• Naoki Tani, Haruhiko Kishima, Hui Ming Khoo, Takufumi Yanagisawa, Satoru Oshino, Tomoyuki Maruo, Koichi Hosomi, Masayuki Hirata, Hiroaki Kazui, Keiko Tokumasu Nomura, Mohamed M Aly, Amami Kato, and Toshiki Yoshimine.
• Departments of 1 Neurosurgery and.
• J. Neurosurg. 2016 Nov 1; 125 (5): 1053-1060.

AbstractOBJECTIVE Epilepsy surgery is of known benefit for drug-resistant temporal lobe epilepsy (TLE); however, a certain number of patients suffer significant decline in verbal memory after hippocampectomy. To prevent this disabling complication, a reliable test for predicting postoperative memory decline is greatly desired. Therefore, the authors assessed the value of electrical stimulation of the parahippocampal gyrus (PHG) as a provocation test of verbal memory decline after hippocampectomy on the dominant side. METHODS Eleven right-handed, Japanese-speaking patients with medically intractable left TLE participated in the study. Before surgery, they underwent provocative testing via electrical stimulation of the left PHG during a verbal encoding task. Their pre- and posthippocampectomy memory function was evaluated according to the Wechsler Memory Scale-Revised (WMS-R) and/or Mini-Mental State Examination (MMSE) before and 6 months after surgery. The relationship between postsurgical memory decline and results of the provocative test was evaluated. RESULTS Left hippocampectomy was performed in 7 of the 11 patients. In 3 patients with a positive provocative recognition test, verbal memory function, as assessed by the WMS-R, decreased after hippocampectomy, whereas in 4 patients with a negative provocative recognition test, verbal memory function, as assessed by the WMS-R or MMSE, was preserved. CONCLUSIONS Results of the present study suggest that electrical stimulation of the PHG is a reliable provocative test to predict posthippocampectomy verbal memory decline.

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