title: Interictal rhythmical midline theta differentiates frontal from temporal lobe epilepsies.
abstract: OBJECTIVE
  We evaluated the role of interictal rhythmical midline theta (RMT) in the identification of frontal lobe epilepsy (FLE) and its differentiation from temporal lobe epilepsy (TLE) and nonepileptic controls.
  
  
  METHODS
  We included 162 individuals in the study: 54 FLE patients, 54 TLE patients, and 54 nonepileptic controls. Continuous electroencephalographic (EEG)-video monitoring was performed in all individuals. Interictal RMT was included only if it occurred during definite awake states. RMT associated with drowsiness or mental activation and ictal RMT was excluded.
  
  
  RESULTS
  We identified RMT significantly more frequently in FLE patients (48.1%, 26 of 54) than in TLE patients (3.7%, 2 of 54) (p < 0.01), and not in the control group. The average frequency was 6 Hz (range 5-7 Hz), and the average RMT bursts lasted 8 s (3-12 s). Interestingly, all mesial FLE patients (n = 4) (as established by invasive EEG recordings) showed RMT, whereas this was less frequently the case in the other FLE patients (44%, 22 of 50) (p = 0.03). Thirteen of our 54 patients with FLE (24%) did not have any interictal epileptiform discharges (IEDs), but RMT was observed in the majority of these patients (62%, 8 of 13).
  
  
  CONCLUSIONS
  Interictal RMT is common and has a localizing value in patients with FLE, provided that conditions such as drowsiness and mental activation as confounding factors for RMT are excluded. RMT should be included in the evaluation of patients considered for resective epilepsy surgery.
authors.affiliation: Epilepsy Center, Department of Neurology, University of Munich, Munich, Germany.
authors.forename: Pedro
authors.initials: P
authors.lastname: Beleza
authors.forename: Ozgür
authors.initials: O
authors.lastname: Bilgin
authors.forename: Soheyl
authors.initials: S
authors.lastname: Noachtar
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D003937:Diagnosis, Differential; D003952:Diagnostic Imaging; D004292:Dominance, Cerebral / Q000502:physiology; D004569:Electroencephalography; D017034:Epilepsy, Frontal Lobe / Q000175:diagnosis / Q000209:etiology / Q000503:physiopathology* / Q000601:surgery; D004833:Epilepsy, Temporal Lobe / Q000175:diagnosis / Q000209:etiology / Q000503:physiopathology* / Q000601:surgery; D005071:Evoked Potentials / Q000502:physiology; D005260:Female; D005625:Frontal Lobe / Q000503:physiopathology; D006624:Hippocampus / Q000503:physiopathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D012815:Signal Processing, Computer-Assisted; D013826:Theta Rhythm; D014741:Video Recording; D055815:Young Adult