Location, symptoms, and management of plexiform neurofibromas in 127 children with neurofibromatosis 1, attending the National Complex Neurofibromatosis 1 service, 2018-2019.

We report on the location, symptoms, and management of plexiform neurofibroma (PN) in children with Neurofibromatosis Type 1 (NF1) attending the 2 National Complex Neurofibromatosis 1 Services at Guy's and St. Thomas' NHS Foundation Trust, London and St Mary's Hospital, Manchester. Retrospective data collection was performed from patient chart reviews from April 2018 to April 2019. There were 127 NF1 patients with PN, age range 0.8-17.0, mean age was 9.9 years (SD ± 4.2 years). The main location of the PN was craniofacial in 35%, and limb in 19%. Disfigurement was present in 57%, pain in 28%, impairment of function in 23%, and threat to function in 9% of children. Fifty-four percent of patients were managed conservatively, 28% surgically, and 19% are either taking or due to start a mitogen-activated protein kinase kinase (MEK) inhibitor (selumetinib or trametinib), either through a clinical trial or compassionate usage scheme. This national study provides a comprehensive overview of the management of children with PN in an era where new therapies (MEK inhibitors) are becoming more widely available. We anticipate that there will be a shift to more patients receiving MEK inhibitor therapy and combination therapy (surgery and MEK inhibitor) in the future.

A recent surge of fulminant and early onset subacute sclerosing panencephalitis (SSPE) in the United Kingdom: An emergence in a time of measles.

BACKGROUND: Subacute Sclerosing Panencephalitis (SSPE) is a fatal progressive neurological disorder following measles infection. METHODS: Cases were collated from Paediatric Neurology centres in the UK over 24 months from 2017 to 2019 and represent all cases referred to the National Viral Reference Department (VRD). Diagnosis was established with detection of a raised measles index, demonstrating intrathecal measles antibody production. FINDINGS: Six children presented with SSPE over two years, with median age five years (range 2-7 years) and median latency period three years (range 2-6 years). The majority were exposed to measles during infancy. Atypical features were common, including visual impairment, focal and generalised tonic-clonic seizures, headache, vomiting and movement disorders. EEG demonstrated typical features in five cases, though not always at presentation. Initial MRI was normal in four cases, with two showing focal and widespread white matter changes. Antiviral and immunomodulatory treatment led to minimal or no improvement. All progressed to cognitive regression, seizures and neurological decline within six months. INTERPRETATION: These cases demonstrate the highest incidence of SSPE in the UK since 2000, all progressing to acute fulminant disease, following younger age of onset, short latency period and atypical presentations. Recent global surges in measles cases raise the importance of clinician awareness of SSPE as a potential diagnosis in children with neurological regression. Herd immunity remains the key protective mechanism for infants and groups that cannot be vaccinated. Health care providers, educators and governments must ensure resources continue to target effective education and access to immunisation programmes, the only means to combat this devastating and fatal condition.

Systemic Inflammation Is Associated With Neurologic Involvement in Pediatric Inflammatory Multisystem Syndrome Associated With SARS-CoV-2.

OBJECTIVE: Pediatric inflammatory multisystem syndrome temporally associated with SARS-CoV-2 (PIMS-TS) is a severe immune-mediated disorder. We aim to report the neurologic features of children with PIMS-TS. METHODS: We identified children presenting to a large children's hospital with PIMS-TS from March to June 2020 and performed a retrospective medical note review, identifying clinical and investigative features alongside short-term outcome of children presenting with neurologic symptoms. RESULTS: Seventy-five patients with PIMS-TS were identified, 9 (12%) had neurologic involvement: altered conciseness (3), behavioral changes (3), focal neurology deficits (2), persistent headaches (2), hallucinations (2), excessive sleepiness (1), and new-onset focal seizures (1). Four patients had cranial images abnormalities. At 3-month follow-up, 1 child had died, 1 had hemiparesis, 3 had behavioral changes, and 4 completely recovered. Systemic inflammatory and prothrombotic markers were higher in patients with neurologic involvement (mean highest CRP 267 vs 202 mg/L, p = 0.05; procalcitonin 30.65 vs 13.11 µg/L, p = 0.04; fibrinogen 7.04 vs 6.17 g/L, p = 0.07; d-dimers 19.68 vs 7.35 mg/L, p = 0.005). Among patients with neurologic involvement, these markers were higher in those without full recovery at 3 months (ferritin 2284 vs 283 µg/L, p = 0.05; d-dimers 30.34 vs 6.37 mg/L, p = 0.04). Patients with and without neurologic involvement shared similar risk factors for PIMS-TS (Black, Asian and Minority Ethnic ethnicity 78% vs 70%, obese/overweight 56% vs 42%). CONCLUSIONS: Broad neurologic features were found in 12% patients with PIMS-TS. By 3-month follow-up, half of these surviving children had recovered fully without neurologic impairment. Significantly higher systemic inflammatory markers were identified in children with neurologic involvement and in those who had not recovered fully.

Phenotypic and genetic spectrum of epilepsy with myoclonic atonic seizures.

OBJECTIVE: We aimed to describe the extent of neurodevelopmental impairments and identify the genetic etiologies in a large cohort of patients with epilepsy with myoclonic atonic seizures (MAE). METHODS: We deeply phenotyped MAE patients for epilepsy features, intellectual disability, autism spectrum disorder, and attention-deficit/hyperactivity disorder using standardized neuropsychological instruments. We performed exome analysis (whole exome sequencing) filtered on epilepsy and neuropsychiatric gene sets to identify genetic etiologies. RESULTS: We analyzed 101 patients with MAE (70% male). The median age of seizure onset was 34 months (range = 6-72 months). The main seizure types were myoclonic atonic or atonic in 100%, generalized tonic-clonic in 72%, myoclonic in 69%, absence in 60%, and tonic seizures in 19% of patients. We observed intellectual disability in 62% of patients, with extremely low adaptive behavioral scores in 69%. In addition, 24% exhibited symptoms of autism and 37% exhibited attention-deficit/hyperactivity symptoms. We discovered pathogenic variants in 12 (14%) of 85 patients, including five previously published patients. These were pathogenic genetic variants in SYNGAP1 (n = 3), KIAA2022 (n = 2), and SLC6A1 (n = 2), as well as KCNA2, SCN2A, STX1B, KCNB1, and MECP2 (n = 1 each). We also identified three new candidate genes, ASH1L, CHD4, and SMARCA2 in one patient each. SIGNIFICANCE: MAE is associated with significant neurodevelopmental impairment. MAE is genetically heterogeneous, and we identified a pathogenic genetic etiology in 14% of this cohort by exome analysis. These findings suggest that MAE is a manifestation of several etiologies rather than a discrete syndromic entity.

Early predictors of epilepsy and subsequent relapse in children with acute disseminated encephalomyelitis.

OBJECTIVE: To identify predictors of epilepsy and clinical relapses in children presenting with acute disseminated encephalomyelitis (ADEM). METHODS: Children presenting with ADEM between 2005 and 2017 and tested clinically for MOG-Ab were identified from three tertiary paediatric neurology centres in the United Kingdom. Patients were followed up for a median of 6 years (range, 1-16 years). RESULTS: A total of 74 children were studied (38 females; median age at first presentation: 4.5 years (range, 1.4-16 years)). MOG-Ab was positive in 50/74 (67.6%) of cases, and 27 (54%) of MOG-Ab positive children presented with a neurological relapse over time. MOG-Ab was more frequently positive in the relapsing group than in the monophasic group (27/31 vs 23/43; odds ratio 5.9 (95% CI: 1.8-19.7); p = 0.002). 16/74 (22%) children had seizures during the acute presentation with ADEM and 12/74 (16.2%) patients were diagnosed with post-ADEM epilepsy. The diagnosis of post-ADEM epilepsy was more frequently observed in children with relapsing disease than monophasic disease (10/31 vs 2/43; odds ratio 9.8 (95% confidence interval (CI): 2.0-48.7); p = 0.003), in children who had positive intrathecal oligoclonal bands than those with negative bands (4/7 vs 4/30; odds ratio 8.7 (95% CI: 1.4-54.0); p = 0.027) and in children who had positive MOG-Ab than negative MOG-Ab cases (11/12 vs 39/62; odds ratio 6.5 (95% CI:0.8-53.6); p = 0.051). CONCLUSION: A higher relapse rate and a greater risk of post-ADEM epilepsy in children with MOG-Ab-associated disease may indicate a chronic disease with immune-mediated seizures in these children.

PIGT-CDG, a disorder of the glycosylphosphatidylinositol anchor: description of 13 novel patients and expansion of the clinical characteristics.

PURPOSE: To provide a detailed electroclinical description and expand the phenotype of PIGT-CDG, to perform genotype-phenotype correlation, and to investigate the onset and severity of the epilepsy associated with the different genetic subtypes of this rare disorder. Furthermore, to use computer-assisted facial gestalt analysis in PIGT-CDG and to the compare findings with other glycosylphosphatidylinositol (GPI) anchor deficiencies. METHODS: We evaluated 13 children from eight unrelated families with homozygous or compound heterozygous pathogenic variants in PIGT. RESULTS: All patients had hypotonia, severe developmental delay, and epilepsy. Epilepsy onset ranged from first day of life to two years of age. Severity of the seizure disorder varied from treatable seizures to severe neonatal onset epileptic encephalopathies. The facial gestalt of patients resembled that of previously published PIGT patients as they were closest to the center of the PIGT cluster in the clinical face phenotype space and were distinguishable from other gene-specific phenotypes. CONCLUSION: We expand our knowledge of PIGT. Our cases reaffirm that the use of genetic testing is essential for diagnosis in this group of disorders. Finally, we show that computer-assisted facial gestalt analysis accurately assigned PIGT cases to the multiple congenital anomalies-hypotonia-seizures syndrome phenotypic series advocating the additional use of next-generation phenotyping technology.

The spectrum of intermediate SCN8A-related epilepsy.

OBJECTIVE: Pathogenic variants in SCN8A have been associated with a wide spectrum of epilepsy phenotypes, ranging from benign familial infantile seizures (BFIS) to epileptic encephalopathies with variable severity. Furthermore, a few patients with intellectual disability (ID) or movement disorders without epilepsy have been reported. The vast majority of the published SCN8A patients suffer from severe developmental and epileptic encephalopathy (DEE). In this study, we aimed to provide further insight on the spectrum of milder SCN8A-related epilepsies. METHODS: A cohort of 1095 patients were screened using a next generation sequencing panel. Further patients were ascertained from a network of epilepsy genetics clinics. Patients with severe DEE and BFIS were excluded from the study. RESULTS: We found 36 probands who presented with an SCN8A-related epilepsy and normal intellect (33%) or mild (61%) to moderate ID (6%). All patients presented with epilepsy between age 1.5 months and 7 years (mean = 13.6 months), and 58% of these became seizure-free, two-thirds on monotherapy. Neurological disturbances included ataxia (28%) and hypotonia (19%) as the most prominent features. Interictal electroencephalogram was normal in 41%. Several recurrent variants were observed, including Ile763Val, Val891Met, Gly1475Arg, Gly1483Lys, Phe1588Leu, Arg1617Gln, Ala1650Val/Thr, Arg1872Gln, and Asn1877Ser. SIGNIFICANCE: With this study, we explore the electroclinical features of an intermediate SCN8A-related epilepsy with mild cognitive impairment, which is for the majority a treatable epilepsy.

Trends in phenotype in the English paediatric neurofibromatosis type 2 cohort stratified by genetic severity.

Childhood onset neurofibromatosis type 2 can be severe and genotype dependent. We present a retrospective phenotypic analysis of all ascertained children in England 1.0). Focal cortical dysplasia occurred in 26% group 3 and 4% 2A. A total of 48% of group 3 underwent ≥1 major intervention (intracranial/spinal surgery/Bevacizumab/radiotherapy) compared to 35% of 2A; with 23% group 3 undergoing spinal surgery (schwannoma/ependymoma/meningioma resection) compared to 4% of 2A. Mean age starting Bevacizumab was 12.7 in group 3 and 14.9 years in 2A. In conclusion, group 3 phenotype manifests earlier with greater tumour load, poorer visual outcomes and more intervention.

Further refinement of COL4A1 and COL4A2 related cortical malformations.

Mutations in COL4A1 have been reported in schizencephaly and porencephaly combined with microbleeds or calcifications, often associated with ocular and renal abnormalities, myopathy, elevated creatine kinase levels and haemolytic anaemia. In this study, we aimed to clarify the phenotypic spectrum of COL4A1/A2 mutations in the context of cortical malformations that include schizencephaly, polymicrogyria and/or heterotopia. METHODS: We screened for COL4A1/A2 mutations in 9 patients with schizencephaly and/or polymicrogyria suspected to be caused by vascular disruption and leading to a cerebral haemorrhagic ischaemic event. These included 6 cases with asymmetrical or unilateral schizencephaly and/or polymicrogyria and 3 cases with bilateral schizencephaly. RESULTS: One de novo missense COL4A1 mutation (c.3715 G > A, p.(Gly1239Arg)) and two COL4A2 mutations were found, respectively in one familial case (c.4129G > A, p.(Gly1377Arg)) and one sporadic patient (c.1776+1G > A). In three other cases, COL4A1 variants of unknown significance were identified. None of our patients demonstrated neuromuscular or hematological anomalies. Brain malformations included a combination of schizencephaly, mainly asymmetrical, with porencephaly or ventriculomegaly (3/3 mutated patients). We did not observe microbleeds or microcalcifications in any of our cases, hence we do not believe that they represent a distinctive feature of COL4A1/A2 mutations. CONCLUSIONS: Our study further emphasizes the need to search for both COL4A1 and COL4A2 mutations in children presenting with uni- or bilateral polymicrogyria with schizencephaly, even in the absence of intracranial microbleeds, calcification or associated systemic features.

Cerebral vasculopathy in childhood neurofibromatosis type 2: cause for concern?

Unlike adult neurofibromatosis type 2 (NF2), which presents with symptoms related to bilateral vestibular schwannomas, children with NF2 most frequently present with ocular, dermatological, and neurological symptoms. Arteriopathy, a well-established feature in neurofibromatosis type 1, is not a widely recognized feature of NF2. Here we report three children with NF2 with cerebral arteriopathy and/or arterial ischaemic stroke. Bevacizumab, a vascular endothethial growth factor inhibitor, is an established treatment for rapidly growing vestibular schwannomas; however, it carries a risk of both ischaemic and haemorrhagic stroke. Thus, the role of screening and risk to benefit ratio of bevacizumab in NF2 merit further consideration. WHAT THIS PAPER ADDS: Children with neurofibromatosis type 2 (NF2) may be at increased risk of cerebral vasculopathy and arterial ischaemic stroke. Targeted magnetic resonance angiography should be performed in children with NF2 who are being considered for bevacizumab therapy.

Diagnosis of sporadic neurofibromatosis type 2 in the paediatric population.

OBJECTIVE: Onset of symptoms in severe sporadic neurofibromatosis type 2 (NF2) is typically within childhood; however, there is poor awareness of presenting features in young children, potentially resulting in delayed diagnosis and poorer outcome. We have reviewed presentation of sporadic paediatric NF2 to raise awareness of early features, highlighting those requiring further investigation. DESIGN: Patients diagnosed with NF2 at age ≤16 and seen between 2012 and 2015 were notified via the British Paediatric Neurology Surveillance Unit or identified through the English NF2 service. RESULTS: Epidemiological data estimate that 1 in 110 611 births are affected with childhood-onset NF2. Notes of 32 patients with sporadic NF2 were reviewed. Of those presenting under the age of 5, 89% (17/19) had ocular, 74% (14/19) dermatological and 58% (11/19) neurological signs; in 84% (16/19) features were multisystemic. Sixty-six per cent (21/32) had ≥1 atypical feature, including cerebellar hypoplasia in three cases (9%) and focal cortical dysplasia in five out of seven seizure-related presentations. Five cases presented with a sometimes transient or intermittent cranial nerve mononeuropathy. The mean delay to diagnosis was 3.16 years; in eight cases (25%) this exceeded 6 years. Most significant delay occurred in mononeuropathy, ophthalmological and/or seizure presentations, with a mean delay of 3, 4.5 and 6 years, respectively. Eighty-four per cent (27/32) of cases needed intervention in childhood. CONCLUSIONS: All non-vestibular schwannoma NF2 presentations in childhood had significant diagnostic delay. We emphasise the importance of detailed assessment of skin and eyes in unusual presentations and propose an aide to prompt timely referral to specialist services.

Clinical and molecular characterization of KCNT1-related severe early-onset epilepsy.

OBJECTIVE: To characterize the phenotypic spectrum, molecular genetic findings, and functional consequences of pathogenic variants in early-onset KCNT1 epilepsy. METHODS: We identified a cohort of 31 patients with epilepsy of infancy with migrating focal seizures (EIMFS) and screened for variants in KCNT1 using direct Sanger sequencing, a multiple-gene next-generation sequencing panel, and whole-exome sequencing. Additional patients with non-EIMFS early-onset epilepsy in whom we identified KCNT1 variants on local diagnostic multiple gene panel testing were also included. When possible, we performed homology modeling to predict the putative effects of variants on protein structure and function. We undertook electrophysiologic assessment of mutant KCNT1 channels in a xenopus oocyte model system. RESULTS: We identified pathogenic variants in KCNT1 in 12 patients, 4 of which are novel. Most variants occurred de novo. Ten patients had a clinical diagnosis of EIMFS, and the other 2 presented with early-onset severe nocturnal frontal lobe seizures. Three patients had a trial of quinidine with good clinical response in 1 patient. Computational modeling analysis implicates abnormal pore function (F346L) and impaired tetramer formation (F502V) as putative disease mechanisms. All evaluated KCNT1 variants resulted in marked gain of function with significantly increased channel amplitude and variable blockade by quinidine. CONCLUSIONS: Gain-of-function KCNT1 pathogenic variants cause a spectrum of severe focal epilepsies with onset in early infancy. Currently, genotype-phenotype correlations are unclear, although clinical outcome is poor for the majority of cases. Further elucidation of disease mechanisms may facilitate the development of targeted treatments, much needed for this pharmacoresistant genetic epilepsy.

Clinical presentation and prognostic indicators in 100 adults and children with neurofibromatosis 1 associated non-optic pathway brain gliomas.

Type 1 Neurofibromatosis (NF1) is a common autosomal dominant condition, with a major impact on the nervous system, eye, bone, and skin, and a predisposition to malignancy. At present it is not possible to predict clinically or on imaging, whether a brain tumour will remain indolent or undergo high-grade change. There are no consensus guidelines on the follow-up of non-optic pathway glioma (non-OPG) tumours in NF1. One hundred patients from the National NF1 Service with generalised NF1 and a diagnosis of non-OPG glioma were followed up for a median time of 63 months after glioma detection. Forty-two patients underwent surgical intervention. Ninety-one percent (38) of those requiring surgery did so within 5 years of diagnosis of glioma. Serial neuroimaging was undertaken in 88 patients. In 66 (75%), the lesion on the scan was stable or had improved at follow-up. High-grade lesions were present in five patients and were strongly associated with tumours in the thalamus (p = 0.001). Five patients died during follow-up. The diagnosis of high-grade glioma had a HR of 99.7 (95% CI 11.1-898.9, p < 000.1) on multivariate Cox regression to evaluate predictive factors related to death. In our cohort of 100 patients with NF1, we have shown that tumours in the thalamus are more likely to be associated with radiological progression, high-grade tumours, and surgical intervention. As a result of this finding, heightened surveillance with more frequent imaging should be considered in thalamic involvement. We have also demonstrated that over 40% of patients underwent surgery, and did so within 5 years of tumour diagnosis. Serial imaging should be undertaken for at the very least, 5 years from tumour detection.

Mutations in PROSC Disrupt Cellular Pyridoxal Phosphate Homeostasis and Cause Vitamin-B6-Dependent Epilepsy.

Pyridoxal 5'-phosphate (PLP), the active form of vitamin B6, functions as a cofactor in humans for more than 140 enzymes, many of which are involved in neurotransmitter synthesis and degradation. A deficiency of PLP can present, therefore, as seizures and other symptoms that are treatable with PLP and/or pyridoxine. Deficiency of PLP in the brain can be caused by inborn errors affecting B6 vitamer metabolism or by inactivation of PLP, which can occur when compounds accumulate as a result of inborn errors of other pathways or when small molecules are ingested. Whole-exome sequencing of two children from a consanguineous family with pyridoxine-dependent epilepsy revealed a homozygous nonsense mutation in proline synthetase co-transcribed homolog (bacterial), PROSC, which encodes a PLP-binding protein of hitherto unknown function. Subsequent sequencing of 29 unrelated indivduals with pyridoxine-responsive epilepsy identified four additional children with biallelic PROSC mutations. Pre-treatment cerebrospinal fluid samples showed low PLP concentrations and evidence of reduced activity of PLP-dependent enzymes. However, cultured fibroblasts showed excessive PLP accumulation. An E.coli mutant lacking the PROSC homolog (ΔYggS) is pyridoxine sensitive; complementation with human PROSC restored growth whereas hPROSC encoding p.Leu175Pro, p.Arg241Gln, and p.Ser78Ter did not. PLP, a highly reactive aldehyde, poses a problem for cells, which is how to supply enough PLP for apoenzymes while maintaining free PLP concentrations low enough to avoid unwanted reactions with other important cellular nucleophiles. Although the mechanism involved is not fully understood, our studies suggest that PROSC is involved in intracellular homeostatic regulation of PLP, supplying this cofactor to apoenzymes while minimizing any toxic side reactions.

From splitting GLUT1 deficiency syndromes to overlapping phenotypes.

INTRODUCTION: Glucose transporter type 1 deficiency syndrome (GLUT1DS) is a rare genetic disorder due to mutations or deletions in SLC2A1, resulting in impaired glucose uptake through the blood brain barrier. The classic phenotype includes pharmacoresistant epilepsy, intellectual deficiency, microcephaly and complex movement disorders, with hypoglycorrhachia, but milder phenotypes have been described (carbohydrate-responsive phenotype, dystonia and ataxia without epilepsy, paroxysmal exertion-induced dystonia). The aim of our study was to provide a comprehensive overview of GLUT1DS in a French cohort. METHODS: 265 patients were referred to the French national laboratory for molecular screening between July 2006 and January 2012. Mutations in SLC2A1 were detected in 58 patients, with detailed clinical data available in 24, including clinical features with a focus on their epileptic pattern and electroencephalographic findings, biochemical findings and neuroimaging findings. RESULTS: 53 point mutations and 5 deletions in SLC2A1 were identified. Most patients (87.5%) exhibited classic phenotype with intellectual deficiency (41.7%), epilepsy (75%) or movement disorder (29%) as initial symptoms at a medium age of 7.5 months, but diagnostic was delayed in most cases (median age at diagnostic 8 years 5 months). Sensitivity to fasting or exertion in combination with those 3 main symptoms were the main differences between mutated and negative patients (p < 0.001). Patients with myoclonic seizures (52%) evolved with more severe intellectual deficiency and movement disorders compared with those with Early Onset Absence Epilepsy (38%). Three patients evolved from a classic phenotype during early childhood to a movement disorder predominant phenotype at a late childhood/adulthood. CONCLUSIONS: Our data confirm that the classic phenotype is the most frequent in GLUT1DS. Myoclonic seizures are a distinctive feature of severe forms. However a great variability among patients and overlapping through life from milder classic phenotype to paroxysmal-prominent- movement-disorder phenotype are possible, thus making it difficult to identify definite genotype-phenotype correlations.

Mutations in tubulin genes are frequent causes of various foetal malformations of cortical development including microlissencephaly.

Complex cortical malformations associated with mutations in tubulin genes are commonly referred to as "Tubulinopathies". To further characterize the mutation frequency and phenotypes associated with tubulin mutations, we studied a cohort of 60 foetal cases. Twenty-six tubulin mutations were identified, of which TUBA1A mutations were the most prevalent (19 cases), followed by TUBB2B (6 cases) and TUBB3 (one case). Three subtypes clearly emerged. The most frequent (n = 13) was microlissencephaly with corpus callosum agenesis, severely hypoplastic brainstem and cerebellum. The cortical plate was either absent (6/13), with a 2-3 layered pattern (5/13) or less frequently thickened (2/13), often associated with neuroglial overmigration (4/13). All cases had voluminous germinal zones and ganglionic eminences. The second subtype was lissencephaly (n = 7), either classical (4/7) or associated with cerebellar hypoplasia (3/7) with corpus callosum agenesis (6/7). All foetuses with lissencephaly and cerebellar hypoplasia carried distinct TUBA1A mutations, while those with classical lissencephaly harbored recurrent mutations in TUBA1A (3 cases) or TUBB2B (1 case). The third group was polymicrogyria-like cortical dysplasia (n = 6), consisting of asymmetric multifocal or generalized polymicrogyria with inconstant corpus callosum agenesis (4/6) and hypoplastic brainstem and cerebellum (3/6). Polymicrogyria was either unlayered or 4-layered with neuronal heterotopias (5/6) and occasional focal neuroglial overmigration (2/6). Three had TUBA1A mutations and 3 TUBB2B mutations. Foetal TUBA1A tubulinopathies most often consist in microlissencephaly or classical lissencephaly with corpus callosum agenesis, but polymicrogyria may also occur. Conversely, TUBB2B mutations are responsible for either polymicrogyria (4/6) or microlissencephaly (2/6).

The wide spectrum of tubulinopathies: what are the key features for the diagnosis?

Complex cortical malformations associated with mutations in tubulin genes: TUBA1A, TUBA8, TUBB2B, TUBB3, TUBB5 and TUBG1 commonly referred to as tubulinopathies, are a heterogeneous group of conditions with a wide spectrum of clinical severity. Among the 106 patients selected as having complex cortical malformations, 45 were found to carry mutations in TUBA1A (42.5%), 18 in TUBB2B (16.9%), 11 in TUBB3 (10.4%), three in TUBB5 (2.8%), and three in TUBG1 (2.8%). No mutations were identified in TUBA8. Systematic review of patients' neuroimaging and neuropathological data allowed us to distinguish at least five cortical malformation syndromes: (i) microlissencephaly (n = 12); (ii) lissencephaly (n = 19); (iii) central pachygyria and polymicrogyria-like cortical dysplasia (n = 24); (iv) generalized polymicrogyria-like cortical dysplasia (n = 6); and (v) a 'simplified' gyral pattern with area of focal polymicrogyria (n = 19). Dysmorphic basal ganglia are the hallmark of tubulinopathies (found in 75% of cases) and are present in 100% of central pachygyria and polymicrogyria-like cortical dysplasia and simplified gyral malformation syndromes. Tubulinopathies are also characterized by a high prevalence of corpus callosum agenesis (32/80; 40%), and mild to severe cerebellar hypoplasia and dysplasia (63/80; 78.7%). Foetal cases (n = 25) represent the severe end of the spectrum and show specific abnormalities that provide insights into the underlying pathophysiology. The overall complexity of tubulinopathies reflects the pleiotropic effects of tubulins and their specific spatio-temporal profiles of expression. In line with previous reports, this large cohort further clarifies overlapping phenotypes between tubulinopathies and although current structural data do not allow prediction of mutation-related phenotypes, within each mutated gene there is an associated predominant pattern of cortical dysgenesis allowing some phenotype-genotype correlation. The core phenotype of TUBA1A and TUBG1 tubulinopathies are lissencephalies and microlissencephalies, whereas TUBB2B tubulinopathies show in the majority, centrally predominant polymicrogyria-like cortical dysplasia. By contrast, TUBB3 and TUBB5 mutations cause milder malformations with focal or multifocal polymicrogyria-like cortical dysplasia with abnormal and simplified gyral pattern.