCP were significantly associated with global cognition (standardized beta (stβ) = 0.324 and stβ= 0.326) and with memory scores (stβ≥0.297 and stβ≥0.264) across all participants. Associations of tCBF and GCP with memory scores were also significant in CN (stβ= 0.327 and stβ= 0.284) and in aMCI (stβ= 0.627 and stβ= 0.485).

CONCLUSION

Reduced tCBF and GCP are sensitive biomarkers of early aMCI that likely precede brain tissue loss.

Blood and cerebrospinal fluid flow oscillations measured with real-time phase-contrast MRI: breathing mode matters

BACKGROUND

Cervical blood and cerebrospinal fluid (CSF) flow rates can be quantified with Phase-contrast (PC) MRI, which is routinely used for clinical studies. Previous MRI studies showed that venous and CSF flow alterations are linked to various pathological conditions. Since it is well known that, besides the heart beating, the thoracic pump influences the blood and CSF dynamics, we studied the effect of different respiration modes on blood and CSF flow rates using a real-time (RT)-PC prototype.

METHODS

Thirty healthy volunteers were examined with a 3 T scanner. A RT-PC sequence was acquired at the first cervical level to quantify the flow rates of internal carotid arteries, internal jugular veins (IJVs) and CSF. Each RT-PC acquisition was repeated three times, while the subjects were asked to breathe in three different ways for 60 s each: freely (F), with a constant rate (PN) and with deep and constant respiration rate (PD). The average flow rates were computed, they were removed from the respective signals and integrated in the inspiratory and expiratory phases (differential volumes). Finally, the power spectral density was computed for each detrended flow rate. High- and very-high frequency peaks were identified on the spectra while their frequencies were compared to the respiratory and cardiac frequencies estimated using a thoracic belt and a pulse oximeter. The area under the spectra was computed in four 0.5 Hz-wide ranges, centered on the high-frequency peak, on very-high frequency peak and its 2nd and 3rd harmonics, and then they were normalized by the flow rate variance. The effect of breathing patterns on average flow rates, on systolic and diastolic peaks, and on the normalized power was tested. Finally, the differential volumes of inspiration were compared to those of expiration.

RESULTS

The frequencies of the high- and very-high spectral peaks corresponded to the respiratory and cardiac frequencies. The average flow rate progressively decreased from F to PN to PD breathing, and the cardiac modulations were less predominant especially for the IJVs. The respiratory modulation increased with PD breathing. The average volumes displaced in the inspiratory phases were not significantly different from those of the expiratory one.

CONCLUSIONS

The spectral analyses demonstrated higher respiratory modulations in PD compared to free breathing, even prevailing the cardiac modulation in the IJVs, showing an increment of the thoracic pump affecting the flow rate shape.

Measuring respiratory and cardiac influences on blood and cerebrospinal fluid flow with real-time MRI

Background. A link between various pathological conditions and blood and cerebrospinal fluid (CSF) flow alterations has been suggested by numerous studies.1 The blood and CSF dynamics are influenced by many factors, such as posture,2 heart beating, and thoracic pressure changes during respiration.2,3 The blood/CSF can be estimated using phase-contrast (PC) – magnetic resonance imaging (MRI). However, the clinical cardiac-gated cine PC-MRI requires several heartbeats to form the time-resolved flow images covering the entire cardiac cycle, not allowing to assess beat-by-beat variability differences and respiratory-driven flow changes. To overcome these limitations, we recently used a real-time (RT)-PC prototype for the study of blood and CSF flow rate modulations, showing low-frequency oscillations (Mayer waves).4 With the same MRI technique, in the current study we focused on assessing the cardiac and respiratory modulations on the blood and CSF flow rates, and the effects of different respiration modes. Methods. Thirty healthy volunteers (21 females, median age=26 years old, age range= 19-57 years old) were examined with a 3 T scanner. RT-PC sequences (Figure 1) allowed for a quantification of the flow rates of internal carotid arteries (ICAs), internal jugular veins (IJVs), and CSF at the first cervical level. The superior sagittal sinus (SSS) was also studied in 16 subjects.5 The flow rates were estimated with a temporal resolution of 58.5 ms for the blood, and 94 ms for the CSF. Each RT-PC lasted 60 seconds and was repeated three times: while the subject breathed with free (F) breathing, at a constant rate with a normal (PN) or forced (PD) strength. The systolic, diastolic and average flow rates and their power spectral densities were computed. High and very-high frequency peaks were identified on the spectra. Frequencies associated to the identified peaks were compared to the respiratory and cardiac frequencies estimated by a thoracic band and a pulse oximeter. The area under the spectra, normalized by the flow rate variance, was computed in the respiratory and cardiac frequency ranges (0.5 Hz-wide ranges, centered on the cardiac or breathing frequency peaks, respectively). Results. The frequencies associated with the spectral peaks were not significantly different compared to the respiratory and cardiac frequencies, for all regions and breathing modes. The average blood flow rate and the diastolic CSF peak progressively decreased from F to PN to PD breathing, the flow rate variance remained stable, and only the ICAs cross-sectional area decreased. The respiratory modulation increased with PD breathing compared with F and PN, while the cardiac modulations were less predominant for all the structures of interest. Conclusions. Using the RT-PC sequence we showed that the blood and CSF flow rates were modulated at the respiratory and cardiac frequencies. The observed reduced blood flow rate during forced breathing in the arteries and consequently in the extra and intracranial veins are suggestive of compensatory vasoconstriction in response to decreased CO2 blood concentration. Breathing modulation of flow rates was observed both in the extracranial and intracranial compartments, and it was greater during forced breathing than free breathing, due to the greater thoracic pump effect on the flow rates.

Structural Basal Ganglia Correlates of Subjective Fatigue in Middle-Aged and Older Adults

OBJECTIVE

Fatigue is among the most common complaints in community-dwelling older adults, yet its etiology is poorly understood. Based on models implicating frontostriatal pathways in fatigue pathogenesis, we hypothesized that smaller basal ganglia volume would be associated with higher levels of subjective fatigue and reduced set-shifting in middle-aged and older adults without dementia or other neurologic conditions.

METHODS

Forty-eight non-demented middle-aged and older adults (M_age = 68.1, SD = 9.4; M_MMSE = 27.3, SD = 1.9) completed the Fatigue Symptom Inventory, set-shifting measures, and structural MRI as part of a clinical evaluation for subjective cognitive complaints. Associations were examined cross-sectionally.

RESULTS

Linear regression analyses showed that smaller normalized basal ganglia volumes were associated with more severe fatigue (β = -.29, P = .041) and poorer Trail Making Test B-A (TMT B-A) performance (β = .30, P = .033) controlling for depression, sleep quality, vascular risk factors, and global cognitive status. Putamen emerged as a key structure linked with both fatigue (r = -.43, P = .003) and TMT B-A (β = .35, P = .021). The link between total basal ganglia volume and reduced TMT B-A was particularly strong in clinically fatigued patients.

CONCLUSION

This study is among the first to show that reduced basal ganglia volume is an important neurostructural correlate of subjective fatigue in physically able middle-aged and older adults without neurological conditions. Findings suggest that fatigue and rapid set-shifting deficits may share common neural underpinnings involving the basal ganglia, and provide a framework for studying the neuropathogenesis and treatment of subjective fatigue.

Poor sleep accelerates hippocampal and posterior cingulate volume loss in cognitively normal healthy older adults

Poor sleep quality is a known risk factor for Alzheimer's disease. This longitudinal imaging study aimed to determine the acceleration in the rates of tissue loss in cognitively critical brain regions due to poor sleep in healthy elderly individuals. Cognitively-normal healthy individuals, aged ≥60 years, reported Pittsburgh Sleep Quality Index (PSQI) and underwent baseline and 2-year follow-up magnetic resonance imaging brain scans. The links between self-reported sleep quality, rates of tissue loss in cognitively-critical brain regions, and white matter hyperintensity load were assessed. A total of 48 subjects were classified into normal (n = 23; PSQI score <5) and poor sleepers (n = 25; PSQI score ≥5). The two groups were not significantly different in terms of age, gender, years of education, ethnicity, handedness, body mass index, and cognitive performance. Compared to normal sleepers, poor sleepers exhibited much faster rates of volume loss, over threefold in the right hippocampus and fivefold in the right posterior cingulate over 2 years. In contrast, there were no significant differences in the rates of volume loss in the cerebral and cerebellar grey and white matter between the two groups. Rates of volume loss in the right posterior cingulate were negatively associated with global PSQI scores. Poor sleep significantly accelerates volume loss in the right hippocampus and the right posterior cingulate cortex. These findings demonstrate that self-reported sleep quality explains inter-individual differences in the rates of volume loss in cognitively-critical brain regions in healthy older adults and provide a strong impetus to offer sleep interventions to cognitively normal older adults who are poor sleepers.

Decreased Craniocervical CSF Flow in Patients with Normal Pressure Hydrocephalus: A Pilot Study

BACKGROUND AND PURPOSE

Normal pressure hydrocephalus is characterized by systolic peaks of raised intracranial pressure, possibly due to a reduced compliance of the spinal CSF spaces. This concept of a reduced spinal CSF buffer function may be reflected by a low cervical CSF outflow from the cranium. The aim of this study was to investigate craniospinal CSF flow rates by phase-contrast MR imaging in patients with normal pressure hydrocephalus.

MATERIALS AND METHODS

A total of 42 participants were included in this prospective study, consisting of 3 study groups: 1) 10 patients with normal pressure hydrocephalus (mean age, 74 [SD, 6] years, with proved normal pressure hydrocephalus according to current scientific criteria); 2) eighteen age-matched healthy controls (mean age, 71 [SD, 5] years); and 3) fourteen young healthy controls (mean age, 21 [SD, 2] years, for investigation of age-related effects). Axial phase-contrast MR imaging was performed, and the maximal systolic CSF and total arterial blood flow rates were measured at the level of the upper second cervical vertebra and compared among all study groups (2-sample unpaired t test).

RESULTS

The maximal systolic CSF flow rate was significantly decreased in patients with normal pressure hydrocephalus compared with age-matched and young healthy controls (53 [SD,  40] mL/m; 329 [SD,  175] mL/m; 472 [SD, 194] mL/m; each P < .01), whereas there were no significant differences with regard to maximal systolic arterial blood flow (1160 [SD, 404] mL/m; 1470 [SD,  381] mL/m; 1400 [SD, 254] mL/m; each P > .05).

CONCLUSIONS

The reduced maximal systolic craniospinal CSF flow rate in patients with normal pressure hydrocephalus may be reflective of a reduced compliance of the spinal CSF spaces and an ineffective spinal CSF buffer function. Systolic craniospinal CSF flow rates are an easily obtainable MR imaging-based measure that may support the diagnosis of normal pressure hydrocephalus.

Machine learning-based estimation of cognitive performance using regional brain MRI markers: the Northern Manhattan Study

High dimensional neuroimaging datasets and machine learning have been used to estimate and predict domain-specific cognition, but comparisons with simpler models composed of easy-to-measure variables are limited. Regularization methods in particular may help identify regions-of-interest related to domain-specific cognition. Using data from the Northern Manhattan Study, a cohort study of mostly Hispanic older adults, we compared three models estimating domain-specific cognitive performance: sociodemographics and APOE ε4 allele status (basic model), the basic model and MRI markers, and a model with only MRI markers. We used several machine learning methods to fit our regression models: elastic net, support vector regression, random forest, and principal components regression. Model performance was assessed with the RMSE, MAE, and R² statistics using 5-fold cross-validation. To assess whether prediction models with imaging biomarkers were more predictive than prediction models built with randomly generated biomarkers, we refit the elastic net models using 1000 datasets with random biomarkers and compared the distribution of the RMSE and R² in models using these random biomarkers to the RMSE and R² from observed models. Basic models explained ~ 31-38% of the variance in domain-specific cognition. Addition of MRI markers did not improve estimation. However, elastic net models with only MRI markers performed significantly better than random MRI markers (one-sided P < .05) and yielded regions-of-interest consistent with previous literature and others not previously explored. Therefore, structural brain MRI markers may be more useful for etiological than predictive modeling.

MRI Volumetrics and Image Texture Analysis in Assessing Systemic Treatment Response in Extra-Abdominal Desmoid Fibromatosis

Purpose To determine whether MRI volumetric and image texture analysis correlates with treatment-induced biologic changes in desmoid fibromatosis (DF) earlier than conventional response criteria. Materials and Methods This retrospective study included 27 patients with histologically proven extra-abdominal DF who were managed with active surveillance or systemic therapy (from 2004 to 2016). MRI volumetric and image texture parameters were derived from manual tumor segmentations, and tumor signal intensity was normalized to muscle. Results were compared with objective response rates based on Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1, World Health Organization (WHO) lesion response, volumetrics, and MRI-modified Choi criteria. Correlation coefficients (r) between image texture features and maximum tumor diameters were obtained by using a meta-analysis approach. Results The 27 included patients (mean age, 39 years; 74% women) were followed for an average of 4 years, comprising 207 distinct time-point assessments. The mean baseline tumor maximum diameter was 7.9 cm (range, 3.4-15.2 cm). Partial response (PR) rates as best response were 37%, 44%, 70%, and 81% by RECIST, WHO, volumetrics, and MRI-modified Choi criteria, respectively. Among the 10 tumors showing RECIST PR, a preceding MRI-modified Choi PR was observed in 70% (seven of 10), on average 1.3 years earlier. Multiple image texture parameters showed associations with objective measurements of tumor diameter including mean tumor-to-muscle signal ratio (r = 0.51; P = .004), median tumor-to-muscle signal ratio (r = 0.52; P = .003), energy (r = 0.48; P < .001), run entropy (r = 0.32, P = .04), and gray-level nonuniformity (r = 0.54; P ≤ .001). Conclusion Volumetric signal and image texture assessment allows more comprehensive analysis of DF biologic change and may permit early prediction of DF behavior and therapeutic response. Keywords: MR Imaging, Soft Tissues/Skin, Neoplasms-Primary © RSNA, 2021.

Cognitive and Neuroimaging Correlates of the Insomnia Severity Index in Obstructive Sleep Apnea: A Pilot-Study

We aim to determine the sleep correlates of age-related brain loss in a sample of middle-aged to older males with obstructive sleep apnea (OSA). We recruited consecutive treatment naïve male patients with moderate to severe OSA from January to November of 2019. We excluded participants if they had dementia, stroke or heart disease. We collected demographic variables and vascular risk factors. We also obtained the insomnia severity index, the Epworth sleepiness scale and the Pittsburgh sleep quality index. We also obtained computerized neurocognitive testing with the go-no-go response inhibition test, Stroop interference test, catch game test, staged information processing speed test, verbal memory test and non-verbal memory test. We derived age and education adjusted domain-specific Z-scores for global cognition, memory, attention, processing speed and executive function. We used brain MRI T1-weighted images to derive total hippocampal and gray matter volumes. Partial correlations evaluated associations between variables from sleep questionnaires (e.g., insomnia severity index score), and polysomnographic variables (the apnea-hypopnea index, average oxygen levels during sleep) with cognitive domains and brain volumes. We examined 16 participants with an age range of 40–76 years, 73% Hispanic/Latino. The mean apnea-hypopnea index was 48.9 ± 25.5 and average oxygen saturation during sleep was 91.4% ± 6.9%. Hypertension was seen in 66% and diabetes mellitus in 27%. We found that the insomnia severity index score and average oxygen levels during sleep had the strongest correlations with brain volumes and cognition. These preliminary findings may aid in developing future strategies to improve age-related brain loss in patients with OSA.

Quantification of Regional Cerebral Blood Flow Using Diffusion Imaging With Phase Contrast

BACKGROUND

The perfusion-related diffusion coefficient obtained from triexponential diffusion analysis is closely correlated with regional cerebral blood flow (rCBF), as assessed by arterial spin labeling (ASL) methods. However, this provides only a semiquantitative measure of rCBF, thereby making absolute rCBF quantification challenging.

PURPOSE

To obtain rCBF in a noninvasive manner using a novel diffusion imaging method with phase contrast (DPC), in which the total CBF from phase-contrast (PC) MRI was utilized to convert perfusion-related diffusion coefficients to rCBF values.

STUDY TYPE

Prospective.

SUBJECTS

Eleven healthy volunteers (nine men and two women; mean age, 23.9 years) participated in this study.

FIELD STRENGTH/SEQUENCE

A 3.0 T, single-shot diffusion echo-planar imaging with multiple b-values (0-3000 s/mm² ), PC-MRI, pulsed continuous ASL, and 3D T₁ -weighted fast field echo.

ASSESSMENT

rCBF and its correlations in the gray matter (GM) and white matter (WM) were compared between DPC and ASL methods. rCBF in the GM and WM and the GM/WM ratio were compared with the literature values obtained using [¹⁵ O]-water positron emission tomography (¹⁵ O-H₂ O PET).

STATISTICAL TESTS

Spearman's correlation coefficient and Wilcoxon signed-rank test were used. Significance was set at P < 0.05.

RESULTS

A significant positive correlation between DPC and ASL in terms of rCBF was observed in GM (R = 0.9), whereas the correlation between the two methods was poor in WM (R = 0.09). The rCBF in GM and WM and the GM/WM ratio obtained using DPC were consistent with the literature values assessed using ¹⁵ O-H₂ O PET. The rCBF value obtained using DPC was significantly higher in the GM and WM than that using ASL.

DATA CONCLUSION

DPC enabled noninvasive quantification of rCBF.

EVIDENCE LEVEL

2 TECHNICAL EFFICACY: Stage 1.

Poor sleep is associated with small hippocampal subfields in cognitively normal elderly individuals

Recent studies demonstrated reduced hippocampal volumes in elderly healthy individuals who are cognitively normal but poor sleepers. The association between sleep quality and the pattern of volume loss across hippocampal subfields (HSs) is not well known. Thus, it is the focus of the present study. Sleep quality was self-assessed using the Pittsburgh Sleep Quality Index (PSQI). The HS volumes were measured using sub-millimetre in-plane resolution T2-weighted magnetic resonance imaging data. A total of 67 cognitively normal elderly individuals aged 60-83 years were classified into 30 normal sleepers with a PSQI <5 and 37 poor sleepers with a PSQI ≥5. The two groups were equivalent in age, gender distribution, ethnicity, education attainment, handedness and cognitive performance. Compared to normal sleepers, poor sleepers exhibited significantly lower normalised volumes in the left cornu ammonis field 1 (CA1), dentate gyrus (DG) and subiculum. In contrast, there were no significant differences in normalised grey and white matter volumes between the two groups. The global PSQI was negatively associated with the normalised volumes of the left CA1, DG and subiculum. Sleep duration was associated with the normalised volumes of the bilateral CA1, DG, left CA2 and subiculum. Verbal memory scores were associated with the left CA1 volume. In conclusion, poor sleep quality, especially insufficient sleep duration, was associated with volume loss in several HSs that are involved in specific learning and memory tasks. As the hippocampus does not regulate sleep, it is more likely that poor sleep leads to small hippocampi. Thus, based on this assumption, improving sleep quality of poor sleeper elderly individuals could benefit hippocampal health.

Cholinergic White Matter Lesions, AD-Signature Cortical Thickness, and Change in Cognition: The Northern Manhattan Study

BACKGROUND

How cerebrovascular disease and neurodegeneration affect each other to impact cognition is not yet known. We aimed to test whether Alzheimer's disease-signature (AD) cortical thickness mediates the association between cholinergic white matter lesion load and change in domain-specific cognition.

METHODS

Clinically stroke-free participants from the Northern Manhattan Study with both regional white matter hyperintensity volume (WMHV) and gray matter measurements were included (N = 894). Tract-specific WMHVs were quantified through FSL using the Johns Hopkins University white matter tract atlas. We used Freesurfer 5.1 to estimate regional cortical thickness. We fit structural equation models, including multiple indicator latent change score models, to examine associations between white matter hyperintensity volume (WMHV) in cholinergic tracts, AD-signature region cortical thickness (CT), and domain-specific cognition.

RESULTS

Our sample (N = 894) had a mean (SD) age = 70 (9) years, years of education = 10 (5), 63% women, and 67% Hispanics/Latinos. Greater cholinergic WMHV was significantly related to worse processing speed at baseline (standardized β = -0.17, SE = 0.05, p = .001) and over time (standardized β = -0.28, SE = 0.09, p = .003), with a significant indirect effect of AD-signature region CT (baseline: standardized β = -0.02, SE = 0.01, p = .023; change: standardized β = -0.03, SE = 0.02, p = .040).

CONCLUSIONS

Cholinergic tract WMHV is associated with worse processing speed, both directly and indirectly through its effect on AD-signature region CT.

Role of the spinal canal compliance in regulating posture-related cerebrospinal fluid hydrodynamics in humans

Mechanical compliance of a compartment is defined by the change in its volume with respect to a change in the inside pressure. The compliance of the spinal canal regulates the intracranial pressure (ICP) under postural changes. Understanding how gravity affects ICP is beneficial for poorly understood cerebrospinal fluid (CSF)-related disorders. The aim of this study was to evaluate postural effects on cranial hemo- and hydrodynamics. This was a prospective study, which included 10 healthy volunteers (three males, seven females, mean ± standard deviation age: 29 ± 7 years). Cine gradient-echo phase-contrast sequence acquired at 0.5 T, "GE double-doughnut" scanner was used. Spinal contribution to overall craniospinal compliance (CSC), craniospinal CSF stroke volume (SV), magnetic resonance (MR)-derived ICP (MR-ICP), and total cerebral blood flow (TCBF) were measured in supine and upright postures using automated blood and CSF flows quantification. Statistical tests performed were two-sided Student's t-test, Cohen's d, and Pearson correlation coefficient. MR-ICP and the craniospinal CSF SV were significantly correlated with the spinal contribution to the overall CSC (r = 0.83, p < 0.05) and (r = 0.62, p < 0.05), respectively. Cranial contribution to CSC increased from 44.5% ± 16% in supine to 74.9% ± 8.4% in upright posture. The average MR-ICP dropped from 9.9 ± 3.4 mmHg in supine to -3.5 ± 1.5 mmHg. The CSF SV was over 2.5 times higher in the supine position (0.55 ± 0.14 ml) than in the upright position (0.21 ± 0.13 ml). In contrast, TCBF was slightly higher in the supine posture (822 ± 152 ml/min) than in the upright posture (761 ± 139 ml/min), although not statistically significant (p = 0.16). The spinal-canal compliance contribution to CSC is larger than the cranial contribution in the supine posture and smaller in the upright posture. Thereby, the spinal canal plays a role in modulating ICP upon postural changes. The lower pressure craniospinal CSF system was more affected by postural changes than the higher-pressure cerebral vascular system. Craniospinal hydrodynamics is affected by gravity and is likely to be altered by its absence in space. LEVEL OF EVIDENCE: 4 TECHNICAL EFFICACY STAGE: 2.

Measures of Adiposity and Alzheimer's Disease-Related MRI Markers: The Northern Manhattan Study

BACKGROUND

Adiposity may increase risk for dementia and Alzheimer's disease (AD), but mechanisms are unclear.

OBJECTIVE

To examine associations between measures of adiposity with AD-signature region cortical thickness and hippocampal volume.

METHODS

We used data from the Northern Manhattan Study, a clinically stroke-free cohort of mostly Hispanic participants. Exposures of interest included body mass index (BMI), waist-hip-ratio (WHR), waist circumference (WC), and adiponectin concentration, measured at study entry. AD-signature region cortical thickness and hippocampal volume were obtained using Freesurfer. We estimated associations using multivariable linear regression, adjusting for sociodemographics and health behaviors. We re-examined estimates after adjustment for APOEɛ4 allele status or carotid intima-media thickness (cIMT), among those cognitively unimpaired, and after weighting for the inverse probability of selection into the MRI sub-study. We also repeated analyses for cortical thickness in non-AD signature regions.

RESULTS

The sample (N = 947, 63% women, 66% Hispanic/Latino, 26% obese) had a mean (SD) age = 63 (8) years. Greater BMI and WC (both z-scored) were associated with thinner AD-signature region cortex (also z-scored) (BMI: β [95% CI] = -0.09 [-0.18, -0.01], WC: β [95% CI] = -0.11 [-0.20, -0.02]). We did not find evidence that adiposity was related to hippocampal volume. Results were consistent after adjustment for APOEɛ4 allele status or cIMT, after weighting for selection, among those cognitively unimpaired, and for non-AD signature region cortical thickness.

CONCLUSION

Greater BMI and WC were related to cortical thinning within and outside the AD-signature region, suggesting a global effect not specific to AD.

0835 Elucidating the Effect of Sleep Apnea on Cognitive Health: A Preliminary Report

Introduction

We aim to determine the cognitive domains associated with obstructive sleep apnea (OSA) age-related brain atrophy in a sample of middle-aged to older males.

Methods

We evaluated consecutive treatment naïve male OSA patients (AHI≥15) without dementia, stroke or heart disease (infarction, heart failure), from March to November of 2019. We obtained demographic variables, vascular risk factors, the Epworth sleepiness scale (ESS) and the Pittsburgh sleep quality index (PSQI). We also obtained computerized neurocognitive testing with the Go-NoGo Response Inhibition Test, Stroop Interference Test, Catch Game Test, Staged Information Processing Speed Test, Verbal Memory Test and Non-Verbal Memory Test. We derived domain-specific Z-scores age and education adjusted for global cognition, memory, attention, processing speed and executive function. Pearson correlation was used to evaluate bivariate associations between the sleep exposures and neurocognitive outcomes. Linear regression was used to evaluate associations between AHI and neurocognitive domains, adjusting for the ESS.

Results

A total of 15 participants 40 to 76 years of age, 73% of Hispanic/Latino background, completed neurocognitive testing. The average ESS was 8.2±6.0, PSQI=5.7±4.9, and AHI=48.9±25.5. Hypertension was seen in 66% and diabetes in 27%. The AHI was correlated with global cognition (r= -0.66; p=0.008), memory (r= -0.73; p=0.002) and attention (r= -0.67; p =0.007), but not executive function or processing speed. In addition, the AHI correlated with verbal memory (r= -0.76; p=0.001), but not with non-verbal memory. In adjusted models, the AHI was associated with global cognition (β= -0.60; p=0.05) and decreased memory (β= -0.85; p=0.006). However, the association with attention was explained by the ESS. The PSQI was not correlate with the cognitive domains.

Conclusion

In this pilot-study, the AHI was associated with decreased global cognition, and verbal memory accounting for sleepiness. Findings suggest the left-hippocampus as a region vulnerable to early age-related brain loss in OSA.

Support

Scientific Advisory Committee, Pilot grant, Miller School of Medicine; R21AG056952; R21HL140437.

0647 The Effect of CPAP on the Blood Flow to the Brain: A Preliminary Report

Introduction

We aim to determine the effect of positive airway pressure (PAP) on total cerebral blood flow in a sample of middle-aged to older male patients with obstructive sleep apnea (OSA).

Methods

We evaluated consecutive treatment-naïve male OSA patients with Apnea hypopnea Index (AHI)≥15, from January to November of 2019. We obtained demographic variables, vascular risk factors, the Epworth sleepiness scale (ESS) and the Pittsburgh sleep quality index (PSQI). Brain magnetic resonance imaging (MRI) consisted of high resolution anatomical imaging and velocity encoded phase contrast MRI to measure volumetric blood flow rate to the brain, or the total cerebral blood flow (tCBF), by summation of the flow rate through the two internal carotid and vertebral arteries. Positive airway pressure at various pressures was provided during the MRI, while subjects were awake, starting at 0 cm H20, then 5 cmH20, 10, 15, and 20 cmH20. Each setting was applied for six minutes. Two subjects did not tolerate pressure setting of 20 cmH2O.

Results

We had a total of 11 participants’ age 40-73 years, 70% Hispanic/Latino background. The average ESS was 8.2±6.0, PSQI=5.7±4.9, and AHI=48.9±25.5. Five of the subjects had hypertension and a quarter had diabetes. In all subjects total CBF monotonically decreased with increasing PAP. The initial decreases in total CBF (PAP from 0 to 5 and 5 to 10) where significantly larger than the decrease in the higher pressure range. In two subjects the total decrease in tCBF was nearly 50%. The average tCBF was 682.3 mL/min at 0 cmH20 and 506.3 ml/min at 20 cmH20.

Conclusion

Incremental increases in PAP lead to substantial decrease in tCBF during wake. Substantial decrease in tCBF is possibly explained by decreasing end tidal CO2 pressure. The specific physiologic cause and the neurologic impact of prolonged decreased tCBF during CPAP therapy needs to be further investigated.

Support

Scientific Advisory Committee, Pilot grant, Miller School of Medicine; R21AG056952; R21HL140437; Jazz-Pharmaceutical.

Diastolic Blood Pressure Is Associated With Regional White Matter Lesion Load: The Northern Manhattan Study

Background and Purpose- Few studies have examined the separate contributions of systolic blood pressure and diastolic blood pressures (DBP) on subclinical cerebrovascular disease, especially using the 2017 American College of Cardiology/American Heart Association Blood Pressure Guidelines. Furthermore, associations with region-specific white matter hyperintensity volume (WMHV) are underexplored. Methods- Using data from the NOMAS (Northern Manhattan Study), a prospective cohort study of stroke risk and cognitive aging, we examined associations between systolic blood pressure and DBP, defined by the 2017 American College of Cardiology/American Heart Association guidelines, with regional WMHV. We used a linear mixed model approach to account for the correlated nature of regional brain measures. Results- The analytic sample (N=1205; mean age 64±8 years) consisted of 61% women and 66% Hispanics/Latinos. DBP levels were significantly related to WMHV differentially across regions (P for interaction<0.05). Relative to those with DBP 90+ mm Hg, participants with DBP <80 mm Hg had 13% lower WMHV in the frontal lobe (95% CI, -21% to -3%), 11% lower WMHV in the parietal lobe (95% CI, -19% to -1%), 22% lower WMHV in the anterior periventricular region (95% CI, -30% to -14%), and 16% lower WMHV in the posterior periventricular region (95% CI, -24% to -6%). Participants with DBP 80 to 89 mm Hg also exhibited about 12% (95% CI, -20% to -3%) lower WMHV in the anterior periventricular region and 9% (95% CI, -18% to -0.4%) lower WMHV in the posterior periventricular region, relative to participants with DBP 90≥ mm Hg. Post hoc pairwise t tests showed that estimates for periventricular WMHV were significantly different from estimates for temporal WMHV (Holms stepdown-adjusted P<0.05). Systolic blood pressure was not strongly related to regional WMHV. Conclusions- Lower DBP levels, defined by the 2017 American College of Cardiology/American Heart Association guidelines, were related to lower white matter lesion load, especially in the periventricular regions relative to the temporal region.

Measures of obesity are associated with MRI markers of brain aging: The Northern Manhattan Study

OBJECTIVE

To examine associations between measures of obesity in middle to early-old age with later-life MRI markers of brain aging.

METHODS

We analyzed data from the Northern Manhattan MRI Sub-Study (n = 1,289). Our exposures of interest were body mass index (BMI), waist circumference (WC), waist-to-hip ratio, and plasma adiponectin levels. Our outcomes of interest were total cerebral volume (TCV), cortical thickness, white matter hyperintensity volume (WMHV), and subclinical brain infarcts (SBI). Using multivariable linear and logistic regression models adjusted for sociodemographics, health behaviors, and vascular risk factors, we estimated β coefficients (or odds ratios) and 95% confidence intervals (CIs) and tested interactions with age, sex, and race/ethnicity.

RESULTS

On average at baseline, participants were aged 64 years and had 10 years of education; 60% were women and 66% were Caribbean Hispanic. The mean (SD) time lag between baseline and MRI was 6 (3) years. Greater BMI and WC were significantly associated with thinner cortices (BMI β [95% CI] -0.089 [-0.153, -0.025], WC β [95% CI] -0.103 [-0.169, -0.037]) in fully adjusted models. Similarly, compared to those with BMI <25, obese participants (BMI ≥30) exhibited smaller cortical thickness (β [95% CI] -0.207 [-0.374, -0.041]). These associations were particularly evident for those aged <65 years. Similar but weaker associations were observed for TCV. Most associations with WMHV and SBI did not reach statistical significance.

CONCLUSIONS

Adiposity in early-old age is related to reduced global gray matter later in life in this diverse sample. Future studies are warranted to elucidate causal relationships and explore region-specific associations.

Brain arterial dilatation modifies the association between extracranial pulsatile hemodynamics and brain perivascular spaces: the Northern Manhattan Study

Pulsatile hemodynamics are associated with brain small perivascular spaces (SPVS). It is unknown whether the stiffness of intermediary arteries connecting the aorta and brain modifies this association. Participants from the Northern Manhattan Study were assessed for SPVS (defined as ≤3 mm T1 voids) and white matter hyperintensity volume (WMH) using MRI. Middle (MCA) and anterior cerebral arterial (ACA) diameters (measured on time-of-flight MRA) and CCA strain (assessed by ultrasound) were used as surrogates of stiffness. Brachial and aortic pulse pressure (PP) and aortic augmentation index (Aix, assessed by applanation tonometry) were used as markers of pulsatility. We tested whether stiffness in intermediary arteries modifies the association between extracranial pulsatility with SPVS and WMH. We found that among 941 participants (mean age 71 ± 9 years, 60% women, 66% Hispanic), the right MCA/ACA diameter was associated with right anterior SPVS (B = 0.177, P = 0.002). Brachial PP was associated with right anterior SPVS (B = 0.003, P = 0.02), and the effect size was bigger with right MCA/ACA diameter in the upper tertile (P = 0.001 for the interaction). The association between right CCA strain and ipsilateral SPVS was modified by MCA/ACA diameter, with the largest effect size in those with ipsilateral MCA/ACA diameter in the upper tertile (P = 0.001 for the interaction). Similar dose-effects and statistical interactions were replicated using aortic AIx or aortic PP. We found no evidence of effect modification between pulsatile measures and WMH by stiffness measures. In summary, pulsatile hemodynamics relate to brain SPVS, and the association is the strongest among individuals with dilated brain arteries.

Effect of sleep quality on amnestic mild cognitive impairment vulnerable brain regions in cognitively normal elderly individuals

STUDY OBJECTIVES

This study aims to evaluate the extent to which sleep quality impacts amnestic mild cognitive impairment (aMCI)-related brain regions in a cognitively normal cohort of individuals.

METHODS

Seventy-four participants were rigorously evaluated using a battery of cognitive tests and a detailed clinical assessment to verify normal cognitive status. We then screened for sleep quality using the Pittsburgh Sleep Quality Index (PSQI) and depressive symptoms using the Geriatric Depression Scale (GDS). Five subjects were excluded due to mild depression. Overall 38 individuals with mean age 70.7 ± 7 were classified as poor sleepers and 31 with mean age of 69.6 ± 6 years as normal sleepers. Structural MRI and Freesurfer brain parcellation were used to measure aMCI-related brain regions.

RESULTS

Relative to normal sleepers, poor sleepers exhibited significant reductions in cortical and subcortical volumes bilaterally in the hippocampi, as well as in the superior parietal lobules and left amygdala. The effects were strongest in the left superior parietal lobule (p < .015), followed by the hippocampi. Diffuse patterns of cortical thinning were observed in the frontal lobes, but significant effects were concentrated in the right mesial frontal cortex. Lower sleep duration was most correlated with cortical volume and thickness reductions among all subjects.

CONCLUSIONS

Atrophy related to poor sleep quality impacted a number of regions implicated in aMCI and Alzheimer's disease (AD). As such, interventions targeted towards improving sleep quality amongst the elderly may prove an effective tool for modulating the course of aMCI and AD.

Comparing invasive with MRI-derived intracranial pressure measurements in healthy elderly and brain trauma cases: A pilot study

BACKGROUND

Intracranial pressure (ICP) is an important physiological parameter in several neurological disorders. Considerable effort has been made to measure ICP noninvasively. MR-based ICP (MR-ICP) is a nonempirical method based on principles of cerebrospinal fluid (CSF) physiology, where ICP is obtained from measurements of blood and CSF flows to and from the cranium during the cardiac cycle.

PURPOSE

To compare MR-ICP with invasive ICP measurements obtained using lumbar puncture (LP) or external ventricular drainage (EVD).

STUDY TYPE

Prospective, cross-sectional, observational study.

SUBJECTS

Ten cognitively healthy elderly subjects (age 69.6 ± 6.6 years; seven females) and six brain trauma patients (age 36.8 ± 19.7 years; two females).

FIELD STRENGTH

Velocity encoding cine phase-contrast at 1.5 T and 3 T.

ASSESSMENT

MR-ICP and craniospinal compliance distribution were estimated from arterial inflow and venous outflow to and from cranium, and craniospinal CSF flow at the upper cervical region, measured using cine phase contrast MRI. LP (done 177 ± 163 days after scan) and EVD measurements (at the time of scan) were performed in lateral recumbent and supine positions, respectively.

STATISTICAL TESTS

Linear regression was used to assess the relationships of MR-ICP with invasive ICP, and the dependency of these measurements on age, weight, height, and BMI. A Shapiro-Wilks test and Bland-Altman plot were respectively used to evaluate the normality and agreement between these two pressure distributions. Student's t-test was used throughout the analysis to compare differences between the EVD and LP cohorts.

RESULTS

In the combined cohort, MR-ICP and invasive ICP were positively correlated (r = 0.95, P < 0.001), with invasive ICP being higher than MR-ICP by 2.2 mmHg on average. In the healthy cohort, the cranial contribution to total craniospinal compliance was negatively correlated with MR-ICP (r = -0.90, P < 0.001).

DATA CONCLUSION

MR-ICP provides a reliable estimate of ICP, with 14 out of 16 datapoints within the clinically acceptable error. Craniospinal compliance distribution plays a role in modulating ICP in supine position.

LEVEL OF EVIDENCE

3 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2019;50:975-981.

Abstract TMP52: Basilar Artery Tortuosity and Elongation and Risk of Ischemic Stroke and Death: The Northern Manhattan Study

Background: Basilar artery (BA) dolichoectasia is defined as dilatation, tortuosity, and/or elongation of the basilar artery. Hospital-based studies have demonstrated an association between BA dilatation and risk of death and stroke. We hypothesized that BA tortuosity and elongation increase risk of death and stroke independent of BA dilatation.

Methods: We included stroke-free participants in the Northern Manhattan Study, a population-based prospective cohort study, with an available time of flight MRA. BA tortuosity was defined as BA localization lateral to margin of the clivus, and BA elongation as BA tip distal to margin of the sella. BA diameters were obtained with semi-automated in-house software. Primary outcomes were any death and ischemic stroke. Cox proportional hazards models were used to obtain hazards ratios [HR] and 95% confidence intervals [CI] after adjusting for demographics and vascular risks.

Results: Participants (N=1032, mean age 70.7 years, 39.5% men, 65.7% Hispanic) were followed on average for 10.4 ± 3.1 years after their MRA. Among these, 97 (9.4%) had BA tortuosity, 294 (28.5%) had BA elongation, and 98 (9.5%) had both tortuosity and elongation. Participants with BA tortuosity were more likely men, and participants with BA elongation were older, more likely women, non-Hispanic white and were more likely hypertensive. There was no association between BA tortuosity (HR 0.89; 95% CI 0.73 – 1.09, P=0.27), BA elongation (HR 1.12; 0.96 – 1.31, P=0.14), or BA dilatation (HR 1.03; 95% CI 0.84 – 1.27, P=0.76) and risk of death. There was an interaction between BA tortuosity and elongation (P for interaction=0.02); BA elongation was associated with an increased risk of death only among those with BA tortuosity (HR 2.06; 1.29 – 3.29; P=0.002). Adjusting for BA dilatation attenuated the association (HR 1.66; 0.99 – 2.81, P=0.05). We found no association between BA tortuosity (HR 0.92; 95% CI 0.77 – 1.10) or elongation (HR 1.07; 95% CI 0.92 – 1.23), or their combination, and ischemic stroke.

Conclusion: Stroke-free individuals with both basilar elongation and tortuosity may have a higher risk of death, but not stroke. Further studies of vasculopathy seen in dolichoectasia and its relationship to systemic vascular disease and mortality are warranted.

Patient-specific cranio-spinal compliance distribution using lumped-parameter model: its relation with ICP over a wide age range

Background

The distribution of cranio-spinal compliance (CSC) in the brain and spinal cord is a fundamental question, as it would determine the overall role of the compartments in modulating ICP in healthy and diseased states. Invasive methods for measurement of CSC using infusion-based techniques provide overall CSC estimate, but not the individual sub-compartmental contribution. Additionally, the outcome of the infusion-based method depends on the infusion site and dynamics. This article presents a method to determine compliance distribution between the cranium and spinal canal non-invasively using data obtained from patients. We hypothesize that this CSC distribution is indicative of the ICP.

Methods

We propose a lumped-parameter model representing the hydro and hemodynamics of the cranio-spinal system. The input and output to the model are phase-contrast MRI derived volumetric transcranial blood flow measured in vivo, and CSF flow at the spinal cervical level, respectively. The novelty of the method lies in the model mathematics that predicts CSC distribution (that obeys the physical laws) from the system dc gain of the discrete-domain transfer function. 104 healthy individuals (48 males, 56 females, age 25.4 ± 14.9 years, range 3–60 years) without any history of neurological diseases, were used in the study. Non-invasive MR assisted estimate of ICP was calculated and compared with the cranial compliance to prove our hypothesis.

Results

A significant negative correlation was found between model-predicted cranial contribution to CSC and MR-ICP. The spinal canal provided majority of the compliance in all the age groups up to 40 years. However, no single sub-compartment provided majority of the compliance in 41–60 years age group. The cranial contribution to CSC and MR-ICP were significantly correlated with age, with gender not affecting the compliance distribution. Spinal contribution to CSC significantly positively correlated with CSF stroke volume.

Conclusions

This paper describes MRI-based non-invasive way to determine the cranio-spinal compliance distribution in the brain and spinal canal sub-compartments. The proposed mathematics makes the model always stable and within the physiological range. The model-derived cranial compliance was strongly negatively correlated to non-invasive MR-ICP data from 104 patients, indicating that compliance distribution plays a major role in modulating ICP.

Ideal Cardiovascular Health and Biomarkers of Subclinical Brain Aging: The Northern Manhattan Study

Background The American Heart Association Life's Simple 7 metric defines ideal cardiovascular health (CVH) on 7 factors: smoking, diet, physical activity, body mass index, blood sugar, blood pressure, and cholesterol. This metric has been used to define optimal brain health, but data relative to subclinical imaging biomarkers of brain aging are lacking. This study examines the association between Life's Simple 7 with white matter hyperintensity volume, silent brain infarcts, and cerebral volume. Methods and Results A subsample of stroke-free participants from the population-based Northern Manhattan Study underwent brain magnetic resonance imaging an average of 7 years after baseline. Linear and logistic regression models were constructed to estimate associations between the number of ideal CVH metrics achieved with imaging biomarkers of brain aging, adjusting for sociodemographics. Among 1031 participants (mean age at magnetic resonance imaging=72±8, 40% men, 19% black, 16% white, and 65% Hispanic), no one had ideal status in all 7 factors, 1% had ideal status in 6 factors, 18% in 4 to 5 factors, 30% in 3 factors, 33% in 2 factors, and 18% in 0 to 1 factors. The number of ideal CVH factors achieved was inversely associated with white matter hyperintensity volume (beta per factor=-0.047; P=0.04) and silent brain infarct (odds ratio per factor=0.84; 95% confidence interval=0.72-0.97) and positively associated with cerebral volume (beta per factor=0.300; P=0.002). Conclusions An increasing ideal CVH score was associated with less white matter hyperintensity volume and silent brain infarcts and greater cerebral volumes, supporting the Life's Simple 7 metric as a useful measure to quantify optimal brain health. Monitoring and promoting achievement of Life's Simple 7 ideal CVH factors may improve subclinical and clinical brain health outcomes.

Regional Subclinical Cerebrovascular Disease Is Associated with Balance in an Elderly Multi-Ethnic Population

INTRODUCTION

White matter hyperintensity volume (WMHV) and subclinical brain infarcts (SBI) are associated with impaired mobility, but less is known about the association of WMHV in specific brain regions. We hypothesized that anterior WMHV would be associated with lower scores on the Short Physical Performance Battery (SPPB), a well-validated mobility scale.

METHODS

The SPPB was measured a median of 5 years after enrollment into the Northern Manhattan MRI sub study. Volumetric distributions for WMHV in 14 brain regions as a proportion of total cranial volume were determined. Multi-variable linear regression was performed to examine the association of SBI and regional log-WMHV with the SPPB score.

RESULTS

Among 668 participants with SPPB measurements (mean 74 ± 9 years, 37% male and 70% Hispanic), the mean SPPB score was 8.2 ± 2.9. Total (beta = -0.3 per SD, p = 0.001), anterior periventricular (beta = -0.4 per SD, p = 0.001), parietal (beta = -0.2 per SD, p = 0.02) and frontal (beta = -0.3 per SD, p = 0.002) WMHVs were associated with SPPB; other WMHV and SBI were not associated with the SPPB.

CONCLUSIONS

WMHV, especially in the anterior -cerebral regions, is associated with a lower SPPB. Prevention of subclinical cerebrovascular disease is a potential target to prevent physical decline in the elderly.

Greater depressive symptoms, cognition, and markers of brain aging: Northern Manhattan Study

OBJECTIVE

We examined whether greater depressive symptoms were associated with domain-specific cognitive performance, change in cognition, and MRI markers of brain atrophy and subclinical cerebrovascular disease in a diverse sample of older adults from the Northern Manhattan Study.

METHODS

Data were analyzed from the Northern Manhattan Study, a prospective cohort study of mostly Caribbean Hispanic, stroke-free, older adults. A total of 1,111 participants had baseline measures of depressive symptoms, measured as the Center of Epidemiological Studies-Depression Scale, MRI markers, and cognitive function. A Center of Epidemiological Studies-Depression score ≥16 was considered indicative of greater depressive symptoms. Multivariable linear and logistic regression models were used to examine the associations of interest.

RESULTS

At baseline, 22% of participants had greater depressive symptoms. Greater depressive symptoms were significantly associated with worse baseline episodic memory in models adjusted for sociodemographic, vascular risk factor, behavioral, and antidepressive medication variables (β [95% confidence interval] = -0.21 [-0.33 to -0.10], p = 0.0003). Greater depressive symptoms were also associated with smaller cerebral parenchymal fraction (β [95% confidence interval] = -0.56 [-1.05 to -0.07], p = 0.02) and increased odds of subclinical brain infarcts (odds ratio [95% confidence interval] = 1.55 [1.00-2.42], p = 0.05), after adjustment for sociodemographic, behavioral, and vascular risk factor variables. Greater depressive symptoms were not significantly associated with white matter hyperintensity volume, hippocampal volume, or change in cognition over an average of 5 years. Results were unchanged when stabilized inverse probability weights were applied to address selective attrition during the study period.

CONCLUSIONS

In this sample of mostly Caribbean Hispanic, stroke-free, older adults, greater depressive symptoms were associated with worse episodic memory, smaller cerebral volume, and silent infarcts.

Recovery from Proactive Semantic Interference in Mild Cognitive Impairment and Normal Aging: Relationship to Atrophy in Brain Regions Vulnerable to Alzheimer's Disease

BACKGROUND

There is growing evidence that proactive semantic interference (PSI) and failure to recover from PSI may represent early features of Alzheimer's disease (AD).

OBJECTIVE

This study investigated the association between PSI, recovery from PSI, and reduced MRI volumes in AD signature regions among cognitively impaired and unimpaired older adults.

METHODS

Performance on the LASSI-L (a novel test of PSI and recovery from PSI) and regional brain volumetric measures were compared between 38 cognitively normal (CN) elders and 29 older participants with amnestic mild cognitive impairment (MCI). The relationship between MRI measures and performance on the LASSI-L as well as traditional memory and non-memory cognitive measures was also evaluated in both diagnostic groups.

RESULTS

Relative to traditional neuropsychological measures, MCI patients' failure to recover from PSI was associated with reduced volumes in the hippocampus (rs = 0.48), precuneus (rs = 0.50); rostral middle frontal lobules (rs = 0.54); inferior temporal lobules (rs = 0.49), superior parietal lobules (rs = 0.47), temporal pole (rs = 0.44), and increased dilatation of the inferior lateral ventricle (rs = -0.49). For CN elders, only increased inferior lateral ventricular size was associated with vulnerability to PSI (rs = -0.49), the failure to recover from PSI (rs = -0.57), and delayed recall on the Hopkins Verbal Learning Test-Revised (rs = -0.48).

DISCUSSION

LASSI-L indices eliciting failure to recover from PSI were more highly associated with more MRI regional biomarkers of AD than other traditional cognitive measures. These results as well as recent amyloid imaging studies with otherwise cognitively normal subjects, suggest that recovery from PSI may be a sensitive marker of preclinical AD and deserves further investigation.

Abstract TP125: Blood Biomarkers of Systemic Inflammation in Individuals With Brain Arterial Dilatation and Dolichoectasia

Background: Brain arterial dilatation is a core feature of dolichoectasia, and is associated with higher risk of stroke and vascular events. The role of systemic inflammation in brain arterial dilatation is uncertain.

Methods: We measured blood levels of lipoprotein-associated phospholipase A2 (Lp-PLA2), myeloperoxidase (MPO), high-sensitivity C-reactive protein (hsCRP), and procalcitonin (PCT) in 538 NOMAS participants (mean age 71±8, 42% men, 60% Hispanic) who underwent brain time-of-flight MRA. Brain arterial diameters were normalized and averaged to obtain a global, anterior and posterior circulations measures of dilation. The concentration of each inflammatory biomarker was normalized to facilitate comparison, and to create an inflammation score consisting of the average of the four biomarkers. Generalized linear models were used to assess for main effects and statistical interactions by sex given known differences in arterial size.

Results: Greater levels of MPO were associated with global and anterior circulation dilatation whereas greater levels of PCT were associated with posterior circulation dilatation (table 1). A higher inflammation score was associated with global and posterior circulation, but not anterior circulation, dilatation. There was a statistical interaction between MPO and sex (P=0.06). In a stratified model, the association between MPO and global arterial dilatation was significant in men (B=0.164±0.057, P=0.004) but not in women (B=0.053±0.054, P=0.33). There were no sex-based interactions for any of the other three inflammatory biomarkers.

Conclusion: The inflammation markers MPO and PCT were associated with global and regional measures of brain arterial dilatation. The strength of the associations with MPO was greatest in men while the association with PCT was greatest for the posterior circulation. Understanding the physiopathology of these associations may uncover novel therapeutic targets for dolichoectasia.

Abstract WP423: Adiponectin and Components of Metabolic Syndrome are Associated With Cortical Thickness: The Northern Manhattan Study

Objective: Examine the association of adiponectin and metabolic syndrome components with measures of global and lobar cortical thickness.

Background: Metabolic syndrome has been associated with structural brain changes, but the relationship of adiponectin and cortical thickness is understudied.

Methods: The Northern Manhattan Study MRI Sub-Study is a mostly Hispanic, stroke-free, prospective cohort study of older adults. Cortical thickness (mm) was obtained from T1-weighted brain MRIs using the publically-available Freesurfer software. Regional cortical thickness metrics were averaged to obtain mean lobar cortical thickness. Adiponectin (μg/mL) was measured at baseline (1993-2001). Metabolic syndrome components were measured at MRI Sub-Study baseline (2003-2008). We estimated the cross-sectional associations of adiponectin (per 1 SD) and metabolic syndrome components with global and lobar cortical thickness (per 1 SD) using multivariable linear regression models adjusted for sociodemographic factors, APOE ε4 allele presence, and health-related behaviors. All hypothesis testing was two-sided with an alpha level of 5%.

Results: Freesurfer data were available in 947 participants (mean±SD age=70±9 years, 63% women, 66% Hispanics, 16% black, and 15% white). Global cortical thickness was normally distributed (mean±SD = 2.3±0.1mm). In fully adjusted models, 1 SD (4.9μg/mL) increase in adiponectin was associated with smaller overall (β [95%CI] = -0.07 [-0.14, -0.0002]) and parietal cortical thickness (β [95%CI] = -0.08 [-0.03, -0.0002]). Greater blood glucose levels significantly associated with smaller occipital cortical thickness (β [95%CI] = -0.003 [-0.006, -0.0007]). Greater waist circumference was significantly associated with smaller frontal cortical thickness (β [95%CI] = -0.02 [-0.04, -0.0007]). Neither blood pressure (systolic and diastolic) nor cholesterol (total, HDL-C, and LDL-C) were associated with global or regional cortical thickness.

Conclusions: There was heterogeneity in the cross-sectional associations between adiponectin, metabolic syndrome components, and regional cortical thickness. Further studies are needed to explore the temporal relationship between risk factors and cortical thinning.

Periventricular White Matter Hyperintensities and Functional Decline

BACKGROUND/OBJECTIVES

We previously showed that global brain white matter hyperintensity volume (WMHV) was associated with accelerated long-term functional decline. The objective of the current study was to determine whether WMHV in particular brain regions is more predictive of functional decline.

DESIGN

Prospective population-based study.

SETTING

Northern Manhattan magnetic resonance imaging (MRI) study.

PARTICIPANTS

Individuals free of stroke at baseline (N = 1,195; mean age 71 ± 9; n = 460 (39%) male).

MEASUREMENTS

Participants had brain MRI with axial T1, T2, and fluid attenuated inversion recovery sequences. Volumetric WMHV distribution across 14 brain regions (brainstem; cerebellum; bilateral frontal, occipital, temporal, and parietal lobes; and bilateral anterior and posterior periventricular white matter (PVWM)) was determined using a combination of bimodal image intensity distribution and atlas-based methods. Participants had annual functional assessments using the Barthel Index (BI) (range 0-100) over a mean of 7.3 years and were followed for stroke, myocardial infarction (MI), and mortality. Because there were multiple collinear variables, least absolute shrinkage and selection operator (LASSO) regression-selected regional WMHV variables most associated with outcomes and adjusted generalized estimating equations models were used to estimate associations with baseline BI and change over time.

RESULTS

Using LASSO regularization, only right anterior PVWM was found to meet criteria for selection, and each standard deviation greater WMHV was associated with accelerated functional decline of 0.95 additional BI points per year (95% confidence interval (CI) = -1.20 to -0.70) in an unadjusted model, -0.92 points per year (95% CI = -1.18 to -0.67) with baseline covariate adjustment, and -0.87 points per year (95% CI = -1.12 to -0.62) after adjusting for incident stroke and MI.

CONCLUSION

In this large population-based study with long-term repeated measures of function, periventricular WMHV was particularly associated with accelerated functional decline.

A novel cognitive assessment paradigm to detect Pre-mild cognitive impairment (PreMCI) and the relationship to biological markers of Alzheimer's disease

OBJECTIVE

A number of older adults obtain normal scores on formal cognitive tests, but present clinical concerns that raise suspicion of cognitive decline. Despite not meeting full criteria for Mild Cognitive Impairment (MCI), these PreMCI states confer risk for progression to Alzheimer's disease (AD). This investigation addressed a pressing need to identify cognitive measures that are sensitive to PreMCI and are associated with brain biomarkers of neurodegeneration.

METHOD

Participants included 49 older adults with a clinical history suggestive of cognitive decline but normal scores on an array of neuropsychological measures, thus not meeting formal criteria for MCI. The performance of these PreMCI participants were compared to 117 cognitively normal (CN) elders on the LASSI-L, a cognitive stress test that uniquely assesses the failure to recover from proactive semantic interference effects (frPSI). Finally, a subset of these individuals had volumetric analyses based on MRI scans.

RESULTS

PreMCI participants evidenced greater LASSI- L deficits, particularly with regards to frPSI and delayed recall, relative to the CN group. No differences on MRI measures were observed. Controlling for false discovery rate (FDR), frPSI was uniquely related to increased dilatation of the inferior lateral ventricle and decreased MRI volumes in the hippocampus, precuneus, superior parietal region, and other AD prone areas. In contrast, other LASSI-L indices and standard memory tests were not related to volumetric findings.

CONCLUSIONS

Despite equivalent performance on traditional memory measures, the frPSI distinguished between PreMCI and CN elders and was associated with reductions in brain volume in numerous AD-relevant brain regions.

Magnetic Resonance Imaging of the Levator Veli Palatini Muscle in Speakers with Repaired Cleft Palate

Objective:

To obtain detailed anatomic and physiologic information on the levator veli palatini muscle from MRI in individuals with repaired cleft palate and to compare the results with those from normal subjects reported by Ettema et al. (2002).

Design:

Prospective study.

Setting:

University-based hospital.

Participants:

Four men (ages 22 to 43 years) with repaired cleft lip and palate.

Main Outcome Measures:

Four quantitative measurements of the levator veli palatini muscle from rest position and dynamic speech magnetic resonance images were obtained: the distance between the origins of the muscle, angle of origin of the muscle, muscle length, and muscle thickness.

Results:

The length and thickness of the levator veli palatini muscle varied among the subjects and were different from measurements obtained from normal subjects in a previous study. The distance between origin points, length, and thickness of the levator veli palatini muscle were smaller than those of the normal subjects. There were systematic changes of the levator veli palatini muscle, depending upon vowel and consonant types. Levator veli palatini muscle angle of origin and length became progressively smaller from rest, nasal consonants, low vowels, high vowels, and fricative consonants. These changes are consistent with those of the normal subjects.

Conclusions:

This study contributes to a better understanding of cleft palate anatomy in comparison with normal anatomy of the levator veli palatini muscle. The use of MRI shows promise as an important tool in the diagnosis and eventual aid to treatment decisions for individuals born with cleft palate.

Pediatric idiopathic intracranial hypertension - Is the fixed threshold value of elevated LP opening pressure set too high?

BACKGROUND

Idiopathic intracranial hypertension (IIH) in children is a rare condition of unknown etiology and various clinical presentations. The primary aim of this study was to evaluate if our pediatric IIH study group fulfilled the revised diagnostic criteria for IIH published in 2013, particularly with regard to clinical presentation and threshold value of an elevated lumbar puncture opening pressure. Additionally we investigated the potential utilization of MR-based and fundoscopic methods of estimating intracranial pressure for improved diagnosis.

PATIENTS AND METHODS

Clinical data were collected retrospectively from twelve pediatric patients diagnosed with IIH between 2008 and 2012 and revised diagnostic criteria were applied. Comparison with non-invasive methods for measuring intracranial pressure, MRI-based measurement (MR-ICP) and venous ophthalmodynamometry was performed.

RESULTS

Only four of the twelve children (33%) fulfilled the revised diagnostic criteria for a definite diagnosis of IIH. Regarding noninvasive methods, MR-ICP (n = 6) showed a significantly higher mean of intracranial pressure compared to a healthy age- and sex-matched control group (p = 0.0043). Venous ophthalmodynamometry (n = 4) showed comparable results to invasive lumbar puncture.

CONCLUSION

The revised diagnostic criteria for IIH may be too strict especially in children without papilledema. MR-ICP and venous ophthalmodynamometry are promising complementary procedures for monitoring disease progression and response to treatment.

Spaceflight-induced changes in white matter hyperintensity burden in astronauts

Objective:

To assess the effect of weightlessness and the respective roles of CSF and vascular fluid on changes in white matter hyperintensity (WMH) burden in astronauts.

Methods:

We analyzed prespaceflight and postspaceflight brain MRI scans from 17 astronauts, 10 who flew a long-duration mission on the International Space Station (ISS) and 7 who flew a short-duration mission on the Space Shuttle. Automated analysis methods were used to determine preflight to postflight changes in periventricular and deep WMH, CSF, and brain tissue volumes in fluid-attenuated inversion recovery and high-resolution 3-dimensional T1-weighted imaging. Differences between cohorts and associations between individual measures were assessed. The short-term reversibility of the identified preflight to postflight changes was tested in a subcohort of 5 long-duration astronauts who had a second postflight MRI scan 1 month after the first postflight scan.

Results:

Significant preflight to postflight changes were measured only in the long-duration cohort and included only the periventricular WMH and ventricular CSF volumes. Changes in deep WMH and brain tissue volumes were not significant in either cohort. The increase in periventricular WMH volume was significantly associated with an increase in ventricular CSF volume (ρ = 0.63, p = 0.008). A partial reversal of these increases was observed in the long-duration subcohort with a 1-month follow-up scan.

Conclusions:

Long-duration exposure to microgravity is associated with an increase in periventricular WMH in astronauts. This increase was linked to an increase in ventricular CSF volume documented in ISS astronauts. There was no associated change in or abnormal levels of WMH volumes in deep white matter as reported in U-2 high-altitude pilots.

Differential Effect of Left vs. Right White Matter Hyperintensity Burden on Functional Decline: The Northern Manhattan Study

Asymmetry of brain dysfunction may disrupt brain network efficiency. We hypothesized that greater left-right white matter hyperintensity volume (WMHV) asymmetry was associated with functional trajectories. Methods: In the Northern Manhattan Study, participants underwent brain MRI with axial T1, T2, and fluid attenuated inversion recovery sequences, with baseline interview and examination. Volumetric WMHV distribution across 14 brain regions was determined separately by combining bimodal image intensity distribution and atlas based methods. Participants had annual functional assessments with the Barthel index (BI, range 0-100) over a mean of 7.3 years. Generalized estimating equations (GEE) models estimated associations of regional WMHV and regional left-right asymmetry with baseline BI and change over time, adjusted for baseline medical risk factors, sociodemographics, and cognition, and stroke and myocardial infarction during follow-up. Results: Among 1,195 participants, greater WMHV asymmetry in the parietal lobes (-8.46 BI points per unit greater WMHV on the right compared to left, 95% CI -3.07, -13.86) and temporal lobes (-2.48 BI points, 95% CI -1.04, -3.93) was associated with lower overall function. Greater WMHV asymmetry in the parietal lobes (-1.09 additional BI points per year per unit greater WMHV on the left compared to right, 95% CI -1.89, -0.28) was independently associated with accelerated functional decline. Conclusions: In this large population-based study with long-term repeated measures of function, greater regional WMHV asymmetry was associated with lower function and functional decline. In addition to global WMHV, WHMV asymmetry may be an important predictor of long-term functional status.

MRI-based assessment of acute effect of head-down tilt position on intracranial hemodynamics and hydrodynamics

PURPOSE

To quantify the acute effect of the head-down tilt (HDT) posture on intracranial hemodynamics and hydrodynamics.

MATERIALS AND METHODS

We evaluated the intracranial physiological parameters, blood flow-related parameters, and brain morphology in the HDT (-6° and -12°) and the horizontal supine (HS) positions. Seven and 15 healthy subjects were scanned for each position using 3.0 T magnetic resonance imaging system. The peak-to-peak intracranial volume change, the peak-to-peak cerebrospinal fluid (CSF) pressure gradient (PG_p-p ), and the intracranial compliance index were calculated from the blood and CSF flow determined using a cine phase-contrast technique. The brain volumetry was conducted using SPM12. The measurements were compared using the Wilcoxon signed-rank test or a paired t-test.

RESULTS

No measurements changed in the -6° HDT. The PG_p-p and venous outflow of the internal jugular veins (IJVs) in the -12° HDT were significantly increased compared to the HS (P < 0.001 and P = 0.025, respectively). The cross-sectional areas of the IJVs were significantly larger (P < 0.001), and the maximum, minimum, and mean blood flow velocity of the IJVs were significantly decreased (P = 0.003, < 0.001, and = 0.001, respectively) in the -12° HDT. The mean blood flow velocities of the internal carotid arteries were decreased (P = 0.023). Neither position affected the brain volume.

CONCLUSION

Pressure gradient and venous outflow were increased in accordance with the elevation of the intracranial pressure as an acute effect of the HDT. However, the CSF was not constantly shifted from the spinal canal to the cranium.

LEVEL OF EVIDENCE

2 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2018;47:565-571.

Technical Note: Development of a cranial phantom for assessing perfusion, diffusion, and biomechanics

PURPOSE

A novel cranial phantom was developed to simulate the relationships among factors such as blood perfusion, water diffusion, and biomechanics in intracranial tissue.

METHODS

The cranial phantom consisted of a high-density polypropylene filter (mimicking brain parenchyma) with intra- and extrafilter spaces (mimicking cerebral artery and vein, respectively), and a capacitor space (mimicking the cerebrospinal fluid space). Pulsatile and steady flow with different flow rates were applied to the cranial phantom using a programmable pump. On 3.0-T MRI, the measurements of the internal pressure in the phantom, apparent diffusion coefficient (ADC) with monoexponential analysis in the filter, and total simulated cerebral blood flow (tSCBF) into the phantom were synchronized with the pulsatile flow. We obtained their maximum changes during the pulsation period (ΔP, ΔADC, and ΔtSCBF, respectively). Then, the compliance index (CI) was calculated by dividing the volume change (ΔV) by the ΔP in the phantom. Moreover, the same measurements were repeated after the compliance of the phantom was reduced by increasing the water volume in the capacitor space. Under steady flow conditions, we determined the regional SCBF (rSCBF) and perfusion-related and restricted diffusion coefficients (D* and D, respectively) with biexponential analysis in the filter.

RESULTS

The internal pressure, ADC, and tSCBF varied over the pulsation period depending on the input flow. Moreover, the ΔP, ΔADC, ΔtSCBF, and rSCBF increased with the input flow rate. Compared to the high compliance condition, in the low compliance condition, the ΔP and ΔADC were higher by factors of 2.5 and 1.3, respectively, and the CI was smaller by a factor of 2.7, whereas the ΔV was almost unchanged. The D* was strongly affected by the input flow.

CONCLUSION

Our original phantom models the relationships among the blood perfusion, water diffusion, and biomechanics of the intracranial tissue, potentially facilitating the validation of novel MRI techniques and optimization of imaging parameters.

Abstract WP192: Periventricular White Matter Hyperintensities Are Associated With Functional Decline: The Northern Manhattan Study

Background: We previously showed that overall brain white matter hyperintensity volume (WMHV) was associated with accelerated long-term functional decline. However, it was unclear whether WMHV in particular brain regions was more predictive of decline. We hypothesized that WMHV in particular brain regions would be more predictive of functional decline.

Methods: In the Northern Manhattan MRI study, participants had brain MRI with axial T1, T2, and fluid attenuated inversion recovery sequences, with baseline interview and examination. Volumetric WMHV distribution across 14 brain regions (brainstem, cerebellum, and bilateral frontal, occipital, temporal, and parietal lobes, and bilateral anterior and posterior periventricular white matter [PVWM]) was determined separately by combining bimodal image intensity distribution and atlas based methods. Participants had annual functional assessments with the Barthel index (BI, range 0-100) over a mean of 7.3 years and were followed for stroke and myocardial infarction (MI). Due to multiple collinear variables, lasso regression was used to select regional WMHV variables, and adjusted generalized estimating equations models estimated associations with baseline BI and change over time.

Results: Among 1195 participants, mean age was 71 (SD 9) years, 460 (39%) were male, 802 (67%) had hypertension and 224 (19%) diabetes. Using lasso regularization, only right anterior PVWM was selected, and each SD increase was associated with accelerated functional decline, of -0.95 additional BI points per year (95% CI -1.20, -0.70) in an unadjusted model, -0.92 points per year (95% CI -1.18, -0.67) with baseline covariate adjustment, and -0.87 points per year (95% CI -1.12, -0.62) after adjusting for stroke and MI. This decline was in addition to a mean decline of -1.13 (95% CI -1.29, -0.97), -1.19 (95% CI -1.36, -1.01), and -1.04 (95% CI -1.21, -0.88) BI points per year, respectively.

Conclusions: In this large population-based study with long-term repeated measures of function, periventricular WMHV was particularly associated with accelerated functional decline. Periventricular WMHV may have a greater effect on mobility due to dysfunction in descending leg motor tracts.

Abstract TMP56: Differential Effect of Left versus Right White Matter Hyperintensity Burden on Functional Decline: The Northern Manhattan Study

Background: We previously showed that overall brain white matter hyperintensity volume (WMHV) was associated with accelerated long-term functional decline. Asymmetry of brain dysfunction may disrupt brain network efficiency. We hypothesized that greater left-right WMHV asymmetry was associated with functional trajectories.

Methods: In the Northern Manhattan MRI study, participants had brain MRI with axial T1, T2, and fluid attenuated inversion recovery sequences, with baseline interview and examination. Volumetric WMHV distribution across 14 brain regions (brainstem, cerebellum, and bilateral frontal, occipital, temporal, and parietal lobes, and bilateral anterior and posterior periventricular white matter) was determined separately by combining bimodal image intensity distribution and atlas based methods.. Participants had annual functional assessments with the Barthel index (BI, range 0-100) over a mean of 7.3 years. Generalized estimating equations models estimated associations of regional WMHV and regional left-right asymmetry with baseline BI and change over time, adjusted for baseline medical risk factors, sociodemographics, and cognition, and stroke and myocardial infarction during follow-up.

Results: Among 1195 participants, mean age was 71 (SD 9) years, 39% were male, 67% had hypertension and 19% diabetes. Greater WMHV asymmetry in the frontal lobes (-3.53 BI points per unit greater WMHV on the right compared to left, 95% CI -0.18, -6.88) and whole brain (-7.23 BI points, 95% CI 0.07, -14.54) was associated with lower overall function. Greater WMHV asymmetry in the frontal lobes (-0.74 additional BI points per year per unit greater WMHV on the right compared to left, 95% CI 0.05, -1.54) and parietal lobes (1.11 additional BI points per year, 95% CI 0.30, 1.93) was independently associated with accelerated functional decline. Periventricular WMHV asymmetry was not associated with function.

Conclusions: In this large population-based study with long-term repeated measures of function, greater regional WMHV asymmetry was associated with lower function and functional decline, especially with greater WMHV on the right. In addition to global WMHV, WHMV asymmetry may be an important predictor of long-term functional decline.

Systemic Atherosclerosis Relate to Brain Arterial Diameters: The Northern Manhattan Study

BACKGROUND

Phenotypic expressions of arterial disease vary throughout the body and it is not clear to what extent systemic atherosclerosis influences brain arterial remodeling. We aim to test the hypothesis that systemic atherosclerosis is associated with brain arterial diameters.

METHODS

Stroke-free participants in the Northern Manhattan Study MRI subcohort in whom carotid ultrasound, transthoracic echocardiogram, and brain MRA (n = 482) were performed were included in this analysis. Brain arterial diameters were measured with semi-automated software as continuous and categorical variables. Ultrasound and echocardiography provided the sum of maximum carotid plaque thickness (sMCPT) and aortic plaque thickness. Associations between brain arterial diameters and aortic and carotid plaque thickness were assessed with semi-parametric generalized additive models.

RESULTS

Aortic plaque thickness was inversely and linearly associated with brain arterial diameters (B per mm = -0.073 ± 0.034, p = 0.03), while sMCPT was associated nonlinearly in a u-shaped curve with anterior brain arterial diameters (spline regression χ2 = 9.19, p = 0.02). Coexisting carotid and aortic atherosclerosis were more prevalent in participants with small luminal diameters (40%) compared with participants with average (30%) or with large (13%) luminal diameters, while carotid atherosclerosis without aortic atherosclerosis was more prevalent among participants with large luminal diameters (31%) compared with those with average (12%) or small luminal diameters (2%, p < 0.001 for both trends).

CONCLUSIONS

We confirmed the hypothesis that systemic arterial disease is associated with brain arterial diameters. Gaining knowledge about the origin of these phenotypic expressions of atherosclerosis in the human body may lead to a better understanding of the cerebrovascular consequences of the systemic arterial disease.

Magnetic resonance imaging-based measures predictive of short-term surgical outcome in patients with Chiari malformation Type I: a pilot study

OBJECTIVE This study identifies quantitative imaging-based measures in patients with Chiari malformation Type I (CM-I) that are associated with positive outcomes after suboccipital decompression with duraplasty. METHODS Fifteen patients in whom CM-I was newly diagnosed underwent MRI preoperatively and 3 months postoperatively. More than 20 previously described morphological and physiological parameters were derived to assess quantitatively the impact of surgery. Postsurgical clinical outcomes were assessed in 2 ways, based on resolution of the patient's chief complaint and using a modified Chicago Chiari Outcome Scale (CCOS). Statistical analyses were performed to identify measures that were different between the unfavorable- and favorable-outcome cohorts. Multivariate analysis was used to identify the strongest predictors of outcome. RESULTS The strongest physiological parameter predictive of outcome was the preoperative maximal cord displacement in the upper cervical region during the cardiac cycle, which was significantly larger in the favorable-outcome subcohorts for both outcome types (p < 0.05). Several hydrodynamic measures revealed significantly larger preoperative-to-postoperative changes in the favorable-outcome subcohort. Predictor sets for the chief-complaint classification included the cord displacement, percent venous drainage through the jugular veins, and normalized cerebral blood flow with 93.3% accuracy. Maximal cord displacement combined with intracranial volume change predicted outcome based on the modified CCOS classification with similar accuracy. CONCLUSIONS Tested physiological measures were stronger predictors of outcome than the morphological measures in patients with CM-I. Maximal cord displacement and intracranial volume change during the cardiac cycle together with a measure that reflects the cerebral venous drainage pathway emerged as likely predictors of decompression outcome in patients with CM-I.

Automated Quantitation of Spinal CSF Volume and Measurement of Craniospinal CSF Redistribution following Lumbar Withdrawal in Idiopathic Intracranial Hypertension

BACKGROUND AND PURPOSE

Automated methods for quantitation of tissue and CSF volumes by MR imaging are available for the cranial but not the spinal compartment. We developed an iterative method for delineation of the spinal CSF spaces for automated measurements of CSF and cord volumes and applied it to study craniospinal CSF redistribution following lumbar withdrawal in patients with idiopathic intracranial hypertension.

MATERIALS AND METHODS

MR imaging data were obtained from 2 healthy subjects and 8 patients with idiopathic intracranial hypertension who were scanned before, immediately after, and 2 weeks after diagnostic lumbar puncture. Imaging included T1-weighted and T2-weighted sequences of the brain and T2-weighted scans of the spine. Repeat scans in 4 subjects were used to assess measurement reproducibility. Whole CNS CSF volumes measured prior to and following lumbar puncture were compared with the withdrawn amounts of CSF.

RESULTS

CSF and cord volume measurements were highly reproducible with mean variabilities of -0.7% ± 1.4% and -0.7% ± 1.0%, respectively. Mean spinal CSF volume was 77.5 ± 8.4 mL. The imaging-based pre- to post-CSF volume differences were consistently smaller and strongly correlated with the amounts removed (R = 0.86, P = .006), primarily from the lumbosacral region. These differences are explained by net CSF formation of 0.41 ± 0.18 mL/min between withdrawal and imaging.

CONCLUSIONS

Automated measurements of the craniospinal CSF redistribution following lumbar withdrawal in idiopathic intracranial hypertension reveal that the drop in intracranial pressure following lumbar puncture is primarily related to the increase in spinal compliance and not cranial compliance due to the reduced spinal CSF volume and the nearly unchanged cranial CSF volume.

Imaging-Based Features of Headaches in Chiari Malformation Type I

BACKGROUND

Suboccipital cough-induced headaches are considered a hallmark symptom of Chiari malformation type I (CMI). However, non--Valsalva-related suboccipital headaches and headaches in other locations are also common in CMI. The diagnostic significance and the underlying factors associated with these different headaches types are not well understood.

OBJECTIVE

To compare cranial morphology and hydrodynamics in 3 types of headaches in CMI to better understand the pathophysiological basis for the different headache characteristics.

METHODS

Twenty-two cranial physiological and morphological measures were obtained with specialized magnetic resonance imaging scans from 63 symptomatic pretreated CMI patients, 40 with suboccipital headaches induced by Valsalva maneuvers (34 women; age, 36 ± 10 years), 15 with non--Valsalva-related suboccipital headaches (10 women; age, 33 ± 9 years), 8 with nonsuboccipital non--Valsalva-induced headaches (8 women; age, 39 ± 13 years), and 37 control subjects (24 women; age, 36 ± 12 years). Group differences were identified with the use of the 2-tailed Student t test.

RESULTS

Posterior cranial fossa markers of CMI were similar among the 3 headache subtypes. However, the Valsalva-related suboccipital headaches cohort demonstrated a significantly lower intracranial compliance index than the non--Valsalva-related suboccipital headaches cohort (7.5 ± 3.4 vs 10.9 ± 4.9), lower intracranial volume change during the cardiac cycle (0.48 ± 0.19 vs 0.61 ± 0.16 mL), and higher magnetic resonance imaging--derived intracranial pressure (11.1 ± 4.3 vs 7.7 ± 2.8 mm Hg; P = .02). The Valsalva-related suboccipital headaches cohort had smaller intracranial and lateral ventricular volumes compared with the healthy cohort. The non--Valsalva-related suboccipital headaches cohort had reduced venous drainage through the jugular veins.

CONCLUSION

Valsalva-induced worsening of occipital headaches appears to be related to a small intracranial volume rather than the smaller posterior cranial fossa. This explains the reduced intracranial compliance and corresponding higher pressure measured in CMI patients with headaches affected by Valsalva maneuvers.