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Electro-clinical criteria and surgical outcome: Is there a difference between mesial and lesional temporal lobe
M Wassenaar1,2, F S S Leijten2, G-J de Haan1
1Stichting Epilepsie Instellingen Nederland (SEIN), Heemstede, The Netherlands.
Objectives:
Mesial temporal lobe epilepsy syndrome (MTLE) with specific electrophysiological and clinical characteristics and hippocampal sclerosis (HS) on MRI is considered the prototype of a syndrome with good surgical prognosis. Ictal onset zones in MTLE have been found to extend outside the hippocampus and neocortical seizures often involve mesial structures. It can, thus, be questioned whether MTLE with HS is different from lesional temporal epilepsies with respect to electro-clinical characteristics and surgical prognosis. We assessed whether MTLE with HS is distinguishable from lesional TLE and which criteria determine surgical outcome.
Methods:
People in a retrospective cohort of 389 individuals with MRI abnormalities who underwent temporal lobectomy, were divided into "HS only" or "lesional" TLEs. Twenty-six presented with dual pathology and were excluded from further analysis. We compared surgical outcome and electro-clinical characteristics.
Results:
Over half (61%) had "HS only." Four electro-clinical characteristics (age at epilepsy onset, febrile seizures, memory dysfunction and contralateral dystonic posturing) distinguished "HS only" from "lesional" TLE, but there was considerable overlap. Seizure freedom 2 years after surgery (Engel class 1) was similar: 67% ("HS only") vs 69% ("lesional" TLE). Neither presence of HS nor electro-clinical criteria was associated with surgical outcome.
Conclusions:
Despite small differences in electrophysiological and clinical characteristics between MTLE with HS and lesional TLE, surgical outcomes are similar, indicating that aetiology seems irrelevant in the referral for temporal surgery.
Insights
Mesial temporal lobe epilepsy with hippocampal sclerosis (MTLE-HS) and lesional temporal lobe epilepsy (TLE) show similar surgical outcomes despite minor electro-clinical differences. Etiology does not appear to influence referral for temporal surgery.
Area of Science:
- Neurology
- Epileptology
- Neurosurgery
Background:
- Mesial temporal lobe epilepsy syndrome with hippocampal sclerosis (MTLE-HS) is a well-recognized epilepsy syndrome with a generally good surgical prognosis.
- However, seizures in MTLE can originate outside the hippocampus, and neocortical seizures may involve mesial structures, raising questions about its distinction from lesional temporal lobe epilepsies (TLE).
Purpose of the Study:
- To determine if MTLE-HS is distinguishable from lesional TLE based on electro-clinical characteristics and surgical prognosis.
- To identify criteria that predict surgical outcomes in these epilepsy subtypes.
Main Methods:
- A retrospective analysis of 389 individuals with MRI abnormalities who underwent temporal lobectomy.
- Participants were categorized into "HS only" (MTLE-HS) or "lesional" TLE groups, with 26 dual pathology cases excluded.
- Comparison of surgical outcomes and electro-clinical characteristics between the groups.
Main Results:
- 61% of the cohort had "HS only" epilepsy.
- Four electro-clinical features differentiated "HS only" from "lesional" TLE, though with significant overlap.
- Seizure freedom rates at 2 years post-surgery (Engel class 1) were comparable: 67% for "HS only" vs. 69% for "lesional" TLE.
- Neither hippocampal sclerosis presence nor specific electro-clinical criteria correlated with surgical outcomes.
Conclusions:
- Despite subtle electrophysiological and clinical variations, MTLE-HS and lesional TLE exhibit similar surgical prognoses.
- The underlying etiology appears to be of minimal importance when considering patients for temporal epilepsy surgery.
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