A Novel Operation for Temporal Lobe Epilepsy

Trans-parahippocampal Selective Amydalo-hippocampectomy for Temporal Lobe Epilepsy in Children

by T.S. Park, MD
Dr. Park is the Shi H. Huang Professor of Neurosurgery and professor of pediatrics at Washington University School of Medicine and Neurosurgeon-in-Chief and Surgical Director of the Pediatric Epilepsy Center at St. Louis Children’s Hospital.

Introduction

Currently several different variations of temporal lobe resections are employed for surgical treatment of temporal lobe epilepsy. Among these operations is selective resection of the mesial temporal structures.

We refined the operation in 1994 in which only the amygdala, hippocampus and parahippocampal gyrus are resected while sparing the rest of the temporal lobe. We call the operation “trans-parahippocamal selective amygdalo-hippocampectomy.” (1.3).

We have recently reported efficacy and cognitive morbidity of the operation in a series of children and adolescents on whom we performed the operation from 1994-1998 (3). Our experience indicates that the “trans-parahippocampal selective amygdalo-hippocampectomy” offers important advantages over other techniques of amygadalo-hippocampectomy or conventional temporal lobectomy.

Advantage of this operation

This operation spares all of the language areas and thus language mapping is unnecessary. Because children often can not cooperate for precise language mapping, the ability to avoid language mapping prior to temporal lobe resection is particularly important in children.

Injury to the temporal lobe white matter (temporal stem) can be prevented. The remaining temporal lobe has a better chance for normal functioning.

This operation may offer neuropsychological benefits.

Candidate for this operation

Children and adults who suffer from mesial temporal lobe epilepsy that has been refractory to medical treatment for at least 2 years.

Best candidates are those with mesial temporal sclerosis ascertained by MRI.

Patients with normal MRI are also surgical candidates provided their epilepsy arises from the mesial temporal lobe.

Patients with tumors and vascular malformations involving the hippocampus,,amygdala and/or parahippocampalgyrus are also suitable for the operation.

Evaluation prior to operation

All potential candidates undergo a comprehensive preoperative evaluation that includes:

  • Scalp EEG/video monitoring
  • Magnetic resonance imaging (MRI)
  • Positron emission tomography (PET)
  • Neuropsychological tests
  • In some potential candidates, following additional tests are done;
  • Sodium amobarbital test (Wada test) or functional MRI
  • Invasive EEG/video monitoring with subdural strip or depth electrodes

Surgical Technique

  • Figure 1. Extent of resection of the hippocampus and amygdala. The hippocampus is approached from below the temporal lobe
  • Figure 2. Scalp incision and craniotomy for the operation.
  • Figure 3. Postoperative MRI showing selective resection of the hippocampus and the underlying parahippocampal gyrus.

Outcomes

In a prospective study on 22 consecutive children and adolescents who underwent the trans-parahipoppocampal selective amygdalo-hippocampectomy, we examined seizure outcome, and cognitive and psychological morbidity (2).

Seizure outcome: Seizure control was achieved in 65% of patients followed for more than 2 years.

Cognitive outcome: Rote memory improved after the operation in patients who underwent right-sided operation. Other cognitive parameters examined was unchanged after the operation.

VIQ: verbal IQ, PIQ: performance IQ; FSIQ: full scale IQ

References

  • Park TS, Bourgeois BFD, Silbergeld DL, Dodson EW: Subtemporal transparahippocampal amygdalo-hippocampectomy for treatment of mesial temporal epilepsy. Technical Note. J Neurosurg, 1996, 85:1172-1176
  • Robinson S, Park TS, Bourgeois BFD, Blackburn LB, Arnold S: Transparahippocampal selective amygadalohippocampectomy in children and adolescents: Efficacy and Cognitive Morbidity. J Neurosurgery 2000, 93:402-409.
  • Park TS: Subtemporal trans-parahippocampal amygdalo-hippocampectomy for mesial temporal sclerosis. Neurosurgical Operative Atlas. American Association of Neurological Surgeons 2000; 9:63-68.