Clinical and electroencephalographic study of first-degree relatives and probands with juvenile myoclonic epilepsy

PURPOSE Juvenile myoclonic epilepsy (JME) is a common, well-defined epileptic syndrome. This study aims to examine the clinical and EEG features of probands with JME and to identify the incidence of different types of idiopathic generalized epilepsies (IGEs) and IGE trait in first-degree relatives. METHODS Clinical and EEG data were collected from 132 first-degree relatives and 31 probands with JME. The data were analyzed using descriptive statistics, chi-square test, t-test and ANOVA. RESULTS All probands had a history of generalized tonic clonic seizures (GTCS) and myoclonic jerks; 25.8% had a history of absence seizures. Family history of epilepsy was noted in 42% and epilepsy in first-degree relatives was reported in 38.7%. We found JME in 44% of the symptomatic first-degree relatives. The incidence of epilepsy was higher in siblings (19%) than in offspring (8%) or parents (4%), the difference between the groups being significant (p < 0.05). IGE trait was noted in 6% of the asymptomatic first-degree relatives. Finally, IGE features were found in 61%. Subjects with IGE features were younger (mean age 19.6 years) than those without IGE features (mean age 32.4 years) and the difference between the groups was significant. CONCLUSION The incidence of different kinds of IGEs and typical EEG trait is high in first-degree relatives of JME probands. IGE features were noted in 61% of the families. JME is the most common type of IGE and IGE features were found to be more frequent among siblings than parents. These findings confirm familial susceptibility to IGE.