Severe amnesia: an usual late complication after temporal lobectomy

A patient developed the severe amnesic syndrome 8 years after temporal lobe surgery for epilepsy. He underwent left temporal lobectomy (6 cm, 43.5 g; hippocampal sclerosis) aged 19, and remained seizure free for 8 years until a convulsion followed a head injury. He became severely amnesic after a fourth convulsion 16 months later. He was right-handed, pre-operative IQ was average, verbal memory poor and non-verbal memory normal. Post-operatively, these were unchanged. After the first post-operative seizure he began professional training. After onset of amnesia IQ was unchanged, anterograde memory severely impaired and retrograde amnesia dense for at least 16 months. He died 2 years later. Magnetic resonance imaging before amnesia showed absence of anterior left temporal lobe, atrophy of left fornix and mamillary body, and normal right temporal lobe. Four months after onset of amnesia, right hippocampal volume had reduced by 36%. Autopsy showed: previous left temporal lobectomy with absence of left amygdala and hippocampus, atrophy of fornix and mamillary body; neuronal loss in the right hippocampus, severe in CA1 and CA4; intact right amygdala and parahippocampal gyrus; recent diffuse damage associated with cause of death. A convulsion can cause severe hippocampal damage in adult life. Hippocampal zones CA1 and/or CA4 are critical for maintaining memory and the amygdala and parahippocampal gyrus cortex alone cannot support acquisition of new memories.