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When a patient presents with an episode of transient memory loss without other neurologic symptoms, the diagnosis “transient global amnesia” (TGA) is often made, but the etiology is often unclear. Researchers in the U.K. describe 50 patients, recruited over 18 months, in whom epilepsy was thought to be the cause of otherwise unexplained transient amnesia, resulting in the more specific diagnosis of “transient epileptic amnesia” (TEA).
All patients had recurrent episodes of amnesia in which other cognitive functions were judged by witnesses to have remained intact. Diagnostic criteria for epilepsy were presence of at least one of these conditions: (1) epileptiform abnormalities on electroencephalogram (EEG), (2) presence of other clinical features of epilepsy such as lip-smacking or olfactory hallucinations, and (3) clear response to anticonvulsant therapy. Each of the three conditions was met by 18, 36, and 48 patients, respectively. Mean age at onset was 62, median attack frequency was 12 per year, and median duration of amnestic episodes was 30 to 60 minutes. Compared with age-matched controls, patients had subtle long-term memory problems on standardized tests. A diagnosis of epilepsy was initially considered in only 12 of these patients.
Butler CR et al. The syndrome of transient epileptic amnesia. Ann Neurol 2007 Jun; 61:587-98.
Comment
This is the largest published case series to date of patients with TEA. Because only 18 of the patients had documented epileptiform activity on EEG, one might challenge whether the diagnosis of TEA was certain in all cases. Nevertheless, this report demonstrates that clinicians should consider the diagnosis of nonconvulsive epilepsy in patients with unexplained episodic memory loss.