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Pathogenic variants in A Disintegrin And Metalloproteinase (ADAM) 22, the postsynaptic cell membrane receptor for the glycoprotein leucine-rich repeat glioma-inactivated protein 1 (LGI1), have been recently associated with recessive developmental and epileptic encephalopathy. However, so far, only two affected individuals have been described and many features of this disorder are unknown. We refine the phenotype and report 19 additional individuals harbouring compound heterozygous or homozygous inactivating ADAM22 variants, of whom 18 had clinical data available. Additionally, we provide follow-up data from two previously reported cases. All affected individuals exhibited infantile-onset, treatment-resistant epilepsy. Additional clinical features included moderate to profound global developmental delay/intellectual disability (20/20), hypotonia (12/20) and delayed motor development (19/20). Brain MRI findings included cerebral atrophy (13/20), supported by post-mortem histological examination in patient-derived brain tissue, cerebellar vermis atrophy (5/20), and callosal hypoplasia (4/20). Functional studies in transfected cell lines confirmed the deleteriousness of all identified variants and indicated at least three distinct pathological mechanisms: (i) defective cell membrane expression; (ii) impaired LGI1-binding; and/or (iii) impaired interaction with the postsynaptic density protein PSD-95. We reveal novel clinical and molecular hallmarks of ADAM22 deficiency and provide knowledge that might inform clinical management and early diagnostics.

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BACKGROUND: Traumatic brain injury (TBI) is a major cause of infant morbidity and mortality. In these patients, magnetic resonance imaging (MRI) including diffusion-weighted imaging (DWI) is the test of choice to describe the extent of microstructural injury. CASE PRESENTATION AND DISCUSSION: In this case series, we describe novel acute and chronic MRI findings in four infants (6-19 months) with small, unilateral subdural hematomas in whom the etiology of head injury was suspicious for non-accidental trauma (NAT). Acute (<1-week post-injury) DWI revealed extensive areas of restricted diffusion isolated to the cerebral white matter predominantly ipsilateral to the subdural hematoma. After prolonged pediatric intensive care treatment including subdural evacuation (n = 2) or decompressive craniectomy (n = 1), all patients survived albeit with significant motor and cognitive deficits. Delayed structural MRI (6-9-year post-injury) demonstrated cortical and subcortical atrophy well-correlated with areas of acute restricted diffusion. CONCLUSION: These four cases highlight that relatively small subdural hematomas can be associated with extensive white matter injury-detectable only by early DWI-which have long-term structural and functional consequences.

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Introduction. Acute complete external ophthalmoplegia is a rare finding in clinical practice that is associated with diseases affecting the neuromuscular junction, the oculomotor nerves, or the brainstem. Ophthalmoplegia has been reported with acute ataxia in Miller Fisher syndrome (MFS) and Bickerstaff brainstem encephalitis (BBE). Up to 95% of these cases are associated with anti-GQ1b antibodies. Only a small number of cases of anti-GQ1b negative MFS have been documented in pediatric patients. This is the first case reporting a recurrence of ocular symptoms in an anti-GQ1b antibody negative patient with BBE. Case Presentation. An 8-year-old Caucasian boy presented with complete external ophthalmoplegia without ptosis, cerebellar ataxia, and a disturbance of consciousness. He had recently recovered from a confirmed Campylobacter jejuni infection. On subsequent laboratory testing he was anti-GQ1b antibody negative. He had a recurrence of diplopia at four-week follow-up. Conclusions. This patient's recurrence of diplopia was treated with a five-week course of oral corticosteroids which did not worsen his condition, and this may be a therapeutic option for similar patients. We will discuss the symptoms and treatment of reported pediatric cases of anti-GQ1b antibody negative cases of MFS and the variation between cases representing a spectrum of illness.

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Trisomy 21 is the most common viable trisomy. Although it is invariably associated with mild to severe developmental delay and intellectual disability, no gross central nervous system malformation has been consistently identified in individuals with trisomy 21. We present the case of a monozygotic twin pregnancy in which both fetuses were identified as having trisomy 21 and partial agenesis of the corpus callosum. We discuss this rare association in the context of an emerging understanding of the neurobiology of trisomy 21.

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Pontocerebellar hypoplasia consists of a rare heterogeneous group of congenital neurodevelopmental disorders. It is characterized by hypoplasia and atrophy of the cerebellar cortex, dentate nuclei, pontine nuclei, and inferior olives. We present an 18-month-old infant with pontocerebellar hypoplasia type 3 and severe vitamin A deficiency. This case emphasizes the significance of vitamin A in the proper formation of the hindbrain. The authors conclude that vitamin A screening should be considered in maternal and newborn metabolic screening.

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Abnormal copper metabolism has been linked with neurological disorders, such as Wilson and Menkes disease. Another disorder causing symptoms similar to copper metabolism disorder is Niemann-Pick type C. However, a definite pathophysiological connection between Niemann-Pick type C and copper metabolism disorders has never been established. The authors present an adolescent with an unusual presentation of copper deficiency-dysarthria, ataxia, and vertical gaze paresis, without significant cognitive degeneration or pathological magnetic resonance imaging (MRI). The patient was found to carry 2 mutations in the NPC1 gene. A possible link, explaining how copper deficiency might induce the Niemann-Pick phenotype might involve overproduction of cholesterol and inhibition of acid sphingomyelinase. We suggest that copper metabolism disorders be included in the differential diagnosis for ataxia and dysarthria, even in cases with unusual presentations. Moreover, should the connection between copper and Niemann-Pick be validated, screening for copper metabolism disorders may be advisable in Niemann-Pick type C patients and vice-versa.

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Copper is a trace element that is required for cellular respiration, neurotransmitter biosynthesis, pigment formation, antioxidant defense, peptide amidation, and formation of connective tissue. Abnormalities of copper metabolism have been linked with neurologic disorders that affect movement, such as Wilson disease and Menkes disease; however, the diagnosis of non-Wilson, non-Menkes-type copper-metabolism disorders has been more elusive, especially in cases with atypical characteristics. We present here the case of an adolescent with a novel presentation of copper-metabolism disorder who exhibited acute severe hemilingual dyskinesia and prominent tics, with ballismus of the upper limbs, but had normal brain and spinal MRI results and did not show any signs of dysarthria or dysphagia. His serum copper and ceruloplasmin levels were low, but his urinary copper level was elevated after penicillamine challenge. We conclude that copper-metabolism disorders should be included in the differential diagnosis for movement disorders, even in cases with highly unusual presentations, because many of them are treatable. Moreover, a connection between copper-metabolism disorders and tics is presented, to our knowledge, for the first time in humans; further investigation is needed to better establish this connection and understand its underlying pathophysiology.

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Trisomy 9p is a well-described dysmorphic syndrome. The physical features include hypertelorism, down-slanting palpebral fissures, deep-set eyes, down-turned corners of the mouth, and mild skeletal anomalies including hypoplastic terminal phalanges. We report an infant born with some of the typical features of trisomy 9p syndrome, as well as additional features that include extreme joint hyperlaxity with subluxation of the knees and elbows, arachnodactyly, and total anomalous pulmonary venous return. The karyotype revealed an unbalanced chromosome complement. Specifically, a derivative chromosome from a de-novo unbalanced translocation of chromosomes 9 and 15 resulted in partial trisomy of 9pter to 9q13 and deletion of the long arm of chromosome 15 proximal to band q13. Fluorescence in-situ hybridization studies and methylation analysis by Southern blotting revealed deletion of the SNRPN locus on the paternally derived chromosome 15, consistent with Prader-Willi syndrome. This infant represents the first reported case of trisomy 9p syndrome with total anomalous pulmonary venous return and hypoplasia of the amygdala and hippocampus, with the additional finding of Prader-Willi syndrome resulting from a derivative chromosome arising from an unbalanced de-novo t(9;15) translocation.

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