Genetics of epilepsy: an overview

Familial occurrence of epilepsy in children with newly diagnosed multiple seizures: Dutch Study of Epilepsy in Childhood

PURPOSE

To study the familial occurrence of epilepsy in children with newly diagnosed multiple unprovoked seizures.

METHODS

Between August 1988 and September 1992, 462 children with two or more unprovoked seizures were included in the prospective Dutch Study of Epilepsy in Childhood. Seizures and epilepsy syndromes of probands were classified according to the International Classifications. Probands with at least 1 first-degree relative with epilepsy were selected. Seizures and syndromes of their relatives were classified using medical files and telephone interviews.

RESULTS

In 42% of the probands, the epilepsy was classified as localization-related, in 57% as generalized, and in 1% as undetermined whether focal or generalized. The 47 (10.2%) children with at least 1 first-degree relative with epilepsy less frequently had localization-related epilepsy (23%) and more often had generalized epilepsy (77%) as compared with the total group of probands. Fifty-eight first-degree and 21 other relatives had epilepsy. Thirty-three of the 40 (83%) first-degree relatives with idiopathic or cryptogenic epilepsy had the same seizure type as the proband, but detailed information about their seizures was sometimes difficult to obtain. Of the 12 first-degree relatives with epilepsy syndromes classifiable according to the International League Against Epilepsy (ILAE) 7 (58%) had the same syndrome as the proband.

CONCLUSIONS

In 10% of children with newly diagnosed epilepsy, the condition is familial. Relatively more often, these children have generalized epilepsy syndromes as compared with children with a negative family history. Most of the relatives with idiopathic or cryptogenic epilepsy had the same seizure type as the proband. These findings confirm the role of genetic factors in the pathogenesis of epilepsy.

Short-term mortality after a first episode of status epilepticus

PURPOSE

Studies evaluating short-term mortality among people who experience status epilepticus (SE) have produced conflicting results. Most studies are derived from clinical series with results affected by unspecified follow-up period and select referral of cases. This study was planned to evaluate short-term mortality after a first episode of SE.

METHODS

We performed a population-based retrospective cohort study to determine the short-term mortality following a first episode of SE. Between January 1, 1965 and December 31, 1984, we studied all first episodes of afebrile SE who received medical attention in Rochester, Minnesota. Cases were followed until death or end of the study (February 1996).

RESULTS

Mortality within the first 30 days was 19% (38 deaths out of 201 incident SE). Thirty-four deaths (89%) occurred among those with nonfebrile acute symptomatic SE, while 4 deaths (11%) occurred among those with unprovoked SE. Within the acute symptomatic group, after adjusting for age, there was a decreased risk of death in women (RR = 0.4; 95% CI: 0.2-0.9). No effect of duration or seizure type was shown after adjusting for other risk factors.

CONCLUSIONS

One out of 5 subjects with SE died within the first 30 days. Short-term mortality is associated with the presence of an underlying acute etiology. Among acute symptomatic cases, women had a decreased risk of dying.

Fyn tyrosine kinase is required for normal amygdala kindling

To identify specific genes involved with epileptogenesis kindling was examined in mice carrying mutations engineered by gene targeting. Amygdala kindling was tested in mice with a null-mutation in the Fyn tyrosine kinase gene, a mutation that raises the threshold for the induction of long-term potentiation in the hippocampus. The fyn mutants had a normal threshold, duration and stability of epileptiform after-discharge, which is crucial for kindling. Despite the normal after-discharge, fyn mutants showed a striking retardation in the rate of kindling. Once the kindled state was established in fyn mutants it remained stable. This implicates a Fyn-dependent biochemical pathway in the induction but not the maintenance of normal amygdala kindling. fyn is the first gene identified to be required for normal epileptogenesis.