Crossed cerebellar diaschisis. Further studies

Ataxic hemiparesis: a narrative review for clinical practice in rehabilitation

BACKGROUND

Ataxic hemiparesis (AH) is a well-recognized clinical lacunar stroke syndrome, characterized by paresis with ataxia on the same side of the body. It affects patients with stroke involving the basal ganglia, pons, internal capsule, corona radiata, and thalamus. In the past, lacunar syndrome denotes good functional recovery with low mortality and morbidity rate. However, recent evidence suggests AH has an association with more debilitating outcomes in the long term.

OBJECTIVE

To provide a comprehensive narrative review of published literatures on the topics related with AH and update clinical practice including rehabilitation.

METHODS

Literature review was performed by using the keywords "Subcortical Ataxia," "Lacunar Stroke," "Diaschisis", and "Ataxic Hemiparesis" on PubMed and Google Scholar Engines from 1978 to 2022. All papers published in English were reviewed and manual search of references from retrieved literature was performed for other relevant articles.

RESULTS

A comprehensive review was carried out on the following topics: neuroanatomical localization, pathogenesis, clinical features and clinical assessment scales, pharmacological and non-pharmacological modalities for ataxia treatment, prognosis, and outcome.

CONCLUSION

AH imposes significant challenges on stroke survivors when it comes to remediation of balance and coordination. It is associated with increased risk of mortality, stroke recurrence, and dementia. Though application of the concept of neuroplasticity and the utilization of repetitive transcranial magnetic stimulation have shown early promising results, further research is needed to establish the practice guidelines for rehabilitation of patients with AH.

Neuroanatomy of autism: what is the role of the cerebellum?

Autism (or autism spectrum disorder) was initially defined as a psychiatric disorder, with the likely cause maternal behavior (the very destructive "refrigerator mother" theory). It took several decades for research into brain mechanisms to become established. Both neuropathological and imaging studies found differences in the cerebellum in autism spectrum disorder, the most widely documented being a decreased density of Purkinje cells in the cerebellar cortex. The popular interpretation of these results is that cerebellar neuropathology is a critical cause of autism spectrum disorder. We challenge that view by arguing that if fewer Purkinje cells are critical for autism spectrum disorder, then any condition that causes the loss of Purkinje cells should also cause autism spectrum disorder. We will review data on damage to the cerebellum from cerebellar lesions, tumors, and several syndromes (Joubert syndrome, Fragile X, and tuberous sclerosis). Collectively, these studies raise the question of whether the cerebellum really has a role in autism spectrum disorder. Autism spectrum disorder is now recognized as a genetically caused developmental disorder. A better understanding of the genes that underlie the differences in brain development that result in autism spectrum disorder is likely to show that these genes affect the development of the cerebellum in parallel with the development of the structures that do underlie autism spectrum disorder.

Diaschisis in the human brain reveals specificity of cerebrocerebellar connections

Anatomical studies in animals and imaging studies in humans show that cerebral sensorimotor areas map onto corresponding cerebellar sensorimotor areas and that cerebral association areas map onto cerebellar posterior lobe regions designated as the representation of the association (cognitive and limbic) cerebellum. We report a patient with unilateral left hemispheric status epilepticus, whose brain MRI revealed diffuse unihemispheric cerebral cortical FLAIR and diffusion signal hyperintensity but spared primary motor, somatosensory, visual, and to lesser extent auditory cerebral cortices. Crossed cerebellar diaschisis (dysfunction at a site remote from, but connected to, the location of the primary lesion) showed signal hyperintensity in the right cerebellar posterior lobe and lobule IX, with sparing of the anterior lobe, and lobule VIII. This unique topographic pattern of involvement and sparing of cerebral and cerebellar cortical areas matches the anatomical and functional connectivity specialization in the cerebrocerebellar circuit. This first demonstration of within-hemispheric specificity in the areas affected and spared by cerebrocerebellar diaschisis provides further confirmation in the human brain for topographic organization of connections between the cerebral hemispheres and the cerebellum.

Diaschisis Profiles in the Cerebellar Response to Hemodynamic Stimuli: Insights From Dynamic Measurement of Cerebrovascular Reactivity to Identify Occult and Transient Maxima

BACKGROUND

Crossed cerebellar diaschisis (CCD) refers to depressions in perfusion and metabolism within the cerebellar hemisphere contralateral to supratentorial disease. Prior investigation into CCD in cerebrovascular reactivity (CVR) has been limited to terminal CVR estimations (CVRend ). We recently have demonstrated the presence of unsustained CVR maxima (CVRmax ) using dynamic CVR analysis, offering a fully dynamic characterization of CVR to hemodynamic stimuli.

PURPOSE

To investigate CCD in CVRmax from dynamic blood oxygen level-dependent (BOLD) MRI, by comparison with conventional CVRend estimation.

STUDY TYPE

Retrospective.

POPULATION

A total of 23 patients (median age: 51 years, 10 females) with unilateral chronic steno-occlusive cerebrovascular disease, without prior knowledge of CCD status.

FIELD STRENGTH/SEQUENCE

A 3-T, T1-weighted magnetization-prepared rapid gradient-echo (MPRAGE) and acetazolamide-augmented BOLD imaging performed with a gradient-echo echo-planar imaging (EPI) sequence.

ASSESSMENT

A custom denoising pipeline was used to generate BOLD-CVR time signals. CVRend was established using the last minute of the BOLD response relative to the first-minute baseline. Following classification of healthy versus diseased cerebral hemispheres, CVRmax and CVRend were calculated for bilateral cerebral and cerebellar hemispheres. Three independent observers evaluated all data for the presence of CCD.

STATISTICAL TESTS

Pearson correlations for comparing CVR across hemispheres, two-proportion Z-tests for comparing CCD prevalence, and Wilcoxon signed-rank tests for comparing median CVR. The level of statistical significance was set at P ≤ 0.05.

RESULTS

CCD-related changes were observed on both CVRend and CVRmax maps, with all CCD+ cases identifiable by inspection of either map. Diseased cerebral and contralateral cerebellar hemispheric CVR correlations in CCD+ patients were stronger when using CVRend (r = 0.728) as compared to CVRmax (r = 0.676). CVR correlations between healthy cerebral hemispheres and contralateral cerebellar hemispheres were stronger for CVRmax (r = 0.739) than for CVRend (r = 0.705).

DATA CONCLUSION

CCD-related alterations could be observed in CVR examinations. Conventional CVRend may underestimate CVR and could exaggerate CCD.

EVIDENCE LEVEL

4.

TECHNICAL EFFICACY

Stage 3.

Disability and persistent motor deficits are linked to structural crossed cerebellar diaschisis in chronic stroke

Brain imaging has significantly contributed to our understanding of the cerebellum being involved in recovery after non-cerebellar stroke. Due to its connections with supratentorial brain networks, acute stroke can alter the function and structure of the contralesional cerebellum, known as crossed cerebellar diaschisis (CCD). Data on the spatially precise distribution of structural CCD and their implications for persistent deficits after stroke are notably limited. In this cross-sectional study, structural MRI and clinical data were analyzed from 32 chronic stroke patients, at least 6 months after the event. We quantified lobule-specific contralesional atrophy, as a surrogate of structural CCD, in patients and healthy controls. Volumetric data were integrated with clinical scores of disability and motor deficits. Diaschisis-outcome models were adjusted for the covariables age, lesion volume, and damage to the corticospinal tract. We found that structural CCD was evident for the whole cerebellum, and particularly for lobules V and VI. Lobule VI diaschisis was significantly correlated with clinical scores, that is, volume reductions in contralesional lobule VI were associated with higher levels of disability and motor deficits. Lobule V and the whole cerebellum did not show similar diaschisis-outcome relationships across the spectrum of the clinical scores. These results provide novel insights into stroke-related cerebellar plasticity and might thereby promote lobule VI as a key area prone to structural CCD and potentially involved in recovery and residual motor functioning.

A Systematic Review of PET Contrasted with MRI for Detecting Crossed Cerebellar Diaschisis in Patients with Neurodegenerative Diseases

There has not been extensive research into crossed cerebellar diaschisis (CCD) in neurodegenerative disorders. CCD is frequently detected using positron emission tomography (PET). However, advanced MRI techniques have come forth for the detection of CCD. The correct diagnosis of CCD is crucial for the care of neurological patients and those with neurodegenerative conditions. The purpose of this study is to determine whether PET can offer extra value over MRI or an advanced technique in MRI for detecting CCD in neurological conditions. We searched three main electronic databases from 1980 until the present and included only English and peer-reviewed journal articles. Eight articles involving 1246 participants met the inclusion criteria, six of which used PET imaging while the other two used MRI and hybrid imaging. The findings in PET studies showed decreased cerebral metabolism in the frontal, parietal, temporal, and occipital cortices, as on the opposite side of the cerebellar cortex. However, the findings in MRI studies showed decreased cerebellar volumes. This study concludes that PET is a common, accurate, and sensitive technique for detecting both crossed cerebellar and uncrossed basal ganglia as well as thalamic diaschisis in neurodegenerative diseases, while MRI is better for measuring brain volume. This study suggests that PET has a higher diagnostic value for diagnosing CCD compared to MRI, and that PET is a more valuable technique for predicting CCD.

Case report: Multiple disconnection patterns revealed by a multi-modal analysis explained behavior after a focal frontal damage

Introduction

There is overwhelming evidence that focal lesions cause structural, metabolic, functional, and electrical disconnection of regions directly and indirectly connected with the site of injury. Unfortunately, methods to study disconnection (positron emission tomography, structural and functional magnetic resonance imaging, electroencephalography) have been applied primarily in isolation without capturing their interaction. Moreover, multi-modal imaging studies applied to focal lesions are rare.

Case report

We analyzed with a multi-modal approach the case of a patient presenting with borderline cognitive deficits across multiple domains and recurrent delirium. A post-surgical focal frontal lesion was evident based on the brain anatomical MRI. However, we were able to acquire also simultaneous MRI (structural and functional) and [18F]FDG using a hybrid PET/MRI scan along with EEG recordings. Despite the focality of the primary anatomical lesion, structural disconnection in the white matter bundles extended far beyond the lesion and showed a topographical match with the cortical glucose hypometabolism seen both locally and remotely, in posterior cortices. Similarly, a right frontal delta activity near/at the region of structural damage was associated with alterations of distant occipital alpha power. Moreover, functional MRI revealed even more widespread local and distant synchronization, involving also regions not affected by the structural/metabolic/electrical impairment.

Conclusion

Overall, this exemplary multi-modal case study illustrates how a focal brain lesion causes a multiplicity of disconnection and functional impairments that extend beyond the borders of the anatomical irrecoverable damage. These effects were relevant to explain patient’s behavior and may be potential targets of neuro-modulation strategies.

Crossed Cerebellar Diaschisis Worsens the Clinical Presentation in Acute Large Vessel Occlusion

INTRODUCTION

Initial NIHSS in anterior large vessel occlusion (LVO) correlates partially with the hypoperfusion volume. We aimed at assessing the contribution of crossed cerebellar diaschisis (CCD) from the hypoperfused territory on LVO initial clinical deficit.

METHODS

CCD was retrospectively identified by brain CT perfusion imaging (CTP) in patients with anterior LVO treated by mechanical thrombectomy from January 2017 to July 2021. CCD was defined by CTP parameter alteration in the contralateral cerebellar hemisphere to the LVO. NIHSS, clinical/perfusion variables, and CCD were included in regression models to assess their interrelationships.

RESULTS

206 patients were included. CCD was present in 90 patients (69%). NIHSS scores were higher on admission and at stroke discharge among patients with CCD (17.90 ± 6.1 vs. 11.4 ± 8.4, p < 0.001; 9.6 ± 7.7 vs. 6.6 ± 7.9, p = 0.049; respectively). Patients with a CCD had higher stroke volumes (118.2 ± 60.3 vs. 69.3 ± 59.7, p < 0.001) and lower rate of known atrial fibrillation (22% vs. 41%, p = 0.021). On multivariable logistic regression, CCD independently worsened the initial NIHSS (OR 4.85 [2.37-7.33]; p < 0.001).

CONCLUSION

CCD is found in 69% of LVO on admission CTP, correlates with stroke volumes, and independently worsens initial NIHSS.

Structural cerebellar reserve positively influences outcome after severe stroke

The concept of brain reserve capacity positively influencing the process of recovery after stroke has been continuously developed in recent years. Global measures of brain health have been linked with a favourable outcome. Numerous studies have evidenced that the cerebellum is involved in recovery after stroke. However, it remains an open question whether characteristics of cerebellar anatomy, quantified directly after stroke, might have an impact on subsequent outcome after stroke. Thirty-nine first-ever ischaemic non-cerebellar stroke patients underwent MRI brain imaging early after stroke and longitudinal clinical follow-up. Structural images were used for volumetric analyses of distinct cerebellar regions. Ordinal logistic regression analyses were conducted to associate cerebellar volumes with functional outcome 3-6 months after stroke, operationalized by the modified Rankin Scale. Larger volumes of cerebellar lobules IV, VI, and VIIIB were positively correlated with favourable outcome, independent of the severity of initial impairment, age, and lesion volume (P < 0.01). The total cerebellar volume did not exhibit a significant structure-outcome association. The present study reveals that pre-stroke anatomy of distinct cerebellar lobules involved in motor and cognitive functioning might be linked to outcome after acute non-cerebellar stroke, thereby promoting the emerging concepts of structural brain reserve for recovery processes after stroke.

Circular inference predicts nonuniform overactivation and dysconnectivity in brain-wide connectomes

Schizophrenia is a severe mental disorder whose neural basis remains difficult to ascertain. Among the available pathophysiological theories, recent work has pointed towards subtle perturbations in the excitation-inhibition (E/I) balance within different neural circuits. Computational approaches have suggested interesting mechanisms that can account for both E/I imbalances and psychotic symptoms. Based on hierarchical neural networks propagating information through a message-passing algorithm, it was hypothesized that changes in the E/I ratio could cause a "circular belief propagation" in which bottom-up and top-down information reverberate. This circular inference (CI) was proposed to account for the clinical features of schizophrenia. Under this assumption, this paper examined the impact of CI on network dynamics in light of brain imaging findings related to psychosis. Using brain-inspired graphical models, we show that CI causes overconfidence and overactivation most specifically at the level of connector hubs (e.g., nodes with many connections allowing integration across networks). By also measuring functional connectivity in these graphs, we provide evidence that CI is able to predict specific changes in modularity known to be associated with schizophrenia. Altogether, these findings suggest that the CI framework may facilitate behavioral and neural research on the multifaceted nature of psychosis.

Preservation of Cerebellar Afferent Pathway May Be Related to Good Hand Function in Patients with Stroke

Many chronic stroke patients suffer from worsened hand function, and functional recovery of the hand does not occur well after six months of stroke. Therefore, predicting final hand function after stroke through acute phase imaging would be an important issue in counseling with the patients or their family. Thus, we investigated the remaining white matter integrity in the corticospinal tract (CST) and cortico-ponto-cerebellar tract (CPCT) at the acute stage of stroke and chronic hand function after stroke, and present the cut-off value of fiber number (FN) and fractional anisotropy (FA) of CST and CPCT at the acute stage for predicting final hand function after the recovery period. This retrospective case-control study included 18 stroke patients who were classified into two groups: poor hand function with stroke (n = 11) and good hand function with stroke (n = 7). DTI was done within two months ± 15 days after onset, and the Jebson’s Hand Function test was conducted 6–12 months after onset. The investigation of white matter was focused on the values of FN and FA for CST and CPCT, which were measured separately. The normalized (affected/non-affected) FA and FN values in the CPCT in the good hand function group were higher than those in the poor hand function group. The normalized FN and FA values in the CST were not significantly different between the poor hand function group and the good hand function group. The normalized cut-off value that distinguished the good hand function group from the poor hand function group was 0.8889 for FA in the CPCT. The integrity of the CPCT in the acute stage was associated with hand function in the chronic stage after a stroke. Ultimately, the integrity of the CPCT in the early stage after onset can be used to predict chronic hand function. Based on these results, cerebellar afferent fiber measurements may be a useful addition to predict hand function and plan specific rehabilitation strategies in stroke patients.

Cognitive and Psychological Functioning in Chiari Malformation Type I Before and After Surgical Decompression - A Prospective Cohort Study

BACKGROUND

Chiari Malformation Type I (CM-I) is defined as cerebellar tonsil displacement more than 5 mm below the foramen magnum. This displacement can alter cerebrospinal fluid flow at the cervicomedullary junction resulting in Valsalva-induced headaches and syringomyelia and compress the brainstem resulting in bulbar symptoms. However, little is known about cognitive and psychological changes in CM-I.

OBJECTIVE

To prospectively assess cognitive and psychological performance in CM-I and determine whether changes occur after surgical decompression.

METHODS

Blinded evaluators assessed symptomatic CM-I patients ages ≥18 with a battery of neuropsychological and psychological tests. Testing was conducted preoperatively and 6 to 18 mo postoperatively. Data were converted to Z-scores based on normative data, and t-tests were used to analyze pre-post changes.

RESULTS

A total of 26 patients were included, with 19 completing both pre- and post-op cognitive assessments. All patients had resolution of Valsalva-induced headaches and there was improvement in swallowing dysfunction (P < .0001), ataxia (P = .008), and sleep apnea (P = .021). Baseline performances in visual perception and construction (z = -1.11, P = .001) and visuospatial memory (z = -0.93, P = .002) were below average. Pre-post comparisons showed that CM-I patients had stable cognitive and psychological functioning after surgery, without significant changes from preoperative levels.

CONCLUSION

CM-I patients had below average performance in visuospatial and visuoconstructional abilities preoperatively. Prospective longitudinal data following surgery demonstrated improved neurologic status without any decline in cognition or psychological functioning. Routine pre- and postoperative formal neuropsychological assessment in CM-I patients help quantify cognitive and behavioral changes associated with surgical decompression.

Integrity of the Inferior Cerebellar Peduncle Correlates with Ambulatory Function after Hemorrhagic Stroke

OBJECTIVES

Cerebro-cerebellar connectivity plays a critical role in motor recovery after stroke; however, the underlying mechanism of walking recovery is unclear. The dorsal spinocerebellar pathway has been suggested as a biomarker of poststroke ambulatory function. We aimed to explore the association between ambulatory function and the dorsal spinocerebellar pathway's integrity after intracerebral hemorrhage (ICH).

MATERIALS AND METHODS

Twenty-seven patients with ICH who were admitted for inpatient rehabilitation during the subacute phase of stroke and 27 age-matched healthy controls were included retrospectively. Ambulatory function was assessed using the Berg Balance Scale and Mobility score. We measured the fractional anisotropy (FA) values of the corticospinal tract (CST) and inferior cerebellar peduncle (ICP) as the final route of the dorsal spinocerebellar pathway. The FA laterality indices, representing the degree of degeneration, were calculated. A Spearman correlation analysis and multivariate linear regression models were used to determine the associations between the FA laterality indices and ambulatory function.

RESULTS

An FA reduction was found in both the ipsilesional CST and contralesional ICP of the patients. The ICP FA laterality index exhibited a moderate correlation with ambulatory function (Berg Balance Scale, ρ_BBS=0.589; Mobility score, ρ_MS=0.619). On dividing the patient group into the moderate (mRS 3, 4) and severe disability (mRS 5) groups, a stronger correlation was found (ρ_BBS=0.777, ρ_MS=0.856, moderate disability; ρ_BBS=0.732, ρ_MS=0.797, severe disability). The ICP FA laterality index and age were independently associated with the Mobility score (R²=0.525).

CONCLUSIONS

ICP degeneration occurs after ICH, and its degree is associated with ambulatory function after ICH.

Weighted neurofeedback facilitates greater self-regulation of functional connectivity between the primary motor area and cerebellum

Objective.Brain-computer interface (BCI) is a tool that can be used to train brain self-regulation and influence specific activity patterns, including functional connectivity, through neurofeedback. The functional connectivity of the primary motor area (M1) and cerebellum play a critical role in motor recovery after a brain injury, such as stroke. The objective of this study was to determine the feasibility of achieving control of the functional connectivity between M1 and the cerebellum in healthy subjects. Additionally, we aimed to compare the brain self-regulation of two different feedback modalities and their effects on motor performance.Approach.Nine subjects were trained with a real-time functional magnetic resonance imaging BCI system. Two groups were conformed: equal feedback group (EFG), which received neurofeedback that weighted the contribution of both regions of interest (ROIs) equally, and weighted feedback group (WFG) that weighted each ROI differentially (30% cerebellum; 70% M1). The magnitude of the brain activity induced by self-regulation was evaluated with the blood-oxygen-level-dependent (BOLD) percent change (BPC). Functional connectivity was assessed using temporal correlations between the BOLD signal of both ROIs. A finger-tapping task was included to evaluate the effect of brain self-regulation on motor performance.Main results.A comparison between the feedback modalities showed that WFG achieved significantly higher BPC in M1 than EFG. The functional connectivity between ROIs during up-regulation in WFG was significantly higher than EFG. In general, both groups showed better tapping speed in the third session compared to the first. For WFG, there were significant correlations between functional connectivity and tapping speed.Significance.The results show that it is possible to train healthy individuals to control M1-cerebellum functional connectivity with rtfMRI-BCI. Besides, it is also possible to use a weighted feedback approach to facilitate a higher activity of one region over another.

Crossed cerebellar diaschisis on 18F-FDG PET: Frequency across neurodegenerative syndromes and association with 11C-PIB and 18F-Flortaucipir

We used 18F-FDG-PET to investigate the frequency of crossed cerebellar diaschisis (CCD) in 197 patients with various syndromes associated with neurodegenerative diseases. In a subset of 117 patients, we studied relationships between CCD and cortical asymmetry of Alzheimer's pathology (β-amyloid (11C-PIB) and tau (18F-Flortaucipir)). PET images were processed using MRIs to derive parametric SUVR images and define regions of interest. Indices of asymmetry were calculated in the cerebral cortex, basal ganglia and cerebellar cortex. Across all patients, cerebellar 18F-FDG asymmetry was associated with reverse asymmetry of 18F-FDG in the cerebral cortex (especially frontal and parietal areas) and basal ganglia. Based on our operational definition (cerebellar asymmetry >3% with contralateral supratentorial hypometabolism), significant CCD was present in 47/197 (24%) patients and was most frequent in corticobasal syndrome and semantic and logopenic variants of primary progressive aphasia. In β-amyloid-positive patients, mediation analyses showed that 18F-Flortaucipir cortical asymmetry was associated with cerebellar 18F-FDG asymmetry, but that cortical 18F-FDG asymmetry mediated this relationship. Analysis of 18F-FDG-SUVR values suggested that CCD might also occur in the absence of frank cerebellar 18F-FDG asymmetry due to symmetrical supratentorial degeneration resulting in a bilateral diaschisis process.

Longitudinal changes in the inferior cerebellar peduncle and lower limb motor recovery following subcortical infarction

Background

The cerebellum receives afferent signals from spinocerebellar pathways regulating lower limb movements. However, the longitudinal changes in the spinocerebellar pathway in the early stage of unilateral supratentorial stroke and their potential clinical significance have received little attention.

Methods

Diffusion tensor imaging and Fugl-Meyer assessment of lower limb were performed 1, 4, and 12 weeks after onset in 33 patients with acute subcortical infarction involving the supratentorial areas, and in 33 healthy subjects. We evaluated group differences in diffusion metrics in the bilateral inferior cerebellar peduncle (ICP) and analyzed the correlation between ICP diffusion metrics and changes to the Fugl-Meyer scores of the affected lower limb within 12 weeks after stroke.

Results

Significantly decreased fractional anisotropy and increased mean diffusivity were found in the contralesional ICP at week 12 after stroke compared to controls (all P < 0.01) and those at week 1 (all P < 0.05). There were significant fractional anisotropy decreases in the ipsilesional ICP at week 4 (P = 0.008) and week 12 (P = 0.004) compared to controls. Both fractional anisotropy (r_s = 0.416, P = 0.025) and mean diffusivity (r_s = -0.507, P = 0.005) changes in the contralesional ICP correlated with changes in Fugl-Meyer scores of the affected lower limb in all patients.

Conclusions

Bilateral ICP degeneration occurs in the early phase of supratentorial stroke, and diffusion metric values of the contralesional ICP are useful indicators of affected lower limb function after supratentorial stroke.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12883-021-02346-x.

Genotypic Differences in Networks Supporting Regional Predictors of Speech Rate in Spinocerebellar Ataxia: Preliminary Observations

Background: Disordered speech production, dysarthria, is a common characteristic of the spinocerebellar ataxias (SCAs). Although dysarthric features differ across SCAs, a previous analysis revealed that a combination of regional cerebral blood flow (rCBF) in the left inferior frontal region and the right caudate predicted syllable rate, a pattern reported in normal speakers. This study examined the relationships between primary predictor brain regions and other areas of the brain in three SCA groups. The regions associated with the primary predictors are considered as elements of secondary networks since they are associated with regional speech predictors rather than directly with speech performance.

Methods: Speech and rCBF data from 9 SCA1, 8 SCA5, and 5 SCA6 individuals were analyzed. Partial correlations were used to identify brain regions associated with the primary predictors.

Results: Secondary networks differed across SCA genotypes. SCA1 and SCA6 demonstrated both positive and negative associations between primary and secondary areas, whereas the associations in the SCA5 genotype were only positive. The SCA5 associations were also largely bilaterally symmetrical. Both SCA1 and SCA5 demonstrated secondary associations with the right caudate, whereas the SCA6 group had no such associations.

Conclusions: These results demonstrate that although primary aspects of a brain network may remain functional, pathophysiological processes associated with different SCA genotypes may express themselves in alterations of broader, secondary brain networks. These secondary networks may reflect generic functional associations with the primary predictor regions, compensatory activity in the presence of an SCA, SCA pathology, or some combination of these factors.

Investigating the Association of Wallerian Degeneration and Diaschisis After Ischemic Stroke With BOLD Cerebrovascular Reactivity

Introduction

Wallerian degeneration and diaschisis are considered separate remote entities following ischemic stroke. They may, however, share common neurophysiological denominators, since they are both related to disruption of fiber tracts and brain atrophy over time. Therefore, with advanced multimodal neuroimaging, we investigate Wallerian degeneration and its association with diaschisis.

Methods

In order to determine different characteristics of Wallerian degeneration, we conducted examinations on seventeen patients with chronic unilateral ischemic stroke and persisting large vessel occlusion, conducting high-resolution anatomical magnetic resonance imaging (MRI) and blood oxygenation-level dependent cerebrovascular reactivity (BOLD-CVR) tests, as well as Diamox ¹⁵(O)–H₂O–PET hemodynamic examinations. Wallerian degeneration was determined using a cerebral peduncle asymmetry index (% difference of volume of ipsilateral and contralateral cerebral peduncle) of more than two standard deviations away from the average of age-matched, healthy subjects (Here a cerebral peduncle asymmetry index > 11%). Diaschisis was derived from BOLD-CVR to assess the presence of ipsilateral thalamus diaschisis and/or crossed cerebellar diaschisis.

Results

Wallerian degeneration, found in 8 (47%) subjects, had a strong association with ipsilateral thalamic volume reduction (r² = 0.60) and corticospinal-tract involvement of stroke (p < 0.001). It was also associated with ipsilateral thalamic diaschisis (p = 0.021), No cerebral peduncular hemodynamic differences were found in patients with Wallerian degeneration. In particular, no CBF decrease or BOLD-CVR impairment was found.

Conclusion

We show a strong association between Wallerian degeneration and ipsilateral thalamic diaschisis, indicating a structural pathophysiological relationship.

Crossed Cerebellar Diaschisis in Alzheimer's Disease Detected by Arterial Spin-labelling Perfusion MRI

BACKGROUND

Crossed cerebellar diaschisis (CCD) is a phenomenon with depressed metabolism and hypoperfusion in the cerebellum. Using arterial spin-labelling perfusion weighted magnetic resonance imaging (ASL PWI), we investigated the frequency of CCD in patients with Alzheimer's disease (AD) and differences between patients with and without CCD.

PATIENTS AND METHODS

In patients with AD who underwent a standardized magnetic resonance imaging including ASL PWI cerebral blood flow was evaluated in the cerebellum, and brain segmentation/volumetry was performed using mdbrain (mediaire GmbH, Berlin, Germany) and FSL FIRST (Functional Magnetic Resonance Imaging of the Brain Software Library).

RESULTS

In total, 65 patients were included, and 22 (33.8%) patients were assessed as being CCD-positive. Patients with CCD had a significantly smaller whole brain volume (862.8±49.9 vs. 893.7±62.7 ml, p=0.049) as well as white matter volume (352.9±28.0 vs. 374.3±30.7, p=0.008) in comparison to patients without CCD.

CONCLUSION

It was possible to detect CCD by ASL PWI in approximately one-third of patients with AD and was associated with smaller whole brain and white matter volume.

Brain [F-18]FDG PET for Clinical Dementia Workup: Differential Diagnosis of Alzheimer's Disease and Other Types of Dementing Disorders

PET imaging with [F-18]FDG has been used extensively for research and clinical applications in dementia. In the brain, [F-18]FDG accumulates around synapses and represents local neuronal activity. Patterns of altered [F-18]FDG uptake reflecting local neuronal dysfunction provide differential diagnostic clues for various dementing disorders. Image interpretation can be accomplished by employing statistical brain mapping techniques. Various guidelines have been published to support the appropriate use of [F-18]FDG PET for clinical dementia workup. PET images with [F-18]FDG demonstrate distinct patterns of decreased uptake for Alzheimer's disease (AD), Dementia with Lewy bodies (DLB), and frontotemporal dementia (FTD) as well as its multiple subtypes such as behavioral variant FTD, primary progressive aphasia (PPA), progressive supranuclear palsy, and corticobasal degeneration to aid in the differential diagnoses. Mixed dementia, not only AD + Vascular Dementia, but also AD + other neurodegenerative disorders, should also be considered when interpreting [F-18]FDG PET images. Brain PET imaging with [F-18]FDG remains a valuable component of dementia workup owing to its relatively low cost, differential diagnostic performance, widespread availability, and physicians' experience over more than 40 years since the initial development.

FDG PET/MRI for Visual Detection of Crossed Cerebellar Diaschisis in Patients With Dementia

OBJECTIVE

Depressed regional metabolism and cerebellar blood flow may be caused by dysfunction in anatomically separate but functionally related regions, presumably related to disruption of the corticopontine-cerebellar pathway. The purpose of this study was to evaluate the prevalence of crossed cerebellar diaschisis (CCD) in patients undergoing ¹⁸F-FDG PET/MRI for suspected neurodegenerative disease.

MATERIALS AND METHODS

In total, 75 patients (31 men, 44 women; mean age, 74 years) underwent hybrid FDG PET/MRI for clinical workup of neurodegenerative disease. Images were obtained with an integrated 3-T PET/MRI system. PET surface maps, fused T1-weighted magnetization-prepared rapid acquisition gradient echo and axial FLAIR/PET images were generated with postprocessing software. Two board-certified neuroradiologists and a nuclear medicine physician blinded to patient history evaluated for pattern of neurodegenerative disease and CCD.

RESULTS

Qualitative assessment showed that 10 of 75 (7.5%) patients had decreased FDG activity in the cerebellar hemisphere contralateral to the supratentorial cortical hypometabolism consistent with CCD. Six of the 10 patients had characteristic imaging findings of frontotemporal dementia (three behavioral variant frontotemporal dementia, two semantic primary progressive aphasia, and one logopenic primary progressive aphasia), three had suspected corticobasal degeneration, and one had Alzheimer dementia.

CONCLUSION

Our study results suggest that CCD occurs most commonly in frontotemporal dementia, particularly the behavioral variant, and in patients with cortico-basal degeneration. Careful attention to cerebellar metabolism may assist in the clinical evaluation of patients with cognitive impairment undergoing FDG PET/MRI as part of their routine dementia workup.

Relationship between ischaemic symptoms during the early postoperative period in patients with moyamoya disease and changes in the cerebellar asymmetry index

OBJECTIVE

The aim of this study was to clarify the relationship between ischaemic symptoms during the early postoperative period in patients with moyamoya disease and changes in the cerebellar asymmetry index (AI), a parameter used to quantitatively identify crossed cerebellar diaschisis (CCD).

PATIENTS AND METHODS

We analysed the data of 18 patients with moyamoya disease who underwent quantitative IMP-cerebral blood flow SPECT at least once during the follow-up period. Cerebellar AI scores were calculated using the CBF of the cerebellum calculated automatically from multiple slices of SPECT images with automated ROI setup software and categorized and statistically examined according to the presence or absence of ischaemic symptoms.

RESULTS

The cerebellar AI calculated from SPECT performed in the patients who presented with ischaemic symptoms was 0.094 ± 0.023 (mean ± SD), which was significantly elevated compared to the value of 0.013 ± 0.025 (mean ± SD) calculated from SPECT performed when the patients did not present with ischaemic symptoms (p < 0.0001). Limiting the time of SPECT to calculate the cerebellar AI to be compared to the acute phase within 2 weeks after surgery did not change this trend, and again, the cerebellar AI was statistically significantly elevated in the presence of ischaemic symptoms (0.094 ± 0.023 (mean ± SD)) compared to the AI in the absence of ischaemic symptoms (0.000081 ± 0.026 (mean ± SD)) (p = 0.0003). In patients who underwent quantitative SPECT in the acute phase during the first postoperative week, the cerebellar AI values calculated from the results of SPECT performed during the preoperative period as well as multiple times during postoperative period were followed over time in each case. The cerebellar AI increased in patients who presented with symptoms of ischaemia postoperatively but then tended to decrease reversibly and approach zero with the disappearance of symptoms of ischaemia.

CONCLUSIONS

Since the cerebellar AI reflects the symptom of ischaemia in patients with moyamoya disease, especially in the early stage after revascularization surgery, and is a parameter that improves with symptom improvement, it seems to be useful for understanding the state of cerebral blood flow after bypass surgery in patients with moyamoya disease.

Pervasive White Matter Fiber Degeneration in Ischemic Stroke

Background and Purpose- We examined if ischemic stroke is associated with white matter degeneration predominantly confined to the ipsi-lesional tracts or with widespread bilateral axonal loss independent of lesion laterality. Methods- We applied a novel fixel-based analysis, sensitive to fiber tract-specific differences within a voxel, to assess axonal loss in stroke (N=104, 32 women) compared to control participants (N=40, 15 women) across the whole brain. We studied microstructural differences in fiber density and macrostructural (morphological) changes in fiber cross-section. Results- In participants with stroke, we observed significantly lower fiber density and cross-section in areas adjacent, or connected, to the lesions (eg, ipsi-lesional corticospinal tract). In addition, the changes extended beyond directly connected tracts, independent of the lesion laterality (eg, corpus callosum, bilateral inferior fronto-occipital fasciculus, right superior longitudinal fasciculus). Conclusions- We conclude that ischemic stroke is associated with extensive neurodegeneration that significantly affects white matter integrity across the whole brain. These findings expand our understanding of the mechanisms of brain volume loss and delayed cognitive decline in stroke.

Impact of cortical hemodynamic failure on both subsequent hemorrhagic stroke and effect of bypass surgery in hemorrhagic moyamoya disease: a supplementary analysis of the Japan Adult Moyamoya Trial

OBJECTIVE

Here, the authors aimed to determine whether the presence of cerebral hemodynamic failure predicts subsequent bleeding attacks and how it correlates with the effect of direct bypass surgery in hemorrhagic moyamoya disease.

METHODS

Data from the Japanese Adult Moyamoya (JAM) Trial were used in this study: 158 hemispheres in 79 patients. A newly formed expert panel evaluated the SPECT results submitted at trial enrollment and classified the cortical hemodynamic state of the middle cerebral artery territory of each hemisphere into one of the following three groups: SPECT stage (SS) 0 as normal, SS1 as decreased cerebrovascular reserve (CVR), and SS2 as decreased CVR with decreased baseline blood flow. In the nonsurgical cohort of the JAM Trial, the subsequent hemorrhage rate during the 5-year follow-up was compared between the SS0 (hemodynamic failure negative) and SS1+2 (hemodynamic failure positive) groups. The effect of direct or combined direct/indirect bypass surgery on hemorrhage prevention was examined in each subgroup.

RESULTS

The hemodynamic grade was SS0 in 59 (37.3%) hemispheres, SS1 in 87 (55.1%), and SS2 in 12 (7.6%). In the nonsurgical cohort, subsequent hemorrhage rates in the SS0 and SS1+2 groups were 12 cases per 1000 person-years and 67 cases per 1000 person-years, respectively. Kaplan-Meier analysis revealed that hemorrhagic events were significantly more common in the SS1+2 group (p = 0.019, log-rank test). Cox regression analysis showed that hemodynamic failure was an independent risk factor for subsequent hemorrhage (HR 5.37, 95% CI 1.07-27.02). In the SS1+2 subgroup, bypass surgery significantly suppressed hemorrhagic events during 5 years (p = 0.001, HR 0.16, 95% CI 0.04-0.57), with no significant effect in the SS0 group (p = 0.655, HR 1.56, 95% CI 0.22-11.10). Examination of effect modification revealed that the effect of surgery tended to differ nonsignificantly between these two subgroups (p = 0.056).

CONCLUSIONS

Hemodynamic failure is an independent risk factor for subsequent hemorrhage in hemorrhagic moyamoya disease. Direct bypass surgery showed a significant preventive effect in the hemodynamically impaired hemispheres. Thus, hemodynamic failure, as well as previously proposed factors such as choroidal anastomosis, should be considered for the surgical indication in hemorrhagic moyamoya disease.Clinical trial registration no.: C000000166 (umin.ac.jp).

Cortical atrophy and transcallosal diaschisis following isolated subcortical stroke

Following acute ischemic stroke, isolated subcortical lesions induce gray matter atrophy in anatomically connected, yet distant cortical brain regions. We expand on previous studies by analyzing cortical thinning in contralesional, homologous regions indirectly linked to primary stroke lesions via ipsilesional cortical areas. For this purpose, stroke patients were serially studied by magnetic resonance imaging (diffusion tensor imaging and high-resolution anatomical imaging) in the acute (days 3-5) and late chronic stage one year after stroke. We analyzed changes of gray and white matter integrity in 18 stroke patients (median age 68 years) with subcortical stroke. We applied probabilistic fiber tractography to identify brain regions connected to stroke lesions and contralesional homologous areas. Cortical thickness was quantified by semi-automatic measurements, and fractional anisotropy was analyzed. One year after stroke, significant decrease of cortical thickness was detected in areas connected to ischemic lesions (mean -0.15 mm; 95% CI -0.23 to -0.07 mm) as well as homologous contralateral brain regions (mean -0.13 mm; 95% CI -0.07 to -0.19 mm). We detected reduced white matter integrity of inter- and intrahemispheric fiber tracts. There were no significant associations with clinical recovery. Our results indicate that impact of subcortical lesions extends to homologous brain areas via transcallosal diaschisis.

Degeneration of the Inferior Cerebellar Peduncle After Middle Cerebral Artery Stroke: Another Perspective on Crossed Cerebellar Diaschisis

Background and Purpose- Deafferentation of the cortico-ponto-cerebellar pathway has been proposed as a key mechanism of crossed cerebellar diaschisis. Although the cerebellum receives afferent stimuli from both cortico-ponto-cerebellar and spinocerebellar pathways, evidence on whether spinocerebellar deafferentation contributes to a hypofunctional cerebellum is lacking. Therefore, we aimed to determine whether changes in the spinocerebellar pathway occur after middle cerebral artery stroke. Methods- Twenty-three patients admitted to our inpatient rehabilitation facility and 23 age-matched healthy controls were retrospectively enrolled. Patients' functional ambulation category was determined and the Medical Research Council muscle scale test of the lower limb muscles was performed at admission and discharge. The fractional anisotropy (FA) values of the corticospinal tract and the inferior cerebellar peduncle (ICP), as the final route of the dorsal spinocerebellar pathway, were compared between the groups. The FA laterality indices of the ICP and corticospinal tract were calculated as follows: (FA_affected-FA_unaffected)/(FA_affected+FA_unaffected). Pearson correlation analysis and multivariate linear regression models were used to determine the associations between the FA laterality indices and ambulatory function. Results- The FAs of the corticospinal tract and ICP were lower in the patient group than in the control group. The FA laterality index of the corticospinal tract was not correlated with the functional ambulation category or Medical Research Council muscle scale score at admission or discharge. The FA laterality index of the ICP at the pontomedullary junction was positively correlated with the functional ambulation category and Medical Research Council muscle scale scores of all hemiplegic lower limb muscles at admission and discharge. The FA laterality index of the ICP at the pontomedullary junction was independently associated with the functional ambulation category according to the multivariate regression models. Conclusions- ICP degeneration occurs in the subacute and early chronic phase of middle cerebral artery stroke. The lower FA laterality index of the ICP was indicative of poorer ambulatory and lower limb function.

A complex relation between depression and multiple sclerosis: a descriptive review

BACKGROUND

Multiple sclerosis (MS) is a demyelinating neurodegenerative disease that affects central nervous system (CNS). MS patients are more likely to develop depressive symptoms than patients with other chronic diseases.

OBJECTIVE

In this review, we have analysed if there is a correlation between brain lesions (BL), structural damage (SD) and depressive symptoms (DS).

METHODS

We Searched on PubMed and Web of Science databases and screening references of included studied and some review article for additional citations. From initial 745 studies, only 9 met the inclusion criteria. All studies conducted research on 389 patients with MS associated with DS and 120 HC (healthy controls).

RESULTS

The selected researches highlighted the involvement of limbic system, the role of hippocampus and the impact of brain lesions on the emotional status of MS patients.

DISCUSSION

In the genesis of depression are implicated many mechanisms including genetic, biochemical, immunological and psychosocial factors, even if a prominent role in the onset of DS seem to be associated with structural and functional brain alterations.

Crossed Cerebellar Diaschisis Has an Adverse Effect on Functional Outcome in the Subacute Rehabilitation Phase of Stroke: A Case-Control Study

OBJECTIVE

To investigate whether crossed cerebellar diaschisis (CCD) is associated with functional outcome in the subacute rehabilitation phase of stroke.

DESIGN

Retrospective case-control study.

SETTING

Hospital-based cohort.

PARTICIPANTS

The study enrolled participants who underwent brain single-photon emission computed tomography (N=48). Patients with CCD were identified (n=24). Twenty-four controls were selected for each case-patient by matching age, stroke type (ischemic or hemorrhagic), lesion laterality, and lesion location.

INTERVENTION

Not applicable.

MAIN OUTCOME MEASURES

The functional ambulation category (FAC), modified Barthel Index (MBI), and Mini-Mental State Examination (MMSE) were administered at the initial (initiation of rehabilitation therapy) and the follow-up (4wk after rehabilitation therapy) assessments.

RESULTS

The CCD group had lower MMSE, FAC, MBI, and MMSE scores at the initial assessment (P=.032, .016, and .001, respectively) and lower FAC and MBI scores at the follow-up assessment, than the non-CCD group (P=.001 and .036, respectively). Although CCD was not associated with cognitive impairment, nonambulatory status, and dependent activities of daily living (ADL) at the initial assessment (P=.538, .083, and >.99, respectively), the CCD group had a higher risk of cognitive impairment (adjusted odds ratio [aOR]=4.044; 95% confidence interval [CI], 1.071-15.270; P=.039), nonambulatory status (aOR=7.000; 95% CI, 1.641-29.854; P=.009) and dependent ADL (aOR=13.500; 95% CI, 1.535-118.692; P=.019) at the follow-up assessment.

CONCLUSIONS

CCD is associated with severe functional impairment and may have an adverse effect on functional outcomes related to cognition, ambulatory function, and ADL during the subacute rehabilitation phase of stroke. This suggests that CCD may be a valuable predictor of functional outcome in the subacute rehabilitation phase of stroke.

A case of crossed cerebellar diaschisis on follow-up positron emission tomography/computed tomography with (18F) fluoro-D-glucose after treatment for glioblastoma

Crossed cerebellar diaschisis (CCD) represents the reduction of blood flow, metabolism, and oxygen consumption in the cerebellar hemisphere contralateral to a cerebral focal lesion. This phenomenon is the result of remote metabolic effects of cerebral lesions and it has been described since the first attempts for functional imaging of the brain, almost 40 years ago. Nevertheless, its clinical significance remains uncertain and new ways to use imaging of CCD for prognosis or assessment of novel therapies are being investigated. In this report, we present treatment for glioblastoma as a cause of CCD imaged on positron emission tomography/computed tomography with (¹⁸F) fluoro-D-glucose in our department.

PET Imaging of Crossed Cerebellar Diaschisis after Long-Term Cerebral Ischemia in Rats

Crossed cerebellar diaschisis (CCD) is a decrease of regional blood flow and metabolism in the cerebellar hemisphere contralateral to the injured brain hemisphere as a common consequence of stroke. Despite CCD has been detected in patients with stroke using neuroimaging modalities, the evaluation of this phenomenon in rodent models of cerebral ischemia has been scarcely evaluated so far. Here, we report the in vivo evaluation of CCD after long-term cerebral ischemia in rats using positron emission tomography (PET) imaging with 2-deoxy-2-[¹⁸F]fluoro-D-glucose ([¹⁸F]FDG). Imaging studies were combined with neurological evaluation to assess functional recovery. In the ischemic territory, imaging studies showed a significant decrease in glucose metabolism followed by a progressive recovery later on. Conversely, the cerebellum showed a contralateral hypometabolism from days 7 to 14 after reperfusion. Neurological behavior showed major impaired outcome at day 1 after ischemia followed by a significant recovery of the sensorimotor function from days 7 to 28 after experimental stroke. Taken together, these results suggest that the degree of CCD after cerebral ischemia might be predictive of neurological recovery.

Transient Symptomatic Downregulation of Cortical Neurotransmitter Receptor Function Due to Cerebral Hyperperfusion after Arterial Bypass Surgery for a Patient with Ischemic Moyamoya Disease

Cerebral hyperperfusion syndrome following arterial bypass surgery is known as a surgical complication of moyamoya disease (MMD). How cerebral hyperperfusion affects neural function and causes neurological deficits remains unknown. We report here a case with cerebral hyperperfusion syndrome after arterial bypass surgery for ischemic MMD. Chronological changes of brain perfusion and central benzodiazepine receptor biding potential were observed using single-photon emission computed tomography. A 20-year-old woman with ischemic MMD underwent arterial bypass surgery. Six days later, cerebral hyperperfusion syndrome developed. During this syndrome, contralateral-to-ipsilateral cerebellar asymmetry of blood flow and a decrease in central benzodiazepine receptor binding potential in the area with hyperperfusion were observed. Four months later, these two findings resolved and a neurological examination revealed no abnormal signs. Cerebral hyperperfusion after arterial bypass surgery for ischemic MMD may lead to transient, reversible reduction of cerebral metabolism and downregulation of cortical neurotransmitter receptor function, resulting in transient neurological deficits.

BOLD cerebrovascular reactivity as a novel marker for crossed cerebellar diaschisis

Objective

To study blood oxygen level–dependent cerebrovascular reactivity (BOLD-CVR) as a surrogate imaging marker for crossed cerebellar diaschisis (CCD).

Methods

Twenty-five participants with symptomatic unilateral cerebrovascular steno-occlusive disease underwent a BOLD-CVR and an acetazolamide challenged (15O)-H2O-PET study. CCD and cerebellar asymmetry index were determined from PET and compared to BOLD-CVR quantitative values. Neurologic status at admission and outcome after 3 months were determined with NIH Stroke Scale (NIHSS) and modified Rankin Scale (mRS) scores.

Results

For both the BOLD-CVR and PET examination, a significant cerebellar asymmetry index was found for participants exhibiting CCD (CCD+ vs CCD−: for BOLD-CVR 13.11 ± 9.46 vs 1.52 ± 4.97, p < 0.001; and for PET 7.31 ± 2.75 vs 1.68 ± 2.98, p < 0.001). The area under the curve for BOLD-CVR was 0.89 (95% confidence interval: 0.75–1.0) with 0.91 sensitivity and 0.81 specificity to detect CCD. Participants exhibiting CCD were in poorer clinical condition at baseline (CCD+ vs CCD−: NIHSS 7 vs 1, p = 0.003; mRS 3 vs 1, p = 0.001) and after 3-month follow-up (NIHSS 2 vs 0, p = 0.02; mRS 1 vs 0, p = 0.04). Worse performance on both scores showed an agreement with a larger BOLD-CVR cerebellar asymmetry index. This was not found for PET.

Conclusions

BOLD-CVR demonstrates similar sensitivity to detect CCD as compared to (15O)-H2O-PET in patients with symptomatic unilateral cerebrovascular steno-occlusive disease. Furthermore, participants exhibiting CCD had a poorer baseline neurologic performance and neurologic outcome at 3 months.

Classification of evidence

This study provides Class II evidence that BOLD-CVR identifies CCD in patients with symptomatic unilateral cerebrovascular steno-occlusive disease.

Quantitative assessment of changes in diffusion tensor imaging (DTI) metrics along the courses of the cortico-ponto-cerebellar tracts secondary to supratentorial human brain glial tumors

BACKGROUND

The cortico-ponto-cerebellar tract (CPCT) is the largest projection pathway, which synapses at the pons. Remote effects of supratentorial brain tumors have not been evaluated along the infratentorial course of the CPCT.

AIM

The purpose of this study is to evaluate the possible lateralization of the diffusion tensor metrics of the affected CPCT in patients with supratentorial brain tumor.

METHODS AND RESULTS

We included 39 patients with 29 left-sided tumors (LST) and 10 right-sided tumors, retrospectively. We measured the magnitude of changes of the fractional anisotropy (FA) and apparent diffusion coefficient (ADC) values of the CPCT prior to the brain surgery at the level of crus cerebri and middle cerebellar peduncle. Regions of interest (ROIs) were placed on the lateral side of crus cerebri, and ROI-1 (anterior 1/3), ROI-2 (middle 1/3), ROI-3 (posterior 1/3), and ROI-4 were placed at the level of middle cerebellar peduncle. We hypothesized that there would be decreased FA and increased ADC values of the ipsilesional CPCT compared with contralesional CPCT. Ipsilesional FA values were decreased with simultaneous increased ADC value along the CPCT compared with contralesional CPCT in following ROIs, ROI-1 (LST FA: P = .005, ADC: P = .037) and ROI-3 (LST FA: P = .049, ADC: P = .049), respectively. Affected ROI-4 in LST cases also showed lower FA values, although not statistically significant.

CONCLUSION

We observed a statistically significant FA value decrease and ADC increase along the left ROI-1 and ROI-3 as well as the nonstatistically significant FA decrease of the left ROI-4 at the second neuron level when there was a related supratentorial tumor. These findings are suggestive of presynaptic and postsynaptic microstructural changes of these tracts following the presynaptic involvement by a primary supratentorial brain tumor.

Crossed cerebellar hyperperfusion in patients with seizure-related cerebral cortical lesions: an evaluation with arterial spin labelling perfusion MR imaging

PURPOSE

Crossed cerebellar (CC) diaschisis refers to a decrease in cerebellar perfusion in the presence of contralateral supratentorial lesions. Most of the previous studies have examined stroke patients. In contrast to strokes, seizure-related cerebral cortical lesions (SCCLs) usually show hyperperfusion, and therefore, cerebellar perfusion patterns are expected to be different from those of strokes. With arterial spin labelling (ASL), we evaluated the cerebellar perfusion status in patients with SCCLs.

MATERIALS AND METHODS

Using a search of the recent database over the last 31 months, 26 patients were enrolled in this study. The inclusion criteria were as follows: (1) a history of seizures, (2) MR examination taken within 24 h from the last seizure, (3) the presence of SCCLs on T2/FLAIR or DWI, (4) hyperperfusion in the corresponding areas of SCCLs on ASL, and (5) no structural abnormality in the cerebellum. The perfusion status in the contralateral cerebellum was evaluated and categorized as hyper-, iso- and hypoperfusion. The asymmetric index (AI) of cerebellar perfusion was calculated by ROI measurement of the signal intensity on ASL.

RESULTS

The mean time between the last seizure and MR examinations was 5 h 30 min. CC hyperperfusion was observed in 17 patients (65.4%), hypoperfusion in 7 (26.9%) and isoperfusion in 2 (7.7%). Regarding the location of SCCLs, CC hyperperfusion was more frequent (71.4 vs. 58.3%), and the mean AI was higher (42.0 vs. 11.5) when the lesion involved the frontal lobe.

CONCLUSIONS

In patients with SCCLs, CC hyperperfusion occurred more often than hypo- and isoperfusion, especially when the lesions involved the frontal lobe.

Modification of Cerebellar Afferent Pathway in the Subacute Phase of Stroke

BACKGROUND

This study aims to identify the relationship between corticopontocerebellar tract (CPCT) and corticospinal tract (CST) integrity as well as motor function after stroke.

MATERIALS AND METHODS

A total of 33 patients with stroke (18 left, 15 right hemispheric lesions) who underwent diffusion tensor imaging within 2 months of stroke onset and 17 age- and sex-matched healthy controls were retrospectively enrolled. Tract volume and the asymmetry index based on tract volume (AI_TV) of the CST and CPCT were used to identify structural changes in individual tracts and the correlation between those tracts. Motor function was assessed using the Medical Research Council (MRC) muscle scale, manual function test (MFT), functional ambulation category, and modified Barthel index.

RESULTS

The volume of the affected CPCT was lower, and that of the unaffected CPCT was higher than the volumes in the control group (P < .001, P = .001, respectively). The CPCT AI_TV showed a strong positive correlation with the CST AI_TV in patients with either left or right hemispheric lesions (r_s = .779, P < .001; r_s = .732, P = .003, respectively). The CPCT AI_TV negatively correlated with the MRC muscle scale of the shoulder, wrist, and ankle muscles (r = -.490, -.490, -.416; P = .004, .004, .016, respectively). A higher unaffected CPCT volume was indicative of less affected upper extremity function, as assessed by MFT (r_s= -.546, P = .029).

CONCLUSIONS

Modification of the CPCT depended on CST integrity and was associated with the severity of hemiplegia and hemiplegic upper extremity function. The CPCT may complement the role of the CST and help to predict the motor function.

Pathological factors contributing to crossed cerebellar diaschisis in cerebral gliomas: a study combining perfusion, diffusion, and structural MR imaging

PURPOSE

To investigate imaging features of crossed cerebellar diaschisis (CCD) in cerebral gliomas, and its underlying pathophysiological mechanisms.

METHODS

Thirty-three pre-surgical patients with cerebral gliomas and 33 healthy controls underwent arterial spin-labeling, diffusion tensor imaging, and high-resolution T1-weighted imaging using MRI, in order to estimate cerebral blood flow (CBF), white matter integrity, and lesion volume, respectively. Asymmetry indices of CBF in the cerebellum were used for evaluating the level of CCD in the patients. These indices were correlated with clinical variables (lesion size and position, tumor histological grade, and CBF asymmetry) and diffusion tensor imaging parameters (fractional anisotropy and number of fibers in the cortico-ponto-cerebellar pathway and across the cerebral hemispheres), respectively.

RESULTS

The patients showed decreased CBF in the cerebellar hemisphere contralateral to the supratentorial tumor, and increased CBF asymmetry in the cerebellum (both P < 0.05). CCD levels in high-grade gliomas were higher than those of low-grade gliomas (P < 0.05). CCD levels were negatively correlated with the size of the supratentorial lesions, and positively correlated with FA asymmetry in the cerebral fibers (both P < 0.05).

CONCLUSIONS

CCD in cerebral gliomas was specifically associated with tumor histological grade, lesion size, and white matter impairments in the hemisphere ipsilateral to the tumor. The findings implicated that observing CCD might have potential for assisting grading diagnosis of cerebral gliomas.

Remote effects in the ipsilateral thalamus and/or contralateral cerebellar hemisphere using FDG PET in patients with brain tumors

PURPOSE

To evaluate reduced metabolism in the ipsilateral thalamus (TH) and/or contralateral cerebellum (CE) according to tumor localization and cortical metabolism around the tumor in patients with brain tumors based on FDG uptake.

METHODS

This study investigated 48 consecutive patients with solitary cerebral hemisphere parenchymal brain tumors who underwent PET/CT and MRI. Patients were divided into 4 groups (A: reduced uptake in ipsilateral TH and contralateral CE, B: reduced uptake in ipsilateral TH only, C: reduced uptake in contralateral CE only, and D: no reduced uptake in ipsilateral TH or contralateral CE). FDG uptake and MRI findings were compared among these groups.

RESULTS

Of 48 patients, group A included 24 (50%), group B included 10 (21%), group C included 0, and group D included 14 (29%). No significant tendencies were observed between the groups regarding tumor localization. However, reduced cortical metabolism around the tumor was observed in 22 patients in group A, 7 patients in group B, and 1 patient in group D. All patients in group B showed reduced metabolism from around the tumor up to the ipsilateral TH.

CONCLUSION

Reduced FDG uptake in ipsilateral TH and contralateral CE usually occur simultaneously in patients with solitary brain tumors.

Crossed cerebellar diaschisis in acute ischemic stroke: Impact on morphologic and functional outcome

Crossed cerebellar diaschisis (CCD) is the phenomenon of hypoperfusion and hypometabolism of the contralateral cerebellar hemisphere caused by dysfunction of the related supratentorial region. Our aim was to analyze its influence on morphologic and functional outcome in acute ischemic stroke. Subjects with stroke caused by a large vessel occlusion of the anterior circulation were selected from an initial cohort of 1644 consecutive patients who underwent multiparametric CT including whole-brain CT perfusion. Two experienced readers evaluated the posterior fossa in terms of CCD absence (CCD-) or presence (CCD+). A total of 156 patients formed the study cohort with 102 patients (65.4%) categorized as CCD- and 54 (34.6%) as CCD+. In linear and logistic regression analyses, no significant association between CCD and final infarction volume (β = -0.440, p = 0.972), discharge mRS ≤ 2 (OR = 1.897, p = 0.320), or 90-day mRS ≤ 2 (OR = 0.531, p = 0.492) was detected. CCD+ patients had larger supratentorial cerebral blood flow deficits (median: 164 ml vs. 115 ml; p = 0.001) compared to CCD-patients. Regarding complications, CCD was associated with a higher rate of parenchymal hematomas (OR = 4.793, p = 0.035). In conclusion, CCD is frequently encountered in acute ischemic stroke caused by large vessel occlusion of the anterior circulation. CCD was associated with the occurrence of parenchymal hematoma in the ipsilateral cerebral infarction but did not prove to significantly influence patient outcome.

Metabolic alterations in the rat cerebellum following acute middle cerebral artery occlusion, as determined by 1H NMR spectroscopy

Supratentorial focal ischemia may reduce cerebral blood volume and cerebellar glucose metabolic rate contralateral to the region of ischemia. The present study investigated the effects of middle cerebral artery occlusion (MCAO) on cerebral metabolism in the ischemic cerebral hemisphere and the non‑ischemic cerebellum in rats 1, 3, 9 and 24 h following ischemia using ex vivo proton nuclear magnetic resonance (1H NMR) spectroscopy. The results demonstrated that focal ischemia induced increases in the levels of lactate and alanine, and a decrease in succinate, as early as 1 h following ischemia in the left cerebral hemisphere and the right cerebellum. A continuous increase in lactate levels and decrease in creatine levels were detected in both cerebral areas 3 and 24 h post‑MCAO. The most obvious difference between the two cerebral areas was that there was no statistically significant difference in N‑acetyl aspartate (NAA) levels in the right cerebellum at all time points; however, the amino acid levels of NAA in the left cerebral hemisphere were markedly decreased 3, 9 and 24 h post‑MCAO. In addition, an obvious increase in glutamine was observed in the right and left cerebellum at 3, 9 and 24 h post‑MCAO. Furthermore, the present study demonstrated that γ‑aminobutyric acid levels were decreased at 1 h in the left and right cerebellum and were evidently increased at 24 h in the right cerebellum post‑MCAO. In conclusion, supratentorial ischemia has been indicated to affect the activities of the non‑ischemic contralateral cerebellum. Therefore, these results suggested that an NMR‑based metabonomic approach may be used as a potential means to elucidate cerebral and cerebellar metabolism following MCAO, which may help improve understanding regarding cerebral infarction at a molecular level. Ex vivo 1H NMR analysis may be useful for the assessment of clinical biopsies.

Chronological Changes in Brain Blood Flow and Central Benzodiazepine Receptor Binding Potential in a Patient with Symptomatic Epilepsy after Surgery for Aneurysmal Subarachnoid Hemorrhage: 123I-Iomazenil Single-Photon Emission Computed Tomography Studies

Early ¹²³I-iomazenil single-photon emission computed tomography (SPECT) images are correlated with blood flow in the brain, and late images are correlated with cortical benzodiazepine receptor binding potential. Reduced metabolism in the contralateral cerebral hemisphere is indicated by crossed cerebellar hypoperfusion (CCH). We present the case of a 63-year-old man who developed symptomatic epilepsy 13 days after surgery for an aneurysmal subarachnoid hemorrhage. Early images on ¹²³I-iomazenil SPECT 2 days after seizure onset revealed CCH and hyperperfusion in the affected cerebral hemisphere where benzodiazepine receptor binding potential was reduced in late images on ¹²³I-iomazenil SPECT. These abnormal findings resolved on repeated ¹²³I-iomazenil SPECT 1 month after seizure onset. The case we present here is consistent with the idea that the central benzodiazepine receptor system in the human brain undergoes changes that are related to seizures due to epilepsy.

Ataxic Hemiparesis Associated with Cortical Infarct Localized in the Postcentral Gyrus

Ataxic hemiparesis (AH) is a classic lacunar syndrome associated with localized damage to the pons, internal capsule, thalamus, or corona radiata. A depression of metabolic activity known as crossed cerebellar diaschisis (CCD) is frequently observed in the cerebellar hemisphere contralateral to the site of the lesion in patients with AH. Though small cortical or subcortical lesions may result in AH, such occurrences are rare. The current report details the case of a patient with AH resulting from acute infarction associated with localized lesions of the postcentral gyrus who presented without CCD.

An exploration of the spectrum of peri-ictal MRI change; a comprehensive literature review

PURPOSE

The aim of this review was to identify published studies in the literature relating to ictal induced MRI change and to identify certain common themes, practical points for clinicians and areas for future research.

METHODS

We identified 96 articles that satisfied our inclusion criteria yielding 575 cases. All articles were analysed; number of subjects, spectrum of MRI and EEG change, aetiology, and follow-up (both clinical and imaging) were noted.

RESULTS

The most frequent imaging changes were restricted diffusion, T2-hyperintensity and reduced ADC values. The mesial temporal structures and neocortex were most commonly affected locations though subcortical structures like the thalamus and pulvinar were also described. Practical clinical points included; the development of PLEDS concordant with ictal imaging change was associated with worse clinical prognosis, patients with seizures due to symptomatic aetiology may be more likely to develop ictal related imaging change and follow up is vitally important to ensure that ictal related oedema is not misidentified as a mass lesion or conversely that a mass lesion is not misidentified as ictal related change.

CONCLUSION

Qualitative MRI studies have provided clinicians with useful in-vivo insights into the dynamic ictal neuronal environment. Changes are not only localised to the ictal focus but can be remote and irreversible. Small patient numbers varying study design and high numbers of symptomatic seizures makes comparison between studies problematic. Also there is possible microstructural quantitative MRI changes that are missed on qualitative MRI. There is a need for prospective quantitative MRI studies in patients with epilepsy peri-icatlly with a uniform period of follow up and comparison to control data.

Optimal Brain 99mTc-Ethyl Cysteinate Dimer SPECT Imaging and Analysis to Detect Misery Perfusion on 15O PET Imaging in Patients With Chronic Occlusive Disease of Unilateral Major Cerebral Artery

PURPOSE

Misery perfusion is defined as marginally sufficient cerebral blood supply relative to cerebral metabolic demand. The aim of the present study was to determine the optimal brain Tc-ethyl cysteinate dimer (ECD) SPECT imaging and analysis to detect misery perfusion on O PET imaging in patients with chronic occlusive disease of unilateral internal carotid or middle cerebral artery (MCA).

METHODS

For 97 patients, cerebral blood flow, cerebral metabolic rate of oxygen, and oxygen extraction fraction were measured using O PET; Tc-ECD SPECT was performed using dynamic scanning with a scan duration of 10 minutes each for 50 minutes after tracer administration. A region of interest was placed in the bilateral MCA territories and in the bilateral cerebellar hemispheres in all standardized images using a 3-dimensional stereotaxic region-of-interest template and affected-to-contralateral asymmetry ratio in the MCA territory (ARMCA) and contralateral-to-affected asymmetry ratio in the cerebellar hemisphere (ARcbl) were calculated.

RESULTS

The ARMCA or ARcbl on Tc-ECD SPECT with a scan time of 20 to 30 minutes after tracer administration (ARMCA20-30 or ARcbl20-30) was correlated with ARMCA on PET cerebral blood flow (r = 0.654) or ARMCA on PET cerebral metabolic rate of oxygen (r = 0.576), respectively, more strongly than with other scan times. The area under the receiver operating characteristic curve for detecting abnormally elevated ARMCA on PET oxygen extraction fraction was significantly greater for ARcbl20-30/ARMCA20-30 (0.947) than for ARMCA20-30 alone (0.780) (difference between areas, 0.167; P = 0.0001) on Tc-ECD SPECT.

CONCLUSIONS

Combination of asymmetries in the cerebellar and cerebral hemispheres on Tc-ECD SPECT in a scan time of 20 to 30 minutes after tracer administration optimally detects misery perfusion in unilateral internal carotid artery or MCA occlusive disease.

Detection of crossed cerebellar diaschisis in hyperacute ischemic stroke using arterial spin-labeled MR imaging

Background and purpose

Arterial spin-labeling (ASL) was recently introduced as a noninvasive method to evaluate cerebral hemodynamics. The purposes of this study were to assess the ability of ASL imaging to detect crossed cerebellar diaschisis (CCD) in patients with their first unilateral supratentorial hyperacute stroke and to identify imaging or clinical factors significantly associated with CCD.

Materials and methods

We reviewed 204 consecutive patients who underwent MRI less than 8 hours after the onset of stroke symptoms. The inclusion criteria were supratentorial abnormality in diffusion-weighted images in the absence of a cerebellar or brain stem lesion, bilateral supratentorial infarction, subacute or chronic infarction, and MR angiography showing vertebrobasilar system disease. For qualitative analysis, asymmetric cerebellar hypoperfusion in ASL images was categorized into 3 grades. Quantitative analysis was performed to calculate the asymmetric index (AI). The patients’ demographic and clinical features and outcomes were recorded. Univariate and multivariate analyses were also performed.

Results

A total of 32 patients met the inclusion criteria, and 24 (75%) presented CCD. Univariate analyses revealed more frequent arterial occlusions, higher diffusion-weighted imaging (DWI) lesion volumes and higher initial NIHSS and mRS scores in the CCD-positive group compared with the CCD-negative group (all p < .05). The presence of arterial occlusion and the initial mRS scores were related with the AI (all p < .05). Multivariate analyses revealed that arterial occlusion and the initial mRS scores were significantly associated with CCD and AI.

Conclusion

ASL imaging could detect CCD in 75% of patients with hyperacute infarction. We found that CCD was more prevalent in patients with arterial occlusion, larger ischemic brain volumes, and higher initial NIHSS and mRS scores. In particular, vessel occlusion and initial mRS score appeared to be significantly related with CCD pathophysiology in the hyperacute stage.

Different subregional metabolism patterns in patients with cerebellar ataxia by 18F-fluorodeoxyglucose positron emission tomography

We evaluated cerebellar subregional metabolic alterations in patients with cerebellar ataxia, a representative disease involving the spinocerebellum. We retrospectively analyzed ¹⁸F-fluorodeoxyglucose positron emission tomography (¹⁸F-FDG PET) images in 44 patients with multiple system atrophy of the cerebellar type (MSA-C), 9 patients with spinocerebellar ataxia (SCA) type 2, and 14 patients with SCA type 6 and compared with 15 patients with crossed cerebellar diaschisis (CCD) and 89 normal controls. Cerebellar subregional metabolism was assessed using 13 cerebellar subregions (bilateral anterior lobes [ANT], superior/mid/inferior posterior lobes [SUPP/MIDP/INFP], dentate nucleus [DN], anterior vermis [ANTV], and superior/inferior posterior vermis [SUPV/INFV]) to determine FDG uptake ratios. MSA-C and SCA type 2 showed severely decreased metabolic ratios in all cerebellar subregions compared to normal controls (ANT, 0.58 ± 0.08 and 0.50 ± 0.06 vs. 0.82 ± 0.07, respectively, p < 0.001). SCA type 6 showed lower metabolic ratios in almost all cerebellar subregions (ANT, 0.57 ± 0.06, p < 0.001) except INFV. Anterior-posterior lobe ratio measurements revealed that SCA type 2 (Right, 0.81 ± 0.05 vs. 0.88 ± 0.04, p < 0.001; Left, 0.83 ± 0.05 vs. 0.88 ± 0.04, p = 0.003) and SCA type 6 (Right, 0.72 ± 0.05 vs. 0.88 ± 0.04, p < 0.001; Left, 0.72 ± 0.05 vs. 0.88 ± 0.04, p < 0.001) showed preferential hypometabolism in the anterior lobe compared to normal controls, which was not observed in CCD and MSA-C. Asymmetric indices were higher in CCD and MSA-C than in normal controls (p < 0.001), whereas such differences were not found in SCA types 2 and 6. In summary, quantitative analysis of cerebellar subregional metabolism ratios revealed preferential involvement of the anterior lobe, corresponding to the spinocerebellum, in patients with cerebellar ataxia, whereas patients with CCD and MSA-C exhibited more asymmetric hypometabolism in the posterior lobe.

Longitudinal Changes in Cerebellar and Thalamic Spontaneous Neuronal Activity After Wide-Awake Surgery of Brain Tumors: a Resting-State fMRI Study

Hypometabolism has been observed in the contralesional cerebellar hemisphere after various supratentorial cortical lesions. It is unknown whether the consequences of the dee- and deafferentation subsequent to wide-awake surgery for brain diffuse low-grade glioma can be assessed within remote and unresected subcortical structures such as the cerebellum or thalamus. To answer this question, we have conducted several regional analyses. More specifically, we have performed amplitude of low-frequency fluctuations (neuronal activity magnitude) and regional homogeneity (local temporal correlations) analyses on resting state functional magnetic resonance imaging (rs-fMRI) data and at different time points, before and after surgery. Our main results demonstrated that it is possible to evaluate subtle subcortical changes using these tools dedicated to the analysis of rs-fMRI data. The observed variations of spontaneous neuronal activity were particularly significant within the cerebellum which showed altered regional homogeneity and neuronal activity intensity in very different, specialized and non-overlapping subregions, in accordance to its neuro-anatomo-functional topography. These variations were moreover observed in the immediate postoperative period and recovered after 3 months.

Topographic changes in cerebral blood flow and reduced white matter integrity in the first 2 weeks following revascularization surgery in adult moyamoya disease

OBJECTIVE After revascularization surgery, hyperperfusion and ischemia are associated with morbidity and mortality in adult moyamoya disease (MMD). However, structural changes within the brain following revascularization surgery, especially in the early postsurgical period, have not been thoroughly studied. Such knowledge may enable improved monitoring and clinical management of hyperperfusion and ischemia in MMD. Thus, the objective of this study was to investigate the topographic and temporal profiles of cerebral perfusion and related white matter microstructural changes following revascularization surgery in adult MMD. METHODS The authors analyzed 20 consecutive surgeries performed in 17 adults. Diffusion imaging in parallel with serial measurements of regional cerebral blood flow (rCBF) using SPECT was performed. Both voxel-based and region-of-interest analyses were performed, comparing neuroimaging parameters of postoperative hemispheres with those of preoperative hemispheres at 4 different time points within 2 weeks after surgery. RESULTS Voxel-based analysis showed a distinct topographic pattern of cerebral perfusion, characterized by increased rCBF in the basal ganglia for the first several days and gradually increased rCBF in the lateral prefrontal cortex over 1 week (p < 0.001). Decreased rCBF was also observed in the lateral prefrontal cortex, occipital lobe, and cerebellum contralateral to the surgical hemisphere (p < 0.001). Reduced fractional anisotropy (FA) and axial diffusivity (AD), as well as increased radial diffusivity (RD), were demonstrated in both the anterior and posterior limbs of the internal capsule (p < 0.001). Diffusion parameters demonstrated the greatest changes in both FA and RD on Days 1-2 and in AD on Days 3-6; FA, RD, and AD recovered to preoperative levels on Day 14. Patients with transient neurological deteriorations (TNDs), as compared with those without, demonstrated greater increases in rCBF in both the lateral prefrontal cortex and striatum as well as smaller FAs in the posterior limb of the internal capsule (p < 0.05). CONCLUSIONS The excessively increased rCBF and the recovery process were heterogeneous across brain regions, demonstrating a distinct topographic pattern during the initial 2 weeks following revascularization surgery in MMD. Temporary impairments in the deep white matter tract and immediate postoperative ischemia were also identified. The study results characterized postoperative brain perfusion as well as the impact of revascularization surgery on the brain microstructure. Notably, rCBF and white matter changes correlated to TNDs, suggesting that these changes represent potential neuroimaging markers for tracking tissue structural changes associated with hyperperfusion during the acute postoperative period following revascularization surgery for MMD.

Review : Metabolic Imaging: A Window on Brain Development and Plasticity

Various biochemical and physiological processes that undergo maturational changes during human brain development can be now studied in vivo using PET. The distribution of local cerebral glucose utilization shows regional alterations in the first year of life in agreement with behavioral, neurophysiological, and anatomical changes known to occur during development of the infant. Measurement of the absolute rates of glucose utilization with PET reveals that during the major portion of the first decade, the human brain has a higher energy (glucose) demand compared with both the newborn and adult brains. With adolescence, glucose utilization rates decline to reach adult values by age 16-18 years. This nonlinear course of cerebral glucose 'metabolic' maturation is also seen in a number of animal models and coincides with the develop mental course of transient synaptic exuberance associated with enhanced brain plasticity and efficient learn ing. Evidence of brain reorganization detected with PET is discussed in children with unilateral brain injury and early sensory deprivation. NEUROSCIENTIST 5:29-40, 1999