title: Value of scalp delayed rhythmic ictal transformation (DRIT) in presurgical assessment of temporal lobe epilepsy.
abstract: OBJECTIVE
  To estimate the localising and lateralising value of delayed rhythmic ictal transformation (DRIT) on the scalp EEG during presurgical assessment for temporal lobe epilepsy.
  
  
  METHODS
  Two hundred and eighty eight seizures recorded simultaneously with scalp and foramen ovale (FO) electrodes were studied retrospectively in 110 patients. DRIT was defined as sustained regular rhythmic waveforms seen on scalp recordings after scalp seizure onset. The incidence and laterality of scalp DRIT was evaluated by comparison to FO electrodes.
  
  
  RESULTS
  Scalp DRIT was seen in 192 seizures, 65% of which showed focal mesial temporal onset (FMTO) recorded by FO electrodes. FMTO onset was seen in 73% of the 122 seizures showing unilateral scalp DRIT, in 32% of the 62 seizures showing bilateral asymmetrical scalp DRIT, and in 14% of the seven seizures showing bilateral symmetrical DRIT on the scalp. Among the 89 seizures showing unilateral scalp DRIT and FMTO, both were ipsilateral in 70 seizures (79%). Among the 38 seizures showing bilateral asymmetrical DRIT and FMTO, the largest amplitude of scalp DRIT was ipsilateral to the FO onset in 27 seizures (71%).
  
  
  CONCLUSIONS
  Two thirds of seizures showed unilateral scalp DRIT, which had a lateralising value of up to 79%.
  
  
  CONCLUSIONS
  Scalp DRIT is a reliable marker to lateralise seizure focus in patients without a focal seizure onset on the scalp EEG.
authors: Department of Clinical Neurophysiology, King's College Hospital, London, United Kingdom. gonzalo.alarcon@kcl.ac.uk
authors: Gonzalo
authors: G
authors: Alarcón
authors: Peter
authors: P
authors: Muthinji
authors: Najib
authors: N
authors: Kissani
authors: Charles E
authors: CE
authors: Polkey
authors: Antonio
authors: A
authors: Valentín
mesh_terms: D015415:Biomarkers; D004566:Electrodes; D004569:Electroencephalography / Q000379:methods*; D004833:Epilepsy, Temporal Lobe / Q000503:physiopathology*; D054085:Foramen Ovale / Q000502:physiology*; D007839:Functional Laterality / Q000502:physiology*; D006801:Humans; D015994:Incidence; D010507:Periodicity; D011300:Preoperative Care; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012535:Scalp / Q000502:physiology*; D013997:Time Factors
chemical_list: D015415:Biomarkers