Huntington's disease (HD) results from the expansion of a polyglutamine encoding CAG repeat in a gene of unknown function. The wide expression of this transcript does not correlate with the pattern of neuropathology in HD. To study the HD gene product (huntingtin), we have developed monoclonal antibodies raised against four different regions of the protein. On western blots, these monoclonals detect the approximately 350 kD huntingtin protein in various human cell lines and in neural and non-neural rodent tissues. In cell lines from HD patients, a doublet protein is detected corresponding to the mutated and normal huntingtin. Immunohistochemical studies in the human brain using two of these antibodies detects the huntingtin in perikarya of some neurons, neuropiles, varicosities and as punctate staining likely to be nerve endings.

Aim The aim of this paper is to describe the clinical features of COVID‐19‐related encephalopathy and their metabolic correlates using brain 2‐desoxy‐2‐fluoro‐D‐glucose (FDG)‐positron‐emission tomography (PET)/computed tomography (CT) imaging. Background and purpose A variety of neurological manifestations have been reported in association with COVID‐19. COVID‐19‐related encephalopathy has seldom been reported and studied. Methods We report four cases of COVID‐19‐related encephalopathy. The diagnosis was made in patients with confirmed COVID‐19 who presented with new‐onset cognitive disturbances, central focal neurological signs, or seizures. All patients underwent cognitive screening, brain magnetic resonance imaging (MRI), lumbar puncture, and brain 2‐desoxy‐2‐fluoro‐D‐glucose (FDG)‐positron‐emission tomography (PET)/computed tomography (CT) (FDG‐PET/CT). Results The four patients were aged 60 years or older, and presented with various degrees of cognitive impairment, with predominant frontal lobe impairment. Two patients presented with cerebellar syndrome, one patient had myoclonus, one had psychiatric manifestations, and one had status epilepticus. The delay between first COVID‐19 symptoms and onset of neurological symptoms was between 0 and 12 days. None of the patients had MRI features of encephalitis nor significant cerebrospinal fluid (CSF) abnormalities. SARS‐CoV‐2 RT‐PCR in the CSF was negative for all patients. All patients presented with a consistent brain FDG‐PET/CT pattern of abnormalities, namely frontal hypometabolism and cerebellar hypermetabolism. All patients improved after immunotherapy. Conclusions Despite varied clinical presentations, all patients presented with a consistent FDG‐PET pattern, which may reflect an immune mechanism.

GPR56 mutations cause an autosomal recessive polymicrogyria syndrome that has distinctive radiological features combining bilateral frontoparietal polymicrogyria, white matter abnormalities and cerebellar hypoplasia. Recent investigations of a GPR56 knockout mouse model suggest that bilateral bifrontoparietal polymicrogyria shares some features of the cobblestone brain malformation and demonstrate that loss of GPR56 leads to a dysregulation of the maintenance of the pial basement membrane integrity in the forebrain and the rostral cerebellum. In light of these findings and other data in the literature, this study aimed to refine the clinical features with the first description of a foetopathological case and to define the range of cobblestonelike features in GPR56 bilateral bifrontoparietal polymicrogyria in a sample of 14 patients. We identified homozygous GPR56 mutations in 14 patients from eight consanguineous families with typical bilateral bifrontoparietal polymicrogyria and in one foetal case, out of 30 patients with bifrontoparietal polymicrogyria referred for molecular screening. The foetal case, which was terminated at 35 weeks of gestation in view of suspicion of Walker Warburg syndrome, showed a cobblestone-like lissencephaly with a succession of normal, polymicrogyric and 'cobblestone-like' cortex with ectopic neuronal overmigration, agenesis of the cerebellar vermis and hypoplastic cerebellar hemispheres with additional neuronal overmigration in the pons and the cerebellar cortex. The 14 patients with GPR56 mutations (median 8.25 years, range 1.5-33 years) were phenotypically homogeneous with a distinctive clinical course characterized by pseudomyopathic behaviour at onset that subsequently evolved into severe mental and motor retardation. Generalized seizures (12/14) occurred later with onset ranging from 2.5 to 10 years with consistent electroencephalogram findings of predominantly anterior bursts of low amplitude a-like activity. Neuroimaging demonstrated a common phenotype with bilateral frontoparietally predominant polymicrogyria (13/13), cerebellar dysplasia with cysts mainly affecting the superior vermis (11/13) and patchy to diffuse myelination abnormalities (13/13). Additionally, the white matter abnormalities showed a peculiar evolution from severe hypomyelination at 4 months to patchy lesions later in childhood. Taken as a whole, these observations collectively demonstrate that GPR56 bilateral bifrontoparietal polymicrogyria combines all the features of a cobblestone-like lissencephaly and also suggest that GRP56-related defects produce a phenotypic continuum ranging from bilateral bifrontoparietal polymicrogyria to cobblestone-like lissencephaly.

BackgroundEarly onset epileptic encephalopathies (EOEEs) are dramatic heterogeneous conditions in which aetiology, seizures and/or interictal EEG have a negative impact on neurological development. Several genes have been associated with EOEE and a molecular diagnosis workup is challenging since similar phenotypes are associated with mutations in different genes and since mutations in one given gene can be associated with very different phenotypes. Recently, de novo mutations in KCNQ2, have been found in about 10% of EOEE patients. Our objective was to confirm that KCNQ2 was an important gene to include in the diagnosis workup of EOEEs and to fully describe the clinical and EEG features of mutated patients.MethodsWe have screened KCNQ2 in a cohort of 71 patients with an EOEE, without any brain structural abnormality. To be included in the cohort, patient’s epilepsy should begin before three months of age and be associated with abnormal interictal EEG and neurological impairment. Brain MRI should not show any structural abnormality that could account for the epilepsy.ResultsOut of those 71 patients, 16 had a de novo mutation in KCNQ2 (23%). Interestingly, in the majority of the cases, the initial epileptic features of these patients were comparable to those previously described in the case of benign familial neonatal epilepsy (BFNE) also caused by KCNQ2 mutations. However, in contrast to BFNE, the interictal background EEG was altered and displayed multifocal spikes or a suppression-burst pattern. The ongoing epilepsy and development were highly variable but overall severe: 15/16 had obvious cognitive impairment, half of the patients became seizure-free, 5/16 could walk before the age of 3 and only 2/16 patient acquired the ability to speak.ConclusionThis study confirms that KCNQ2 is frequently mutated de novo in neonatal onset epileptic encephalopathy. We show here that despite a relatively stereotyped beginning of the condition, the neurological and epileptic evolution is variable.

Purpose Little is known about the neuronal substrates of neuropsychiatric symptoms associated with COVID-19 and their evolution during the course of the disease. We aimed at describing the longitudinal brain metabolic pattern in COVID-19related encephalopathy using 18F-FDG-PET/CT. Methods Seven patients with variable clinical presentations of COVID-19-related encephalopathy were explored thrice with brain 18F-FDG-PET/CT, once in the acute phase, 1 month later and 6 months after COVID-19 onset. PET images were analysed with voxel-wise and regions-of-interest approaches in comparison with 32 healthy controls. Results Patients' neurological manifestations during acute encephalopathy were heterogeneous. However, all of them presented with predominant cognitive and behavioural frontal disorders. SARS-CoV-2 RT-PCR in the CSF was negative for all patients. MRI revealed no specific abnormalities for most of the subjects. All patients had a consistent pattern of hypometabolism in a widespread cerebral network including the frontal cortex, anterior cingulate, insula and caudate nucleus. Six months after COVID-19 onset, the majority of patients clinically had improved but cognitive and emotional disorders of varying severity remained with attention/executive disabilities and anxio-depressive symptoms, and lasting prefrontal, insular and subcortical 18F-FDG-PET/CT abnormalities. Conclusion The implication of this widespread network could be the neural substrate of clinical features observed in patients with COVID-19, such as frontal lobe syndrome, emotional disturbances and deregulation of respiratory failure perception. This study suggests that this network remains mildly to severely impaired 6 months after disease onset.