Reflex epilepsy induced by calculation using a "Soroban," a Japanese traditional calculator.

We report three cases of reflex epilepsy with myoclonic jerks of the right arm and fingers precipitated by calculation using a Soroban. An EEG spike-wave complex with left central prevalence was induced. Various types of stimulation were used to induce epileptic discharges, and a simultaneous mental task requiring a high degree of concentration and complicated and delicate finger movements was necessary to induce the epileptic discharges. Comparison of our cases with previously reported reflex epilepsy induced by higher mental activity led to the assumption that the neural mechanism inducing seizures in our cases is similar to that of writing epilepsy. Valproate was effective in reducing epileptic discharges, and all patients became seizure-free.