Electro‐clinical criteria and surgical outcome: Is there a difference between mesial and lesional temporal lobe epilepsy?
Early recognition of mesial temporal lobe epilepsy (MTLE) is important as it is considered the prototype of an epileptic syndrome suited for surgical referral and treatment.1 MTLE is usually diagnosed based on the presence of several electrophysiological and clinical (electro‐clinical) signs and symptoms (seizure semiology), accompanied by the presence of hippocampal sclerosis (HS) on MRI.4 Diagnosing MTLE, however, can be difficult with no diagnostic rule to define the electro‐clinical syndrome.5 Evidence is lacking on how many, and which specific, electro‐clinical criteria are needed for its diagnosis and whether HS is a prerequisite. Structural lesions, such as a tumour, cortical dysplasia, vascular or ischaemic lesion, near the mesial temporal structures may exist or co‐occur with HS, that is “dual pathology,” and give rise to similar electro‐clinical signs and symptoms.3 This may be explained by the fact that complex temporo‐insular and temporo‐opercular networks may be involved in seizure generation, and ictal onset zones may extend outside the hippocampus,6 as shown by intracerebral EEG recordings8 and neuroimaging studies.10 Lesional TLE may thus resemble MTLE due to HS and may have similar prospects regarding surgical outcome.12 Yet, as a whole, people with MTLE with HS still form the largest group being surgically treated.13
We aimed to assess whether MTLE due to HS was different from lesional causes of TLE with respect to electro‐clinical criteria and surgical outcome. We also assessed whether the underlying aetiology or electro‐clinical criteria could predict surgical outcome.