Chronic ischemia alters brain microstructural integrity and cognitive performance in adult moyamoya disease

Alterations in the Glymphatic System and Association with Brain Structure and Cognitive Function in Moyamoya Disease

The glymphatic system is crucial for clearing metabolic waste from the brain, maintaining neural health and cognitive function. This study explores the glymphatic system's role in Moyamoya disease (MMD), characterized by progressive cerebral artery stenosis and brain structural lesions. We assessed 33 MMD patients and 21 healthy controls using diffusion tensor imaging along the perivascular space (DTI-ALPS) and global cortical gray matter-cerebrospinal fluid (CSF) coupling indices (gBOLD-CSF), which are indirect measurements of the glymphatic system. Cerebral perfusion in patients was evaluated via computed tomography perfusion imaging. We also measured the peak width of skeletonized mean diffusivity (PSMD), white matter hyperintensity (WMH) burden, and cognitive function. MMD patients exhibited lower ALPS and gBOLD-CSF coupling indices compared to controls (P < 0.01), indicating disrupted glymphatic function. Significant cognitive impairment was also observed in MMD patients (P < 0.01). ALPS indices varied with cerebral perfusion stages, being higher in earlier ischemic stages (P < 0.05). Analysis of brain structure showed increased CSF volume, PSMD index, and higher WMH burden in MMD patients (P < 0.01). The ALPS index positively correlated with white matter volume and cognitive scores, and negatively correlated with CSF volume, PSMD, and WMH burden (P < 0.05). Mediation analysis revealed the number of periventricular WMH significantly mediated the relationship between glymphatic dysfunction and cognitive impairment. In summary, MMD patients exhibit significant glymphatic system impairments, associated with brain structural changes and cognitive deficits.

MRI hypoperfusion as a determinant of cognitive impairment in adults with Moyamoya angiopathy

INTRODUCTION

In Moyamoya angiopathy (MMA), mechanisms underlying cognitive impairment remain debated. We aimed to assess the association of cognitive impairment with the degree and the topography of cerebral hypoperfusion in MMA.

METHODS

A retrospective analysis of neuropsychological and perfusion MRI data from adults with MMA was performed. Ischemic and haemorrhagic lesion masks were created to account for cerebral lesions in the analysis of cerebral perfusion. Whole brain volume of hypoperfused parenchyma was outlined on perfusion maps using different Tmax thresholds from 4 to 12 s. Regional analysis produced mean Tmax values at different regions of interest. Analyses compared perfusion ratios in patients with and without cognitive impairment, with multivariable logistic regression analysis to identify predictive factors.

RESULTS

Cognitive impairment was found in 20/48 (41.7%) patients. Attention/processing speed and memory were equally impaired (24%) followed by executive domain (23%). After adjustment, especially for lesion volume, hypoperfused parenchyma volume outlined by Tmax > 4 s or Tmax > 5 s thresholds was an independent factor of cognitive impairment (OR for Tmax > 4 s = 1.06 [CI 95% 1.008-1.123]) as well as attention/processing speed (OR for Tmax > 4 s = 1.07 [CI 95% 1.003-1.133]) and executive domains (OR for Tmax > 5 s = 1.08 [CI 95% 1.004-1.158]). Regarding cognitive functions, patients with processing speed and flexibility impairment had higher frontal Tmax compared to other ROIs and to patients with normal test scores.

DISCUSSION

Cerebral hypoperfusion emerged as an independent factor of cognitive impairment in MMA particularly in attention/processing speed and executive domains, with a strong contribution of frontal areas.

CONCLUSION

Considering this association, revascularization surgery could improve cognitive impairment.

Prevalence and characteristics of vascular cognitive impairment in a European cohort of adult patients with Moyamoya angiopathy

INTRODUCTION

Moyamoya angiopathy (MMA) is associated with a high risk of stroke, but it is also increasingly recognized as leading to cognitive impairment. The aim of this study was to determine the prevalence, nature, and severity of vascular cognitive impairment no dementia (VCIND) in adults with MMA and to identify clinical and imaging factors associated with VCIND.

METHODS

We conducted a retrospective study of consecutive adult patients with MMA followed in two tertiary hospitals (Toulouse and Paris Lariboisiere). All patients underwent neuropsychological assessment and brain magnetic resonance imaging (MRI). VCIND was defined as at least two variables of the same cognitive process with z-scores of < 2 standard deviations, regardless of the cognitive domain, that do not interfere in everyday life. Baseline demographic, clinical, and imaging data were compared between patients with and without VCIND.

RESULTS

A total of 102 patients (mean age 43 years; 65% women) were included. Thirty-four patients (33.3%) had VCIND. VCIND was mild in 20/34 (59%), moderate in 8/34 (23%), and severe in 6/34 (18%) patients. Executive function was the most widely affected (25.5%), followed by attention and processing speed (24.8%). In univariable analyses, VCIND was associated with ischemic stroke at diagnosis and the presence of ischemic lesions on MRI.

CONCLUSIONS

VCIND is highly prevalent in adults with MMA. Executive functions and processing speed are predominantly affected. These findings may guide clinicians in their evaluation of patients with MMA. Further research should assess the effect of revascularization therapies on cognitive functions.

White matter hyperintensities in cholinergic pathways correlates of cognitive impairment in moyamoya disease

OBJECTIVE

To investigate the effect of cholinergic pathways damage caused by white matter hyperintensities (WMHs) on cognitive function in moyamoya disease (MMD).

METHODS

We included 62 patients with MMD from a prospectively enrolled cohort. We evaluated the burden of cholinergic pathways damage caused by WMHs using the Cholinergic Pathways Hyperintensities Scale (CHIPS). Cognitive function was evaluated with the Mini-Mental State Examination (MMSE) and Montreal Cognitive Assessment (MoCA). Cognitive impairment was determined according to the cut-off of MMSE and education. Multivariate linear and logistic regression models were used to analyze whether CHIPS was independently associated with cognition. Receiver operating characteristic curve analysis was performed to identify the ability of CHIPS in discriminating cognitive impairment and normal cognition.

RESULTS

CHIPS was associated with both MMSE and MoCA (β = - 0.601 and β = - 0.672, both p < 0.001). After correcting age, sex, education, volumes of limbic areas, and other factors, CHIPS remained to be independently associated with both MMSE and MoCA (β = - 0.388 and β = - 0.334, both p < 0.001). In the logistic regression, only CHIPS was associated with cognitive impairment (odds ratio = 1.431, 95% confidence interval = 1.103 to 1.856, p = 0.007). The optimal cut-off of CHIPS score was 10, yielding a sensitivity of 87.5% and a specificity of 78.3% in identifying MMD patients with cognitive impairment.

CONCLUSIONS

The damage of cholinergic pathways caused by WMHs plays an independent effect on cognition and CHIPS could be a useful method in identifying MMD patients likely to be cognitive impairment.

CLINICAL RELEVANCE STATEMENT

This study shows that Cholinergic Pathways Hyperintensities Scale (CHIPS) could be a simple and reliable method in identifying cognitive impairment for patients with moyamoya disease. CHIPS could be helpful in clinical practice, such as guiding treatment decisions and predicting outcome.

KEY POINTS

• Cholinergic Pathways Hyperintensities Scale was significantly associated with cognitive screening tests in patients with moyamoya disease. • Cholinergic Pathways Hyperintensities Scale plays an independent effect on cognitive impairment in patients with moyamoya disease. • Cholinergic Pathways Hyperintensities Scale shows higher accuracy than education, volumes of limbic areas, and sex in identifying cognitive impairment in moyamoya disease.

Decreased diffusivity along the perivascular space and cerebral hemodynamic disturbance in adult moyamoya disease

Moyamoya disease (MMD) causes cerebral arterial stenosis and hemodynamic disturbance, the latter of which may disrupt glymphatic system activity, the waste clearance system. We evaluated 46 adult patients with MMD and 33 age- and sex-matched controls using diffusivity along the perivascular space (ALPS) measured with diffusion tensor imaging (ALPS index), which may partly reflect glymphatic system activity, and multishell diffusion MRI to generate freewater maps. Twenty-three patients were also evaluated via 15O-gas positron emission tomography (PET), and all patients underwent cognitive tests. Compared to controls, patients (38.4 (13.2) years old, 35 females) had lower ALPS indices in the left and right hemispheres (1.94 (0.27) vs. 1.65 (0.25) and 1.94 (0.22) vs. 1.65 (0.19), P < 0.001). While the right ALPS index showed no correlation, the left ALPS index was correlated with parenchymal freewater (ρ = -0.47, P < 0.001); perfusion measured with PET (cerebral blood flow, ρ = 0.70, P < 0.001; mean transit time, ρ = -0.60, P = 0.003; and oxygen extraction fraction, ρ = -0.52, P = 0.003); and cognitive tests (trail making test part B for executive function; ρ = -0.37, P = 0.01). Adult patients with MMD may exhibit decreased glymphatic system activity, which is correlated with the degree of hemodynamic disturbance, increased interstitial freewater, and cognitive dysfunction, but further investigation is needed.

Brain volume measured by synthetic magnetic resonance imaging in adult moyamoya disease correlates with cerebral blood flow and brain function

Moyamoya disease (MMD) is characterized by progressive arterial occlusion, causing chronic hemodynamic impairment, which can reduce brain volume. A novel quantitative technique, synthetic magnetic resonance imaging (SyMRI), can evaluate brain volume. This study aimed to investigate whether brain volume measured with SyMRI correlated with cerebral blood flow (CBF) and brain function in adult MMD. In this retrospective study, 18 adult patients with MMD were included. CBF was measured using iodine-123-N-isopropyl-p-iodoamphetamine single photon emission computed tomography. Cerebrovascular reactivity (CVR) to acetazolamide challenge was also evaluated. Brain function was measured using the Wechsler Adult Intelligence Scales (WAIS)-III/IV and the WAIS-R tests. Gray matter (GM), white matter, and myelin-correlated volumes were evaluated in six areas. Resting CBF was positively correlated with GM fractions in the right anterior cerebral arterial and right middle cerebral arterial (MCA) territories. CVR was positively correlated with GM fraction in the right posterior cerebral arterial (PCA) territory. Full-Scale Intelligence Quotient and Verbal Comprehension Index scores were marginally positively correlated with GM fractions in the left PCA territory. Processing Speed Index score was marginally positively correlated with GM fraction in the right MCA territory. The SyMRI-measured territorial GM fraction correlated with CBF and brain function in patients with MMD.

Cerebral Vasculopathy in Children with Neurofibromatosis Type 1

Cerebrovascular abnormalities are a severe and often underrecognized complication of childhood neurofibromatosis type 1 (NF1). There are no prospective studies of cerebral vasculopathy in NF1; thus, the estimated frequency of vasculopathy varies between studies. The data is difficult to interpret due to the retrospective data collection and variability in whether imaging is done based on screening/surveillance or due to acute neurologic symptoms. The prevalent NF1-associated cerebral vasculopathy is moyamoya syndrome (MMS). Vascular changes can present without symptoms or with acute TIA or stroke-like symptoms or a range of progressive neurologic deficits. Advanced imaging may enhance sensitivity of neuroimaging in children. Medical and/or surgical interventions may prevent short- and long-term complications. Challenges for establishment of a screening protocol for cerebral vasculopathy in children with NF1 include the relatively large number of patients with NF1, the potential need for sedation to achieve quality imaging and the broad age range at time of detection for cerebral vascular changes. The goal of this review is to present the epidemiology, clinical presentation, imaging features and medical/surgical management of cerebral arteriopathies in children with NF1.

Neuronal Loss in the Bilateral Medial Frontal Lobe Revealed by 123I-iomazenil Single-photon Emission Computed Tomography in Patients with Moyamoya Disease: The First Report from Cognitive Dysfunction Survey of Japanese Patients with Moyamoya Disease (COSMO-Japan Study)

Cognitive impairment in adult patients with moyamoya disease (MMD) is sometimes overlooked and can occur in patients with no ischemic or hemorrhagic lesions. Better profiling and reliable diagnostic methods that characterize the group and associate the impairments and pathology of MMD are required in order to deliver appropriate treatments and support. The potential of 123I-iomazenil single-photon emission computed tomography (SPECT) for this issue has been reported in some studies, but the universality of this method remains unclear. A multicenter study of adult patients (aged 18-60 years) with MMD who experienced difficulties in social lives despite normal activities of daily living was implemented to delineate the common characteristics of this group of patients. In this study, iomazenil SPECT, besides patient characteristics, cognitive functions, and conventional imaging, was acquired to examine whether this method is suitable as a universal diagnostic tool. A total of 36 patients from 12 institutes in Japan were included in this study. Domain scores of world health organization quality of life 26 indicated low self-rating in physical health and psychological domains. The percentages of patients who had <85 in each index were 27.8%-33.3% in the WAIS-III and 16.7%-47.2% in the Wechsler Memory Scale-Revised. The group analysis of iomazenil SPECT demonstrated a decreased accumulation in the bilateral medial frontal areas in comparison with the normal control, whereas there were no specific characteristics on conventional imaging in the cohort. Iomazenil SPECT is a possible universal diagnostic method for the extraction of patients with cognitive impairment in MMD.

Brain perfusion, cognition, and plasma Alzheimer's biomarkers in moyamoya disease

INTRODUCTION

Because growing interest has been focusing on cerebral blood flow (CBF) to predict, prevent, and treat Alzheimer's disease (AD), it is important to clarify the role of CBF in AD pathology and cognitive decline.

METHODS

In a moyamoya disease (MMD) cohort, we examined CBF, specific cognitive domains, and plasma AD biomarkers, as well as correlations among these variables.

RESULTS

CBF was significantly reduced in newly diagnosed MMD patients, while plasma phosphorylated tau181 was elevated and positively correlated with hypoperfusion accumulation. MMD patients scored significantly lower than controls in multiple cognitive tests. Revascularization increased CBF to the recipient brain territories as well as cognitive performance but produced no significant change in AD biomarker levels.

DISCUSSION

These data suggest a link between accumulated reductions in CBF and cognitive decline, as well as a possible role of AD-like pathological burden. Further studies in MMD will provide opportunities to explore new treatment strategies.

Long-term study of the cognitive profile of Moyamoya Disease in adults

Moyamoya Disease (MMD) is a rare cerebrovascular disorder which can have significant cognitive consequences. The aim of the current study was to describe comprehensively the domain-specific cognitive profile of adult patients with MMD and to assess whether this changes in the absence of recurrent stroke over long-term follow-up. Comprehensive neuropsychological assessment covering seven cognitive domains was conducted on 61 adult patients with MMD at baseline and then at up to 3 further time points during follow up (median=2.31, 4.87 and 7.12 years). Although 27 patients had had prior surgical revasculariation, none had surgery between neuropsychological assessments. Cognitive impairment was common. At baseline, impairment in executive functions was most frequent (57%), followed by performance IQ (36%), speed of information processing (31%) and visual memory (30%). We found that the neuropsychological profile remains broadly stable over long-term follow-up with no clear indication of improvement or significant decline. The pattern of impairment also did not differ depending on age of onset or whether there was a history of either prior stroke at presentation or revascularisation surgery at presentation.

Characteristics and Clinical Implication of White Matter Lesions in Patients With Adult Moyamoya Disease

BACKGROUND AND OBJECTIVES

White matter hyperintensities (WMHs) are reportedly increased in moyamoya disease (MMD); however, their clinical importance is not well-established owing to their pathophysiologic heterogeneity by distribution. This study aimed to evaluate the burden and pattern of WMHs and its clinical implications in the MMD trajectory.

METHODS

Adult patients with MMD without significant structural lesions were 1:1 propensity score-matched with healthy controls for sex and vascular risk factors. The total, periventricular, and subcortical WMH volumes were segmented and quantified fully automatically. WMH volumes were detrended by age and compared between the 2 groups. MMD severity based on Suzuki stage and future ischemic events were assessed for their association with WMH volumes.

RESULTS

A total of 161 pairs of patients with MMD and controls were analyzed. MMD significantly correlated with increased total WMH volume (B [standard error], 0.126 [0.030]; p < 0.001), periventricular WMH volume (0.114 [0.027]; p < 0.001), and periventricular-to-subcortical ratio (0.090 [0.034]; p = 0.009). In the MMD subgroup (n = 187), advanced MMD had an independent association with the total WMH volume (0.120 [0.035]; p < 0.001), periventricular WMH volume (0.110 [0.031]; p < 0.001), and periventricular-to-subcortical ratio (0.139 [0.038]; p < 0.001). Periventricular WMH volume (adjusted hazard ratio [95% confidence interval], 5.12 [1.26-20.79]) and periventricular-to-subcortical ratio (3.80 [1.51-9.56]) were associated with future ischemic events in patients with medically followed up MMD. However, no demonstrable association was found between subcortical WMH volume and MMD, MMD severity, or future ischemic events.

DISCUSSION

Periventricular WMHs, but not subcortical WMHs, may represent the main pathophysiology of MMD. Periventricular WMHs may be used as a marker for ischemic vulnerability in patients with MMD.

Two adult patients with moyamoya disease presenting with alexia with agraphia limited to kanji: can revascularization improve characteristic symptoms?

Patients with moyamoya disease (MMD) may exhibit higher brain dysfunction due to hypoperfusion, which may be ameliorated by revascularization. However, few studies have examined the relationship between cerebral perfusion and language function or the ameliorating effect of revascularization on language dysfunction. We present two cases with MMD who presented with alexia with agraphia, specifically for Japanese kanji. The patients had impaired perfusion in the left inferior temporal and lateral occipital lobes. Following superficial temporal artery-middle cerebral artery bypass, the symptoms improved dramatically. Thus, correction of hypoperfusion may be effective even in adult patients with MMD presenting with language dysfunction.

Association between White Matter Hyperintensities Burden and Cognitive Function in Adult Asymptomatic Moyamoya Disease

Background and Purpose: White matter hyperintensities (WMH) caused by chronic cerebral hypoperfusion are common in Moyamoya disease (MMD) patients, but WMH burden with comprehensive cognition in adult asymptomatic MMD remains unknown. This study tried to investigate the association between the WMH burden and cognitive function in adult asymptomatic MMD. Methods: Sixty-four adult asymptomatic MMD patients without surgical revascularization were enrolled in this study and underwent a 3T MRI scan and complete cognitive tests from 2021 to 2022. WMH volume was extracted with brain anatomical analysis using the diffeomorphic deformation (BAAD) toolbox, which works on SPM 12 software. Multivariable linear regression analysis was performed to assess the association between WMH burden and cognitive function in asymptomatic MMD. Results: Firstly, our data showed that lower education levels and higher WMH burden were strongly related to global cognitive impairment after adjusting for other variables. Secondly, WMH severity was significantly associated with several domains of neurocognitive function, including memory, semantic memory, and executive function. Finally, when stratified by sex, the female participants with WMH severity had lower cognitive performance in all areas than male participants. Conclusions: These results suggest that WMH burden was highly correlated with global cognition, memory, semantic memory, and executive function in asymptomatic MMD. Especially in female participants, the relationship became more evident.

Preoperative Brain Functional Connectivity Improve Predictive Accuracy of Outcomes After Revascularization in Moyamoya Disease

BACKGROUND

In patients with moyamoya disease (MMD), focal impairments in cerebral hemodynamics are often inconsistent with patients' clinical prognoses. Evaluation of entire brain functional networks may enable predicting MMD outcomes after revascularization.

OBJECTIVE

To investigate whether preoperative brain functional connectivity could predict outcomes after revascularization in MMD.

METHODS

We included 34 patients with MMD who underwent preoperative MRI scanning and combined revascularization surgery. We used region of interest analyses to explore the differences in functional connectivity for 90 paired brain regions between patients who had favorable outcomes 1 year after surgery (no recurrent stroke, with improved preoperative symptoms, or modified Rankin Scale [mRS]) and those who had unimproved outcomes (recurrent stroke, persistent symptoms, or declined mRS). Variables, including age, body mass index, mRS at admission, Suzuki stage, posterior cerebral artery involvement, and functional connectivity with significant differences between the groups, were included in the discriminant function analysis to predict patient outcomes.

RESULTS

Functional connectivity between posterior cingulate cortex and paracentral lobule within the right hemisphere, and interhemispheric connection between superior parietal gyrus and middle frontal gyrus, precuneus and middle cingulate cortex, cuneus and precuneus, differed significantly between the groups (P < .001, false discovery rate corrected) and had the greatest discriminant function in the prediction model. Although clinical characteristics of patients with MMD showed great accuracy in predicting outcomes (64.7%), adding information on functional connections improved accuracy to 91.2%.

CONCLUSION

Preoperative functional connectivity derived from rs-fMRI may be an early hallmark for predicting patients' prognosis after revascularization surgery for MMD.

18F-FDG PET and a classifier algorithm reveal a characteristic glucose metabolic pattern in adult patients with moyamoya disease and vascular cognitive impairment

Vascular cognitive impairment (VCI) is a critical issue in moyamoya disease (MMD). However, the glucose metabolic pattern in these patients is still unknown. This study aimed to identify the metabolic signature of cognitive impairment in patients with MMD using ¹⁸F-2-fluoro-2-deoxy-D-glucose positron emission tomography (¹⁸F-FDG PET) and establish a classifier to identify VCI in patients with MMD. One hundred fifty-two patients with MMD who underwent brain ¹⁸F-FDG PET scans before surgery were enrolled and classified into nonvascular cognitive impairment (non-VCI, n = 52) and vascular cognitive impairment (VCI, n = 100) groups according to neuropsychological test results. Additionally, thirty-three health controls (HCs) were also enrolled. Compared to HCs, patients in the VCI group exhibited extensive hypometabolism in the bilateral frontal and cingulate regions and hypermetabolism in the bilateral cerebellum, while patients in the non-VCI group showed hypermetabolism only in the cerebellum and slight hypometabolism in the frontal and temporal regions. In addition, we found that the patients in the VCI group showed hypometabolism mainly in the left basal ganglia compared to those in the non-VCI group. The sparse representation-based classifier algorithm taking the SUVr of 116 Anatomical Automatic Labeling (AAL) areas as features distinguished patients in the VCI and non-VCI groups with an accuracy of 82.4%. This study demonstrated a characteristic metabolic pattern that can distinguish patients with MMD without VCI from those with VCI, namely, hypometabolic lesions in the left hemisphere played a more important role in cognitive decline in patients with MMD.

Atrophy in subcortical gray matter in adult patients with moyamoya disease

BACKGROUND

Acute cerebrovascular accidents, long-term hypoperfusion, and/or remote neuronal degeneration may lead to structural alterations in patients with moyamoya disease (MMD). This study sought to comprehensively investigate the distribution characteristics of subcortical gray matter volume and their correlations with angiographic changes in the intracranial artery in patients with MMD.

METHOD

One hundred forty-two patients with MMD and 142 age- and sex-matched healthy controls underwent 3-dimensional high-resolution structural magnetic resonance imaging. Volumes of subcortical gray matter and subregions of the hippocampus and amygdala were calculated, and the degree of stenosis/occlusion of intracranial arteries in patients with MMD was evaluated on MR angiography.

RESULTS

Volume reductions in the thalamus, caudate, putamen, hippocampus, amygdala, pallidum, and nucleus accumbens were found in patients with MMD. Hippocampal subfields and amygdala subnuclei in patients with MMD showed distinct vulnerability, and morphological alterations in specific subregions were more obvious than in the whole hippocampus/amygdala. Volume loss in several subcortical areas was related to disease duration and intracranial arterial changes.

CONCLUSIONS

Our findings revealed structural alteration patterns of subcortical gray matter in MMD. The specific atrophy in subregions of the hippocampus and the amygdala suggested potential cognitive and affective impairments in MMD, which warrants further investigation. Chronic cerebral hemodynamic alterations in MMD may play a pivotal role in morphological changes in subcortical areas.

White matter structural and network topological changes in moyamoya disease with limb paresthesia: A study based on diffusion kurtosis imaging

Purpose

To investigate the structural and network topological changes in the white matter (WM) in MMD patients with limb paresthesia by performing diffusion kurtosis imaging (DKI).

Materials and methods

A total of 151 MMD patients, including 46 with left-limb paresthesia (MLP), 52 with right-limb paresthesia (MRP), and 53 without paresthesia (MWP), and 28 healthy controls (HCs) underwent whole-brain DKI, while the surgical patients were reexamined 3-4 months after revascularization. The data were preprocessed to calculate the fractional anisotropy (FA) and mean kurtosis (MK) values. Voxel-wise statistics for FA and MK images were obtained by using tract-based spatial statistics (TBSS). Next, the whole-brain network was constructed, and global and local network parameters were analyzed using graph theory. All parameters were compared among the HC, MWP, MLP, and MRP groups, and changes in the MMD patients before and after revascularization were also compared.

Results

The TBSS analysis revealed significant reductions in FA and MK in extensive WM regions in the three patient groups. In comparison with the MWP group, the MLP group showed reductions in FA and MK in both right and left WM, mainly in the right WM, while the MRP group mainly showed a reduction in FA in the left WM region and demonstrated no significant change in MK. The graph theoretical analysis showed decreased global network efficiency, increased characteristic path length, and increased sigma in the MWP, MRP, and MLP groups in comparison with the HC group. Among local network parameters, the nodal efficiency decreased in the bilateral MFG and IFGtriang, while the degree decreased in the MFG.L and bilateral IFGtriang. Patients with right-limb paresthesia showed the lowest nodal efficiency and degree in MFG.L and IFGtriang.L, while those with left-limb paresthesia showed the lowest nodal efficiency in MFG.R and IFGtriang.R and the lowest degree in IFGtriang.R.

Conclusion

A DKI-based whole-brain structural and network analysis can be used to detect changes in WM damage and network topological changes in MMD patients with limb paresthesia. FA is more sensitive than MK in detecting WM injury, while MFG and IFGtriang are the key nodes related to the development of acroparesthesia.

Application of DTI and fMRI in moyamoya disease

Moyamoya disease (MMD) is a chronic and progressive cerebrovascular stenosis or occlusive disease that occurs near Willis blood vessels. Diffusion tensor imaging (DTI) and functional magnetic resonance imaging (fMRI) are used to detect the microstructure of white matter and the function of gray matter, respectively. The damage of these structures will lead to the change of cognitive level in patients with moyamoya disease. In this paper, the principles of DTI and fMRI, their applications and challenges in moyamoya disease are reviewed.

Reorganization of the Brain Structural Covariance Network in Ischemic Moyamoya Disease Revealed by Graph Theoretical Analysis

Objective

Ischemic moyamoya (MMD) disease could alter the cerebral structure, but little is known about the topological organization of the structural covariance network (SCN). This study employed structural magnetic resonance imaging and graph theory to evaluate SCN reorganization in ischemic MMD patients.

Method

Forty-nine stroke-free ischemic MMD patients and 49 well-matched healthy controls (HCs) were examined by T1-MPRAGE imaging. Structural images were pre-processed using the Computational Anatomy Toolbox 12 (CAT 12) based on the diffeomorphic anatomical registration through exponentiated lie (DARTEL) algorithm and both the global and regional SCN parameters were calculated and compared using the Graph Analysis Toolbox (GAT).

Results

Most of the important metrics of global network organization, including characteristic path length (Lp), clustering coefficient (Cp), assortativity, local efficiency, and transitivity, were significantly reduced in MMD patients compared with HCs. In addition, the regional betweenness centrality (BC) values of the bilateral medial orbitofrontal cortices were significantly lower in MMD patients than in HCs after false discovery rate (FDR) correction for multiple comparisons. The BC was also reduced in the left medial superior frontal gyrus and hippocampus, and increased in the bilateral middle cingulate gyri of patients, but these differences were not significant after FDR correlation. No differences in network resilience were detected by targeted attack analysis or random failure analysis.

Conclusions

Both global and regional properties of the SCN are altered in MMD, even in the absence of major stroke or hemorrhagic damage. Patients exhibit a less optimal and more randomized SCN than HCs, and the nodal BC of the bilateral medial orbitofrontal cortices is severely reduced. These changes may account for the cognitive impairments in MMD patients.

Moyamoya Disease With Initial Ischemic or Hemorrhagic Attack Shows Different Brain Structural and Functional Features: A Pilot Study

Objective

Cerebral ischemia and intracranial hemorrhage are the two main phenotypes of moyamoya disease (MMD). However, the pathophysiological processes of these two MMD phenotypes are still largely unknown. Here, we aimed to use multimodal neuroimaging techniques to explore the brain structural and functional differences between the two MMD subtypes.

Methods

We included 12 patients with ischemic MMD, 10 patients with hemorrhagic MMD, and 10 healthy controls (HCs). Each patient underwent MRI scans and cognitive assessment. The cortical thickness of two MMD subtypes and HC group were compared. Arterial spin labeling (ASL) and diffusion tensor imaging (DTI) were used to inspect the cerebral blood flow (CBF) of cortical regions and the integrity of related white matter fibers, respectively. Correlation analyses were then performed among the MRI metrics and cognitive function scores.

Results

We found that only the cortical thickness in the right middle temporal gyrus (MTG) of hemorrhagic MMD was significantly greater than both ischemic MMD and HC (p < 0.05). In addition, the right MTG showed higher ASL-CBF, and its associated fiber tract (arcuate fasciculus, AF) exhibited higher fractional anisotropy (FA) values in hemorrhagic MMD. Furthermore, the cortical thickness of the right MTG was positively correlated with its ASL-CBF values (r = 0.37, p = 0.046) and the FA values of right AF (r = 0.67, p < 0.001). At last, the FA values of right AF were found to be significantly correlated with cognitive performances within patients with MMD.

Conclusions

Hemorrhagic MMD shows increased cortical thickness on the right MTG in comparison with ischemic MMD and HCs. The increased cortical thickness is associated with the higher CBF values and the increased integrity of the right AF. These findings are important to understand the clinical symptoms and pathophysiology of MMD and further applied to clinical practice.

Moyamoya disease: A human model for chronic hypoperfusion and intervention in Alzheimer's disease

Introduction

Chronic cerebral hypoperfusion has been considered the etiology for sporadic Alzheimer's disease (AD). However, no valid clinical evidence exists due to the similar risk factors between cerebrovascular disease and AD.

Methods

We used moyamoya disease (MMD) as a model of chronic hypoperfusion and cognitive impairment, without other etiology interference.

Results

Based on the previous reports and preliminary findings, we hypothesized that chronic cerebral hypoperfusion could be an independent upstream crucial variable, resulting in AD, and induce pathological hallmarks such as amyloid beta peptide and hyperphosphorylated tau accumulation.

Discussion

Timely intervention with revascularisation would help reverse the brain damage with AD hallmarks and lead to cognitive improvement.

Predictors of preoperative cognitive dysfunction in adults with Moyamoya disease: a preliminary research

OBJECTIVE

To explore potential risk factors of preoperative cognitive dysfunction in adult patients with moyamoya disease (MMD) and discuss significance of moyamoya vessels.

METHODS

The author reviewed adult MMD patients harboring no parenchymal infarction or hemorrhage underwent a standardized neuropsychological assessment test battery from December 2018 to May 2019. The authors defined patients with cognitive dysfunction as cognitive impairment shown on 3 or more neuropsychological tests. According to the presence of cerebral angiography, arterial stenosis, moyamoya vessels, and compensatory arteries were conducted. Univariate and multivariate analyses were performed to identify predictors for cognitive dysfunction before surgery. Subgroup analyses by onset type and Suzuki stage were carried out to identify specific predictors for preoperative cognitive dysfunction.

RESULTS

In total, 29 of 92 (31.52%) patients had cognitive dysfunction. Multivariate analysis showed that moyamoya vessels generating from left hemisphere was recognized as independent predictor for cognitive dysfunction (P = 0.025, OR [95%CI], 0.085 [0.012-0.874]). For patients in left ICA-moyamoya subgroup, 19 of 45 (42.22%) cases with sparse moyamoya vessels had cognitive dysfunction (P = 0.031), while 22 (91.67%) of patients with dense moyamoya vessels had normal cognition (P = 0.004). Moyamoya vessels arising from ophthalmic artery had no significant association with cognitive dysfunction (P = 0.111). Multivariate analysis found that moyamoya vessels originating from left ICA was recognized as independent predictors for preoperative cognitive dysfunction (P = 0.048, OR [95%CI], 0.394 [0.132-0.926]).

CONCLUSIONS

Moyamoya vessels arising from left hemisphere was a risk factor for the preoperative cognitive dysfunction in adult patients with MMD, with the denser moyamoya vessels, the less cognitive dysfunction. The current study offers a new perspective of moyamoya vessels and supporting data for choosing MMD candidates on cerebral revascularization.

Structural Abnormalities in Pediatric Moyamoya Disease Revealed by Clinical Magnetic Resonance Imaging, Regionally Distributed Relative Signal Intensities and Volumes

Moyamoya disease (MMD) is a rare, progressive cerebrovascular disorder, with an unknown etiology and pathogenesis. It is characterized by steno-occlusive changes at the terminal portion of the internal carotid artery (ICA), which is accompanied by variable development of the basal collaterals called moyamoya vessels. In this study, we investigate the potential for structural T1 magnetic resonance imaging (MRI) to help characterize MMD clinically, with the help of regionally distributed relative signal intensities (RRSIs) and volumes (RRVs). These RRSIs and RRVs provide the ability to characterize aspects of regional brain development and represent an extension to existing automated biomarker extraction technologies. This study included 269 MRI examinations from MMD patients and 993 MRI examinations from neurotypical controls, with regional biomarkers compared between groups with the area under the receiver operating characteristic curve (AUC). Results demonstrate abnormal presentation of RRSIs and RRVs in the insula (15-20 year old cohort, left AUC: 0.74, right AUC: 0.71), and the lateral orbitofrontal region (5-10 year old cohort, left AUC: 0.67; 15-20 year cohort, left AUC: 0.62, right AUC: 0.65). Results indicate that RRSIs and RRVs may help in characterizing brain development, assist in the assessment of the presentation of the brains of children with MMD, and may help overcome standardization challenges in multi-protocol clinical MRI. Further investigation of the potential for RRSIs and RRVs in clinical imaging is warranted and supported through the release of open source software.

Changes of cerebral cortical structure and cognitive dysfunction in "healthy hemisphere" after stroke: a study about cortical complexity and sulcus patterns in bilateral ischemic adult moyamoya disease

Background

Moyamoya disease (MMD) is an uncommon cerebrovascular disease which leads to progressive stenosis and occlusion of the bilateral internal carotid artery and main intracerebral arteries. Concerns are always on how the hemisphere with infarction affects cognitive function, while little attention is paid to the role that the non-infarcted hemisphere plays. Therefore, we aimed to detect cortical indexes, especially cortical complexity in the left or right hemisphere separately in patients with MMD after stroke.

Methods

28 patients with MMD (14 males, 14 females) and 14 healthy controls were included in this study. All participants underwent cognitive tests and magnetic resonance imaging (MRI) scan. The preprocessing of three-dimensional T1 weighted images were performed by standard surface-based morphometry. Surface-based morphometry statistical analysis was carried out with a threshold of False Discovery Rate (FDR) P < 0.05 and fractal dimension (FD) was used to provide a quantitative description of cerebral cortical complexity.

Results

Widespread cognitive dysfunctions were found in MMD patient with stroke. Extensive FD reduction in the left hemisphere with right-sided infarction, mainly in the superior temporal, inferior frontal, and insula, while the post central gyrus, superior parietal, and inferior parietal gyrus also showed a wide range of significant differences (FDR corrected P < 0.05). Meanwhile, FD changes in the right hemisphere with left-sided infarction are restricted to the precuneus and cingulate isthmus (FDR corrected P < 0.05).

Conclusions

Extensive cognitive impairment was reconfirmed in Moyamoya disease with stroke, while wild and asymmetrical decrease of cortical complexity is observed on both sides. These differences could be relative to unbalanced cognitive dysfunction, and may be the result of a long-term chronic ischemia and compensatory of the contralateral hemisphere to the infarction.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12868-021-00672-x.

Changes in Brain Functional Network Connectivity in Adult Moyamoya Diseases

Moyamoya disease (MMD) is a cerebrovascular disease that is characterized by progressive stenosis or occlusion of the internal carotid arteries and its main branches, which leads to the formation of abnormal small collateral vessels. However, little is known about how these special vascular structures affect cortical network connectivity and brain function. By applying EEG analysis and graphic network analyses undergoing EEG recording of subjects with eyes-closed (EC) and eyes-open (EO) resting states, and working memory (WM) tasks, we examined the brain network features of hemorrhagic (H_MMD) and ischemic MMD (I_MMD) brains. For the first time, we observed that I_MMD had the much lower alpha-blocking rate during EO state than healthy controls while H_MMD exhibited the relatively low EEG activity rate across all the behavior states. Further, I_MMD showed strong network connections in the alpha-wave band in frontal and parietal regions during EO and WM states. EEG frequency and network topological maps during both resting and WM states indicated that the left frontal lobe and left parietal lobe in H_MMD patients and the right parietal lobe and temporal lobe in I_MMD patients have clear differences compared with controls, which provides a new insight to understand distinct electrophysiological features of MMD. However, due to the small sample size of recruited patient subjects, the result conclusion may be limited.

Supplementary information

The online version contains supplementary material available at (10.1007/s11571-021-09666-1).

Clinical Management of Moyamoya Patients

Moyamoya angiopathy (MMA) is a peculiar cerebrovascular condition characterized by progressive steno-occlusion of the terminal part of the internal carotid arteries (ICAs) and their proximal branches, associated with the development of a network of fragile collateral vessels at the base of the brain. The diagnosis is essentially made by radiological angiographic techniques. MMA is often idiopathic (moyamoya disease-MMD); conversely, it can be associated with acquired or hereditary conditions (moyamoya Syndrome-MMS); however, the pathophysiology underlying either MMD or MMS has not been fully elucidated to date, and this poor knowledge reflects uncertainties and heterogeneity in patient management. MMD and MMS also have similar clinical expressions, including, above all, ischemic and hemorrhagic strokes, then headaches, seizures, cognitive impairment, and movement disorders. The available treatment strategies are currently shared between idiopathic MMD and MMS, including pharmacological and surgical stroke prevention treatments and symptomatic drugs. No pharmacological treatment able to reverse the progressive disappearance of the ICAs has been found to date in both idiopathic and syndromic cases. Antithrombotic agents are usually prescribed in ischemic MMA, although the coexisting hemorrhagic risk should be considered. Surgical revascularization techniques, which are currently the best available treatment in symptomatic MMA, are associated with good long-term outcomes and reduced ischemic and hemorrhagic risks. Given the lack of dedicated randomized clinical trials, current treatment is mainly based on observational studies and physicians’ and surgeons’ expertise.

Cortical thickness in clinical moyamoya disease: A magnetic resonance imaging study

Moyamoya disease (MMD) is a progressive cerebrovascular disorder, with an unknown pathogenesis and aetiology. MMD is characterized by steno-occlusive changes at the terminal portion of the internal carotid artery (ICA), which is accompanied by variable development of the basal collaterals, also known as moyamoya vessels. Patients with MMD show variable patterns of brain damage and may experience recurrent multiple transient ischaemic attacks, intracranial bleeding and cerebral infarction. In this study, we investigate the potential for structural T1 magnetic resonance imaging (MRI) to help characterize abnormal cortical development in MMD clinically, with an analysis of both average and variability of regional cortical thicknesses. This study also included a machine learning analysis to assess the predictive capacity of the cortical thickness abnormalities observed in this research. This study included 993 MRI examinations from neurotypical controls and 269 MRI examinations from MMD patients. Results demonstrate abnormal cortical presentation of the insula, caudate, postcentral, precuneus and cingulate regions, in agreement with previous literature cortical thickness findings as well as alternative methods such as functional MRI (fMRI) and digital angiography. To the best of our knowledge, this is the first manuscript to report cortical thickness abnormalities in the middle temporal visual area in MMD and the first study to report on cortical thickness variability abnormalities in MMD.

Proteomic Profiling of Exosomes From Hemorrhagic Moyamoya Disease and Dysfunction of Mitochondria in Endothelial Cells

BACKGROUND AND PURPOSE

Moyamoya disease (MMD) is a rare steno-occlusive and slowly progressing cerebrovascular disorder. The detailed mechanism of the underlying pathogenesis is still blurry.

METHODS

Tandem Mass Tag-labeled quantitative proteomics was performed on serum-derived exosomes (SDEs) extracted from adult patients diagnosed with pure ischemic MMD or hemorrhagic MMD and healthy controls. Then mouse brain vascular endothelial cell (EC), human umbilical vein EC, neuroblastoma cell, and human hepatocyte cell were treated with exosomes, and changes of the protein expression in mouse brain vascular EC cells were identified.

RESULTS

Proteomics analysis results showed that 859 shared proteins were detected in SDEs from ischemic and hemorrhagic MMD patients with 231 differently expressed compared with healthy controls. Bioinformatic analysis revealed dysregulated cell growth and maintenance and indicated disturbed actin dynamics in MMD, with CFL1 (Cofilin-1) and ACTR2/3 (actin-related protein 2/3; also known as ARP2/3) downregulated in ischemic and hemorrhagic patients' SDEs. We also found immunity dysfunction in hemorrhagic MMD. Following treatment with MMD SDEs, mouse brain vascular EC cells showed significantly higher levels of proliferation and more ethynyl-2-deoxyuridine-positive cells compared with the healthy control group, while there were no obvious changes in the human umbilical vein EC and human hepatocyte cell. Interestingly, we also found that SDEs from ischemic MMD promoted neuroblastoma cell proliferation. Proteomic analysis of mouse brain vascular EC cells suggested that SDEs from hemorrhagic MMD patients induced dysfunction of the mitochondria in cerebrovascular ECs.

CONCLUSIONS

This study highlighted potential molecular mechanisms underlying the pathogenesis of MMD patients, thereby providing new therapeutic strategies for MMD.

Reconfigured functional network dynamics in adult moyamoya disease: a resting-state fMRI study

Treatment of vascular cognitive impairment (VCI) in adult moyamoya disease (MMD) is still unclear because of its unveiled neural synchronization. This study introduced a dynamic measurement of connectivity number entropy (CNE) to characterize both spatial and temporal dimensions of network interactions. Fifty-one patients with MMD were recruited (27 with VCI and 24 with intact cognition), as well as 26 normal controls (NCs). Static network properties were first examined to confirm its aberrance in MMD with VCI. Then, the dynamic measurement of CNE was used to detect the deteriorated flexibility of MMD with VCI at global, regional, and network levels. Finally, dynamic reconfiguration of flexible and specialized regions was traced across the three groups. Graph theory analysis indicated that MMD exhibited "small-world" network topology but presented with a deviating pattern from NC as the disease progressed in all topologic metrics of integration, segregation, and small-worldness. Subsequent dynamic analysis showed significant CNE differences among the three groups at both global (p < 0.001) and network levels (default mode network, p = 0.004; executive control network, p = 0.001). Specifically, brain regions related to key aspects of information processing exhibited significant CNE changes across the three groups. Furthermore, CNE values of both flexible and specialized regions changed with impaired cognition. This study not only sheds light on both the static and dynamic organizational principles behind network changes in adult MMD for the first time, but also provides a new methodologic viewpoint to acquire more knowledge of its pathophysiology and treatment direction.

Faded Critical Dynamics in Adult Moyamoya Disease Revealed by EEG and fMRI

Criticality is considered a dynamic signature of healthy brain activity that can be measured on the short-term timescale with neural avalanches and long-term timescale with long-range temporal correlation (LRTC). It is unclear how the brain dynamics change in adult moyamoya disease (MMD). We used BOLD-fMRI for LRTC analysis from 16 hemorrhagic (H_MMD) and 34 ischemic (I_MMD) patients and 25 healthy controls. Afterwards, they were examined by EEG recordings in the eyes-closed (EC), eyes-open (EO), and working memory (WM) states. The EEG data of 11 H_MMD and 13 I_MMD patients and 21 healthy controls were in good quality for analysis. Regarding the 4 metrics of neural avalanches (e.g., size (α), duration (β), κ value, and branching parameter (σ)), both MMD subtypes exhibited subcritical states in the EC state. When switching to the WM state, H_MMD remained inactive, while I_MMD surpassed controls and became supercritical (p < 0.05). Regarding LRTC, the amplitude envelope in the EC state was more analogous to random noise in the MMD patients than in controls. During state transitions, LRTC decreased sharply in the controls but remained chaotic in the MMD individuals (p < 0.05). The spatial LRTC reduction distribution based on both EEG and fMRI in the EC state implied that, compared with controls, the two MMD subtypes might exhibit mutually independent but partially overlapping patterns. The regions showing decreased LRTC in both EEG and fMRI were the left supplemental motor area of H_MMD and right pre-/postcentral gyrus and right inferior temporal gyrus of I_MMD. This study not only sheds light on the decayed critical dynamics of MMD in both the resting and task states for the first time but also proposes several EEG and fMRI features to identify its two subtypes.

Linking cortical astrocytic neogenin deficiency to the development of Moyamoya disease-like vasculopathy

Moyamoya-like vasculopathy, the "puff of smoke"-like small vessels in the brain, is initially identified in patients with Moyamoya disease (MMD), a rare cerebrovascular disease, and later found in patients with various types of neurological conditions, including Down syndrome, Stroke, and vascular dementia. It is thus of interest to understand how this vasculopathy is developed. Here, we provided evidence for cortical astrocytic neogenin (NEO1) deficiency to be a risk factor for its development. NEO1, a member of deleted in colorectal cancer (DCC) family netrin receptors, was reduced in brain samples of patients with MMD. Astrocytic Neo1-loss resulted in an increase of small blood vessels (BVs) selectively in the cortex. These BVs were dysfunctional, with leaky blood-brain barrier (BBB), thin arteries, and accelerated hyperplasia in veins and capillaries, resembled to the features of moyamoya-like vasculopathy. Additionally, we found that both MMD patient and Neo1 mutant mice exhibited altered gene expression in their cortex in proteins critical for not only angiogenesis [e.g., an increase in vascular endothelial growth factor (VEGFa)], but also axon guidance (e.g., netrin family proteins) and inflammation. In aggregates, these results suggest a critical role of astrocytic NEO1-loss in the development of Moyamoya-like vasculopathy, providing a mouse model for investigating mechanisms of Moyamoya-like vasculopathy.

Gut microbiota from mice with cerebral ischemia-reperfusion injury affects the brain in healthy mice

Gut microorganisms can profoundly influence brain function in the host and their behavior. Since altered brain functional connectivity (FC) has been implicated in various cerebrovascular disorders, including cerebral ischemia-reperfusion (I/R) injury, we hypothesized that gut microbiota in mice with cerebral I/R injury would affect brain FC when transplanted into germ-free mice. Metagenomic analysis of germ-free male C57BL/6J mice colonized with microbiota from mice with and without cerebral I/R injury showed a clear distinction in microbiota composition between mice colonized with control and I/R microbiota. The I/R microbiota-colonized mice showed decreased FC in the cingulate cortex, hippocampus, and thalamus, and exhibited increased anxiety as well as diminished spatial learning and memory and short-term object recognition memory. I/R microbiota-colonized mice also had significantly reduced dendritic spine density and synaptic protein levels and exhibited increased hippocampal inflammation. These results indicate that gut microbiota components from mice with cerebral I/R injury can alter animal behavior, brain functional connectivity, hippocampal neuronal plasticity, and neuroinflammation. Moreover, they increase our understanding of the mechanisms through which the gut microbiome contributes to the pathobiology of cerebrovascular diseases.

Combined structural and diffusion tensor imaging detection of ischemic injury in moyamoya disease: relation to disease advancement and cerebral hypoperfusion

OBJECTIVE

The microstructural integrity of gray and white matter is decreased in adult moyamoya disease, suggesting covert ischemic injury as a mechanism of cognitive dysfunction. Establishing a microstructural brain imaging marker is critical for monitoring cognitive outcomes following surgical interventions. The authors of the present study determined the pathophysiological basis of altered microstructural brain injury in relation to advanced arterial occlusion, cerebral hypoperfusion, and cognitive function.

METHODS

The authors examined 58 patients without apparent brain lesions and 30 healthy controls by using structural MRI, as well as diffusion tensor imaging (DTI). Arterial occlusion in each hemisphere was classified as early or advanced stage based on MRA and posterior cerebral artery (PCA) involvement. Regional cerebral blood flow (rCBF) was measured with N-isopropyl-p-[123I]-iodoamphetamine SPECT. Furthermore, cognitive performance was examined using the Wechsler Adult Intelligence Scale, Third Edition and the Trail Making Test (TMT). Both voxel- and region of interest-based analyses were performed for groupwise comparisons, as well as correlation analysis, using parameters such as cognitive test scores; gray matter volume; fractional anisotropy (FA) of association fiber tracts, including the inferior frontooccipital fasciculus (IFOF) and superior longitudinal fasciculus (SLF); PCA involvement; and rCBF.

RESULTS

Compared to the early stages, advanced stages of arterial occlusion in the left hemisphere were associated with a lower Performance IQ (p = 0.031), decreased anterior cingulate volumes (p = 0.0001, uncorrected), and lower FA in the IFOF, cingulum, and forceps major (all p < 0.01, all uncorrected). There was no significant difference in rCBF between the early and the advanced stage. In patients with an advanced stage, PCA involvement was correlated with a significantly lower Full Scale IQ (p = 0.036), cingulate volume (p < 0.01, uncorrected), and FA of the left SLF (p = 0.0002, uncorrected) compared to those with an intact PCA. The rCBF was positively correlated with FA of the SLF, IFOF, and forceps major (r > 0.34, p < 0.05). Global gray matter volumes were moderately correlated with TMT part A (r = 0.40, p = 0.003). FA values in the left SLF were moderately associated with processing speed (r = 0.40, p = 0.002).

CONCLUSIONS

Although hemodynamic compensation may mask cerebral ischemia in advanced stages of adult moyamoya disease, the disease progression is detrimental to gray and white matter microstructure as well as cognition. In particular, additional PCA involvement in advanced disease stages may impair key neural substrates such as the cingulum and SLF. Thus, combined structural MRI and DTI are potentially useful for tracking the neural integrity of key neural substrates associated with cognitive function and detecting subtle anatomical changes associated with persistent ischemia, as well as disease progression.

Recognition of Cognitive Impairment in Adult Moyamoya Disease: A Classifier Based on High-Order Resting-State Functional Connectivity Network

Objective: Vascular cognitive impairment (VCI) is a common complication in adult patients with moyamoya disease (MMD), and is reversible by surgical revascularization in its early stage of mild VCI. However, accurate diagnosis of mild VCI is difficult based on neuropsychological examination alone. This study proposed a method of dynamic resting-state functional connectivity (FC) network to recognize global cognitive impairment in MMD. Methods: For MMD, 36 patients with VCI and 43 patients with intact cognition (Non-VCI) were included, as well as 26 normal controls (NCs). Using resting-state fMRI, dynamic low-order FC networks were first constructed with multiple brain regions which were generated through a sliding window approach and correlated in temporal dimension. In order to obtain more information of network interactions along the time, high-order FC networks were established by calculating correlations among each pair of brain regions. Afterwards, a sparse representation-based classifier was constructed to recognize MMD (experiment 1) and its cognitive impairment (experiment 2) with features extracted from both low- and high-order FC networks. Finally, the ten-fold cross-validation strategy was proposed to train and validate the performance of the classifier. Results: The three groups did not differ significantly in demographic features (p > 0.05), while the VCI group exhibited the lowest MMSE scores (p = 0.001). The Non-VCI and NCs groups did not differ significantly in MMSE scores (p = 0.054). As for the classification between MMD and NCs, the area under the receiver operating characteristic curve (AUC), accuracy, sensitivity, and specificity of the classifier reached 90.70, 88.57, 93.67, and 73.08%, respectively. While for the classification between VCI and Non-VCI, the AUC, accuracy, sensitivity, and specificity of the classifier reached 91.02, 84.81, 80.56, and 88.37%, respectively. Conclusion: This study not only develops a promising classifier to recognize VCI in adult MMD in its early stage, but also implies the significance of time-varying properties in dynamic FC networks.

Using postoperative remodeling of donor arteries on MR angiography to predict the development of surgical collaterals in moyamoya disease

OBJECTIVE

The calibers of donor arteries can change dynamically after bypass surgery in patients with moyamoya disease (MMD). The present study aimed to evaluate the cutoffs of caliber changes in donor arteries associated with good surgical revascularization and to assess the impact of clinical factors potentially related to bypass development.

METHODS

The authors studied 71 hemispheres of 30 adults and 16 children with MMD who underwent combined direct and indirect revascularization. They quantitatively measured the calibers of the superficial temporal artery (STA), deep temporal artery (DTA), and middle meningeal artery (MMA) with MR angiography (MRA) source images and calculated the postoperative caliber change ratios (CCRs) to assess direct and indirect bypass development. These values were compared with the findings of digital subtraction angiography, in which revascularization areas were categorized into 3 groups (poor, good, and excellent).

RESULTS

In both adult and pediatric hemispheres, the median STA and DTA CCRs were higher in better-revascularization groups (p < 0.05), while MMA CCRs were not significantly different among the groups. Receiver operating characteristic analysis revealed that the cutoff STA CCRs of > 1.1 and > 1.3 were associated with good direct revascularization in adult and pediatric hemispheres, respectively. Cutoff DTA CCRs of > 1.6 and > 1.2 were associated with good indirect revascularization in adult and pediatric hemispheres, respectively. Considering these cutoff values, STA and DTA CCRs showed high median values, irrespective of age, severity of cerebrovascular reserve, disease stage, and disease-onset type.

CONCLUSIONS

Caliber changes in STAs and DTAs can be easily measured using MRA, and they could be indicators of direct and indirect bypass development. The dual development of a direct and indirect bypass was most frequently observed in the context of a combined bypass procedure in both adults and children with MMD.

Myelin and Axonal Damage in Normal-Appearing White Matter in Patients with Moyamoya Disease

BACKGROUND AND PURPOSE

Although chronic ischemia is known to induce myelin and axonal damage in animal models, knowledge regarding patients with Moyamoya disease is limited. We aimed to investigate the presence of myelin and axonal damage in Moyamoya disease and their relationship with cognitive performance.

MATERIALS AND METHODS

Eighteen patients with Moyamoya disease (16-55 years of age) and 18 age- and sex-matched healthy controls were evaluated with myelin-sensitive MR imaging based on magnetization transfer saturation imaging and 2-shell diffusion MR imaging. The myelin volume fraction, which reflects the amount of myelin sheath; the g-ratio, which represents the ratio of the inner (axon) to the outer (axon plus myelin) diameter of the fiber; and the axon volume fraction, which reflects axonal components, were calculated and compared between the patients and controls. In the patients with Moyamoya disease, the relationship between these parameters and cognitive task-measuring performance speed was also evaluated.

RESULTS

Compared with the healthy controls, the patients with Moyamoya disease showed a significant decrease in the myelin and axon volume fractions (P < .05) in many WM regions, while the increases in the g-ratio values were not statistically significant. Correlations with cognitive performance were most frequently observed with the axon volume fraction (r = 0.52-0.54; P < .03 in the right middle and posterior cerebral artery areas) and were the strongest with the g-ratio values in the right posterior cerebral artery region (r = 0.64; P = .004).

CONCLUSIONS

Myelin-sensitive MR imaging and diffusion MR imaging revealed that myelin and axonal damage exist in patients with Moyamoya disease. The relationship with cognitive performance might be stronger with axonal damage than with myelin damage.

Improvement in cognitive decline after indirect bypass surgery in adult moyamoya disease: implication of 15O-gas positron emission tomography

PURPOSE

To investigate the characteristics of patients with moyamoya disease (MMD) who show improvement in their cognitive decline after bypass surgery by analyzing the hemodynamic and metabolic parameters of ¹⁵O-gas positron emission tomography (PET).

MATERIALS AND METHODS

We retrospectively analyzed adult patients with MMD who were evaluated with PET and cognitive tests before and approximately one year after indirect bypass surgery. The PET parameters of the left Rolandic area were compared between patients who did and did not show improvement in their cognitive decline.

RESULTS

Of the 19 patients analyzed, fourteen (74%) showed improvement in either the verbal or performance intelligence quotient (VIQ or PIQ). Three out of four patients with perioperative infarction experienced significant cognitive decline. The preoperative oxygen extraction fraction (OEF) was significantly higher in patients who showed improvement in their cognitive decline in terms of the PIQ than in those patients who did not (P = 0.03). The postoperative increase in the cerebral metabolic rate of oxygen (CMRO₂) was significantly higher in patients who showed improvement in their cognitive decline in terms of the VIQ than in those who did not (P = 0.02).

CONCLUSION

Adult patients with MMD might show improvement in their cognitive decline after successful indirect bypass surgery if they have a severely increased regional OEF before the surgery and an increased regional CMRO₂ after the surgery.

CLINICAL TRIAL REGISTRATION

URL: https://www.umin.ac.jp/ctr/. Unique identifier: UMIN000027949.

Different aspects of cognitive function in adult patients with moyamoya disease and its clinical subtypes

Objective

Although a few reports suggested that cognitive function impairment could be found in adult patients with moyamoya disease (MMD), there were still many aspects that are unclear. The aim of our study was to assess the cognitive function of adult patients with MMD and its clinical subtypes.

Methods

49 patients with MMD and 23 healthy controls were asked to take cognitive function tests. Cognitive function tests included IQ, prospective memory (PM), immediate memory (IM), verbal fluency (VF), visual breadth, attention, retrospective memory (RM), Stroop test, Wisconsin Card Sorting Test, Trail-Making Test Part A (TMT-A) and Continuous Performance Test (CPT). Independent t-analysis, one-way analysis of variance and Pearson correlation were used to seek for differences between subgroups and the correlation between cognitive variables.

Results

Compared with healthy controls, adult patients with MMD had a comprehensive cognitive impairment, including IQ, PM, VF, attention, RM, Stroop, CPT and TMT-A, with more serious impairment in PM and attention. PM and RM were separated, indicating that they were independent of each other. Pattern of attention was significantly different from healthy controls. Female patients were better than male patients, where significant differences in PM, IM, Stroop and WCST could be found. The haemorrhagic patients exhibited poorer in the dimension of PM and RM than the ischaemic. The headache subtype exhibited poorer than healthy controls. PM, RM, attention and executive function were moderately correlated with each other.

Conclusions

Adult patients with MMD had a wide range of cognitive impairment with more serious impairment in memory and attention. Differences in cognitive function existed between the different subtypes of adult MMD.

MR Diffusional Kurtosis Imaging-Based Assessment of Brain Microstructural Changes in Patients with Moyamoya Disease before and after Revascularization

BACKGROUND AND PURPOSE

Conventional imaging examinations are insufficient to accurately assess brain damage in patients with Moyamoya disease. Our aim was to observe brain microstructural changes in patients with Moyamoya disease by diffusional kurtosis imaging and provide support data for application of this technique in individualized assessment of disease severity and surgical outcome among patients with Moyamoya disease.

MATERIALS AND METHODS

A total of 64 patients with Moyamoya disease and 15 healthy volunteers underwent diffusional kurtosis imaging, and a second scanning was offered to surgical patients 3-4 months after revascularization. The diffusional kurtosis imaging parameter maps were obtained for mean kurtosis, axial kurtosis, radial kurtosis, fractional anisotropy, mean diffusivity, axial diffusivity, and radial diffusivity. The parameter values were measured in sensory pathway-related regions for all subjects. Differences in diffusional kurtosis imaging parameters of these brain regions were examined for healthy volunteers, patients without acroparesthesia, and asymptomatic and symptomatic sides of patients with acroparesthesia. Changes in diffusional kurtosis imaging parameters of patients with Moyamoya disease before and after revascularization were compared.

RESULTS

Compared with healthy volunteers, patients with Moyamoya disease showed decreased mean kurtosis, axial kurtosis, radial kurtosis, and fractional anisotropy in the corona radiata. Similarly, mean kurtosis, radial kurtosis, and fractional anisotropy decreased in the posterior limb of the internal capsule, whereas axial kurtosis decreased and radial kurtosis increased in the thalami of patients with Moyamoya disease compared with healthy volunteers. Compared with the asymptomatic contralateral hemisphere, the symptomatic group showed increased mean kurtosis in the contralateral primary somatosensory cortex, increased fractional anisotropy in the contralateral corona radiata and posterior limb of the internal capsule, and decreased axial kurtosis in the contralateral thalamus. Among patients with Moyamoya disease with acroparesthesia, mean kurtosis decreased in the primary somatosensory cortex on the operated side following revascularization.

CONCLUSIONS

The diffusional kurtosis imaging technique is applicable to patients with Moyamoya disease for detecting brain microstructural changes in white and gray matter before and after revascularization; this feature is useful in the assessment of disease severity and surgical outcome.

Decreased frontal white-matter diffusion and improved cognitive flexibility after burr-hole surgery in moyamoya angiopathy

BACKGROUND

In Moyamoya Angioplasty (MMA), increased apparent diffusion coefficient (ADC) in frontal white matter (WM) with a normal appearance has been associated with frontal hypoperfusion and executive dysfunction. Multiple burr-hole surgery enables the revascularization of large frontal areas.

GOAL

To assess the effect of multiple burr-hole surgery on the ADC and cognitive functions in adults with MMA.

METHODS

ADC was measured in 26 brain hemispheres of 14 consecutive adults with MMA (9 women, mean age ± SD: 38.1 ± 10.7 years) prior to and 6 months after burr-hole surgery. ADC was obtained from regions of interest located in frontal and posterior (temporo-occipital) normal-appearing WM. Ten patients had neuropsychological assessment that focused on executive and attentional functions before and after surgery.

RESULTS

Anterior and posterior ADC values did not differ before surgery (815.8 ± 60.1 vs. 812.1 ± 35.3 mm²/s, p = 0.88). After surgery, frontal ADC was lower than prior to surgery (789.9 ± 64.5 vs. 815.8 ± 60.1 mm²/s; p <0.001) whereas no change occurred in posterior ADC (p = 0.31). Trail-making test part B median z-score increased from - 1.47 to - 0.21 (p = 0.018), suggesting improved cognitive flexibility.

CONCLUSION

In adults with MMA, indirect revascularization with burr-hole is followed by a decrease of ADC in normal-appearing frontal WM and may have improved some executive functions in the flexibility process. Change in ADC may reflect the improvement in cerebral perfusion after surgery. The measuring of ADC may be a promising tool in exploring potentially reversible microstructural WM damage related to hypoperfusion and cognitive change in MMA.

Association of cognitive function with cerebral blood flow in children with moyamoya disease

OBJECTIVE

The cognitive effects of main cerebral artery occlusive lesions are unclear in children with moyamoya disease (MMD). The authors aimed to investigate cognitive function in the presurgical phase of pediatric patients with MMD with no apparent brain lesions.

METHODS

In this prospective, observational, single-center study, 21 children (mean age 10 ± 3.0 years, range 5-14 years) diagnosed with MMD at Hokkaido University Hospital between 2012 and 2018 were enrolled. A cross-sectional evaluation of intellectual ability was performed using the Wechsler Intelligence Scale for Children-Fourth Edition at the initial diagnosis. rCBF was measured using [123I] N-isopropyl p-iodoamphetamine/SPECT. The associations among clinical factors, disease severity, regional cerebral blood flow (rCBF), and intelligence test scores were also examined.

RESULTS

The mean full-scale intelligence quotient (FIQ) was 101.8 ± 12.5 (range 76-125) in children with no apparent brain lesions. A significant difference in the intelligence scale index score was observed, most frequently (42.9%) between working memory index (WMI) and verbal comprehension index (VCI; VCI - WMI > 11 points). Regional CBF was significantly reduced both in the left and right medial frontal cortices (left: 61.3 ± 5.3 ml/100 g/min, right 65.3 ± 5.3 ml/100 g/min; p < 0.001) compared to the cerebellum (77.8 ± 6.8 ml/100 g/min). There was a significant association of rCBF in the left dorsolateral prefrontal cortex (DLPFC) with FIQ (r = 0.46, p = 0.034), perceptual reasoning index (PRI; r = 0.44, p = 0.045), and processing speed index (PSI; r = 0.44, p = 0.045). There was an association between rCBF of the left medial frontal cortex and PSI (r = 0.49, p = 0.026). Age of onset, family history, ischemic symptoms, and angiographic severity were not associated with poor cognitive performance.

CONCLUSIONS

Although average intellectual ability was not reduced in children with MMD, the association of reduced rCBF in the left DLPFC and medial frontal cortex with FIQ, PRI, and PSI suggests mild cognitive dysfunction due to cerebral hypoperfusion.

Neuropsychological profile associated with Moyamoya disease: A case report

BACKGROUND

Moyamoya disease (MMD) is a rare cardiovascular condition characterized by stenosis and gradual occlusion of the internal carotid arteries near the Circle of Willis. Current research on the disease has primarily been restricted to its medical implications, without adequate appreciation for its neurocognitive and/or neuropsychiatric implications.

OBJECTIVES

The current study presents the neurocognitive profile of a 31-year-old woman diagnosed with MMD, further complicated by cerebral vascular accidents (CVAs) and history of bilateral craniotomy aimed at providing maximal revascularization.

METHODS

Although speech and motor disturbances experienced by Ms. Doe around the time of her craniotomy and CVA were resolved at the time of current evaluation, she reported experiencing continued difficulties in processing speed, concentration, memory, word-retrieval, and planning. The patient underwent comprehensive neuropsychological evaluation assessing multiple cognitive domains.

RESULTS

Neurocognitive evaluation revealed the presence of a lateralized profile as well as impairments in simple auditory attention, processing speed, working memory, verbal learning, verbal fluency, and speeded fine-motor dexterity.

CONCLUSIONS

MMD significantly impacts cognition and daily functioning in affected individuals. This is often further exacerbated by additional CVAs requiring surgical intervention. While there is a clear growth of research on MMD, limited information is available on the neurocognitive and neuropsychiatric outcomes of the disease process. Neuropsychological data from the current case study is closely examined to provide a unique example of the lateralized neuropsychological profile and deficit pattern in a historically high functioning individual diagnosed with MMD following a stroke.

Impact of cerebral blood flow changes due to arterial bypass surgery on cognitive function in adult patients with symptomatic ischemic moyamoya disease

OBJECTIVE

Some adult patients with moyamoya disease (MMD) undergoing revascularization surgery show an improvement or decline in cognition postoperatively. Revascularization surgery for ischemic MMD augments cerebral blood flow (CBF) and improves cerebral oxygen metabolism. However, cerebral hyperperfusion, which is a short-term, major increase in ipsilateral CBF that is much greater than the metabolic needs of the brain, sometimes occurs as a complication. Cerebral hyperperfusion produces widespread, minimal injury to the ipsilateral white matter and cortical regions. The aim of the present prospective study was to determine how changes in CBF due to arterial bypass surgery affect cognitive function in adult patients with symptomatic ischemic MMD and misery perfusion.

METHODS

Thirty-two patients with cerebral misery perfusion, as determined on the basis of 15O gas positron emission tomography, underwent single superficial temporal artery-middle cerebral artery (M4 in the precentral region) anastomosis. Brain perfusion single-photon emission computed tomography (SPECT) studies were performed preoperatively, on the 1st postoperative day, and 2 months after surgery. Neuropsychological tests were also performed preoperatively and 2 months after surgery.

RESULTS

Postoperative neuropsychological assessments demonstrated cognitive improvement in 10 cases (31%), no change in 8 cases (25%), and decline in 14 cases (44%). Based on brain perfusion SPECT and symptoms, 10 patients were considered to have cerebral hyperperfusion syndrome, and all of these patients exhibited a postoperative decline in cognition. Relative precentral CBF on the 1st postoperative day was significantly greater in patients with postoperative cognitive decline (167.3% ± 15.3%) than in those with improved (105.3% ± 18.2%; p < 0.0001) or unchanged (131.4% ± 32.1%; p = 0.0029) cognition. The difference between relative precentral CBF 2 months after surgery and that before surgery was significantly greater in patients with postoperative cognitive improvement (17.2% ± 3.8%) than in those with no postoperative change (10.1% ± 2.4%; p = 0.0003) or with postoperative decline (11.5% ± 3.2%; p = 0.0009) in cognition.

CONCLUSIONS

Cerebral hyperperfusion in the acute stage after arterial bypass surgery impairs cognitive function. An increase in CBF in the chronic stage without acute-stage cerebral hyperperfusion improves cognitive function in adult patients with symptomatic ischemic MMD and misery perfusion.

Beneficial Effect of Carotid Artery Stenting on Cerebral Hemodynamic Impairment and Cognitive Function

The aim of this study was to evaluate the effects of the carotid artery stenting (CAS) procedure on cerebral hemodynamics and cognitive performance in patients with internal carotid artery stenosis. In this prospective observational study, 16 consecutive patients in a single institute were treated with CAS from 2010 to 2011 (71.7 ± 7.3 years old, 12 males, and six left-sided procedures). Before and after the CAS procedure, all patients were evaluated with single photon emission computed tomography using ¹²³ I-iodoamphetamine and acetazolamide as well as the Weschler Adult Intelligent Scale (WAIS) to assess three intelligent quotients and four indexes. Patients with decreased preprocedural cerebral blood flow (CBF) and cerebrovascular reserve (CVR) experienced significant increases in CBF and CVR (P = 0.01 and 0.03). Twelve (75%) patients experienced a significant increase in one or more WAIS scores, while two (13%) showed a significant decrease. The most frequently improved scores were the Working Memory Index and Processing Speed Index (seven patients/44%). Preprocedural CBF was significantly correlated with the Full-scale and Performance Intelligent Quotients (r = 0.51–0.56, P = 0.02–0.04), and patients who experienced a significant increase in these scores had larger increases in CVR than patients with unchanged scores (P = 0.0097–0.019). These results indicate that the CAS procedure improved impaired cerebral hemodynamics and might benefit the cognitive function of patients with internal carotid artery stenosis related to impaired cerebral hemodynamics.

Microstructural Damage in Normal-Appearing Brain Parenchyma and Neurocognitive Dysfunction in Adult Moyamoya Disease

Background and Purpose -Microstructural damage in the brain induced by chronic ischemia is suggested to play a pivotal role in the neurocognitive dysfunction of adults with Moyamoya disease (MMD). We investigated specific changes in the brain microstructure and their correlations with neurocognitive dysfunction in patients with MMD using a multishell diffusion magnetic resonance imaging technique called neurite orientation dispersion and density imaging. Methods- We evaluated 26 patients with MMD (16-63 years old, 20 females) and 20 age- and sex-matched normal volunteers using neurite orientation dispersion and density imaging and neuropsychological batteries. Neurite orientation dispersion and density imaging calculates 2 parameters: the intracellular volume fraction (Vic), which reflects the axon density in the white matter and dendrite density in the cortex, and the orientation dispersion index (OD), which reflects the network complexity. The microstructural damage and its correlation with neurocognitive performance were evaluated by performing a whole-brain analysis using SPM12 and correlation analysis with regional values. Results- Patients with MMD had significantly lower Vic in the white matter and a lower OD mainly in the cortex than those of the controls ( P<0.001, family-wise error corrected). Of all neuropsychological scores, Processing Speed Index (PS) exhibited the strongest correlation with Vic in the white matter ( P<0.001, family-wise error corrected). The Vic and OD values for regions with group differences, including both temporoparietal and frontal areas, correlated with neurocognitive performance (absolute r=0.37-0.64; P<0.01). Conclusions- Chronic ischemia in MMD may decrease the axon density in the white matter and dendrite density in the cortex (Vic) and simplify network complexity (OD), leading to neurocognitive dysfunction. Processing Speed Index may be the most sensitive index used to evaluate the ischemic burden, and the posterior part of the brain may play an important role in neurocognitive function. Clinical Trial Registration- URL: http://www.umin.ac.jp/ctr/ . Unique identifier: UMIN000023082.