Transsylvian hippocampal transection for mesial temporal lobe epilepsy: surgical indications, procedure, and postoperative seizure and memory outcomes

Abstract

Object Amygdalohippocampectomy is a well-established, standard surgery for medically intractable mesial temporal lobe epilepsy (MTLE). However, in the case of MTLE without hippocampal atrophy or sclerosis, amygdalohippocampectomy is associated with decreased postoperative memory function. Hippocampal transection (HT) has been developed to overcome this problem. In HT the hippocampus is not removed; rather, the longitudinal hippocampal circuits of epileptic activities are disrupted by transection of the pyramidal layer of the hippocampus. The present study describes a less invasive modification of HT (transsylvian HT) and presents the seizure and memory outcomes for this procedure. Methods Thirty-seven patients with MTLE (18 men and 19 women; age range 9–63 years; 19 with surgery on the right side and 18 with surgery on the left side; seizure onset from 3 to 34 years) who were treated with transsylvian HT were retrospectively analyzed. All patients had left-side language dominance, and follow-up periods ranged from 12 to 94 months (median 49 months). Seizure outcomes were evaluated for all patients by using the Engel classification. Memory function was evaluated for 22 patients based on 3 indices (verbal memory, nonverbal memory, and delayed recall), with those scores obtained using the Wechsler Memory Scale–Revised. Patients underwent evaluation of the memory function before and after surgery (6 months–1 year). Results Engel Class I (completely seizure free) was achieved in 25 patients (67.6%). Class II and Class III designation was achieved in 10 (27%) and 2 patients (5.4%), respectively. There were differences in memory outcome between the sides of operation. On the right side, verbal memory significantly increased postoperatively (p = 0.003) but nonverbal memory and delayed recall showed no significant change after the operation (p = 0.718 and p = 0.210, respectively). On the left side, all 3 indices (verbal memory, nonverbal memory, and delayed recall) showed no significant change (p = 0.331, p = 0.458, and p = 0.366, respectively). Conclusions Favorable seizure outcome and preservation of verbal memory were achieved with transsylvian HT for the treatment of MTLE without hippocampal atrophy or sclerosis.

Surgery for amygdala enlargement with mesial temporal lobe epilepsy: pathological findings and seizure outcome

“…These results indicate the efficacy of surgical treatment for AE. When performing surgery, selective amygdalohippocampectomy is the first choice with regard to preservation of memory function 18. If the affected side is located on the dominant hemisphere, HT is one of the surgical options to preserve memory function, although it is inferior to hippocampectomy with regard to seizure suppression 18.…”

“…When performing surgery, selective amygdalohippocampectomy is the first choice with regard to preservation of memory function 18. If the affected side is located on the dominant hemisphere, HT is one of the surgical options to preserve memory function, although it is inferior to hippocampectomy with regard to seizure suppression 18. Medical treatment should be performed prior to surgical treatment, and only medically intractable cases should be considered for surgical intervention.…”

“…Trans-sylvian selective amygdalohippocampectomy (TSA)13–16 was performed in nine patients, and two patients underwent selective amygdalotomy with hippocampal transection (HT) 17 18. The surgical procedure was as follows.…”

The significance of parahippocampal high gamma activity for memory preservation in surgical treatment of atypical temporal lobe epilepsy

“…We adopt hippocampal transection (HT) in cases with atypical MTLE of the language‐dominant side, particularly in patients whose memory functions are maintained. HT is a novel memory‐preserving procedure developed as a hippocampal counterpart of neocortical multiple subpial transections (MSTs) . Similar to transient cortical dysfunction after MSTs, it is reported that memory functions decline transiently after HT before recovering to the preoperative level within 6 months .…”

Long‐term outcome and neuroradiologic changes after multiple hippocampal transection combined with multiple subpial transection or lesionectomy for temporal lobe epilepsy

“…The seizure outcome of MHT at 1 year after surgery was equivalent to that of temporal lobectomy, and the memory indices were preserved at the preoperative level . Although other groups subsequently reported similar results, the long‐term outcomes after MHT still remain to be clarified, because of the small patient numbers and the limited periods of follow‐up in those studies. Furthermore, the underlying mechanisms for inhibition of seizure and preservation of memory by MHT are largely unknown.…”