Age at focal epilepsy onset varies by sex and hemispheric lateralization.
BACKGROUND
Previous studies have shown that interictal epileptiform discharges favor the left hemisphere in adults but the right side in children up until age 5. This may be due to sex-influenced asymmetric brain maturation. To clarify this relationship, the authors analyzed age at epilepsy onset by sex and by lateralization of epileptiform activity.


METHODS
An adult epilepsy center long-term monitoring database was used to define patients with exclusively unilateral epileptiform findings. Three groups were studied: any epileptiform activity (n = 404), ictal activity (n = 287), and interictal activity (n = 265). The second and third groups were drawn from the first group and the second and third groups overlapped with each other. Side of lateralized finding and sex were analyzed via factorial two-way analysis of variance with the outcome variable being age at epilepsy onset. Comparison analysis included patients with generalized epilepsy (n = 114), nonepileptic seizures (NES, n = 232), and surgical mesial temporal sclerosis (MTS, n = 116).


RESULTS
Patients with unilateral epileptiform activity displayed bimodal epilepsy onset ages with infant and adolescent peaks. For patients with a right-sided focus, epilepsy onset was earlier in men (14.4 years) than women (20.7 years). In contrast, among patients with a left-sided focus, epilepsy began earlier in women (18.2 years) than men (19.9 years, p < 0.01). Parallel results were found in unilateral ictal (p < 0.01) and unilateral interictal activity (p = 0.01). Patients with surgical MTS, NES, or generalized seizure showed no similar patterns.


CONCLUSIONS
In adult patients with focal epilepsy, sex and lateralized epileptiform abnormalities may be related to age at epilepsy onset.
Regional Epilepsy Center and Department of Neurology, University of Washington, Seattle 98195, USA. mdoherty@u.washington.edu
M J
MJ
Doherty
S
S
Jayadev
J W
JW
Miller
D F
DF
Farrell
M D
MD
Holmes
C B
CB
Dodrill
D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D017668:Age of Onset; D000368:Aged; D001921:Brain / Q000473:pathology; D002648:Child; D002675:Child, Preschool; D004828:Epilepsies, Partial / Q000453:epidemiology*; D012739:Gonadal Steroid Hormones / Q000502:physiology; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008875:Middle Aged; D017678:Sex Distribution
D012739:Gonadal Steroid Hormones