Ryuki Matsuura

PIGA mutations cause early-onset epileptic encephalopathies and distinctive features

Objective: To investigate the clinical spectrum caused by mutations in PIGA at Xp22.2, which is involved in the biosynthesis of the glycosylphosphatidylinositol (GPI) anchor, among patients with early-onset epileptic encephalopathies (EOEEs). Methods: Whole-exome sequencing was performed as a comprehensive genetic analysis for a cohort of 172 patients with EOEEs including early myoclonic encephalopathy, Ohtahara syndrome, and West syndrome, and PIGA mutations were carefully investigated. Results: We identified 4 PIGA mutations in probands showing early myoclonic encephalopathy, West syndrome, or unclassified EOEE. Flow cytometry of blood granulocytes from patients demonstrated reduced expression of GPI-anchored proteins. Expression of GPI-anchored proteins in PIGA-deficient JY5 cells was only partially or hardly restored by transient expression of PIGA mutants with a weak TATA box promoter, indicating a variable loss of PIGA activity. The phenotypic consequences of PIGA mutations can be classified into 2 types, severe and less severe, which correlate with the degree of PIGA activity reduction caused by the mutations. Severe forms involved myoclonus and asymmetrical suppression bursts on EEG, multiple anomalies with a dysmorphic face, and delayed myelination with restricted diffusion patterns in specific areas. The less severe form presented with intellectual disability and treatable seizures without facial dysmorphism. Conclusions: Our study confirmed that PIGA mutations are one genetic cause of EOEE, suggesting that GPI-anchor deficiencies may be an underlying cause of EOEE.

Delineating SPTAN1 associated phenotypes: from isolated epilepsy to encephalopathy with progressive brain atrophy

&NA; De novo in‐frame deletions and duplications in the SPTAN1 gene, encoding the non‐erythrocyte &agr;II spectrin, have been associated with severe West syndrome with hypomyelination and pontocerebellar atrophy. We aimed at comprehensively delineating the phenotypic spectrum associated with SPTAN1 mutations. Using different molecular genetic techniques, we identified 20 patients with a pathogenic or likely pathogenic SPTAN1 variant and reviewed their clinical, genetic and imaging data. SPTAN1 de novo alterations included seven unique missense variants and nine in‐frame deletions/duplications of which 12 were novel. The recurrent three‐amino acid duplication p.(Asp2303_Leu2305dup) occurred in five patients. Our patient cohort exhibited a broad spectrum of neurodevelopmental phenotypes, comprising six patients with mild to moderate intellectual disability, with or without epilepsy and behavioural disorders, and 14 patients with infantile epileptic encephalopathy, of which 13 had severe neurodevelopmental impairment and four died in early childhood. Imaging studies suggested that the severity of neurological impairment and epilepsy correlates with that of structural abnormalities as well as the mutation type and location. Out of seven patients harbouring mutations outside the &agr;/&bgr; spectrin heterodimerization domain, four had normal brain imaging and three exhibited moderately progressive brain and/or cerebellar atrophy. Twelve of 13 patients with mutations located within the spectrin heterodimer contact site exhibited severe and progressive brain, brainstem and cerebellar atrophy, with hypomyelination in most. We used fibroblasts from five patients to study spectrin aggregate formation by Triton‐X extraction and immunocytochemistry followed by fluorescence microscopy. &agr;II/&bgr;II aggregates and &agr;II spectrin in the insoluble protein fraction were observed in fibroblasts derived from patients with the mutations p.(Glu2207del), p.(Asp2303_Leu2305dup) and p.(Arg2308_Met2309dup), all falling in the nucleation site of the &agr;/&bgr; spectrin heterodimer region. Molecular modelling of the seven SPTAN1 amino acid changes provided preliminary evidence for structural alterations of the A‐, B‐ and/or C‐helices within each of the mutated spectrin repeats. We conclude that SPTAN1‐related disorders comprise a wide spectrum of neurodevelopmental phenotypes ranging from mild to severe and progressive. Spectrin aggregate formation in fibroblasts with mutations in the &agr;/&bgr; heterodimerization domain seems to be associated with a severe neurodegenerative course and suggests that the amino acid stretch from Asp2303 to Met2309 in the &agr;20 repeat is important for &agr;/&bgr; spectrin heterodimer formation and/or &agr;II spectrin function.

Intravenous immunoglobulin therapy is rarely effective as the initial treatment in West syndrome: A retrospective study of 70 patients

PURPOSE To evaluate factors influencing the efficacy and safety of intravenous immunoglobulins (IVIG) therapy for West syndrome. METHODS We investigated seizure outcomes in 70 patients who received IVIG treatment for West Syndrome during the first 3months after the onset of epileptic spasms. IVIG was administered for 3 consecutive days (initial IVIG treatment) at dosages ranging from 100 to 500mg/kg/day. If spasms disappeared within 2weeks of the initial treatment, maintenance IVIG treatment was commenced. We evaluated seizure outcomes at 2weeks (initial evaluation), at 2years (long-term evaluation), and the last visit (last follow-up evaluation) after the initial IVIG treatment. We analyzed dosages of IVIG, age at onset of spasms, treatment lag, and etiologies between responders and non-responders. RESULTS Among the patients, 7/70 (10.0%) had cessation of spasms and resolution of hypsarrhythmia at the initial evaluation. Another 6/70 patients (8.6%) were found to have cessation of spasms at the long-term evaluations. The treatment lag in responders was shorter than that in non-responders (P<0.01). There were no significant differences between responders and non-responders in IVIG dosages, age at onset of spasms, and etiologies. Two patients had relapse of partial seizures after cessation of spasms at the last follow-up evaluation. Adverse effects occurred in 2/70 patients. CONCLUSIONS The efficacy of IVIG was so low that it should not be considered as first-line treatment in West syndrome. IVIG therapy has a good safety profile and we would recommend it for West syndrome cases with drug resistance, severe complications associated with profound brain damage, severe brain atrophy, and in immunocompromised patients.

Epilepsy with myoclonic atonic seizures and chronic cerebellar symptoms associated with antibodies against glutamate receptors N2B and D2 in serum and cerebrospinal fluid

A 3-year-old boy with normal development presented with acute cerebellitis at one year and 10 months of age. His truncal ataxia resolved without treatment. He experienced a relapse of truncal ataxia and atonic seizures at 2 years and one month of age. Five months later, he experienced myoclonic atonic seizures. By 3 years of age, the truncal ataxia had become severe, and the frequency of myoclonic atonic seizures increased. Compared to controls, we found higher levels of anti-C-terminal GluN2B and anti-N terminal GluD2 antibodies in the serum, and anti-N terminal GluN2B and anti-C terminal GluD2 antibodies in the cerebrospinal fluid (CSF). A cell-based assay revealed the presence of anti-NMDA-type glutamate receptor antibody in the serum, but absence in the CSF. Ictal EEG of myoclonic atonic seizures showed generalized spike and wave complexes. The patient was diagnosed with myoclonic atonic epilepsy. Adrenocorticotrophic hormone therapy resolved the truncal ataxia and myoclonic atonic seizures, along with the decreased serum anti-C-terminal GluN2B and anti-N-terminal GluD2 antibodies, and CSF anti-N-terminal GluN2B and anti-C-terminal anti-GluD2 antibodies. Our results suggest that the anti-GluN2B and anti-GluD2 antibodies may be associated with myoclonic atonic epileptic seizures and chronic cerebellitis.

A novel NR3C2 mutation in a Japanese patient with the renal form of pseudohypoaldosteronism type 1.

Pseudohypoaldosteronism type 1 (PHA1) is a rare disease characterized by congenital resistance to the action of aldosterone on epithelial tissue; PHA1 results in excessive salt wasting despite very high plasma aldosterone and renin levels (1,2,3). There are 3 types of PHA1. The systemic form of PHA1 is inherited in an autosomal recessive manner and manifests as severe life-long salt wasting caused by mineralocorticoid resistance in multiple target tissues (e.g., sweat glands, salivary glands, colonic epithelium, and lung). The renal form of PHA1 (adPHA1) is inherited in an autosomal dominant manner. In this form, mineralocorticoid resistance exists only in the kidney; moreover, salt wasting and other symptoms improve around 1–3 yr of age (1,2,3). The third type of PHA1 is the transient form, which is commonly seen in patients with urinary tract infection or obstructive uropathy. In the transient form, clinical symptoms disappear after treatment. adPHA1 is caused by a heterozygous mutation in NR3C2, which encodes the mineralocorticoid receptor (MR). Herein, we report the case of a young girl with adPHA1, a novel mutation in NR3C2, hyponatremia, and failure to thrive associated with urinary tract infection. We also describe a genetic analysis of her family.

Maturational Changes of Gamma-Aminobutyric Acid A Receptors Measured With Benzodiazepine Binding of Iodine 123 Iomazenil Single-Photon Emission Computed Tomography

BACKGROUND Iodine 123 (I-123) iomazenil is a specific ligand of the central benzodiazepine receptor, which is a part of the postsynaptic gamma-aminobutyric acid A receptor complex. We performed statistical image processing of I-123 iomazenil single-photon emission computed tomography to elucidate maturational changes in the GABAergic system. METHODS Thirty patients (18 boys and 12 girls, aged 17 days to 14 years) with cryptogenic focal epilepsy were enrolled and underwent I-123 iomazenil single-photon emission computed tomography. We used a semiquantitative analytical method consisting of brain surface extraction, anatomic normalization, and a three-parameter exponential model. We then assessed developmental changes in benzodiazepine receptor binding activity in 18 regions of interest in both hemispheres. RESULTS The highest benzodiazepine receptor binding activity was observed during early infancy in all regions of interest. Benzodiazepine receptor binding activity then decreased exponentially across development. Benzodiazepine receptor binding in the primary sensorimotor cortex, primary visual cortex, cerebellar vermis, and striatum declined more rapidly than that in the cerebellar hemispheres and the frontal cortex. The pons and the thalamus had the lowest benzodiazepine receptor binding activities during the neonatal period, and benzodiazepine receptor binding in these areas declined gradually after infancy toward adolescence. There were no differences in adjusted benzodiazepine receptor binding activity according to laterality or sex. CONCLUSIONS Benzodiazepine receptor binding activity decreased exponentially during infancy in all regions of interest. Binding activity in the primary somatosensory and motor cortices (M1 and S1), the primary and association visual areas, the cerebellar vermis, and the striatum (caudate nucleus and putamen) tended to decline more rapidly than that in the cerebellar hemisphere and the frontal association cortex.

Quantitative evaluation of regional cerebral blood flow changes during childhood using 123I-N-isopropyl-iodoamphetamine single-photon emission computed tomography

OBJECTIVE To quantitatively evaluate regional cerebral blood flow (rCBF) and regional developmental changes during childhood using 123I-N-isopropyl-iodoamphetamine single-photon emission computed tomography (SPECT) and autoradiography. METHODS We retrospectively analyzed quantitative values of rCBF in 75 children (29 girls) aged between 16 days and 178 months (median: 12 months), whose brain images, including magnetic resonance imaging and SPECT data, were normal under visual inspection at Saitama Childrens Medical Center between 2005 and 2015. The subjects had normal psychomotor development, no focal neurological abnormalities, and neither respiratory nor cardiac disease at the time of examination. Regions of interest were placed automatically using a three-dimensional stereotactic template. RESULTS rCBF was lowest in neonates, who had greater rCBF in the lenticular nucleus, thalamus, and cerebellum than the cerebral cortices. rCBF increased rapidly during the first year of life, reaching approximately twice the adult levels at 8 years, and then fell to approximately adult levels in the late teenage years. Cerebral cortex rCBF sequentially increased in the posterior, central, parietal, temporal, and callosomarginal regions during infancy and childhood. CONCLUSIONS rCBF changed dramatically throughout childhood and ranged from lower than adult values to approximately two times higher than adult values. It had different trajectories in each region during brain development. Understanding this dynamic developmental change is necessary for SPECT image evaluation in children.

Treatment of infantile spasms by pediatric neurologists in Japan

OBJECTIVE To clarify changes in clinical practice for infantile spasms, including West syndrome, in Japan over the past two decades. METHODS We investigated common treatment strategies for infantile spasms among 157 pediatric neurologists from a designated training facility for pediatric neurology and/or a designated training facility for epilepsy in Japan. A questionnaire was used to investigate use of adrenocorticotropic hormone (ACTH) therapy including daily dose, treatment duration, and tapering off period, and preferred first to fifth-line treatment choices. RESULTS Among 119 responses (75.8%), 107 enabled analysis of ACTH therapy and 112 were used to determine preferred order of first to fifth-line treatments. Over 80% respondents reported an initial ACTH dose of ≤0.0125 mg/kg/day, with a treatment duration of 14 days and various tapering periods. Following an unfavorable response of seizures to ACTH, 80% respondents increased the dose and/or extended treatment duration. The same ACTH therapy regimen was performed for symptomatic and cryptogenic patients at 95 facilities (88.8%). Preferred orders of therapeutic agents were the same for both symptomatic and cryptogenic patients at 64 facilities (57.1%). Over half the respondents selected vitamin B6 or valproate as the first and second-line treatments instead of ACTH therapy, while ACTH therapy was the most frequently selected third-line treatment. CONCLUSIONS Current ACTH therapy regimens have lower doses and shorter durations than previously reported. However, treatment strategies for infantile spasms have not changed much in two decades. ACTH therapy should be the first/second-line treatment rather than third-line or later, especially for cryptogenic infantile spasms.