Selective Amygdalohippocampectomy vs. Anterior Temporal Lobectomy for Epilepsy

Summary and Comment |
May 28, 2013

Selective Amygdalohippocampectomy vs. Anterior Temporal Lobectomy for Epilepsy

  1. Robert C. Knowlton, MD, MSPHAU1922

In a meta-analysis of nonrandomized studies, seizure-free outcome was greater after ATL than after SAH.

  1. Robert C. Knowlton, MD, MSPHAU1922

In the surgical treatment of intractable medial temporal lobe epilepsy (MTLE), an important unanswered question is whether seizure-free outcome is better with standard anterior temporal lobe resection (ATL) or with a more restrictive procedure, selective amygdalohippocampectomy (SAH). In theory, SAH might mitigate some neuropsychological deficits that are associated with ATL. However, seizure freedom also has important psychosocial benefits. To examine this question, researchers conducted an exhaustive systematic review and meta-analysis of published studies on seizure outcomes following either ATL or SAH. They identified 13 studies that compared the two procedures. Nearly all studies were from individual centers, and follow-up was carried out by clinic visits or telephone calls by investigators or unspecified individuals. Duration of outcome measures ranged from 1 year to a median of 10.9 years. Only three studies separated follow-up according to procedure type; in two, follow-up was an average of 14 to 26 months longer for ATL; in the third, follow-up was an average of 2 months longer for SAH. Other differences in study populations were not specified.

From 11 studies that provided dichotomous outcomes (Engel class I vs. Engel class II–IV), 583 participants had SAH and 620 had ATL. Seizure-free outcome was significantly greater with ATL at final follow-up (relative risk, 1.32; risk difference, 8%; number needed to treat, 13). Results were similar with a more conservative random effects model, in the subset of studies with standardized outcome duration, and among patients with only hippocampal sclerosis. Cumulative addition of studies to the meta-analysis demonstrated a stable RR estimate starting before the most recent three studies were added. Five studies providing data on surgical complications in 392 after ATL and 309 after SAH showed no significant difference.


This thorough meta-analysis exploited a sufficiently large number of cases, roughly balanced between anterior temporal lobe resection and selective amygdalohippocampectomy, to provide meaningful information regarding the difference in seizure-free outcomes. This study is particularly valuable because a randomized, controlled trial (RCT) — which the authors say is “justified” — is unlikely to be funded. And yet, an RCT is a compelling proposal if only to address the need for balance in each treatment arm of known variables that affect seizure outcome. Further, only an RCT can answer whether the central postulated benefit of SAH — reduced neuropsychological deficits — exists.

Editor Disclosures at Time of Publication

  • Disclosures for Robert C. Knowlton, MD, MSPH at time of publication Grant / research support NIH-NINDS Leadership positions in professional societies Southern Epilepsy and EEG Society (Treasurer)


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