A Case of Postictal Transient Anterograde and Retrograde Amnesia

We report the uncommon case of a 27-year-old man with transient epileptic amnesia (TEA) with long-lasting episodes. Seizures (one to five monthly) began 2 years after the spectacular recovery from a cerebral hemorrhagic contusion with coma for 1 month at age 18 years. The usual manifestation of his seizures is an ascending wave from the abdomen. At age 25 years, he had his first grouped seizures (20 to 30 within 3 days), resulting in an amnesic state, which reoccurred 10 times since then. Magnetic resonance imaging (MRI) revealed multiple punctiform hemosiderin deposits in the white matter underlying the pars triangularis of the right frontal lobe and the right posteromedial parietal lobe, as well as lesions in the right amygdala and entorhinal cortex. During video-EEG monitoring, we recorded 28 seizures (0.5–3 min), spread over a period of 3 days, starting in the anterior right hemisphere, involving secondarily the left side, with occasionally a temporal predominance. We completed a neuropsychological evaluation before these grouped seizures. Almost all nonmemory scores were within 1 SD of the mean. Immediate memory performances revealed minor difficulties. Delayed memory tests demonstrated deficits in recall but not recognition. Performances for autobiographic events and personal semantic memories showed no interictal difficulty (Table 1). The second memory evaluation (Table 1), carried out on the first 2 postictal days when the EEG was completely normal, revealed severe memory impairments in immediate recall (50% less information recalled than interictally) and in delayed recall. For some tasks, no material could be evoked, but recognition was spared. Retrograde memory assessment was based on autobiographic memories collected interictally, by providing the necessary minimal clue to elicit each memory. When no memory could be evoked, additional clues were given. Remote memory of events before his traumatic cerebral contusion showed a good report. By contrast, memories occurring after his trauma and his first seizure (at age 20 years) required additional clues and were poorly reported, those from the last 4 months being not reported at all. Thus a temporal gradient for autobiographic events was observed. Personal semantic memories were equivalent to the interictal memories. Two weeks later, his mother reported very little improvement, but interictal abilities were recovered 2 months later. His TEA includes anterograde and retrograde amnesia. EEG established that his amnesia is postictal and thus analogous to Todd's paralysis. Few cases of unusual functional paralysis after seizures have been reported: one with apraxia, and one with hemineglect lasting for >70 h (1). The particularly long amnesia (weeks) and the early apparition of TEA (at age 25 years) contrast with previously reported TEA cases (2–5). His anterograde memory reveals good recognition but impaired recall performance, suggesting retrieval difficulties with preserved encoding abilities. Such dissociations have been explained by frontal lobe dysfunctions (6–9). In this patient, the presence of frontal lobe lesions and the fact that seizures start in anterior regions might be responsible for these findings. The transient retrograde amnesia documented here selectively affects memories acquired after, but not before, his head trauma or his first seizure or both. These memories appear to be particularly vulnerable to TEA. The temporal gradient associated with transient retrograde amnesia suggests that the dysfunction interferes with hippocampal consolidation (10), arguing for a mediotemporal-related deficit.

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