Some observations on memory impairment after temporal lobectomy for epilepsy

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Abstract
Memory impairment was assessed in 34 patients who experienced unilateral temporal lobectomy for epilepsy. The assessment was clinical in nature and sphenoidal electronencephalo-graphic recordings were studied on some patients at intervals of one to five years following surgery. In 7 of the 34 patients some memory impairment persisted 2 to 9 years after the operation but in no case was it disabling. Normal, post-operative E.E.G. records were found in 27 patients and only one of these developed a persistent memory defect. In contrast, however, 6 out of 7 who post-operatively showed a spike-discharging focus at the sphenoidal electrode of the opposite temporal lobe, developed such a memory defect. This second group also showed a higher incidence of persistent epilepsy. The findings support the hypothesis that the greatest incidence of recent memory impairment following unilateral temporal lobectomy occurs in those patients who have persistent E.E.G. abnormalities in the mesial portion of the contralateral temporal lobe beneath the sphenoidal electrode. Cases without post-operative memory defects usually have normal post-operative E.E.G''s or unspecific changes involving only the temporal lobe convexities, unilaterally or bilaterally.