A framework for individualized splice-switching oligonucleotide therapy.

Splice-switching antisense oligonucleotides (ASOs) could be used to treat a subset of individuals with genetic diseases1, but the systematic identification of such individuals remains a challenge. Here we performed whole-genome sequencing analyses to characterize genetic variation in 235 individuals (from 209 families) with ataxia-telangiectasia, a severely debilitating and life-threatening recessive genetic disorder2,3, yielding a complete molecular diagnosis in almost all individuals. We developed a predictive taxonomy to assess the amenability of each individual to splice-switching ASO intervention; 9% and 6% of the individuals had variants that were 'probably' or 'possibly' amenable to ASO splice modulation, respectively. Most amenable variants were in deep intronic regions that are inaccessible to exon-targeted sequencing. We developed ASOs that successfully rescued mis-splicing and ATM cellular signalling in patient fibroblasts for two recurrent variants. In a pilot clinical study, one of these ASOs was used to treat a child who had been diagnosed with ataxia-telangiectasia soon after birth, and showed good tolerability without serious adverse events for three years. Our study provides a framework for the prospective identification of individuals with genetic diseases who might benefit from a therapeutic approach involving splice-switching ASOs.

Integrative systems biology characterizes immune-mediated neurodevelopmental changes in murine Zika virus microcephaly.

Characterizing perturbation of molecular pathways in congenital Zika virus (ZIKV) infection is critical for improved therapeutic approaches. Leveraging integrative systems biology, proteomics, and RNA-seq, we analyzed embryonic brain tissues from an immunocompetent, wild-type congenital ZIKV infection mouse model. ZIKV induced a robust immune response accompanied by the downregulation of critical neurodevelopmental gene programs. We identified a negative correlation between ZIKV polyprotein abundance and host cell cycle-inducing proteins. We further captured the downregulation of genes/proteins, many of which are known to be causative for human microcephaly, including Eomesodermin/T-box Brain Protein 2 (EOMES/TBR2) and Neuronal Differentiation 2 (NEUROD2). Disturbances of distinct molecular pathways in neural progenitors and post-mitotic neurons may contribute to complex brain phenotype of congenital ZIKV infection. Overall, this report on protein- and transcript-level dynamics enhances understanding of the ZIKV immunopathological landscape through characterization of fetal immune response in the developing brain.

Disruption of RFX family transcription factors causes autism, attention-deficit/hyperactivity disorder, intellectual disability, and dysregulated behavior.

PURPOSE: We describe a novel neurobehavioral phenotype of autism spectrum disorder (ASD), intellectual disability, and/or attention-deficit/hyperactivity disorder (ADHD) associated with de novo or inherited deleterious variants in members of the RFX family of genes. RFX genes are evolutionarily conserved transcription factors that act as master regulators of central nervous system development and ciliogenesis. METHODS: We assembled a cohort of 38 individuals (from 33 unrelated families) with de novo variants in RFX3, RFX4, and RFX7. We describe their common clinical phenotypes and present bioinformatic analyses of expression patterns and downstream targets of these genes as they relate to other neurodevelopmental risk genes. RESULTS: These individuals share neurobehavioral features including ASD, intellectual disability, and/or ADHD; other frequent features include hypersensitivity to sensory stimuli and sleep problems. RFX3, RFX4, and RFX7 are strongly expressed in developing and adult human brain, and X-box binding motifs as well as RFX ChIP-seq peaks are enriched in the cis-regulatory regions of known ASD risk genes. CONCLUSION: These results establish a likely role of deleterious variation in RFX3, RFX4, and RFX7 in cases of monogenic intellectual disability, ADHD and ASD, and position these genes as potentially critical transcriptional regulators of neurobiological pathways associated with neurodevelopmental disease pathogenesis.

Nav1.2 haplodeficiency in excitatory neurons causes absence-like seizures in mice.

Mutations in the SCN2A gene encoding a voltage-gated sodium channel Nav1.2 are associated with epilepsies, intellectual disability, and autism. SCN2A gain-of-function mutations cause early-onset severe epilepsies, while loss-of-function mutations cause autism with milder and/or later-onset epilepsies. Here we show that both heterozygous Scn2a-knockout and knock-in mice harboring a patient-derived nonsense mutation exhibit ethosuximide-sensitive absence-like seizures associated with spike-and-wave discharges at adult stages. Unexpectedly, identical seizures are reproduced and even more prominent in mice with heterozygous Scn2a deletion specifically in dorsal-telencephalic (e.g., neocortical and hippocampal) excitatory neurons, but are undetected in mice with selective Scn2a deletion in inhibitory neurons. In adult cerebral cortex of wild-type mice, most Nav1.2 is expressed in excitatory neurons with a steady increase and redistribution from proximal (i.e., axon initial segments) to distal axons. These results indicate a pivotal role of Nav1.2 haplodeficiency in excitatory neurons in epilepsies of patients with SCN2A loss-of-function mutations.

Somatic mosaic deletions involving SCN1A cause Dravet syndrome.

Somatic mosaicism in single nucleotide variants of SCN1A is known to occur in a subset of parents of children with Dravet syndrome (DS). Here, we report recurrent somatic mosaic microdeletions involving SCN1A in children diagnosed with DS. Through the evaluation of 237 affected individuals with DS who did not show SCN1A or PCHD19 mutations in prior sequencing analyzes, we identified two children with mosaic microdeletions covering the entire SCN1A region. The allele frequency of the mosaic deletions estimated by multiplex ligation-dependent probe amplification and array comparative genomic hybridization was 25-40%, which was comparable to the mosaic ratio in lymphocytes and buccal mucosa cells observed by fluorescence in situ hybridization analysis. The minimal prevalence of SCN1A mosaic deletion is estimated to be 0.9% (95% confidence level: 0.11-3.11%) of DS with negative for SCN1A and PCDH19 mutations. This study reinforces the importance of somatic mosaicism caused by copy number variations in disease-causing genes, and provides an alternative spectrum of SCN1A mutations causative of DS. Somatic deletions in SCN1A should be considered in cases with DS when standard screenings for SCN1A mutations are apparently negative for mutations.

Deficient activity of alanyl-tRNA synthetase underlies an autosomal recessive syndrome of progressive microcephaly, hypomyelination, and epileptic encephalopathy.

Aminoacyl-transfer RNA (tRNA) synthetases ligate amino acids to specific tRNAs and are essential for protein synthesis. Although alanyl-tRNA synthetase (AARS) is a synthetase implicated in a wide range of neurological disorders from Charcot-Marie-Tooth disease to infantile epileptic encephalopathy, there have been limited data on their pathogenesis. Here, we report loss-of-function mutations in AARS in two siblings with progressive microcephaly with hypomyelination, intractable epilepsy, and spasticity. Whole-exome sequencing identified that the affected individuals were compound heterozygous for mutations in AARS gene, c.2067dupC (p.Tyr690Leufs*3) and c.2738G>A (p.Gly913Asp). A lymphoblastoid cell line developed from one of the affected individuals showed a strong reduction in AARS abundance. The mutations decrease aminoacylation efficiency by 70%-90%. The p.Tyr690Leufs*3 mutation also abolished editing activity required for hydrolyzing misacylated tRNAs, thereby increasing errors during aminoacylation. Our study has extended potential mechanisms underlying AARS-related disorders to include destabilization of the protein, aminoacylation dysfunction, and defective editing activity.

Dramatic response after functional hemispherectomy in a patient with epileptic encephalopathy carrying a de novo COL4A1 mutation.

We describe the first case of a successful functional hemispherectomy in a patient with epileptic encephalopathy and a de novo collagen type IV alpha 1 (COL4A1) mutation. A 4-year-old girl was COL4A1 mutation-positive and suffered from drug-resistant epilepsy, hemiplegia, and developmental delay. Magnetic resonance imaging detected no porencephaly, and she had no cataract or renal abnormality. Following a presurgical evaluation for epilepsy, she underwent a functional hemispherectomy. She has been seizure free with no intracranial hemorrhage or other perioperative complications. Patients with a COL4A1 mutation have an increased risk for intracranial hemorrhage because of disrupted integrity in the vascular basement membrane due to the mutation. After weighing the risks and benefits to these patients, epilepsy surgery may not be absolutely contraindicated. Furthermore, pediatric neurologists should be aware of an undiagnosed COL4A1 mutation when a patient presents with an unexplained neurological phenotype, such as mild hemiparesis, even in the absence of porencephaly.

Mutations in mitochondrial enzyme GPT2 cause metabolic dysfunction and neurological disease with developmental and progressive features.

Mutations that cause neurological phenotypes are highly informative with regard to mechanisms governing human brain function and disease. We report autosomal recessive mutations in the enzyme glutamate pyruvate transaminase 2 (GPT2) in large kindreds initially ascertained for intellectual and developmental disability (IDD). GPT2 [also known as alanine transaminase 2 (ALT2)] is one of two related transaminases that catalyze the reversible addition of an amino group from glutamate to pyruvate, yielding alanine and α-ketoglutarate. In addition to IDD, all affected individuals show postnatal microcephaly and ∼80% of those followed over time show progressive motor symptoms, a spastic paraplegia. Homozygous nonsense p.Arg404* and missense p.Pro272Leu mutations are shown biochemically to be loss of function. The GPT2 gene demonstrates increasing expression in brain in the early postnatal period, and GPT2 protein localizes to mitochondria. Akin to the human phenotype, Gpt2-null mice exhibit reduced brain growth. Through metabolomics and direct isotope tracing experiments, we find a number of metabolic abnormalities associated with loss of Gpt2. These include defects in amino acid metabolism such as low alanine levels and elevated essential amino acids. Also, we find defects in anaplerosis, the metabolic process involved in replenishing TCA cycle intermediates. Finally, mutant brains demonstrate misregulated metabolites in pathways implicated in neuroprotective mechanisms previously associated with neurodegenerative disorders. Overall, our data reveal an important role for the GPT2 enzyme in mitochondrial metabolism with relevance to developmental as well as potentially to neurodegenerative mechanisms.

Acute encephalitis with refractory, repetitive partial seizures: Pathological findings and a new therapeutic approach using tacrolimus.

Acute encephalitis with refractory, repetitive partial seizures (AERRPS) is characterized by prolonged severe seizures and a high-grade fever. We experienced a boy with severe AERRPS with frequent partial seizures that exhibited right-side predominance. The patient required the continuous intravenous administration of many antiepileptic drugs and respirator management for several months. Methylprednisolone pulse therapy and intravenous immunoglobulin administration were only temporarily effective. The MRI and EEG showed the abnormality in the left occipital lobe. Although occipital lobectomy was performed, his seizures continued. His cerebrospinal fluid exhibited elevated protein and proinflammatory cytokine levels, and was positive for anti-glutamate receptor ε2 antibodies. Pathological examination showed infiltration of many neutrophilic leukocytes, T cells, and microglia in the area exhibiting severe spongiosis. We thought that the exaggerated microglia and T-cell responses were related to the pathogenesis of the patient's seizures, and we therefore initiated treatment with tacrolimus. As a result, many of the daily seizure clusters were ameliorated, and the patient was discharged. We attempted to discontinue the tacrolimus twice, but the patient's seizure clusters recurred each time. This is the first case report of the pathological findings of AERRPS and showing an effective therapeutic approach using tacrolimus. Tacrolimus may be an effective immunosuppressant, especially for patients with severe AERRPS.

A case of 3p deletion syndrome associated with cerebellar hemangioblastoma.

We described clinical course of a 24-year-old woman with 3p deletion syndrome associated with cerebellar hemangioblastoma at the age of 16 years old. She presented dysmorphic facial features, growth retardation and severe psychomotor retardation associated with 3p deletion syndrome. We identified de novo 3p deletion encompassing p25 by using array-based comparative genomic hybridization, where causative gene of von Hippel-Lindau (VHL) disease located. Surgical therapy for cerebellar hemangioblastoma was performed, and histological examination was consistent in cerebellar hemangioblastoma. She showed no other tumors associated VHL disease till 24 years old. This is the first case report of a patient with 3p deletion syndrome whose cerebellar hemangioblastoma may be associated with VHL disease. Repeat imaging studies were recommended for the patients with 3p deletion syndrome.

Novel missense mutation in CLN8 in late infantile neuronal ceroid lipofuscinosis: The first report of a CLN8 mutation in Japan.

Neuronal ceroid lipofuscinoses (NCLs) are clinically and genetically heterogeneous neurodegenerative lysosomal diseases. Fourteen distinct NCL subtypes (CLN1-CLN14) are known, and they are caused by mutations in different genes. CLN8 was first identified in Finnish patients, and the phenotype was subsequently found in Turkish, Italian, and Pakistani patients. We report a 6-year-old Japanese boy with NCL with a novel missense mutation in CLN8. At the age of 3years, he manifested frequent drop seizures, and then progressively developed motor difficulties with an ataxic gait, myoclonus, left conjugate deviation, and rotational nystagmus. At age 5, he developed profound visual difficulty and dysphagia, and he has now lost his mobility. A bone marrow examination at age 5 showed sea-blue histiocytes. An electroretinogram was non-recordable. No giant somatosensory evoked potentials were found. Brain magnetic resonance imaging revealed bilateral diffuse hyperintensities in the white matter around the lateral ventricles and cerebellar and pontine atrophy on T2-weighted images. In a lysosomal enzyme study, the palmitoyl-protein-thioesterase and pepinase activity was within normal limits. Whole-exome sequencing revealed a homozygous CLN8 mutation: c.620T>G (p.L207R). His parents were both heterozygous for this mutation. To our knowledge, this is the first report of a CLN8 mutation in late infantile NCL in Japan.

Efficacy of vigabatrin therapy for tuberous sclerosis with infantile spasms.

Objective: To evaluate the effects and tolerability of vigabatrin (VGB) in children with tuberous sclerosis (TS) with infantile spasms or tonic seizures. Methods: We examined the impact of VGB on a series of 17 children with TS visiting Tohoku University Hospital in Japan during April 2010 and May 2015. To minimize potential adverse effects, VGB was given to the patients for limited 6 months with titration from 30 mg/kg/day as an initial dose. Results: Main seizure types were classified into spasms (n=10) or tonic seizures (n=7). Seizure reduction was positively associated with seizure type of infantile spasms, lower maximum dosage, younger age on VGB administration, and earlier VGB treatment after the diagnosis. Seizure type of infantile spasm was an independent favorable predictor and also associated with long-term seizure reduction. Major adverse events included psychiatric symptoms (n=7) and electroretinogram (ERG) abnormalities (n=2). All symptoms were recovered by reducing the dosage of VGB. Conclusion: VGB is effective and well tolerated as first-line treatment for TS children with infantile spasms. Our "low dosage and limited period" protocol is efficient for improving seizure control as well as minimizing the potential risks of VGB.

[A patient with an early diagnosis of PCDH19-related epilepsy].

An abnormality in PCDH19 causes intractable early-onset epilepsy limited to females, and its significance in pediatric epilepsy is currently increasing. We report the case of a girl with an early diagnosis of PCDH19-related epilepsy. Focal seizures, consisting of eye deviation and asymmetrical tonic posturing, first appeared in clusters at the age of 5 months. Although each seizure was brief (less than a few minutes), seizures occurred in clusters. Cluster was observed at ages of 7, 10, 11, 14, and 19 months, respectively, and all were intractable to multiple treatments. Each cluster continued for 3 days to 2 weeks. However, no seizures occurred outsides the clusters. The pattern of seizure occurrences was characteristic of PCDH19-related epilepsy, which we first suspected when the patient was 11 months old. Genetic analysis of PCDH19 revealed two novel missense substitutions: c.1294G≥C (p.D417H) and c.1786G≥T (p.D596Y). Her psychomotor development was normal at the last follow-up at age of 1 year and 9 months. Currently, the pathogenesis and best treatments of PCDH19-related epilepsy remain unclear. However, to provide correct diagnosis and genetic counseling, and to avoid overtreatments, the possibility of this disease should be considered early in girls with intractable seizure clusters which starting during infancy to early childhood.

Mutations in PYCR2, Encoding Pyrroline-5-Carboxylate Reductase 2, Cause Microcephaly and Hypomyelination.

Despite recent advances in understanding the genetic bases of microcephaly, a large number of cases of microcephaly remain unexplained, suggesting that many microcephaly syndromes and associated genes have yet to be identified. Here, we report mutations in PYCR2, which encodes an enzyme in the proline biosynthesis pathway, as the cause of a unique syndrome characterized by postnatal microcephaly, hypomyelination, and reduced cerebral white-matter volume. Linkage mapping and whole-exome sequencing identified homozygous mutations (c.355C>T [p.Arg119Cys] and c.751C>T [p.Arg251Cys]) in PYCR2 in the affected individuals of two consanguineous families. A lymphoblastoid cell line from one affected individual showed a strong reduction in the amount of PYCR2. When mutant cDNAs were transfected into HEK293FT cells, both variant proteins retained normal mitochondrial localization but had lower amounts than the wild-type protein, suggesting that the variant proteins were less stable. A PYCR2-deficient HEK293FT cell line generated by genome editing with the clustered regularly interspaced short palindromic repeat (CRISPR)-Cas9 system showed that PYCR2 loss of function led to decreased mitochondrial membrane potential and increased susceptibility to apoptosis under oxidative stress. Morpholino-based knockdown of a zebrafish PYCR2 ortholog, pycr1b, recapitulated the human microcephaly phenotype, which was rescued by wild-type human PYCR2 mRNA, but not by mutant mRNAs, further supporting the pathogenicity of the identified variants. Hypomyelination and the absence of lax, wrinkly skin distinguishes this condition from that caused by previously reported mutations in the gene encoding PYCR2's isozyme, PYCR1, suggesting a unique and indispensable role for PYCR2 in the human CNS during development.

Genomic analysis identifies candidate pathogenic variants in 9 of 18 patients with unexplained West syndrome.

West syndrome, which is narrowly defined as infantile spasms that occur in clusters and hypsarrhythmia on EEG, is the most common early-onset epileptic encephalopathy (EOEE). Patients with West syndrome may have clear etiologies, including perinatal events, infections, gross chromosomal abnormalities, or cases followed by other EOEEs. However, the genetic etiology of most cases of West syndrome remains unexplained. DNA from 18 patients with unexplained West syndrome was subjected to microarray-based comparative genomic hybridization (array CGH), followed by trio-based whole-exome sequencing in 14 unsolved families. We identified candidate pathogenic variants in 50% of the patients (n = 9/18). The array CGH revealed candidate pathogenic copy number variations in four cases (22%, 4/18), including an Xq28 duplication, a 16p11.2 deletion, a 16p13.1 deletion and a 19p13.2 deletion disrupting CACNA1A. Whole-exome sequencing identified candidate mutations in known epilepsy genes in five cases (36%, 5/14). Three candidate de novo mutations were identified in three cases, with two mutations occurring in two new candidate genes (NR2F1 and CACNA2D1) (21%, 3/14). Hemizygous candidate mutations in ALG13 and BRWD3 were identified in the other two cases (14%, 2/14). Evaluating a panel of 67 known EOEE genes failed to identify significant mutations. Despite the heterogeneity of unexplained West syndrome, the combination of array CGH and whole-exome sequencing is an effective means of evaluating the genetic background in unexplained West syndrome. We provide additional evidence for NR2F1 as a causative gene and for CACNA2D1 and BRWD3 as candidate genes for West syndrome.

Efficacy of long term weekly ACTH therapy for intractable epilepsy.

BACKGROUND: Adrenocorticotropic hormone (ACTH) therapy is the first-line therapy for infantile spasms, and is effective for many other intractable epilepsies. While spasms may respond to ACTH for weeks, a substantial proportion of patients develop recurrent seizures over a yearly period. To maintain efficacy, we treated two children with intractable epilepsy with weekly ACTH therapy for 1 year and described the changes in clinical seizures, electroencephalograms, developmental assessments and side effects. SUBJECTS AND METHODS: A girl with infantile spasms due to lissencephaly and a boy with atypical absence seizures were studied. In both cases, seizures were frequent and resistant to antiepileptic drugs; electroencephalograms showed continuous epileptiform activities, and the patients' development was delayed and stagnant prior to ACTH treatment. The initial ACTH therapy (daily 0.015 mg/kg for 2 weeks, 0.015 mg/kg every 2 days for 1 week, 0.0075 mg/kg every 2 days for 1 week), was transiently effective in both cases. The second-round ACTH therapy consisted of the initial ACTH therapy protocol followed by weekly ACTH injections (0.015 mg/kg or 0.0075 mg/kg) for 1 year. Both cases were followed for at least 1 year after therapy. RESULTS: In both patients, clinical seizures were completely controlled during and 1 year after the second-round AHCH therapy. Continuous epileptiform discharges disappeared, while intermittent interictal epileptiform discharges remained. Both patients showed some developmental gains after achieving seizure control. No serious side effects were recorded. CONCLUSION: Further studies are warranted to determine if a long-term weekly ACTH is a safe and effective treatment for intractable epilepsy.

Myoclonic axial jerks for diagnosing atypical evolution of ataxia telangiectasia.

BACKGROUND: Ataxia telangiectasia (A-T) is a common inherited cause of early childhood-onset ataxia, distinguished by progressive cerebellum malfunction, capillary vessel extension, and immunodeficiency. The diagnosis of A-T is sometimes difficult to establish in patients with atypical clinical evolution. CASE REPORT: We experienced a pediatric 12-years-old female patient, who was finally diagnosed with classic A-T, demonstrating progressive dystonic-myoclonic axial jerks with ataxia as a predominant clinical feature. Oculocutaneous telangiectasias and immune status were unremarkable. Her myoclonic jerks were spontaneous or stimulus-sensitive, and partially ameliorated by levodopa treatment, but the ataxia was slowly progressive. A laboratory examination showed moderate atrophy of the vermis and cerebellum on brain magnetic resonance imaging, elevated serum alpha fetoprotein (AFP) levels, and total absence of A-T mutated (ATM) protein activity. We subsequently confirmed compound heterozygous truncating mutations of the ATM gene in this patient. CONCLUSION: Our findings highlight the importance of recognizing dystonic-myoclonic jerks as one of the extrapyramidal signs of classic A-T. Measurement of AFP levels should be considered in patients with unexplained myoclonic jerk movements with ataxia in whom definitive diagnoses are not identified. Physicians should be aware that there are cases where typical findings of A-T may not be fulfilled.

Early replacement therapy in a first Japanese case with autosomal recessive guanosine triphosphate cyclohydrolase I deficiency with a novel point mutation.

Autosomal recessive guanosine triphosphate cyclohydrolase I (GTPCH) deficiency is an inborn error of tetrahydrobiopterin (BH4) synthesis from GTP. GTPCH deficiency causes severe reduction of BH4, resulting in hyperphenylalaninemia (HPA) and decreased dopamine and serotonin synthesis. Without treatment, a patient with GTPCH deficiency develops complex neurological dysfunctions, including dystonia and developmental delays. The first Japanese patient with GTPCH deficiency was discovered by HPA during asymptomatic newborn screening. The phenylalanine level at the age of 5days was 1273µmol/L (cutoff value, 180.0µmol/L). The high serum phenylalanine level was decreased to normal after adequate BH4 oral supplementation. Serum and urinary pteridine examination revealed very low levels of neopterin and biopterin. Sequence analysis of GCH1 revealed compound heterozygous point mutations, including a novel point mutation (p.R235W). Replacement therapy with BH4 and L-dopa/carbidopa were started at the age of 1month, and 5-hydroxytryptophan (5-HTP) was started at the age of 5months. At 10months of age, the patient showed slight dystonia but no obvious developmental delay. Cerebrospinal fluid should be examined to determine the appropriate dosage of supplement drugs. In conclusion, it is important to control the serum phenylalanine level and perform early replacement of neurotransmitters to prevent neurological dysfunction.

RBPJ is disrupted in a case of proximal 4p deletion syndrome with epilepsy.

Proximal 4p deletion syndrome is characterized clinically by mental retardation, minor dysmorphic facial features, and is occasionally complicated with epilepsy. More than 20 cases of proximal 4p deletion syndrome have been reported, but the causative gene(s) remain elusive. We describe here a 2-year-old female patient with a common manifestation of proximal 4p deletion syndrome and infantile epileptic encephalopathy possessing a de novo balanced translocation t(4;13)(p15.2;q12.13). The patient was diagnosed as infantile spasms at 9 months of age. She presented with dysmorphic facial features and global developmental delay, compatible with proximal 4p deletion syndrome. Using fluorescence in situ hybridization, we determined the translocation breakpoint at 4p15.2 to be within RBPJ. RBPJ is a transcription factor in the Notch/RBPJ signaling pathway, playing a crucial role in the developing human brain, and particularly telencephalon development. Our findings, combined with those of previous studies, strongly suggest that RBPJ is causative for proximal 4p deletion syndrome and epilepsy in this case.

Effect of a blackout in pediatric patients with home medical devices during the 2011 eastern Japan earthquake.

BACKGROUND: during the eastern Japan earthquake in 2011 and the following prolonged blackout, pediatric patients with home medical devices sought electricity at the pediatric department. We retrospectively studied the effect of this earthquake and the following blackout. METHODS: we hand-reviewed pediatric admission records in Tohoku University Hospital for new inpatients attributed to the earthquake from March 11, 2011 to April 12, 2011. A survey by questionnaire regarding the situation during the earthquake was performed for parents of technology-assisted patients. RESULTS: during the study period, 24 pediatric patients were admitted to the pediatric department. Eighteen technology-assisted pediatric patients, including those with home respirators, accounted for 75% of new pediatric admissions. Patients who were admitted for electricity shortage stayed in the hospital for a mean of 11.0days (3-25days). The questionnaire survey showed that 55% of technology-assisted patients were admitted to medical centers for evacuation. The majority of patients (89%) with ventilators were eventually admitted to medical centers during the earthquake. Most of the parents of technology-assisted patients experienced a prolonged petrol shortage and difficulty in communications with medical centers. CONCLUSION: the current study suggests that technology-assisted pediatric patients with neurological disorders as the primary disease can overwhelm the capacity of hospital inpatient facilities in certain situations. Disaster preparedness should consider assuring power requirements in healthcare facilities and preparing backup power generators lasting for at least 24h for these patients. Preparing alternative measures for emergent electricity and communications could remedy serious conditions during a disaster.