Is ethosuximide a risk factor for generalised tonic-clonic seizures in absence epilepsy?

The occurrence of generalised tonic-clonic seizures (GTCS) was investigated in patients with absence epilepsy (AE), evaluating the opinion that ethosuximide does not protect against GTCS. Our retrospective study included 238 patients with absences and generalised 3-Hz spike waves (SW). We analysed the efficacy of antiepileptic drugs (AED) and the occurrence of GTCS before, during and after treatment. We surveyed family history, treatment delay and EEG findings. Family history of epilepsy was positive in 28%. Children with 3-Hz SW lasting >10 s suffered less frequently from GTCS (p=0.002). Photosensitivity (3-Hz SW during photic stimulation) recorded in 47 children was more frequent in juvenile AE (p=0.0001), but not associated with higher rates of GTCS. GTCS occurred in 27 children (11%) before treatment, in 14 (5.8%) during treatment and in 8 (4.8%) after tapering AED. Valproate and ethosuximide monotherapy were equally effective on absences, carrying the same low risk of GTCS during treatment (2 valproate, 1 ethosuximide). Most GTCS occurred on drug combinations considered effective against GTCS. Risk factors for relapses after tapering AED were photosensitivity (p=0.002) and GTCS during treatment (p=0.02). GTCS are rare in patients with typical AE. Our data do not support the current opinion that ethosuximide is inefficacious on GTCS in AE.