Introduction:

A prevalence of 1 to 71 % of electroencephalogram (EEG) abnormalities has been reported in asymptomatic relatives of patients with juvenile myoclonic epilepsy (JME).

Objective:

To determine the frequency of EEG abnormalities in asymptomatic relatives of patients with JME according to the degree of kinship.

Methods:

Prospective, analytical study. First-, second- and third-degree relatives of patients with JME who agreed to participate and signed informed consent were included. The analysis was descriptive, bivariate.

Results:

209 asymptomatic relatives were included, out of which 115 (55 %) were females and 94 (45 %) were males, with a mean age of 35.9 ± 16.9 (range between 6 and 73 years). Forty-four (21.1 %) relatives had abnormal EEGs. First-degree relatives (12 %) had abnormalities more frequently in comparison with second- and third-degree relatives (p = 0.007).

Conclusions:

EEG abnormalities were observed in one third of asymptomatic relatives. It is important to highlight that there were more alterations among first-degree relatives. In the future, these findings might enable for the risk of clinically developing the disease to be estimated and for genetic counseling to be provided.