Transient epileptic amnesia-A rare phenomenon in temporal lobe epilepsies

Abstract

Transient epileptic amnesia (TEA) is arare phenomenon in temporal lobe epilepsy that is often unrecognized or misdiagnosed as transient global amnesia (TGA). It is postulated that TEA is due to both ictal and postictal disturbances. Response to antiseizure medication underlines its epileptic nature. In view of the increasing incidence of new-onset epilepsies in old age, an increase in TEA can be expected in the future. Analysis of TEA features in amonocentric case series. Asearch in our electronic patient data base yielded 10patients with TEA out of 7899patients over aperiod of 8years. Clinical and paraclinical features as well as findings of additional examinations were retrospectively collected. Data are given as mean ± SD. All 10patients were diagnosed with temporal lobe epilepsy. The mean age at manifestation of TEA was 59.1 ± 6.7years, the diagnosis was made with adelay of 21.9 ± 26.3months. The TEA lasted on average 56 ± 37 min, and 16 ± 9.9 TEA episodes per year were reported by the patients; out of the 10patients 6 reported that TEA usually occurred upon awakening. In 9of 10patients, there was evidence of typical seizure symptoms or other semiological elements during TEA. Interictal neuropsychological disturbances of temporal functions were seen in 8of 10patients and evidence of depressive disorder in 6of 10patients. Video EEG recordings revealed epileptiform activity during sleep in 4patients over the left and in 2patients over both temporal regions. In 3patients, magnetic resonance imaging displayed typical alterations of the temporomesial structures (in 2patients on the left and in 1the right side). Antiseizure medication improved seizure control in 7of 10patients (seizure freedom in 6patients), 3patients were lost to follow-up. TEA is rare, occurs in older adults and is correctly diagnosed after about 2years. Thorough assessment of additional symptoms and circumstances, the recurrent occurrence as well as typical EEG and imaging findings of temporal lobe epilepsy enables the distinction between TEA and TGA.