Migrating partial seizures of infancy: expansion of the electroclinical, radiological and pathological disease spectrum
BRAIN
Authors: McTague, Amy; Appleton, Richard; Avula, Shivaram; Cross, J. Helen; King, Mary D.; Jacques, Thomas S.; Bhate, Sanjay; Cronin, Anthony; Curran, Andrew; Desurkar, Archana; Farrell, Michael A.; Hughes, Elaine; Jefferson, Rosalind; Lascelles, Karine; Livingston, John; Meyer, Esther; McLellan, Ailsa; Poduri, Annapurna; Scheffer, Ingrid E.; Spinty, Stefan; Kurian, Manju A.; Kneen, Rachel
Abstract
Migrating partial seizures of infancy, also known as epilepsy of infancy with migrating focal seizures, is a rare early infantile epileptic encephalopathy with poor prognosis, presenting with focal seizures in the first year of life. A national surveillance study was undertaken in conjunction with the British Paediatric Neurology Surveillance Unit to further define the clinical, pathological and molecular genetic features of this disorder. Fourteen children with migrating partial seizures of infancy were reported during the 2 year study period (estimated prevalence 0.11 per 100 000 children). The study has revealed that migrating partial seizures of infancy is associated with an expanded spectrum of clinical features (including severe gut dysmotility and a movement disorder) and electrographic features including hypsarrhythmia (associated with infantile spasms) and burst suppression. We also report novel brain imaging findings including delayed myelination with white matter hyperintensity on brain magnetic resonance imaging in one-third of the cohort, and decreased N-acetyl aspartate on magnetic resonance spectroscopy. Putaminal atrophy (on both magnetic resonance imaging and at post-mortem) was evident in one patient. Additional neuropathological findings included bilateral hippocampal gliosis and neuronal loss in two patients who had post-mortem examinations. Within this cohort, we identified two patients with mutations in the newly discovered KCNT1 gene. Comparative genomic hybridization array, SCN1A testing and genetic testing for other currently known early infantile epileptic encephalopathy genes (including PLCB1 and SLC25A22) was non-informative for the rest of the cohort.
A targeted resequencing gene panel for focal epilepsy
NEUROLOGY
Authors: Hildebrand, Michael S.; Myers, Candace T.; Carvill, Gemma L.; Regan, Brigid M.; Damiano, John A.; Mullen, Saul A.; Newton, Mark R.; Nair, Umesh; Gazina, Elena V.; Milligan, Carol J.; Reid, Christopher A.; Petrou, Steven; Scheffer, Ingrid E.; Berkovic, Samuel F.; Mefford, Heather C.
Abstract
Objectives:We report development of a targeted resequencing gene panel for focal epilepsy, the most prevalent phenotypic group of the epilepsies.Methods:The targeted resequencing gene panel was designed using molecular inversion probe (MIP) capture technology and sequenced using massively parallel Illumina sequencing.Results:We demonstrated proof of principle that mutations can be detected in 4 previously genotyped focal epilepsy cases. We searched for both germline and somatic mutations in 251 patients with unsolved sporadic or familial focal epilepsy and identified 11 novel or very rare missense variants in 5 different genes: CHRNA4, GRIN2B, KCNT1, PCDH19, and SCN1A. Of these, 2 were predicted to be pathogenic or likely pathogenic, explaining approximate to 0.8% of the cohort, and 8 were of uncertain significance based on available data.Conclusions:We have developed and validated a targeted resequencing panel for focal epilepsies, the most important clinical class of epilepsies, accounting for about 60% of all cases. Our application of MIP technology is an innovative approach that will be advantageous in the clinical setting because it is highly sensitive, efficient, and cost-effective for screening large patient cohorts. Our findings indicate that mutations in known genes likely explain only a small proportion of focal epilepsy cases. This is not surprising given the established clinical and genetic heterogeneity of these disorders and underscores the importance of further gene discovery studies in this complex syndrome.