Objective: Dravet syndrome or severe myoclonic epilepsy of infancy (SMEI) is a baleful epileptic encephalopathy that begins in the first year of life. This syndrome specified by febrile seizures followed by intractable epilepsy, disturbed psychomotor development, and ataxia. Clinical similarities between Dravet syndrome and generalized epilepsy with febrile seizure plus (GEFS+) includes occurrence of febrile seizures and joint molecular genetic etiology. Shared features of these two diseases support the idea that these two disorders represent a severity spectrum of the same illness. Nowadays, more than 60 heterozygous pattern SCN1A mutations, which many are de novo mutations, have been detected in Dravet syndrome.
Materials & methods: From May 2008 to August 2012, 35 patients who referred to Pediatric Neurology Clinic of Mofid Children Hospital in Tehran were enrolled in this study. Entrance criterion of this study was having equal or more than four criteria for Dravet syndrome. We compared clinical features and genetic findings of the patients diagnosed as Dravet syndrome or GEFS+.
Results: 35 patients (15 girls and 20 boys) underwent genetic testing. Mean age of them was 7.7 years (a range of 13 months to 15 years). Three criteria that were best evident in SCN1A mutation positive patients are as follows: "Normal development before the onset of seizures, onset of seizure before age of one year, and psychomotor retardation after onset of seizures. Our genetic testing showed that 1 of 3 (33.3%) patients with clinical Dravet syndrome and 3 of 20 (15%) patients that diagnosed as GEFS+, had SCN1A mutation.
Conclusion: In this study, normal development before seizure onset, seizures beginning before age of one year and psychomotor retardation after age of two years are the most significant criteria in SCN1A mutation positive patients.
Keywords: Dravet syndrome; GEFS+; SCN1A mutations.