NEW YORK (Reuters Health) - Episodes of transient amnesia, which frequently occur on awakening and are associated with other memory problems, may be a symptom of a distinct type of epilepsy. A British team describes this condition they call "transient epileptic amnesia" in a study published in the Annals of Neurology.

Dr. Adam Z. J. Zeman, of the Peninsula Medical School in Exeter, and colleagues recruited 50 patients over an 18-month period who had recurrent episodes of amnesia that were witnessed by another person; otherwise intact mental functioning; and evidence suggesting epilepsy, including EEG abnormalities, response to anticonvulsant therapy; or clinical features, such as hallucinations involving the sense of smell.

In correspondence with Reuters Health, Zeman described transient epileptic amnesia as "repeated short episodes of transient amnesia, occurring about once a month, usually lasting about half an hour, often occurring on waking, typically in middle-aged people around the age of 60."

"There can be other manifestations of epilepsy during the attack, like a hallucination of a smell, or a brief period of loss of awareness, but often the amnesia is the sole manifestation of the seizure," he added.

Zeman's team found that the condition was often misdiagnosed -- only 12 of the 50 patients in the study had received an initial diagnosis of epilepsy.

Anticonvulsant medication was effective in 44 of the 47 patients treated. "Most of our patients were treated with carbamazepine, sodium valproate or lamotrigine and the response to treatment was generally excellent," Zeman said.

Among the 50 patients, 40 described persistent memory difficulties. Patients demonstrated a "loss of autobiographical memory for events extending back over 40 years." They had a normal performance on standard memory tests, but they exhibited "accelerated forgetting of verbal and visual material over three weeks by comparison with matched control subjects," the researchers report.

"We propose that transient amnesic epilepsy is a distinctive epilepsy syndrome, typically misdiagnosed...and associated with accelerated long-term forgetting and autobiographical amnesia," Zeman and his colleagues conclude.

SOURCE: Annals of Neurology, June 2007.

REUTERS