Transient amnesia in a patient with left temporal tumor: symptomatic transient global amnesia or an epileptic amnesia?

BACKGROUND

An isolated prolonged episode of transient amnesia can be a major manifestation of transient global amnesia (TGA) and transient epileptic amnesia (TEA). We report a case of transient amnesia associated with a left temporal tumor and try to elucidate the possible mechanism of the amnesia.

CASE REPORT: A 67-year-old right-handed man with the past history of migraine developed a transient declarative amnesia with a permanent memory gap for 5 hours. During the attack, he drove for 100 km flawlessly, but was not aware of his memory deficit. Selective retrograde amnesia during the episode was also observed. Investigations revealed an impaired verbal memory on neuropsychological tests, a possible metastatic tumor in the left temporal lobe by cerebral MRI, isolated wicket temporal spikes in the left mesial temporal area by sphenoidal electroencephalogram (EEG), and an additional brief phase of confusion. No recurrence of a similar attack occurred by 17 months after treatment with radiotherapy and chemotherapy.

DISCUSSION: This case serves to emphasize that transient dense anterograde amnesia resembling TGA might possibly occur as a manifestation of TEA and that there is a risk of subsequent epileptic features. The amnesia in this case also supports the hypothesis of spreading depression in patients with TGA and migraine and could support the epileptic hypothesis for the pathogenesis of TGA.