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Updated: May 9, 2026
Anteromesial Temporal Lobectomy for Medically Intractable Temporal Lobe Epilepsy: An Operative Study
Published on: August 15, 2025
Transsylvian hippocampal transection for mesial temporal lobe epilepsy: surgical indications, procedure, and
Takehiro Uda1, Michiharu Morino, Hirotaka Ito
1Department of Neurosurgery, Tokyo Metropolitan Neurological Hospital, Tokyo, Japan.
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.
Insights
Transsylvian hippocampal transection (HT) offers a less invasive surgical option for mesial temporal lobe epilepsy (MTLE) without hippocampal atrophy. This procedure effectively controls seizures while preserving verbal memory function.
Area of Science:
- Neurosurgery
- Epilepsy Research
- Cognitive Neuroscience
Background:
- Mesial temporal lobe epilepsy (MTLE) is often treated with amygdalohippocampectomy.
- Standard amygdalohippocampectomy can lead to memory deficits in MTLE patients without hippocampal atrophy or sclerosis.
- Hippocampal transection (HT) disrupts epileptic circuits without removing the hippocampus, aiming to mitigate memory loss.
Purpose of the Study:
- To evaluate the efficacy and safety of a less invasive surgical technique, transsylvian HT.
- To assess seizure outcomes and postoperative memory function in patients with MTLE treated with transsylvian HT.
Main Methods:
- Retrospective analysis of 37 patients with MTLE who underwent transsylvian HT.
- Seizure outcomes were classified using the Engel classification.
- Memory function (verbal, nonverbal, delayed recall) was assessed using the Wechsler Memory Scale-Revised before and after surgery.
Main Results:
- 67.6% of patients achieved Engel Class I (seizure-free) status.
- No significant change in nonverbal memory or delayed recall was observed after surgery on the right side.
- Verbal memory showed a significant increase after right-sided surgery, while all memory indices remained stable after left-sided surgery.
Conclusions:
- Transsylvian HT is an effective treatment for MTLE without hippocampal atrophy or sclerosis.
- The procedure demonstrates favorable seizure control.
- Preservation of verbal memory function is achievable with this surgical approach.
