title: Nonlesional atypical mesial temporal epilepsy: electroclinical and intracranial EEG findings.
abstract: OBJECTIVE
  Misleading manifestations of common epilepsy syndromes might account for some epilepsy surgery failures, thus we sought to characterize patients with difficult to diagnose (atypical) mesial temporal lobe epilepsy (mTLE).
  
  
  METHODS
  We retrospectively reviewed our surgical database over 12 years to identify patients who underwent a standard anterior temporal lobectomy after undergoing intracranial EEG (ICEEG) evaluation with a combination of depth and subdural electrodes. We carefully studied electroclinical manifestations, neuroimaging data, neuropsychological findings, and indications for ICEEG.
  
  
  RESULTS
  Of 835 patients who underwent anterior temporal lobectomy, 55 were investigated with ICEEG. Ten of these had atypical mTLE features and were not considered to have mTLE preoperatively. All of them had Engel class I outcome for 3 to 7 years (median 3.85). Five reported uncommon auras, and 3 had no auras. Scalp-EEG and nuclear imaging studies failed to provide adequate localization. None had MRI evidence of hippocampal sclerosis. However, ICEEG demonstrated exclusive mesial temporal seizure onset in all patients. Clues suggesting the possibility of mTLE were typical auras when present, anterior temporal epileptiform discharges or ictal patterns, small hippocampi, asymmetrical or ipsilateral temporal hypometabolism on PET, anterior temporal hyperperfusion on ictal SPECT, and asymmetry of memory scores. Histopathology revealed hippocampal sclerosis in 6 patients and gliosis in 2.
  
  
  CONCLUSIONS
  Atypical electroclinical presentation may be deceptive in some patients with mTLE. We emphasize the importance of searching for typical mTLE features to guide ICEEG study of mesial temporal structures in such patients, who may otherwise mistakenly undergo extramesial temporal resections or be denied surgery.
authors.affiliation: From the Cleveland Clinic Epilepsy Center (K.U., A.V.A., R.M.B., T.W., D.N., W.E.B., I.M.N.), Neurological Institute, Cleveland, OH; Department of Neurology (K.U.), Prasat Neurological Institute, Bangkok, Thailand; and Institute of Neurology (T.W.), University College London, UK.
authors.forename: Kanjana
authors.initials: K
authors.lastname: Unnwongse
authors.forename: Andreas V
authors.initials: AV
authors.lastname: Alexopoulos
authors.forename: Robyn M
authors.initials: RM
authors.lastname: Busch
authors.forename: Tim
authors.initials: T
authors.lastname: Wehner
authors.forename: Dileep
authors.initials: D
authors.lastname: Nair
authors.forename: William E
authors.initials: WE
authors.lastname: Bingaman
authors.forename: Imad M
authors.initials: IM
authors.lastname: Najm
mesh_terms: D000293:Adolescent; D000328:Adult; D004567:Electrodes, Implanted; D004569:Electroencephalography / Q000295:instrumentation / Q000379:methods*; D004833:Epilepsy, Temporal Lobe / Q000000981:diagnostic imaging / Q000503:physiopathology* / Q000601:surgery; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D011877:Radionuclide Imaging; D012189:Retrospective Studies; D016896:Treatment Outcome; D055815:Young Adult