Magnetic resonance imaging (MRI) sequences commonly used in simultaneous electroencephalogram (EEG)-MRI studies include blood oxygenation level-dependent (BOLD) and anatomical T 1 -weighted MRI. Safety and electrode heating profiles for these sequences have been well-characterized. However, recent improvements in EEG design may allow for additional sequences to be performed with similar expectations of heating safety, which would expand the EEG-MRI infrastructure for quantitative physiological studies. We evaluated temperature changes ex vivo and in vivo over a wider range of preparation and readout modules with differing specific absorption rate (SAR). A 32-channel EEG cap was used at 3 T and ex vivo heating was assessed for 2D- and 3D-pseudo-continuous-arterial-spin-labeling, 2D-cine, 2D-phase-contrast, 2D T 2 -Relaxation-Under-Spin-Tagging, 32-direction b = 1000 s/mm 2 and b = 2000 s/mm 2 2D-diffusion tensor imaging, multiband-BOLD, 3D-T1 MPRAGE, 3D-FLAIR, and 3D-T2. Temperature was monitored with a fiberoptic probe system and plotted over six different electrodes, the amplifier, and battery pack. In vivo assessments were conducted in three participants with the same system. A further in vivo supplemental cohort (n = 10) was used to further evaluate qualitative self-reported heating. Device integrity was evaluated by the manufacturer following experiments. Peak temperature and maximum temperature increases were 23.0°C and 0.4°C respectively ex vivo, and 37.6°C and 0.7°C respectively in vivo. Temperatures did not approach the safety heating threshold of 40°C (defined as a conservative threshold based on manufacturer recommendations and burn injury data). Participants completed in vivo scans without adverse events. No manufacturer-reported device damage was identified. Overall, the tested scans induced heating below critical limits at the clinical field strength of 3 T.

Temporal encephaloceles (TEs) are herniations of cerebral parenchyma through structural defects in the floor of the middle cranial fossa. They are a relatively common, but only relatively recently identified potential cause of drug-resistant epilepsy. Uncontrolled epilepsy is associated with many negative long term health consequences including a heightened risk of death. The most effective treatment for drug-resistant epilepsy is surgery. One of the most predictive factors associated with successful surgery is identification of an abnormality on imaging. However, TEs can be difficult to detect and are often overlooked on neuroimaging studies. Improving our ability to accurately detect TEs by MRI is an important step in improving surgical outcomes in patients with drug-resistant epilepsy. We performed a review on existing imaging modalities for detecting TEs and report on our attempt to use a voxel-based morphometry (VBM) algorithm to detect TEs in T1-weighted MRIs of 81 patients from a database comprised of 25 patients with confirmed encephaloceles and 56 controls. Our program's sensitivity and specificity were compared to those of two neuroradiologists and two epileptologists using visualization during surgery as the gold standard. On average, the neuroradiologists and epileptologists had sensitivities of 41 % and 58 % and specificities of 81 % and 60 % while our VBM-based approach had sensitivities and specificities ranging from 11 % to 50 % and 0.2 % to 17 %, respectively. This work provides an overview of the different imaging modalities utilized in the detection of TEs and highlights the difficulties associated with their detection for both experienced physicians and cutting-edge computational methods. Our findings suggest that VBM-based methods could potentially be used to enhance clinicians' ability to detect TEs thereby facilitating surgical planning, improving surgical outcomes by allowing for more specific targeting, and bettering the long-term health and well-being of patients with drug-resistant epilepsy secondary to TEs.

Histopathologic studies report higher concentrations of multiple sclerosis white matter lesions in watershed areas of the brain, suggesting that areas with relatively lower oxygen levels may be more vulnerable to disease. However, it is unknown at what point in the disease course lesion predilection for watershed territories begins. Accordingly, we studied a cohort of people with newly diagnosed disease and asked whether (1) white matter lesions disproportionally localize to watershed-regions and (2) the degree of microstructural injury in watershed-lesions is more severe. Fifty-four participants, i.e. 38 newly diagnosed people with multiple sclerosis, clinically isolated syndrome or radiologically isolated syndrome, and 16 age- and sex-matched healthy controls underwent brain magnetic resonance imaging. T1-weighted and T2-weighted fluid-attenuated inversion recovery sequences, selective inversion recovery quantitative magnetisation transfer images, and the multi-compartment diffusion imaging with the spherical mean technique were acquired. We computed the macromolecular-to-free pool size ratio, and the apparent axonal volume fraction maps to indirectly estimate myelin and axonal integrity, respectively. We produced a flow territory atlas in each subject's native T2-weighted fluid-attenuated inversion recovery images using a T1-weighted magnetic resonance imaging template in the Montreal Neurological Institute 152 space. Lesion location relative to the watershed, non-watershed and mixed brain vascular territories was annotated. The same process was performed on the T2-weighted fluid-attenuated inversion recovery images of the healthy controls using 294 regions of interest. Generalized linear mixed models for continuous outcomes were used to assess differences in size, pool size ratio and axonal volume fraction between lesions/regions of interests (in healthy controls) situated in different vascular territories. In patients, we assessed 758 T2-lesions and 356 chronic black holes (cBHs). The watershed-territories had higher relative and absolute concentrations of T2-lesions (P <= 0.041) and cBHs (P <= 0.036) compared to either non-watershed- or mixed-zones. T2-lesions in watershed-areas also had lower pool size ratio relative to T2-lesions in either non-watershed- or mixed-zones (P = 0.039). These results retained significance in the sub-cohort of people without vascular comorbidities and when accounting for periventricular lesions. In healthy controls, axonal volume fraction was higher only in mixed-areas regions of interest compared to non-watershed-ones (P = 0.008). No differences in pool size ratio were seen. We provide in vivo evidence that there is an association between arterial vascularisation of the brain and multiple sclerosis-induced tissue injury as early as the time of disease diagnosis. Our findings underline the importance of oxygen delivery and healthy arterial vascularisation to prevent lesion formation and foster a better outcome in multiple sclerosis. Toubasi et al. report that in newly diagnosed patients with multiple sclerosis, watershed areas of the brain are associated with a higher number of T2-lesions, chronic black holes and greater tissue injury. This underscores the importance of healthy brain vascularisation to foster lesion repair. Graphical Abstract

BACKGROUND AND PURPOSE:Choroid plexus (ChP) hyperemia has been observed in patients with intracranial vasculopathy and to reduce following successful surgical revascularization. This observation may be attributable to impaired vascular reserve of the ChP or other factors, such as the ChP responding to circulating markers of stress. We extend this work to test the hypothesis that vascular reserve of the ChP is unrelated to intracranial vasculopathy.METHODS:We performed hypercapnic reactivity (blood oxygenation level-dependent; echo time = 35 ms; spatial resolution = 3.5 × 3.5 × 3.5 mm, repetition time = 2000 ms) and catheter angiography assessments of ChP reserve capacity and vascular patency in moyamoya patients (n = 53) with and without prior surgical revascularization. Time regression analyses quantified maximum cerebrovascular reactivity and reactivity delay time in ChP and cortical flow territories of major intracranial vessels with steno-occlusion graded as <70%, 70%-99%, and occlusion using Warfarin-Aspirin-Symptomatic-Intracranial-Disease stenosis grading criteria. Analysis of variance (significance: two-sided Bonferroni-corrected p < .05) was applied to evaluate cortical and ChP reactivity, after accounting for end-tidal carbon dioxide change, for differing vasculopathy categories.RESULTS:In patients without prior revascularization, arterial vasculopathy was associated with reduced cortical reactivity and lengthened reactivity delay (p ≤ .01), as expected. Regardless of surgical history, the ChP reactivity metrics were not significantly related to the degree of proximal stenosis, consistent with ChP reactivity being largely preserved in this population.CONCLUSIONS:Findings are consistent with ChP reactivity in moyamoya not being dependent on observed vasculopathy. Future work may investigate the extent to which ChP hyperemia in chronic ischemia reflects circulating markers of glial or ischemic stress.

Abstract Background Parkinson’s disease is characterized by dopamine-responsive symptoms as well as aggregation of α-synuclein protofibrils. New diagnostic methods assess α-synuclein aggregation characteristics from cerebrospinal fluid (CSF) and recent pathophysiologic mechanisms suggest that CSF circulation disruptions may precipitate α-synuclein retention. Here, diffusion-weighted MRI with low-to-intermediate diffusion-weightings was applied to test the hypothesis that CSF motion is reduced in Parkinson’s disease relative to healthy participants. Methods Multi-shell diffusion weighted MRI (spatial resolution = 1.8 × 1.8 × 4.0 mm) with low-to-intermediate diffusion weightings (b-values = 0, 50, 100, 200, 300, 700, and 1000 s/mm2) was applied over the approximate kinetic range of suprasellar cistern fluid motion at 3 Tesla in Parkinson’s disease (n = 27; age = 66 ± 6.7 years) and non-Parkinson’s control (n = 32; age = 68 ± 8.9 years) participants. Wilcoxon rank-sum tests were applied to test the primary hypothesis that the noise floor-corrected decay rate of CSF signal as a function of b-value, which reflects increasing fluid motion, is reduced within the suprasellar cistern of persons with versus without Parkinson’s disease and inversely relates to choroid plexus activity assessed from perfusion-weighted MRI (significance-criteria: p < 0.05). Results Consistent with the primary hypothesis, CSF decay rates were higher in healthy (D = 0.00673 ± 0.00213 mm2/s) relative to Parkinson’s disease (D = 0.00517 ± 0.00110 mm2/s) participants. This finding was preserved after controlling for age and sex and was observed in the posterior region of the suprasellar cistern (p < 0.001). An inverse correlation between choroid plexus perfusion and decay rate in the voxels within the suprasellar cistern (Spearman’s-r=-0.312; p = 0.019) was observed. Conclusions Multi-shell diffusion MRI was applied to identify reduced CSF motion at the level of the suprasellar cistern in adults with versus without Parkinson’s disease; the strengths and limitations of this methodology are discussed in the context of the growing literature on CSF flow.

Background The choroid plexus functions as the blood-cerebrospinal fluid (CSF) barrier, plays an important role in CSF production and circulation, and has gained increased attention in light of the recent elucidation of CSF circulation dysfunction in neurodegenerative conditions. However, methods for routinely quantifying choroid plexus volume are suboptimal and require technical improvements and validation. Here, we propose three deep learning models that can segment the choroid plexus from commonly-acquired anatomical MRI data and report performance metrics and changes across the adult lifespan. Methods Fully convolutional neural networks were trained from 3D T 1 -weighted, 3D T 2 -weighted, and 2D T 2 -weighted FLAIR MRI using gold-standard manual segmentations in control and neurodegenerative participants across the lifespan (n = 50; age = 21–85 years). Dice coefficients, 95% Hausdorff distances, and area-under-curve (AUCs) were calculated for each model and compared to segmentations from FreeSurfer using two-tailed Wilcoxon tests (significance criteria: p < 0.05 after false discovery rate multiple comparisons correction). Metrics were regressed against lateral ventricular volume using generalized linear models to assess model performance for varying levels of atrophy. Finally, models were applied to an expanded cohort of adult controls (n = 98; age = 21–89 years) to provide an exemplar of choroid plexus volumetry values across the lifespan. Results Deep learning results yielded Dice coefficient = 0.72, Hausdorff distance = 1.97 mm, AUC = 0.87 for T 1 -weighted MRI, Dice coefficient = 0.72, Hausdorff distance = 2.22 mm, AUC = 0.87 for T 2 -weighted MRI, and Dice coefficient = 0.74, Hausdorff distance = 1.69 mm, AUC = 0.87 for T 2 -weighted FLAIR MRI; values did not differ significantly between MRI sequences and were statistically improved compared to current commercially-available algorithms (p < 0.001). The intraclass coefficients were 0.95, 0.95, and 0.96 between T 1 -weighted and T 2 -weighted FLAIR, T 1 -weighted and T 2 -weighted, and T 2 -weighted and T 2 -weighted FLAIR models, respectively. Mean lateral ventricle choroid plexus volume across all participants was 3.20 ± 1.4 cm 3 ; a significant, positive relationship (R 2 = 0.54-0.60) was observed between participant age and choroid plexus volume for all MRI sequences (p < 0.001). Conclusions Findings support comparable performance in choroid plexus delineation between standard, clinically available, non-contrasted anatomical MRI sequences. The software embedding the evaluated models is freely available online and should provide a useful tool for the growing number of studies that desire to quantitatively evaluate choroid plexus structure and function ( https://github.com/hettk/chp_seg ).

Sickle cell disease (SCD) is the most common genetic blood disorder, characterized by red cell hemolysis, anemia, and corresponding increased compensatory cerebral blood flow (CBF). SCD patients are at high risk for cerebral infarcts and CBF quantification is likely critical to assess infarct risk. Infarcts primarily localize to white matter (WM), yet arterial spin labeling (ASL) MRI, the most common non-invasive CBF approach, has poor WM CBF sensitivity owing to low WM CBF and long WM bolus arrival time (BAT). We hypothesize that anemia, and associated cerebral hyperemia, in SCD leads to improved WM detection with ASL. We performed 3-Tesla multi-delay pulsed ASL in SCD (n = 35; age = 30.5 ± 8.3 years) and control (n = 15; age = 28.7 ± 4.5 years) participants and applied t-tests at each inversion time within different flow territories, and determined which regions were significantly above noise floor (criteria: one-sided p < 0.05). Total WM CBF-weighted signal was primarily detectable outside of borderzone regions in SCD (CBF = 17.7 [range = 12.9–25.0] mL/100 g/min), but was largely unphysiological in control (CBF = 8.1 [range = 7.6–9.9)] mL/100 g/min) participants. WM BAT was reduced in SCD versus control participants (ΔBAT = 37 [range = 46–70] ms) and BAT directly correlated with hematocrit (Spearman’s-ρ = 0.62; p < 0.001). Findings support the feasibility of WM CBF quantification using ASL in SCD participants for appropriately parameterized protocols.

Intravenous arachnoid granulations (AGs) are protrusions of the arachnoid membrane into the venous lumen and function as contributors to the cerebrospinal fluid (CSF) flow circuit. Patients with Parkinson disease (PD) often present with accumulation of alpha synuclein. Previous works have provided evidence for neurofluid circulation dysfunction in neurodegenerative diseases associated with changes in CSF egress, which may have implications regarding AG morphology. The present study aims to investigate group differences in AG volumetrics between healthy and PD participants, as well as relationships between AG characteristics and clinical assessments. Generalized linear models revealed significant increases in AG volumetrics and number in PD compared to healthy controls. Partial Spearman-rank correlation analyses demonstrated significant relationships between AG metrics and motor and cognitive assessments. Finally, AG volumetrics were positively correlated with objective actigraphy measures of sleep dysfunction, but not self-report sleep symptoms.

AbstractObjectiveParamagnetic rim lesions (PRLs) are a biomarker of chronic active lesions (CALs), and an important driver of neurological disability in multiple sclerosis (MS). The reason subtending some acute lesions evolvement into CALs is not known. Here we ask whether a relatively lower oxygen content is linked to CALs.MethodsIn this prospective cross‐sectional study, 64 people with multiple sclerosis (PwMS), clinically isolated syndrome and radiologically isolated syndrome underwent a 7.0 Tesla (7 T) brain magnetic resonance imaging (MRI). The scanning protocol included a T2‐w fluid‐attenuated inversion recovery (FLAIR), and a single echo gradient echo from which susceptibility‐weighted imaging (SWI) was derived. WM lesions were identified on the T2‐w‐FLAIR whilst PRLs were identified on the SWI sequence. T2‐lesions were classified as PRLs and rimless lesions (PRLs‐). We registered a universal vascular atlas to each subject's T2‐w‐FLAIR and classified each T2‐lesions according to its location into watershed‐ (ws), non‐watershed‐ (nws), and mixed‐lesion (m). Ws‐lesions were defined as lesions that were fully located in a region between the territories of two major arteries.ResultsOut of 1,975 T2‐lesions, 88 (4.5%) were PRLs. Ws‐regions had a higher number (p = 0.005) and proportion (p < 0.001) of PRLs‐ compared to nws‐regions. Ws‐PRL‐ were larger compared to nws‐ones (p = 0.009). The number (p = 0.043) and proportion (p < 0.001) of PRLs was higher in ws‐regions compared to nws‐ones. Ws‐PRLs were not significantly larger than nws‐ones (p = 0.195).InterpretationWe propose the novel concept of a link between arterial vascularization and chronic activity in MS by demonstrating a preferential localization of CALs in ws‐territories.

Objective: To investigate the relationship between sleep quality and cerebrospinal fluid (CSF) flow in individuals with Parkinson's disease (PD). Background: Previous studies have emphasized the role of CSF circulation in the clearance of brain waste products, with recent findings demonstrating increased CSF flow during sleep. CSF circulation impairment could play a major role in neurodegenerative proteinopathies such as PD, a commonly encountered feature of which is disrupted sleep. Here, we assessed the relationship between patient-reported sleep quality and imaging assays of CSF flow. Design/Methods: Imaging and clinical assessments were completed in 23 PD participants aged 56 to 79 (Mage=66.70; 16 males). The Montreal Cognitive Assessment (MoCA) and Unified Parkinson's Disease Rating Scale (UPDRS) were administered; subjective sleep measurements were recorded using the Sleep Disturbance (SD) and Sleep-Related Impairment (SRI) items from the Patient-Reported Outcomes Measurement Information System (PROMIS) scale. MRI phase contrast sequences quantified CSF flux (mL/min) via the cerebral aqueduct. Net CSF flow was defined as the difference between caudal and cranial flow, whereas absolute flow was calculated as the sum of total caudal and cranial flow per cardiac cycle. Results: Participants had mean MoCA scores of 24.17 (range 13–30) and UPDRS scores of 30.70 (7–59). PROMIS scores for SD and SRI were 20.14 (9–32) and 15.00 (8–24), respectively. Mean CSF measurements were 0.25 mL/min (−0.29–0.88) for net and 8.11 mL/min (3.55–16.34) for absolute flow. Higher SRI scores correlated with greater net CSF flow while awake (r=0.531, p=0.023). Additionally, SRI and age explained 73.4% of variation in absolute CSF flow in a linear regression model (F(3,15)=24.5, p<0.0001). Conclusions: Self-reported sleep impairment is associated with increased CSF flow in awake individuals with PD. This study is the first to link patient-reported measures of sleep with alterations to CSF flow. These data support novel outcomes for clinical studies that improve sleep. Disclosure: Mr. Ponzo has nothing to disclose. Dr. Hett has nothing to disclose. Mr. Eisma has nothing to disclose. Mr. Elenberger has nothing to disclose. Mr. Song has nothing to disclose. An immediate family member of Dr. McKnight has received personal compensation in the range of $500-$4,999 for serving as a Consultant for Deciphera. The institution of Dr. McKnight has received research support from RSNA. Dr. Considine has received personal compensation in the range of $5,000-$9,999 for serving as a Consultant for MDisrupt. Dr. Considine has received personal compensation in the range of $10,000-$49,999 for serving as an Expert Witness for Park Dietz & Associates. The institution of Dr. Considine has received research support from NIH. The institution of Dr. Considine has received research support from DoD. The institution of Dr. Considine has received research support from Acadia Pharmaceuticals. Manus Donahue, 13717 has received personal compensation for serving as an employee of Alterity. Manus Donahue, 13717 has received personal compensation in the range of $500-$4,999 for serving as a Consultant for Alterity. Manus Donahue, 13717 has received personal compensation in the range of $5,000-$9,999 for serving as a Consultant for Pfizer. Manus Donahue, 13717 has received personal compensation in the range of $500-$4,999 for serving as a Consultant for Global Blood Therapeutics. Manus Donahue, 13717 has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Pfizer. The institution of Manus Donahue, 13717 has received research support from National Institutes of Health. Dr. Claassen has received personal compensation in the range of $5,000-$9,999 for serving as a Consultant for Teva Neuroscience. Dr. Claassen has received personal compensation in the range of $500-$4,999 for serving as a Consultant for Spark . The institution of Dr. Claassen has received personal compensation in the range of $50,000-$99,999 for serving as a Consultant for Alterity. Dr. Claassen has received personal compensation in the range of $5,000-$9,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Teva Neuroscience. Dr. Claassen has received personal compensation in the range of $500-$4,999 for serving as an Editor, Associate Editor, or Editorial Advisory Board Member for HD Insights. The institution of Dr. Claassen has received research support from NIH. The institution of Dr. Claassen has received research support from CHDI. The institution of Dr. Claassen has received research support from HDSA. The institution of Dr. Claassen has received research support from Department of Defense. The institution of Dr. Claassen has received research support from Griffin Family Foundation. The institution of Dr. Claassen has received research support from Neurocrine. The institution of Dr. Claassen has received research support from Vaccinex. The institution of Dr. Claassen has received research support from AbbVie. The institution of Dr. Claassen has received research support from CHDI. The institution of Dr. Claassen has received research support from Genentech/ Roche. The institution of Dr. Claassen has received research support from Prilenia. The institution of Dr. Claassen has received research support from Neurocrine/ HSG.

The choroid plexus (ChP) has gained recent attention due to its potential functional relevance for cerebral glymphatic circulation. Here, a novel arterial spin labelling sequence and deep learning algorithm were applied to quantify ChP volume, perfusion, and volumetric flow across the healthy lifespan and in neurodegenerative participants with Parkinson’s disease (PD) to test the hypotheses that ChP hypertrophy and hypoperfusion are associated with increasing age and neurodegeneration. ChP volume increased with age, whereas perfusion decreased with age (p<0.01). In PD, ChP volumetric flow increases were more pronounced relative to age-matched healthy controls, consistent with compensatory stimulation of cerebrospinal fluid production.

One of the pathological hallmarks of Alzheimer's and related diseases is the increased accumulation of protein amyloid-beta in the brain parenchyma. As such, recent studies have focused on characterizing protein and related clearance pathways involving perivascular flow of neurofluids, but human studies of these pathways are limited owing to limited methods for evaluating neurofluid circulation non-invasively in vivo. Here, we utilize non-invasive MRI methods to explore surrogate measures of CSF production, bulk flow and egress in the context of independent PET measures of amyloid-beta accumulation in older adults. Participants (N = 23) were scanned at 3.0 T with 3D T-2-weighted turbo spin echo, 2D perfusion-weighted pseudo-continuous arterial spin labelling and phase-contrast angiography to quantify parasagittal dural space volume, choroid plexus perfusion and net CSF flow through the aqueduct of Sylvius, respectively. All participants also underwent dynamic PET imaging with amyloid-beta tracer C-11-Pittsburgh Compound B to quantify global cerebral amyloid-beta accumulation. Spearman's correlation analyses revealed a significant relationship between global amyloid-beta accumulation and parasagittal dural space volume (rho = 0.529, P = 0.010), specifically in the frontal (rho = 0.527, P = 0.010) and parietal (rho = 0.616, P = 0.002) subsegments. No relationships were observed between amyloid-beta and choroid plexus perfusion nor net CSF flow. Findings suggest that parasagittal dural space hypertrophy, and its possible role in CSF-mediated clearance, may be closely related to global amyloid-beta accumulation. These findings are discussed in the context of our growing understanding of the physiological mechanisms of amyloid-beta aggregation and clearance via neurofluids.

Objective Investigations of cerebrospinal fluid (CSF) flow aberrations in Huntington's disease (HD) are of growing interest, as impaired CSF flow may contribute to mutant Huntington retention and observed heterogeneous responsiveness to intrathecally administered therapies. Method We assessed net cerebral aqueduct CSF flow and velocity in 29 HD participants (17 premanifest and 12 manifest) and 51 age‐ and sex matched non‐HD control participants using 3‐Tesla magnetic resonance imaging methods. Regression models were applied to test hypotheses regarding: (i) net CSF flow and cohort, (ii) net CSF flow and disease severity (CAP‐score), and (iii) CSF volume after correcting for age and sex. Results Group‐wise analyses support a decrease in net CSF flow in HD (mean 0.14 ± 0.27 mL/min) relative to control (mean 0.32 ± 0.20 mL/min) participants ( p = 0.02), with lowest flow in the manifest HD cohort (mean 0.04 ± 0.25 mL/min). This finding was explained by hyperdynamic CSF movement, manifesting as higher caudal systolic CSF flow velocity and higher diastolic cranial CSF flow velocity across the cardiac cycle, in HD (caudal flow: 0.17 ± 0.07 mL/s, cranial flow: 0.14 ± 0.08 mL/s) compared to control (caudal flow: 0.13 ± 0.06 mL/s, cranial flow: 0.11 ± 0.04 mL/s) participants. A positive correlation between cranial diastolic flow and disease severity was observed ( p = 0.02). Interpretations Findings support aqueductal CSF flow dynamics changing with disease severity in HD. These accelerated changes are consistent with changes observed over the typical adult lifespan, and may have relevance to mutant Huntington retention and intrathecally administered therapeutics responsiveness. ANN NEUROL 2023;94:885–894

BACKGROUND: Parkinson’s disease is characterized by dopamine-responsive symptoms as well as aggregation and accumulation of a-synuclein protofibrils. New diagnostic methods assess a-synuclein aggregation characteristics from cerebrospinal fluid and recent pathophysiologic mechanisms suggest that cerebrospinal fluid circulation disruptions may precipitate a-synuclein retention. Here, we test the hypothesis that cerebrospinal fluid motion at the level of the suprasellar cistern is reduced in Parkinson’s disease relative to healthy participants and this reduction relates to choroid plexus perfusion. METHODS: Diffusion weighted imaging (spatial resolution=1.8x1.8x4 mm) magnetic resonance imaging with cycling of diffusion weightings ( b -values=0, 50, 100, 200, 300, 700, and 1000 s/mm 2 ) over the approximate kinetic range of suprasellar cistern neurofluid motion was applied at 3-Tesla in Parkinson’s disease (n=27; age=66±6.7 years) and healthy (n=32; age=68±8.9 years) participants. Wilcoxon rank-sum tests were applied to test the primary hypothesis that the decay rate of cerebrospinal fluid signal as a function of b -value, which reflects increasing fluid motion, is reduced in persons with versus without Parkinson’s disease and inversely relates to choroid plexus activity assessed from perfusion-weighted magnetic resonance imaging (Spearman rank-order correlation; significance-criteria: p <0.05). RESULTS: Consistent with the primary hypothesis, decay rates were higher in healthy ( D =0.00328±0.00123mm 2 /s) relative to Parkinson’s disease ( D =0.00256±0.0094mm 2 /s) participants ( p =0.016). This finding was preserved after controlling for age and sex. An inverse correlation between choroid plexus perfusion and decay rate ( p =0.011) was observed in Parkinson’s disease participants. CONCLUSIONS: Cerebrospinal fluid motion at the level of the suprasellar cistern is often reduced in adults with versus without Parkinson’s disease and this reduction correlates on average with choroid plexus perfusion.

The choroid plexus (ChP) comprises a collection of modified ependymal cells that play an important role in the production of brain cerebrospinal fluid (CSF), and ChP perfusion aberrations have been implicated in a range of cerebrovascular and neurodegenerative disorders. To provide an exemplar for the growing interest in ChP activity, we evaluated ChP perfusion and bulk CSF flow cross-sectionally across the healthy adult lifespan. Participants (n = 77; age range = 21–86 years) were scanned at 3T using T1-weighted, T2-weighted-FLAIR, perfusion-weighted pCASL, and phase contrast MRI to calculate ChP anatomy, perfusion, and aqueductal CSF flow, respectively. Regression models were applied to evaluate aging effects on ChP volume and ChP perfusion in the lateral ventricles, as well as CSF flow. ChP volume (mean ± std = 2.81 ± 1.1 cm3) increased (p < 0.001), ChP perfusion (36.3 ± 8.6 mL/100 g/min) decreased (p = 0.0078), and ChP total blood flow (1.13 ± 0.34 mL/min) increased (p < 0.001) with age. Cranial-to-caudal net CSF flow (0.245 ± 0.20 mL/min) decreased, absolute CSF flow (4.86 ± 2.96 mL/min) increased, and CSF regurgitant fraction (0.87 ± 0.126) increased with age (all: p < 0.001). ChP perfusion was directly related to net cranial-to-caudal CSF flow through the aqueduct (p = 0.033). The implications of these findings are discussed in the context of the growing literature on CSF circulatory dysfunction in neurodegeneration and cerebrovascular disease.

Abstract Background Recent studies have suggested alternative cerebrospinal fluid (CSF) clearance pathways for brain parenchymal metabolic waste products. One fundamental but relatively under-explored component of these pathways is the anatomic region surrounding the superior sagittal sinus, which has been shown to have relevance to trans-arachnoid molecular passage. This so-called parasagittal dural (PSD) space may play a physiologically significant role as a distal intracranial component of the human glymphatic circuit, yet fundamental gaps persist in our knowledge of how this space changes with normal aging and intracranial bulk fluid transport. Methods We re-parameterized MRI methods to assess CSF circulation in humans using high resolution imaging of the PSD space and phase contrast measures of flow through the cerebral aqueduct to test the hypotheses that volumetric measures of PSD space (1) are directly related to CSF flow (mL/s) through the cerebral aqueduct, and (2) increase with age. Multi-modal 3-Tesla MRI was applied in healthy participants (n = 62; age range = 20–83 years) across the adult lifespan whereby phase contrast assessments of CSF flow through the aqueduct were paired with non-contrasted T 1-weighted and T 2-weighted MRI for PSD volumetry. PSD volume was extracted using a recently validated neural networks algorithm. Non-parametric regression models were applied to evaluate how PSD volume related to tissue volume and age cross-sectionally, and separately how PSD volume related to CSF flow (significance criteria: two-sided p < 0.05). Results A significant PSD volume enlargement in relation to normal aging (p < 0.001, Spearman’s- $$\rho$$ ρ = 0.6), CSF volume (p < 0.001, Spearman’s- $$\rho$$ ρ = 0.6) and maximum CSF flow through the aqueduct of Sylvius (anterograde and retrograde, p < 0.001) were observed. The elevation in PSD volume was not significantly related to gray or white matter tissue volumes. Findings are consistent with PSD volume increasing with age and bulk CSF flow. Conclusions Findings highlight the feasibility of quantifying PSD volume non-invasively in vivo in humans using machine learning and non-contrast MRI. Additionally, findings demonstrate that PSD volume increases with age and relates to CSF volume and bi-directional flow. Values reported should provide useful normative ranges for how PSD volume adjusts with age, which will serve as a necessary pre-requisite for comparisons to persons with neurodegenerative disorders.

Cognitive control processes encompass many distinct components, including response inhibition (stopping a prepotent response), proactive control (using prior information to enact control), reactive control (last-minute changing of a prepotent response), and conflict monitoring (choosing between two competing responses). While frontal midline theta activity is theorized to be a general marker of the need for cognitive control, a stringent test of this hypothesis would require a quantitative, within-subject comparison of the neural activation patterns indexing many different cognitive control strategies, an experiment lacking in the current literature. We recorded EEG from 176 participants as they performed tasks that tested inhibitory control (Go/Nogo Task), proactive and reactive control (AX-Continuous Performance Task), and resolving response conflict (Global/Local Task-modified Flanker Task). As activity in the theta (4–8 Hz) frequency band is thought to be a common signature of cognitive control, we assessed frontal midline theta activation underlying each cognitive control strategy. In all strategies, we found higher frontal midline theta power for trials that required more cognitive control (target conditions) versus control conditions. Additionally, reactive control and inhibitory control had higher theta power than proactive control and response conflict, and proactive control had higher theta power than response conflict. Using decoding analyses, we were able to successfully decode control from target trials using classifiers trained exclusively on each of the other strategies, thus firmly demonstrating that theta representations of cognitive control generalize across multiple cognitive control strategies. Our results confirm that frontal midline theta-band activity is a common mechanism for initiating and executing cognitive control, but theta power also differentiates between cognitive control mechanisms. As theta activation reliably differs depending on the cognitive control strategy employed, future work will need to focus on the differential role of theta in differing cognitive control strategies.