Early onset epilpetic encephalopathies are severe neurological disorders which result in impairesd motor, cognitive and sensory development. It has been found that genetic testing provided a diagnosis in one-fourth children whose cause would have otherwise been unresolved.

Objectives- To find out the spectrum of genetic mutations in patients with early infantile epileptic encephalopathy of unknown etiology.

Methods- Next generation sequencing was performed in 51 children (51% females) between January 2014 and June 2016 with any of the following features- 1. Early onset epileptic encephalopathy without clear etiology with normal/ non conclusive MRI and/or metabolic screen. 2. Clinical suspicion of SCN related severe epilepsy.

Results- Significant gene mutations were seen in 26/51(51%) subjects, 17 and 8 had variations of uncertain significance and normal panels respectively. The most common gene mutation seen was SCN1A (13/26) and the other mutations seen were KCNT1, SLC2A1, CDKL5, WWOX, TREX1, PCDH19, ARX, GABRG2 and STXBP1. Parental analysis was done in 19 subjects and helped in assessing non-pathogenicity of some mutations which were earlier thought to be of possible significance.

Conclusions- More than half of our patients had significant genetic mutations and this shows the importance of NGS for early onset epileptic encephalopathy with unknown etiology. Parental studies, genetic counselling and prenatal diagnosis should be offered to all patients with positive diagnosis. Knowing the etiology can dictate managementi.e. ketogenic diet for SLC2A1 mutation and avoiding sodium channel blockers in SCN1A mutation, early use of stiripentol in SCN1A/ KCNT1 gene mutations etc.