Researchers at thirteen university medical schools in Japan report 15 patients with Dravet syndrome complicated by acute encephalopathy. Cases were collected through the mailing list of the Annual Zao Conference on Pediatric Neurology. Seven were boys and eight girls. Nine showed a mutation of the SCN1A gene (truncation in 6 and missense in 3). The onset of encephalopathy at a median age of 44 months (range 8-184 months) was preceded by status epilepticus and coma as the initial manifestation. Seven children had seizures monthly during 3 months before the onset of acute encephalopathy. MRI during the acute phase showed cerebral cortex-dominant lesions with or without deep gray matter involvement or subcortical-dominant lesions. Four children died; 9 survived with severe sequelae, and 2 had moderate sequelae. [1]

COMMENT. Acute encephalopathy complicating Dravet syndrome in children and presenting with status epilepticus has a poor prognosis. The authors define acute encephalopathy as a decreased consciousness lasting >24 hours in association with symptoms of infection. SCN1A gene mutations were present in 60% of their childhood series, a similar prevalence to that reported in a series of 22 adult cases (Ped Neur Briefs Nov 2011;25:85) [2]. In a series of 16 Dravet syndrome patients followed at Children's Memorial Hospital, Chicago, 6 of 7 patients (86%) tested positive for SCN1A mutations. [3]

A review of the genetics of Dravet syndrome (severe myoclonic epilepsy of infancy, SMEI) finds a genetic etiology and SCN1A mutations in 70% - 80% of patients; in 20% the cause is unknown. Are SCN1A gene abnormalities essential for the diagnosis of Dravet syndrome, or are other genes sometimes involved? [4]. Five alleged cases of pertussis vaccine encephalopathy were rediagnosed years later as Dravet syndrome, testing positive for SCN1A mutations [5]. More frequent SCN1A genetic testing in infants with refractory myoclonic seizures should lead to earlier diagnosis and more effective treatment of Dravet syndrome cases.