Abstracts

Aim: To determine whether non-lesional TLE without HS on MRI represents a variant of, or a different clinicopathological syndrome to that of MTLE.
Most patients with medically refractory non-lesional TLE have the syndrome of mesial temporal lobe epilepsy (MTLE) associated with typical findings of hippocampal sclerosis (HS) on MRI. However, a significant group of patients with well lateralised temporal lobe seizures on ictal EEG, often with significant focal temporal hypometabolism on positron emission tomography (PET), do not have HS on MRI. The underlying pathophysiological basis of this syndrome is uncertain.
METHODS: The clinical, EEG, FDG-PET, histopathology and surgical outcome of 15 consecutive non-lesional patients without HS on MRI (HS-) were compared with 15 consecutive patients with typical HS (HS+).
RESULTS: The HS- group less frequently had a history of a remote symptomatic neurological insult (13% vs. 58%, p[lt]0.05), and this occurred at an older age (median 18.5 vs. 2 years, p[lt]0.05). Febrile convulsions were only seen in the HS+ group (42%). The ictal EEG pattern in the HS- group more frequently showed a focal delta rhythm (58% vs. 10%, p[lt]0.05), compared with a focal theta rhythm in the HS+ group (60% vs. 25%, p=0.20). Blinded review of the FDG-PET scans detected unilateral focal hypometabolism in 100% of both groups, but its pattern did not differ between the groups. Nine patients in both groups have had epilepsy surgery with no significant difference in outcome (67% vs. 89% seizure free, p[gt]0.05) despite most of the HS- patients having a hippocampal sparing procedure.
CONCLUSIONS: We conclude, based on the clinical, EEG, pathology and surgical outcome differences identified, that non-lesional TLE without HS may be a distinct surgically remediable clinicopathological syndrome, rather than being a part of the spectrum of MTLE.
[Supported by: Epilepsy Fellowship Sanofi-Synthelabo]; (Disclosure: Grant - Sanofi Epilepsy Fellowship)