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.