Longitudinal Metabolite Changes in Progressive Multiple Sclerosis: A Study of 3 Potential Neuroprotective Treatments

BACKGROUND

1H-magnetic resonance spectroscopy (1H-MRS) may provide a direct index for the testing of medicines for neuroprotection and drug mechanisms in multiple sclerosis (MS) through measures of total N-acetyl-aspartate (tNAA), total creatine (tCr), myo-inositol (mIns), total-choline (tCho), and glutamate + glutamine (Glx). Neurometabolites may be associated with clinical disability with evidence that baseline neuroaxonal integrity is associated with upper limb function and processing speed in secondary progressive MS (SPMS).

PURPOSE

To assess the effect on neurometabolites from three candidate drugs after 96-weeks as seen by 1H-MRS and their association with clinical disability in SPMS.

STUDY-TYPE

Longitudinal.

POPULATION

108 participants with SPMS randomized to receive neuroprotective drugs amiloride [mean age 55.4 (SD 7.4), 61% female], fluoxetine [55.6 (6.6), 71%], riluzole [54.6 (6.3), 68%], or placebo [54.8 (7.9), 67%].

FIELD STRENGTH/SEQUENCE

3-Tesla. Chemical-shift-imaging 2D-point-resolved-spectroscopy (PRESS), 3DT1.

ASSESSMENT

Brain metabolites in normal appearing white matter (NAWM) and gray matter (GM), brain volume, lesion load, nine-hole peg test (9HPT), and paced auditory serial addition test were measured at baseline and at 96-weeks.

STATISTICAL TESTS

Paired t-test was used to analyze metabolite changes in the placebo arm over 96-weeks. Metabolite differences between treatment arms and placebo; and associations between baseline metabolites and upper limb function/information processing speed at 96-weeks assessed using multiple linear regression models. P-value<0.05 was considered statistically significant.

RESULTS

In the placebo arm, tCho increased in GM (mean difference = -0.32 IU) but decreased in NAWM (mean difference = 0.13 IU). Compared to placebo, in the fluoxetine arm, mIns/tCr was lower (β = -0.21); in the riluzole arm, GM Glx (β = -0.25) and Glx/tCr (β = -0.29) were reduced. Baseline tNAA(β = 0.22) and tNAA/tCr (β = 0.23) in NAWM were associated with 9HPT scores at 96-weeks.

DATA CONCLUSION

1H-MRS demonstrated altered membrane turnover over 96-weeks in the placebo group. It also distinguished changes in neuro-metabolites related to gliosis and glutaminergic transmission, due to fluoxetine and riluzole, respectively. Data show tNAA is a potential marker for upper limb function.

LEVEL OF EVIDENCE

1 TECHNICAL EFFICACY: Stage 4.

Deep learning segmentation of endothelial cell images using an active learning paradigm with guided label corrections

Purpose

To create Guided Correction Software for informed manual editing of automatically generated corneal endothelial cell (EC) segmentations and apply it to an active learning paradigm to analyze a diverse set of post-keratoplasty EC images.

Approach

An original U-Net model trained on 130 manually labeled post-Descemet stripping automated endothelial keratoplasty (EK) images was applied to 841 post-Descemet membrane EK images generating "uncorrected" cell border segmentations. Segmentations were then manually edited using the Guided Correction Software to create corrected labels. This dataset was split into 741 training and 100 testing EC images. U-Net and DeepLabV3+ were trained on the EC images and the corresponding uncorrected and corrected labels. Model performance was evaluated in a cell-by-cell analysis. Evaluation metrics included the number of over-segmentations, under-segmentations, correctly identified new cells, and endothelial cell density (ECD).

Results

Utilizing corrected segmentations for training U-Net and DeepLabV3+ improved their performance. The average number of over- and under-segmentations per image was reduced from 23 to 11 with the corrected training set. Predicted ECD values generated by networks trained on the corrected labels were not significantly different than the ground truth counterparts (p = 0.02 , paired t -test). These models also correctly segmented a larger percentage of newly identified cells. The proposed Guided Correction Software and semi-automated approach reduced the time to accurately segment EC images from 15 to 30 to 5 min, an ∼ 80 % decrease compared to manual editing.

Conclusions

Guided Correction Software can efficiently label new training data for improved deep learning performance and generalization between EC datasets.

Cerebrovascular Reactivity in Patients With Small Vessel Disease: A Cross-Sectional Study

BACKGROUND

Cerebrovascular reactivity (CVR) is inversely related to white matter hyperintensity severity, a marker of cerebral small vessel disease (SVD). Less is known about the relationship between CVR and other SVD imaging features or cognition. We aimed to investigate these cross-sectional relationships.

METHODS

Between 2018 and 2021 in Edinburgh, we recruited patients presenting with lacunar or cortical ischemic stroke, whom we characterized for SVD features. We measured CVR in subcortical gray matter, normal-appearing white matter, and white matter hyperintensity using 3T magnetic resonance imaging. We assessed cognition using Montreal Cognitive Assessment. Statistical analyses included linear regression models with CVR as outcome, adjusted for age, sex, and vascular risk factors. We reported regression coefficients with 95% CIs.

RESULTS

Of 208 patients, 182 had processable CVR data sets (median age, 68.2 years; 68% men). Although the strength of association depended on tissue type, lower CVR in normal-appearing tissues and white matter hyperintensity was associated with larger white matter hyperintensity volume (BNAWM=-0.0073 [95% CI, -0.0133 to -0.0014] %/mm Hg per 10-fold increase in percentage intracranial volume), more lacunes (BNAWM=-0.00129 [95% CI, -0.00215 to -0.00043] %/mm Hg per lacune), more microbleeds (BNAWM=-0.00083 [95% CI, -0.00130 to -0.00036] %/mm Hg per microbleed), higher deep atrophy score (BNAWM=-0.00218 [95% CI, -0.00417 to -0.00020] %/mm Hg per score point increase), higher perivascular space score (BNAWM=-0.0034 [95% CI, -0.0066 to -0.0002] %/mm Hg per score point increase in basal ganglia), and higher SVD score (BNAWM=-0.0048 [95% CI, -0.0075 to -0.0021] %/mm Hg per score point increase). Lower CVR in normal-appearing tissues was related to lower Montreal Cognitive Assessment without reaching convention statistical significance (BNAWM=0.00065 [95% CI, -0.00007 to 0.00137] %/mm Hg per score point increase).

CONCLUSIONS

Lower CVR in patients with SVD was related to more severe SVD burden and worse cognition in this cross-sectional analysis. Longitudinal analysis will help determine whether lower CVR predicts worsening SVD severity or vice versa.

REGISTRATION

URL: https://www.isrctn.com; Unique identifier: ISRCTN12113543.

Virtual Peer Groups Reduce HbA1c and Increase Continuous Glucose Monitor Use in Adolescents and Young Adults with Type 1 Diabetes

Background: Adolescents and young adults (AYA) from diverse and marginalized backgrounds with type 1 diabetes (T1D) generally have higher hemoglobin A1c (HbA1c) levels and less frequent continuous glucose monitor (CGM) use than AYA from more privileged backgrounds. Further, scant data address the impact of virtual peer groups (VPG) on health-related outcomes for ethnically and racially diverse AYA with T1D. Methods: CoYoT1 to California was a 15-month randomized controlled trial for AYA aged 16-25 years. In this study, AYA were randomized to receive standard care (n = 28), or CoYoT1 care (n = 40), which consisted of person-centered provider visits and bimonthly VPG. VPG were AYA-driven discussions. AYA completed the Diabetes Distress Scale (DDS), Center for Epidemiologic Studies Depression (CES-D), and Diabetes Empowerment Scale-Short Form (DES-SF) scales at baseline and all study visits. Results: Participants were 50% Latinx and 75% publicly insured. Among CoYoT1 care participants, 19 attended at least 1 VPG session (VPG attendees) and 21 did not attend any VPG sessions. VPG attendees participated in 4.1 VPG sessions on average. VPG attendees had a relative reduction in HbA1C (treatment effect -1.08%, effect sizes values [ES] = -0.49, P = 0.04) and increase in CGM use (treatment effect +47%, ES = 1.00, P = 0.02) compared to standard care. VPG participation was not associated with statistically significant changes in DDS, CES-D, and DES-SF scores. Conclusions: In a 15-month randomized controlled trial, AYA with T1D who participated in VPG reported significant improvements in HbA1c and CGM use. Peer interactions may support unmet needs of AYA with T1D from diverse and marginalized backgrounds. ClinicalTrials.gov Identifier: NCT03793673.

Repeatability and comparison of 2D and 4D flow MRI measurement of intracranial blood flow and pulsatility in healthy individuals and patients with cerebral small vessel disease

Introduction

While 2D phase-contrast MRI is often used to examine intracranial vessels in neurovascular disease contexts, the ability of 4D flow to assess many vessels at once makes it an attractive alternative. We aimed to assess the repeatability, reliability, and conformity of 2D and 4D flow across intracranial vessels.

Methods

Using correlation analyses and paired t-tests, test-retest repeatability, intra-rater reliability, and inter-method conformity for measurements of pulsatility index (PI) and mean flow were assessed in the arteries and veins of 11 healthy volunteers. Inter-method conformity was also assessed in 10 patients with small vessel disease.

Results

Repeatability for PI measurements was mostly classed as good using both 2D (median ICC = 0.765) and 4D (0.772) methods, and for mean flow was mostly moderate across both (2D: 0.711, 4D: 0.571). 4D reliability was good for PI (0.877-0.906) and moderate for mean flow (0.459-0.723). Arterial PI measurements were generally higher using the 2D method, while mean flow was mostly higher using 4D flow.

Discussion

These results imply that PI measurement using 4D flow is repeatable and reliable across intracranial arteries and veins, but care should be paid to absolute flow measurements as they are susceptible to variation depending on slice placement, resolution, and lumen segmentation practices.

Sexual precocity in the setting of parental use of a compounded testosterone cream: case report and review of the literature

OBJECTIVES

Person-to-person transmission of transdermal testosterone - termed secondary exposure - is a rare but important cause of precocious puberty.

CASE PRESENTATION

A 3.5-year-old male was evaluated for precocious puberty based on a 6 month history of penile growth, development of secondary sexual characteristics, and growth spurt. Total testosterone level was significantly elevated at 1,460 ng/dL with normal prepubertal gonadotropin levels. Further history revealed that the father had been using transdermal testosterone for about 1 year. Within 2 months of discontinuation, total testosterone level was 20 ng/dL.

CONCLUSIONS

Given the recent increase in transdermal testosterone prescriptions, clinicians must consider exogenous hormonal exposure as an etiology for precocious puberty. Prescribers should counsel their patients about the significant risk of secondary exposure.

A National Survey of United States-based Endocrinologists who Prescribe Gender-Affirming Hormone Therapy

OBJECTIVE

The World Professional Association for Transgender Health (WPATH) Standards of Care (SOC) Version 7 recommended that before initiating gender-affirming hormone therapy (GAHT), patients should seek a psychosocial evaluation from a mental health professional documenting a diagnosis of persistent gender dysphoria. The Endocrine Society published guidelines in 2017 recommending against an obligatory psychosocial evaluation, which was affirmed in the recently published WPATH SOC Version 8 from 2022. Little is known about how endocrinologists ensure appropriate psychosocial assessment for their patients. This study assessed the protocols and characteristics of United States-based adult endocrinology clinics that prescribe GAHT.

METHODS

An anonymous electronic survey sent to members of a professional organization and the "Endocrinologists" Facebook group was responded to by 91 practicing board-certified adult endocrinologists who prescribe GAHT.

RESULTS

Thirty-one states were represented by the respondents. Overall, 83.1% of GAHT-prescribing endocrinologists reported accepting Medicaid. They reported working in university practices (28.4%), community practices (22.7%), private practices (27.3%), and other practice settings (21.6%). Overall, 42.9% of the respondents reported that their practice required documentation of a psychosocial evaluation from a mental health professional before initiating GAHT.

CONCLUSION

Endocrinologists who prescribe GAHT are divided about requiring a baseline psychosocial evaluation before prescribing GAHT. Further work is needed to understand the impact of psychosocial assessment on patient care and facilitate the uptake of new guidelines into clinical practice.

Cerebrovascular reactivity measurements using 3T BOLD MRI and a fixed inhaled CO2 gas challenge: Repeatability and impact of processing strategy

Introduction: Cerebrovascular reactivity (CVR) measurements using blood oxygen level dependent (BOLD) magnetic resonance imaging (MRI) are commonly used to assess the health of cerebral blood vessels, including in patients with cerebrovascular diseases; however, evidence and consensus regarding reliability and optimal processing are lacking. We aimed to assess the repeatability, accuracy and precision of voxel- and region-based CVR measurements at 3 T using a fixed inhaled (FI) CO₂ stimulus in a healthy cohort. Methods: We simulated the effect of noise, delay constraints and voxel- versus region-based analysis on CVR parameters. Results were verified in 15 healthy volunteers (28.1±5.5 years, female: 53%) with a test-retest MRI experiment consisting of two CVR scans. CVR magnitude and delay in grey matter (GM) and white matter were computed for both analyses assuming a linear relationship between the BOLD signal and time-shifted end-tidal CO₂ (EtCO₂) profile. Results: Test-retest repeatability was high [mean (95% CI) inter-scan difference: -0.01 (-0.03, -0.00) %/mmHg for GM CVR magnitude; -0.3 (-1.2,0.6) s for GM CVR delay], but we detected a small systematic reduction in CVR magnitude at scan 2 versus scan 1, accompanied by a greater EtCO2 change [±1.0 (0.4,1.5) mmHg] and lower heart rate [-5.5 (-8.6,-2.4] bpm]. CVR magnitude estimates were higher for voxel- versus region-based analysis [difference in GM: ±0.02 (0.01,0.03) %/mmHg]. Findings were supported by simulation results, predicting a positive bias for voxel-based CVR estimates dependent on temporal contrast-to-noise ratio and delay fitting constraints and an underestimation for region-based CVR estimates. Discussion: BOLD CVR measurements using FI stimulus have good within-day repeatability in healthy volunteers. However, measurements may be influenced by physiological effects and the analysis protocol. Voxel-based analyses should be undertaken with care due to potential for systematic bias; region-based analyses are more reliable in such cases.

Corrigendum: Cerebrovascular reactivity measurement using magnetic resonance imaging: A systematic review

[This corrects the article DOI: 10.3389/fphys.2021.643468.].

Non-invasive in vivo assessment of 11β-hydroxysteroid dehydrogenase type 1 activity by 19F-Magnetic Resonance Spectroscopy

11β-Hydroxysteroid dehydrogenase type 1 (11β-HSD1) amplifies tissue glucocorticoid levels and is a pharmaceutical target in diabetes and cognitive decline. Clinical translation of inhibitors is hampered by lack of in vivo pharmacodynamic biomarkers. Our goal was to monitor substrates and products of 11β-HSD1 non-invasively in liver via ¹⁹Fluorine magnetic resonance spectroscopy (¹⁹F-MRS). Interconversion of mono/poly-fluorinated substrate/product pairs was studied in Wistar rats (male, n = 6) and healthy men (n = 3) using 7T and 3T MRI scanners, respectively. Here we show that the in vitro limit of detection, as absolute fluorine content, was 0.625 μmole in blood. Mono-fluorinated steroids, dexamethasone and 11-dehydrodexamethasone, were detected in phantoms but not in vivo in human liver following oral dosing. A non-steroidal polyfluorinated tracer, 2-(phenylsulfonyl)-1-(4-(trifluoromethyl)phenyl)ethanone and its metabolic product were detected in vivo in rat liver after oral administration of the keto-substrate, reading out reductase activity. Administration of a selective 11β-HSD1 inhibitor in vivo in rats altered total liver ¹⁹F-MRS signal. We conclude that there is insufficient sensitivity to measure mono-fluorinated tracers in vivo in man with current dosage regimens and clinical scanners. However, since reductase activity was observed in rats using poly-fluorinated tracers, this concept could be pursued for translation to man with further development.

A daily temperature rhythm in the human brain predicts survival after brain injury

Patients undergo interventions to achieve a 'normal' brain temperature; a parameter that remains undefined for humans. The profound sensitivity of neuronal function to temperature implies the brain should be isothermal, but observations from patients and non-human primates suggest significant spatiotemporal variation. We aimed to determine the clinical relevance of brain temperature in patients by establishing how much it varies in healthy adults. We retrospectively screened data for all patients recruited to the Collaborative European NeuroTrauma Effectiveness Research in Traumatic Brain Injury (CENTER-TBI) High Resolution Intensive Care Unit Sub-Study. Only patients with direct brain temperature measurements and without targeted temperature management were included. To interpret patient analyses, we prospectively recruited 40 healthy adults (20 males, 20 females, 20-40 years) for brain thermometry using magnetic resonance spectroscopy. Participants were scanned in the morning, afternoon, and late evening of a single day. In patients (n = 114), brain temperature ranged from 32.6 to 42.3°C and mean brain temperature (38.5 ± 0.8°C) exceeded body temperature (37.5 ± 0.5°C, P < 0.0001). Of 100 patients eligible for brain temperature rhythm analysis, 25 displayed a daily rhythm, and the brain temperature range decreased in older patients (P = 0.018). In healthy participants, brain temperature ranged from 36.1 to 40.9°C; mean brain temperature (38.5 ± 0.4°C) exceeded oral temperature (36.0 ± 0.5°C) and was 0.36°C higher in luteal females relative to follicular females and males (P = 0.0006 and P < 0.0001, respectively). Temperature increased with age, most notably in deep brain regions (0.6°C over 20 years, P = 0.0002), and varied spatially by 2.41 ± 0.46°C with highest temperatures in the thalamus. Brain temperature varied by time of day, especially in deep regions (0.86°C, P = 0.0001), and was lowest at night. From the healthy data we built HEATWAVE-a 4D map of human brain temperature. Testing the clinical relevance of HEATWAVE in patients, we found that lack of a daily brain temperature rhythm increased the odds of death in intensive care 21-fold (P = 0.016), whilst absolute temperature maxima or minima did not predict outcome. A warmer mean brain temperature was associated with survival (P = 0.035), however, and ageing by 10 years increased the odds of death 11-fold (P = 0.0002). Human brain temperature is higher and varies more than previously assumed-by age, sex, menstrual cycle, brain region, and time of day. This has major implications for temperature monitoring and management, with daily brain temperature rhythmicity emerging as one of the strongest single predictors of survival after brain injury. We conclude that daily rhythmic brain temperature variation-not absolute brain temperature-is one way in which human brain physiology may be distinguished from pathophysiology.

Impaired Glymphatic Function and Pulsation Alterations in a Mouse Model of Vascular Cognitive Impairment

Large vessel disease and carotid stenosis are key mechanisms contributing to vascular cognitive impairment (VCI) and dementia. Our previous work, and that of others, using rodent models, demonstrated that bilateral common carotid stenosis (BCAS) leads to cognitive impairment via gradual deterioration of the neuro-glial-vascular unit and accumulation of amyloid-β (Aβ) protein. Since brain-wide drainage pathways (glymphatic) for waste clearance, including Aβ removal, have been implicated in the pathophysiology of VCI via glial mechanisms, we hypothesized that glymphatic function would be impaired in a BCAS model and exacerbated in the presence of Aβ. Male wild-type and Tg-SwDI (model of microvascular amyloid) mice were subjected to BCAS or sham surgery which led to a reduction in cerebral perfusion and impaired spatial learning acquisition and cognitive flexibility. After 3 months survival, glymphatic function was evaluated by cerebrospinal fluid (CSF) fluorescent tracer influx. We demonstrated that BCAS caused a marked regional reduction of CSF tracer influx in the dorsolateral cortex and CA1-DG molecular layer. In parallel to these changes increased reactive astrogliosis was observed post-BCAS. To further investigate the mechanisms that may lead to these changes, we measured the pulsation of cortical vessels. BCAS impaired vascular pulsation in pial arteries in WT and Tg-SwDI mice. Our findings show that BCAS influences VCI and that this is paralleled by impaired glymphatic drainage and reduced vascular pulsation. We propose that these additional targets need to be considered when treating VCI.

Evidence That the Etiology of Congenital Hypopituitarism Has a Major Genetic Component but Is Infrequently Monogenic

Purpose

Congenital hypopituitarism usually occurs sporadically. In most patients, the etiology remains unknown.

Methods

We studied 13 children with sporadic congenital hypopituitarism. Children with non-endocrine, non-familial idiopathic short stature (NFSS) (n = 19) served as a control group. Exome sequencing was performed in probands and both unaffected parents. A burden testing approach was used to compare the number of candidate variants in the two groups.

Results

First, we assessed the frequency of rare, predicted-pathogenic variants in 42 genes previously reported to be associated with pituitary gland development. The average number of variants per individual was greater in probands with congenital hypopituitarism than those with NFSS (1.1 vs. 0.21, mean variants/proband, P = 0.03). The number of probands with at least 1 variant in a pituitary-associated gene was greater in congenital hypopituitarism than in NFSS (62% vs. 21%, P = 0.03). Second, we assessed the frequency of rare, predicted-pathogenic variants in the exome (to capture undiscovered causes) that were inherited in a fashion that could explain the sporadic occurrence of the proband's condition with a monogenic etiology (de novo mutation, autosomal recessive, or X-linked recessive) with complete penetrance. There were fewer monogenic candidates in the probands with congenital hypopituitarism than those with NFSS (1.3 vs. 2.5 candidate variants/proband, P = 0.024). We did not find any candidate variants (0 of 13 probands) in genes previously reported to explain the phenotype in congenital hypopituitarism, unlike NFSS (8 of 19 probands, P = 0.01).

Conclusion

Our findings provide evidence that the etiology of sporadic congenital hypopituitarism has a major genetic component but may be infrequently monogenic with full penetrance, suggesting a more complex etiology.

Sources of systematic error in DCE-MRI estimation of low-level blood-brain barrier leakage

PURPOSE

Dynamic contrast-enhanced (DCE) -MRI with Patlak model analysis is increasingly used to quantify low-level blood-brain barrier (BBB) leakage in studies of pathophysiology. We aimed to investigate systematic errors due to physiological, experimental, and modeling factors influencing quantification of the permeability-surface area product PS and blood plasma volume v_p , and to propose modifications to reduce the errors so that subtle differences in BBB permeability can be accurately measured.

METHODS

Simulations were performed to predict the effects of potential sources of systematic error on conventional PS and v_p quantification: restricted BBB water exchange, reduced cerebral blood flow, arterial input function (AIF) delay and B 1 + error. The impact of targeted modifications to the acquisition and processing were evaluated, including: assumption of fast versus no BBB water exchange, bolus versus slow injection of contrast agent, exclusion of early data from model fitting and B 1 + correction. The optimal protocol was applied in a cohort of recent mild ischaemic stroke patients.

RESULTS

Simulation results demonstrated substantial systematic errors due to the factors investigated (absolute PS error ≤ 4.48 × 10^-4 min^-1 ). However, these were reduced (≤0.56 × 10^-4 min^-1 ) by applying modifications to the acquisition and processing pipeline. Processing modifications also had substantial effects on in-vivo normal-appearing white matter PS estimation (absolute change ≤ 0.45 × 10^-4 min^-1 ).

CONCLUSION

Measuring subtle BBB leakage with DCE-MRI presents unique challenges and is affected by several confounds that should be considered when acquiring or interpreting such data. The evaluated modifications should improve accuracy in studies of neurodegenerative diseases involving subtle BBB breakdown.

Cerebrovascular Reactivity Measurement Using Magnetic Resonance Imaging: A Systematic Review

Cerebrovascular reactivity (CVR) magnetic resonance imaging (MRI) probes cerebral haemodynamic changes in response to a vasodilatory stimulus. CVR closely relates to the health of the vasculature and is therefore a key parameter for studying cerebrovascular diseases such as stroke, small vessel disease and dementias. MRI allows in vivo measurement of CVR but several different methods have been presented in the literature, differing in pulse sequence, hardware requirements, stimulus and image processing technique. We systematically reviewed publications measuring CVR using MRI up to June 2020, identifying 235 relevant papers. We summarised the acquisition methods, experimental parameters, hardware and CVR quantification approaches used, clinical populations investigated, and corresponding summary CVR measures. CVR was investigated in many pathologies such as steno-occlusive diseases, dementia and small vessel disease and is generally lower in patients than in healthy controls. Blood oxygen level dependent (BOLD) acquisitions with fixed inspired CO₂ gas or end-tidal CO₂ forcing stimulus are the most commonly used methods. General linear modelling of the MRI signal with end-tidal CO₂ as the regressor is the most frequently used method to compute CVR. Our survey of CVR measurement approaches and applications will help researchers to identify good practice and provide objective information to inform the development of future consensus recommendations.

4D flow MRI for non-invasive measurement of blood flow in the brain: A systematic review

The brain's vasculature is essential for brain health and its dysfunction contributes to the onset and development of many dementias and neurological disorders. While numerous in vivo imaging techniques exist to investigate cerebral haemodynamics in humans, phase-contrast magnetic resonance imaging (MRI) has emerged as a reliable, non-invasive method of quantifying blood flow within intracranial vessels. In recent years, an advanced form of this method, known as 4D flow, has been developed and utilised in patient studies, where its ability to capture complex blood flow dynamics within any major vessel across the acquired volume has proved effective in collecting large amounts of information in a single scan. While extremely promising as a method of examining the vascular system's role in brain-related diseases, the collection of 4D data can be time-consuming, meaning data quality has to be traded off against the acquisition time. Here, we review the available literature to examine 4D flow's capabilities in assessing physiological and pathological features of the cerebrovascular system. Emerging techniques such as dynamic velocity-encoding and advanced undersampling methods, combined with increasingly high-field MRI scanners, are likely to bring 4D flow to the forefront of cerebrovascular imaging studies in the years to come.

NAA is a Marker of Disability in Secondary-Progressive MS: A Proton MR Spectroscopic Imaging Study

BACKGROUND AND PURPOSE

The secondary progressive phase of multiple sclerosis is characterised by disability progression due to processes that lead to neurodegeneration. Surrogate markers such as those derived from MRI are beneficial in understanding the pathophysiology that drives disease progression and its relationship to clinical disability. We undertook a 1H-MRS imaging study in a large secondary progressive MS (SPMS) cohort, to examine whether metabolic markers of brain injury are associated with measures of disability, both physical and cognitive.

MATERIALS AND METHODS

A cross-sectional analysis of individuals with secondary-progressive MS was performed in 119 participants. They underwent ¹H-MR spectroscopy to obtain estimated concentrations and ratios to total Cr for total NAA, mIns, Glx, and total Cho in normal-appearing WM and GM. Clinical outcome measures chosen were the following: Paced Auditory Serial Addition Test, Symbol Digit Modalities Test, Nine-Hole Peg Test, Timed 25-foot Walk Test, and the Expanded Disability Status Scale. The relationship between these neurometabolites and clinical disability measures was initially examined using Spearman rank correlations. Significant associations were then further analyzed in multiple regression models adjusting for age, sex, disease duration, T2 lesion load, normalized brain volume, and occurrence of relapses in 2 years preceding study entry.

RESULTS

Significant associations, which were then confirmed by multiple linear regression, were found in normal-appearing WM for total NAA (tNAA)/total Cr (tCr) and the Nine-Hole Peg Test (ρ = 0.23; 95% CI, 0.06-0.40); tNAA and tNAA/tCr and the Paced Auditory Serial Addition Test (ρ = 0.21; 95% CI, 0.03-0.38) (ρ = 0.19; 95% CI, 0.01-0.36); mIns/tCr and the Paced Auditory Serial Addition Test, (ρ = -0.23; 95% CI, -0.39 to -0.05); and in GM for tCho and the Paced Auditory Serial Addition Test (ρ = -0.24; 95% CI, -0.40 to -0.06). No other GM or normal-appearing WM relationships were found with any metabolite, with associations found during initial correlation testing losing significance after multiple linear regression analysis.

CONCLUSIONS

This study suggests that metabolic markers of neuroaxonal integrity and astrogliosis in normal-appearing WM and membrane turnover in GM may act as markers of disability in secondary-progressive MS.

Severe hyperthyroidism without symptoms due to nonthyroidal illness in a child with acute hepatitis: case report and literature review

While liver enzyme changes are frequently reported in hyperthyroidism, liver dysfunction itself can lead to alterations in thyroid hormone metabolism. However, the exact relationship between hyperthyroidism and liver dysfunction is unclear. We report an 11-year-old boy presenting with acute hepatitis of unknown etiology, who was incidentally found to have asymptomatic biochemical hyperthyroidism. Despite significant total and free T4 elevation, clinical evidence of thyrotoxicosis was absent. Thyroid I-123 uptake was also reduced. Additional testing revealed slight T3 elevation and significant rT3 elevation. Graves' and Hashimoto's thyroiditis testing was negative. We hypothesize that the biochemical hyperthyroidism was due to transient thyroiditis. Although an etiology for the boy's hepatitis was never determined, and an undiagnosed infectious etiology causing subacute thyroiditis was considered, subsequent testing showing positive thyroid peroxidase antibodies, suggesting autoimmune Hashimoto's thyroiditis as the likely cause of the hyperthyroidism. We believe, furthermore, that the absence of symptoms was the result of concurrent nonthyroidal illness resulting in the biochemical findings of slight T3 elevation and significant rT3 increase despite significant T4 elevation.

A Review of Translational Magnetic Resonance Imaging in Human and Rodent Experimental Models of Small Vessel Disease

Cerebral small vessel disease (SVD) is a major health burden, yet the pathophysiology remains poorly understood with no effective treatment. Since much of SVD develops silently and insidiously, non-invasive neuroimaging such as MRI is fundamental to detecting and understanding SVD in humans. Several relevant SVD rodent models are established for which MRI can monitor in vivo changes over time prior to histological examination. Here, we critically review the MRI methods pertaining to salient rodent models and evaluate synergies with human SVD MRI methods. We found few relevant publications, but argue there is considerable scope for greater use of MRI in rodent models, and opportunities for harmonisation of the rodent-human methods to increase the translational potential of models to understand SVD in humans. We summarise current MR techniques used in SVD research, provide recommendations and examples and highlight practicalities for use of MRI SVD imaging protocols in pre-selected, relevant rodent models.

Diagnostic quality assessment of IR-prepared 3D magnetic resonance neuroimaging accelerated using compressed sensing and k-space sampling order optimization

PURPOSE

To evaluate the clinical diagnostic efficacy of accelerated 3D magnetic resonance (MR) neuroimaging by radiological assessment for image quality and artefacts.

STUDY TYPE

Prospective healthy volunteer study.

SUBJECTS

Eight healthy subjects.

FIELD STRENGTH/SEQUENCE

Inversion Recovery (IR) prepared 3D Gradient Echo (GRE) sequence on a 1.5 T GE Signa HDx scanner.

ASSESSMENT

Independent radiological diagnostic quality assessments of accelerated 3D MR brain datasets were carried out by four experienced neuro-radiologists who were blinded to the acceleration factor and to the subject. The radiological grading was based on a previously reported radiological scoring key that was used for image quality assessment of human brains.

STATISTICAL TESTS

Bland-Altman analysis.

RESULTS

Optimization of the k-space sampling order was important for preserving contrast in accelerated scans. Despite having lower scores than fully sampled datasets, the majority of the compressed sensing (CS) accelerated brain datasets with k-space sampling order optimization (19/24 datasets by Radiologist 1, 24/24 datasets by Radiologist 2 and 16/24 datasets by Radiologist 3) were graded to be fully diagnostic indicating that there was adequate confidence for performing gross structural assessment of the brain.

CONCLUSION

Optimization of k-space acquisition order improves the clinical utility of CS accelerated 3D neuroimaging. This method may be appropriate for routine radiological assessment of the brain.

Rationale and design of a longitudinal study of cerebral small vessel diseases, clinical and imaging outcomes in patients presenting with mild ischaemic stroke: Mild Stroke Study 3

Background

Cerebral small vessel disease is a major cause of dementia and stroke, visible on brain magnetic resonance imaging. Recent data suggest that small vessel disease lesions may be dynamic, damage extends into normal-appearing brain and microvascular dysfunctions include abnormal blood–brain barrier leakage, vasoreactivity and pulsatility, but much remains unknown regarding underlying pathophysiology, symptoms, clinical features and risk factors of small vessel disease.

Patients and Methods: The Mild Stroke Study 3 is a prospective observational cohort study to identify risk factors for and clinical implications of small vessel disease progression and regression among up to 300 adults with non-disabling stroke. We perform detailed serial clinical, cognitive, lifestyle, physiological, retinal and brain magnetic resonance imaging assessments over one year; we assess cerebrovascular reactivity, blood flow, pulsatility and blood–brain barrier leakage on magnetic resonance imaging at baseline; we follow up to four years by post and phone. The study is registered ISRCTN 12113543.

Summary

Factors which influence direction and rate of change of small vessel disease lesions are poorly understood. We investigate the role of small vessel dysfunction using advanced serial neuroimaging in a deeply phenotyped cohort to increase understanding of the natural history of small vessel disease, identify those at highest risk of early disease progression or regression and uncover novel targets for small vessel disease prevention and therapy.

Intracranial hemodynamic relationships in patients with cerebral small vessel disease

Objective

To investigate cerebrovascular reactivity (CVR), blood flow, vascular and CSF pulsatility, and their independent relationship with cerebral small vessel disease (SVD) features in patients with minor ischemic stroke and MRI evidence of SVD.

Methods

We recruited patients with minor ischemic stroke and assessed CVR using blood oxygen level–dependent MRI during a hypercapnic challenge, cerebral blood flow (CBF), vascular and CSF pulsatility using phase-contrast MRI, and structural magnetic resonance brain imaging to quantify white matter hyperintensities (WMHs) and perivascular spaces (PVSs). We used multiple regression to identify parameters associated with SVD features, controlling for patient characteristics.

Results

Fifty-three of 60 patients completed the study with a full data set (age 68.0% ± 8.8 years, 74% male, 75% hypertensive). After controlling for age, sex, and systolic blood pressure, lower white matter CVR was associated with higher WMH volume (−0.01%/mm Hg per log10 increase in WMH volume, p = 0.02), basal ganglia PVS (−0.01%/mm Hg per point increase in the PVS score, p = 0.02), and higher venous pulsatility (superior sagittal sinus −0.03%/mm Hg, p = 0.02, per unit increase in the pulsatility index) but not with CBF (p = 0.58). Lower foramen magnum CSF stroke volume was associated with worse white matter CVR (0.04%/mm Hg per mL increase in stroke volume, p = 0.04) and more severe basal ganglia PVS (p = 0.09).

Conclusions

Lower CVR, higher venous pulsatility, and lower foramen magnum CSF stroke volume indicate that dynamic vascular dysfunctions underpin PVS dysfunction and WMH development. Further exploration of microvascular dysfunction and CSF dynamics may uncover new mechanisms and intervention targets to reduce SVD lesion development, cognitive decline, and stroke.

Relationship Between Venules and Perivascular Spaces in Sporadic Small Vessel Diseases

Supplemental Digital Content is available in the text.

Perivascular spaces (PVS) around venules may help drain interstitial fluid from the brain. We examined relationships between suspected venules and PVS visible on brain magnetic resonance imaging.

Small vessel disease is associated with altered cerebrovascular pulsatility but not resting cerebral blood flow

Cerebral small vessel disease (SVD) contributes to 25% of ischemic strokes and 45% of dementias. We aimed to investigate the role of cerebral blood flow (CBF) and intracranial pulsatility in SVD. We scanned 60 patients with minor ischemic stroke, representing a range of white matter hyperintensities (WMH). We rated WMH and perivascular spaces (PVS) using semi-quantitative scales and measured WMH volume. We measured flow and pulsatility in the main cerebral vessels and cerebrospinal fluid (CSF) using phase-contrast MRI. We investigated the association between flow, pulsatility and SVD features. In 56/60 patients (40 male, 67.8±8.3 years) with complete data, median WMH volume was 10.7 mL (range 1.4-75.0 mL), representing median 0.77% (0.11-5.17%) of intracranial volume. Greater pulsatility index (PI) in venous sinuses was associated with larger WMH volume (e.g. superior sagittal sinus, β = 1.29, P < 0.01) and more basal ganglia PVS (e.g. odds ratio = 1.38, 95% confidence interval 1.06, 1.79, per 0.1 increase in superior sagittal sinus PI) independently of age, sex and blood pressure. CSF pulsatility and CBF were not associated with SVD features. Our results support a close association of SVD features with increased intracranial pulsatility rather than with low global CBF, and provide potential targets for mechanistic research, treatment and prevention of SVD.

Model-based super-resolution reconstruction of T2 maps

PURPOSE

High-resolution isotropic T₂ mapping of the human brain with multi-echo spin-echo (MESE) acquisitions is challenging. When using a 2D sequence, the resolution is limited by the slice thickness. If used as a 3D acquisition, specific absorption rate limits are easily exceeded due to the high power deposition of nonselective refocusing pulses. A method to reconstruct 1-mm³ isotropic T₂ maps is proposed based on multiple 2D MESE acquisitions. Data were undersampled (10-fold) to compensate for the prolonged scan time stemming from the super-resolution acquisition.

THEORY AND METHODS

The proposed method integrates a classical super-resolution with an iterative model-based approach to reconstruct quantitative maps from a set of undersampled low-resolution data. The method was tested on numerical and multipurpose phantoms, and in vivo data. T₂ values were assessed with a region-of-interest analysis using a single-slice spin-echo and a fully sampled MESE acquisition in a phantom, and a MESE acquisition in healthy volunteers.

RESULTS

Numerical simulations showed that the best trade-off between acceleration and number of low-resolution datasets is 10-fold acceleration with 4 acquisitions (acquisition time = 18 min). The proposed approach showed improved resolution over low-resolution images for both phantom and brain. Region-of-interest analysis of the phantom compartments revealed that at shorter T₂ , the proposed method was comparable with the fully sampled MESE. For the volunteer data, the T₂ values found in the brain structures were consistent across subjects (8.5-13.1 ms standard deviation).

CONCLUSION

The proposed method addresses the inherent limitations associated with high-resolution T₂ mapping and enables the reconstruction of 1 mm³ isotropic relaxation maps with a 10 times faster acquisition.

Heterophile antibody interference affecting multiple Roche immunoassays: A case study

BACKGROUND

Analysis of many clinically important analytes is dependent on antibody-based assays. However, depending on the design, these assays are vulnerable to interference from endogenous molecules including circulating antibodies and free biotin. In this case report, we describe a patient whose laboratory findings from immunoassay based methodologies, are inconsistent with the clinical presentation.

CASE PRESENTATION

A 14-year-old male was referred to Pediatric Endocrinology for suspected hyperthyroidism based on critically elevated free thyroxine (fT4) levels although clinical assessment was inconsistent with hyperthyroidism. Because repeat testing was discrepant, Endocrinology questioned the validity of the results prompting consultation with the laboratory to investigate the source of the inconsistent findings. Review of discordant results revealed that fT4 levels measured in laboratories utilizing Roche instrumentation were critically high, while results from laboratories using alternative platforms (i.e. Siemens Centaur) were within normal limits.

CONCLUSION

After a comprehensive evaluation which included testing of paired specimens on multiple platforms, measurement of serially diluted specimens and a formal evaluation for the presence of heterophile antibodies, it was determined that a heterophile antibody interference was the most likely cause of the aberrant results in this patient.

Transgender men, pregnancy, and the "new" advanced paternal age: A review of the literature

Transgender men are assigned female at birth, but self-identify as male. Although some transgender men undergo gender-affirming hormonal treatment and/or surgery that preclude pregnancy, many (if not most) retain their female reproductive organs and, as a result, their capacity to become pregnant. Although the visibility of the transgender community has increased, the exposure of healthcare providers to transgender individuals, especially transgender men during pregnancy, as well as research that addresses evidence-based practice remain limited. In this review, we discuss obstetrical issues for transgender men who are ≥35 years old, termed the "new" advanced paternal age. We review preconception care and focus on fertility issues, the impact of stopping gender-affirming hormonal treatment, and age-appropriate health maintenance. We review antepartum and postpartum care, including labor and delivery, monitoring for perinatal depression, contraception, and chest feeding. Finally, we conclude with suggestions for areas for further research and study.

A mutation inactivating the distal SF1 binding site on the human anti-Müllerian hormone promoter causes persistent Müllerian duct syndrome

The persistent Müllerian duct syndrome (PMDS) is a 46,XY disorder of sexual development characterized by the persistence of Müllerian duct derivatives, uterus and tubes, in otherwise normally masculinized males. The condition, transmitted as a recessive autosomal trait, is usually due to mutations in either the anti-Müllerian hormone (AMH) gene or its main receptor. Many variants of these genes have been described, all targeting the coding sequences. We report the first case of PMDS due to a regulatory mutation. The AMH promoter contains two binding sites for steroidogenic factor 1 (SF1), one at −102 and the other at −228. Our patient carries a single base deletion at −225, significantly decreasing its capacity for binding SF1, as measured by the electrophoresis mobility shift assay. Furthermore, by linking the AMH promoter to the luciferase gene, we show that the transactivation capacity of the promoter is significantly decreased by the mutation, in contrast to the disruption of the −102 binding site. To explain the difference in impact we hypothesize that SF1 could partially overcome the lack of binding to the −102 binding site by interacting with a GATA4 molecule linked to a nearby response element. We show that disruption of both the −102 SF1 and the −84 GATA response elements significantly decreases the transactivation capacity of the promoter. In conclusion, we suggest that the distance between mutated SF1 sites and potentially rescuing GATA binding motifs might play a role in the development of PMDS.

MRI Relaxometry for Quantitative Analysis of USPIO Uptake in Cerebral Small Vessel Disease

A protocol for evaluating ultrasmall superparamagnetic particles of iron oxide (USPIO) uptake and elimination in cerebral small vessel disease patients was developed and piloted. B₁-insensitive R₁ measurement was evaluated in vitro. Twelve participants with history of minor stroke were scanned at 3-T MRI including structural imaging, and R₁ and R₂* mapping. Participants were scanned (i) before and (ii) after USPIO (ferumoxytol) infusion, and again at (iii) 24–30 h and (iv) one month. Absolute and blood-normalised changes in R₁ and R₂* were measured in white matter (WM), deep grey matter (GM), white matter hyperintensity (WMH) and stroke lesion regions. R₁ measurements were accurate across a wide range of values. R₁ (p < 0.05) and R₂* (p < 0.01) mapping detected increases in relaxation rate in all tissues immediately post-USPIO and at 24–30 h. R₂* returned to baseline at one month. Blood-normalised R₁ and R₂* changes post-infusion and at 24–30 h were similar, and were greater in GM versus WM (p < 0.001). Narrower distributions were seen with R₂* than for R₁ mapping. R₁ and R₂* changes were correlated at 24–30 h (p < 0.01). MRI relaxometry permits quantitative evaluation of USPIO uptake; R₂* appears to be more sensitive to USPIO than R₁. Our data are explained by intravascular uptake alone, yielding estimates of cerebral blood volume, and did not support parenchymal uptake. Ferumoxytol appears to be eliminated at 1 month. The approach should be valuable in future studies to quantify both blood-pool USPIO and parenchymal uptake associated with inflammatory cells or blood-brain barrier leak.

A Type 1 Diabetes Genetic Risk Score Predicts Progression of Islet Autoimmunity and Development of Type 1 Diabetes in Individuals at Risk

OBJECTIVE

We tested the ability of a type 1 diabetes (T1D) genetic risk score (GRS) to predict progression of islet autoimmunity and T1D in at-risk individuals.

RESEARCH DESIGN AND METHODS

We studied the 1,244 TrialNet Pathway to Prevention study participants (T1D patients' relatives without diabetes and with one or more positive autoantibodies) who were genotyped with Illumina ImmunoChip (median [range] age at initial autoantibody determination 11.1 years [1.2-51.8], 48% male, 80.5% non-Hispanic white, median follow-up 5.4 years). Of 291 participants with a single positive autoantibody at screening, 157 converted to multiple autoantibody positivity and 55 developed diabetes. Of 953 participants with multiple positive autoantibodies at screening, 419 developed diabetes. We calculated the T1D GRS from 30 T1D-associated single nucleotide polymorphisms. We used multivariable Cox regression models, time-dependent receiver operating characteristic curves, and area under the curve (AUC) measures to evaluate prognostic utility of T1D GRS, age, sex, Diabetes Prevention Trial-Type 1 (DPT-1) Risk Score, positive autoantibody number or type, HLA DR3/DR4-DQ8 status, and race/ethnicity. We used recursive partitioning analyses to identify cut points in continuous variables.

RESULTS

Higher T1D GRS significantly increased the rate of progression to T1D adjusting for DPT-1 Risk Score, age, number of positive autoantibodies, sex, and ethnicity (hazard ratio [HR] 1.29 for a 0.05 increase, 95% CI 1.06-1.6; P = 0.011). Progression to T1D was best predicted by a combined model with GRS, number of positive autoantibodies, DPT-1 Risk Score, and age (7-year time-integrated AUC = 0.79, 5-year AUC = 0.73). Higher GRS was significantly associated with increased progression rate from single to multiple positive autoantibodies after adjusting for age, autoantibody type, ethnicity, and sex (HR 2.27 for GRS >0.295, 95% CI 1.47-3.51; P = 0.0002).

CONCLUSIONS

The T1D GRS independently predicts progression to T1D and improves prediction along T1D stages in autoantibody-positive relatives.

Characterisation of tissue-type metabolic content in secondary progressive multiple sclerosis: a magnetic resonance spectroscopic imaging study

Proton magnetic resonance spectroscopy yields metabolic information and has proved to be a useful addition to structural imaging in neurological diseases. We applied short-echo time Spectroscopic Imaging in a cohort of 42 patients with secondary progressive multiple sclerosis (SPMS). Linear modelling with respect to brain tissue type yielded metabolite levels that were significantly different in white matter lesions compared with normal-appearing white matter, suggestive of higher myelin turnover (higher choline), higher metabolic rate (higher creatine) and increased glial activity (higher myo-inositol) within the lesions. These findings suggest that the lesions have ongoing cellular activity that is not consistent with the usual assumption of ‘chronic’ lesions in SPMS, and may represent a target for repair therapies.

Cerebrovascular reactivity measurement in cerebral small vessel disease: Rationale and reproducibility of a protocol for MRI acquisition and image processing

Background

Impaired autoregulation may contribute to the pathogenesis of cerebral small vessel disease. Reliable protocols for measuring microvascular reactivity are required to test this hypothesis and for providing secondary endpoints in clinical trials.

Aims

To develop and assess a protocol for acquisition and processing of cerebrovascular reactivity by MRI, in subcortical tissue of patients with small vessel disease and minor stroke.

Methods

We recruited 15 healthy volunteers, testing paradigms using 1- and 3-min 6% CO2 challenges with repeat scanning, and 15 patients with history of minor stroke. We developed a protocol to measure cerebrovascular reactivity and delay times, assessing tolerability and reproducibility in grey and white matter areas.

Results

The 3-min paradigm yielded more reproducible data than the 1-min paradigm (CV respectively: 7.9–15.4% and 11.7–70.2% for cerebrovascular reactivity in grey matter), and was less reproducible in white matter (16.1–24.4% and 27.5–141.0%). Tolerability was similar for the two paradigms, but mean cerebrovascular reactivity and cerebrovascular reactivity delay were significantly higher for the 3-min paradigm in most regions. Patient tolerability was high with no evidence of greater failure rate (1/15 patients vs. 2/15 volunteers withdrew at the first visit). Grey matter cerebrovascular reactivity was lower in patients than in volunteers (0.110–0.234 vs. 0.172–0.313%/mmHg; p < 0.05 in 6/8 regions), as was the white matter cerebrovascular reactivity delay (16.2–43.9 vs. 31.1–47.9 s; p < 0.05 in 4/8 regions).

Conclusions

An effective and well-tolerated protocol for measurement of cerebrovascular reactivity was developed for use in ongoing and future trials to investigate small vessel disease pathophysiology and to measure treatment effects.

Long-term cilostazol treatment reduces gliovascular damage and memory impairment in a mouse model of chronic cerebral hypoperfusion

Chronic cerebral hypoperfusion is a major cause of age-related vascular cognitive impairment. A well-characterised mouse model has shown that hypoperfusion results in gliovascular and white matter damage and impaired spatial working memory. In this study, we assessed whether cilostazol, a phosphodiesterase III inhibitor, could protect against these changes. Adult, male C57Bl/6J mice were subjected to bilateral common carotid artery stenosis or a sham operation and fed normal or cilostazol diet for three months. Cilostazol treatment reduced the impairment in working memory and white matter function after hypoperfusion. Endothelial adhesion molecules and gliosis, increased after hypoperfusion, were ameliorated with cilostazol treatment. Interestingly, the improvement in working memory was closely correlated with reduced microglia and endothelial adhesion molecules. Further, the number of stroke lesions after hypoperfusion was reduced in the cilostazol-treated group. Altogether cilostazol showed potential to ameliorate the gliovascular damage and working memory impairments after hypoperfusion possibly via endothelial protection supporting its potential use in the treatment of vascular cognitive impairment.

AMP-activated Protein Kinase Deficiency Blocks the Hypoxic Ventilatory Response and Thus Precipitates Hypoventilation and Apnea

RATIONALE

Modulation of breathing by hypoxia accommodates variations in oxygen demand and supply during, for example, sleep and ascent to altitude, but the precise molecular mechanisms of this phenomenon remain controversial. Among the genes influenced by natural selection in high-altitude populations is one for the adenosine monophosphate-activated protein kinase (AMPK) α1-catalytic subunit, which governs cell-autonomous adaptations during metabolic stress.

OBJECTIVES

We investigated whether AMPK-α1 and/or AMPK-α2 are required for the hypoxic ventilatory response and the mechanism of ventilatory dysfunctions arising from AMPK deficiency.

METHODS

We used plethysmography, electrophysiology, functional magnetic resonance imaging, and immediate early gene (c-fos) expression to assess the hypoxic ventilatory response of mice with conditional deletion of the AMPK-α1 and/or AMPK-α2 genes in catecholaminergic cells, which compose the hypoxia-responsive respiratory network from carotid body to brainstem.

MEASUREMENTS AND MAIN RESULTS

AMPK-α1 and AMPK-α2 deletion virtually abolished the hypoxic ventilatory response, and ventilatory depression during hypoxia was exacerbated under anesthesia. Rather than hyperventilating, mice lacking AMPK-α1 and AMPK-α2 exhibited hypoventilation and apnea during hypoxia, with the primary precipitant being loss of AMPK-α1 expression. However, the carotid bodies of AMPK-knockout mice remained exquisitely sensitive to hypoxia, contrary to the view that the hypoxic ventilatory response is determined solely by increased carotid body afferent input to the brainstem. Regardless, functional magnetic resonance imaging and c-fos expression revealed reduced activation by hypoxia of well-defined dorsal and ventral brainstem nuclei.

CONCLUSIONS

AMPK is required to coordinate the activation by hypoxia of brainstem respiratory networks, and deficiencies in AMPK expression precipitate hypoventilation and apnea, even when carotid body afferent input is normal.

Rare Presentation of Neurofibromatosis and Turner Syndrome in a Pediatric Patient

Neurofibromatosis type 1 (NF1) is classically defined by the presence of multiple café-au-lait macules as one of the diagnostic criteria. Turner syndrome (TS) can also present with café-au-lait macules along with short stature. Our patient is the fifth reported with both NF1 and TS and the first who has been on growth hormone for short stature associated with TS.

Ageing causes prominent neurovascular dysfunction associated with loss of astrocytic contacts and gliosis

AIMS

Normal neurovascular coupling, mediated by the fine interplay and communication of cells within the neurovascular unit, is critical for maintaining normal brain activity and cognitive function. This study investigated whether, with advancing age there is disruption of neurovascular coupling and specific cellular components of the neurovascular unit, and whether the effects of increasing amyloid (a key feature of Alzheimer's disease) would exacerbate these changes.

METHODS

Wild-type mice, in which amyloid deposition is absent, were compared to transgenic amyloid precursor protein (APP) littermates (TgSwDI) which develop age-dependent increases in amyloid. Baseline cerebral blood flow and responses to whisker stimulation were measured. Components of the neurovascular unit (astrocytes, end-feet, pericytes, microglia) were measured by immunohistochemistry.

RESULTS

Neurovascular coupling was progressively impaired with increasing age (starting at 12 months) but was not further altered in TgSwDI mice. Aged mice showed reduced vascular pericyte coverage relative to young but this was not related to neurovascular function. Aged mice displayed significant reductions in astrocytic end-feet expression of aquaporin-4 on blood vessels compared to young mice, and a prominent increase in microglial proliferation which correlated with neurovascular function.

CONCLUSIONS

Strategies aimed to restore the loss of astrocytic end feet contact and reduce gliosis may improve neurovascular coupling.

Workshop on reconstruction schemes for magnetic resonance data: summary of findings and recommendations

The high-fidelity reconstruction of compressed and low-resolution magnetic resonance (MR) data is essential for simultaneously improving patient care, accuracy in diagnosis and quality in clinical research. Sponsored by the Royal Society through the Newton Mobility Grant Scheme, we held a half-day workshop on reconstruction schemes for MR data on 17 August 2016 to discuss new ideas from related research fields that could be useful to overcome the shortcomings of the conventional reconstruction methods that have been evaluated to date. Participants were 21 university students, computer scientists, image analysts, engineers and physicists from institutions from six different countries. The discussion evolved around exploring new avenues to achieve high resolution, high quality and fast acquisition of MR imaging. In this article, we summarize the topics covered throughout the workshop and make recommendations for ongoing and future works.

Prevalence and risk factors for vitamin D insufficiency and deficiency at birth and associated outcome

Background

Occurrence and consequence of cord blood (CB) vitamin D insufficiency/deficiency has not been adequately explored despite rising concern regarding this topic in pediatrics. This study was designed to determine the rate, maternal risk factors, and clinical outcomes in infants in association with vitamin D insufficient/deficient status at birth.

Methods

American Academy of Pediatrics (AAP) defined levels (ng/mL) were utilized to categorize the vitamin D status in CB samples as deficient (5–15), insufficient (16–20), and sufficient (21–100). We used descriptive statistics and multiple regression models to identify the rate and factors associated with vitamin D deficiency/insufficiency and related outcomes in the enrolled mother-infant pairs.

Results

This prospective study was conducted at a single center on postpartum women and their infants. Vitamin D deficiency and insufficiency was recorded in 38.9 and 29.8% respectively of the 265 CB samples. Deficient CB vitamin D levels in infants were associated with maternal Black, Hispanic, or Asian race/ethnicity, younger age, and increased number of pregnancies. The likelihood for infants to be born with an insufficient vitamin D level increases with younger maternal age and the number of pregnancies as well as Asian ethnicity. We did not find an association between the vitamin D status at birth and pre-discharge clinical characteristics of the neonates.

Conclusions

The likelihood for an infant to be born with vitamin D deficiency/insufficiency is relatively high and is related mainly to younger maternal age, gravidity, and non-White race/ethnicity. Our findings raise a question regarding the adequacy of the AAP recommended vitamin D supplementation requirements without knowing the infant’s vitamin D status at birth.

Delayed methimazole-induced agranulocytosis in a 6-year old patient with Graves’ disease

Background

Agranulocytosis is regarded as a rare side effect of methimazole (MMI) therapy that occurs in a dose dependent manner and that usually develops within the first 3–6 months of treatment. Although delayed development beyond this timeline has been documented in adults, very few children have been reported with this presentation.

Case presentation

We present a 6-year old patient who developed agranulocytosis 18 months after the start of MMI therapy.

Conclusions

This is an unusual case of a 6-year old patient who developed this serious side effect on stable MMI therapy well beyond the typical timeline. Our review of the literature revealed that there really is inconclusive data on the incidence, time, and dose-dependency of MMI-induced agranulocytosis in the pediatric Graves’ disease population.

Cerebral blood flow in small vessel disease: A systematic review and meta-analysis

White matter hyperintensities are frequent on neuroimaging of older people and are a key feature of cerebral small vessel disease. They are commonly attributed to chronic hypoperfusion, although whether low cerebral blood flow is cause or effect is unclear. We systematically reviewed studies that assessed cerebral blood flow in small vessel disease patients, performed meta-analysis and sensitivity analysis of potential confounders. Thirty-eight studies (n = 4006) met the inclusion criteria, including four longitudinal and 34 cross-sectional studies. Most cerebral blood flow data were from grey matter. Twenty-four cross-sectional studies (n = 1161) were meta-analysed, showing that cerebral blood flow was lower in subjects with more white matter hyperintensity, globally and in most grey and white matter regions (e.g. mean global cerebral blood flow: standardised mean difference-0.71, 95% CI -1.12, -0.30). These cerebral blood flow differences were attenuated by excluding studies in dementia or that lacked age-matching. Four longitudinal studies (n = 1079) gave differing results, e.g., more baseline white matter hyperintensity predated falling cerebral blood flow (3.9 years, n = 575); cerebral blood flow was low in regions that developed white matter hyperintensity (1.5 years, n = 40). Cerebral blood flow is lower in subjects with more white matter hyperintensity cross-sectionally, but evidence for falling cerebral blood flow predating increasing white matter hyperintensity is conflicting. Future studies should be longitudinal, obtain more white matter data, use better age-correction and stratify by clinical diagnosis.

Magnetic resonance imaging for assessment of cerebrovascular reactivity in cerebral small vessel disease: A systematic review

Cerebral small vessel disease (SVD) pathophysiology is poorly understood. Cerebrovascular reactivity (CVR) impairment may play a role, but evidence to date is mainly indirect. Magnetic resonance imaging (MRI) allows investigation of CVR directly in the tissues affected by SVD. We systematically reviewed the use of MRI to measure CVR in subjects with SVD. Five studies (total n = 155 SVD subjects, 84 controls) provided relevant data. The studies included different types of patients. Each study used blood oxygen level dependent (BOLD) MRI to assess CVR but a different vasoactive stimulus and method of calculating CVR. CVR decreased with increasing white matter hyperintensities in two studies (n = 17, 11%) and in the presence of microbleeds in another. Three studies (n = 138, 89%) found no association of CVR with white matter hyperintensities. No studies provided tissue-specific CVR values. CVR decreased with age in three studies, and with female gender and increasing diastolic blood pressure in one study. Safety and tolerability data were limited. Larger studies using CVR appear to be feasible and are needed, preferably with more standardized methods, to determine if specific clinical or radiological features of SVD are more or less associated with impaired CVR.

The role of brain-derived neurotrophic factor in learned fear processing: an awake rat fMRI study

Brain‐derived neurotrophic factor (BDNF) signaling is implicated in the etiology of many psychiatric disorders associated with altered emotional processing. Altered peripheral (plasma) BDNF levels have been proposed as a biomarker for neuropsychiatric disease risk in humans. However, the relationship between peripheral and central BDNF levels and emotional brain activation is unknown. We used heterozygous BDNF knockdown rats (BDNF^+/−) to examine the effects of genetic variation in the BDNF gene on peripheral and central BDNF levels and emotional brain activation as assessed by awake functional magnetic resonance imaging (fMRI). BDNF^+/− and control rats were trained to associate a flashing light (conditioned stimulus; CS) with foot‐shock, and brain activation in response to the CS was measured 24 h later in awake rats using fMRI. Central and peripheral BDNF levels were decreased in BDNF^+/− rats compared with control rats. Activation of fear circuitry (amygdala, periaqueductal gray, granular insular) was seen in control animals; however, activation of this circuitry was absent in BDNF^+/− animals. Behavioral experiments confirmed impaired conditioned fear responses in BDNF^+/− rats, despite intact innate fear responses. These data confirm a positive correlation [r = 0.86, 95% confidence interval (0.55, 0.96); P = 0.0004] between peripheral and central BDNF levels and indicate a functional relationship between BDNF levels and emotional brain activation as assessed by fMRI. The results demonstrate the use of rodent fMRI as a sensitive tool for measuring brain function in preclinical translational studies using genetically modified rats and support the use of peripheral BDNF as a biomarker of central affective processing.

Imaging learned fear circuitry in awake mice using fMRI

Functional magnetic resonance imaging (fMRI) of learned behaviour in ‘awake rodents’ provides the opportunity for translational preclinical studies into the influence of pharmacological and genetic manipulations on brain function. fMRI has recently been employed to investigate learned behaviour in awake rats. Here, this methodology is translated to mice, so that future fMRI studies may exploit the vast number of genetically modified mouse lines that are available. One group of mice was conditioned to associate a flashing light (conditioned stimulus, CS) with foot shock (PG; paired group), and another group of mice received foot shock and flashing light explicitly unpaired (UG; unpaired group). The blood oxygen level‐dependent signal (proxy for neuronal activation) in response to the CS was measured 24 h later in awake mice from the PG and UG using fMRI. The amygdala, implicated in fear processing, was activated to a greater degree in the PG than in the UG in response to the CS. Additionally, the nucleus accumbens was activated in the UG in response to the CS. Because the CS signalled an absence of foot shock in the UG, it is possible that this region is involved in processing the safety aspect of the CS. To conclude, the first use of fMRI to visualise brain activation in awake mice that are completing a learned emotional task is reported. This work paves the way for future preclinical fMRI studies to investigate genetic and environmental influences on brain function in transgenic mouse models of disease and aging.