title: Applicability of nTMS in locating the motor cortical representation areas in patients with epilepsy.
abstract: BACKGROUND
  Transcranial magnetic stimulation (TMS) is increasingly used for non-invasive functional mapping in preoperative evaluation for brain surgery, and the reliability of navigated TMS (nTMS) motor representation maps has been studied in the healthy population and in brain tumor patients. The lesions behind intractable epilepsy differ from typical brain tumors, ranging from developmental cortical malformations to injuries early in development, and may influence the functional organization of the cortical areas. Moreover, the interictal cortical epileptic activity and antiepileptic medication may affect the nTMS motor threshold. The reliability of the nTMS motor representation localization in epilepsy patients has not been addressed.
  
  
  METHODS
  We compared the nTMS motor cortical representation maps of hand and arm muscles with the results of invasive electrical cortical stimulation (ECS) in 13 patients with focal epilepsy. The nTMS maps were projected to the cortical surface segmented from preoperative magnetic resonance images (MRI), and the positions of the subdural electrodes were extracted from the postoperative low-dose computed tomography (CT) images registered with preoperative MRI.
  
  
  RESULTS
  The 3D distance between the average nTMS site and average ECS electrode location was 11 ± 4 mm for the hand and 16 ± 7 mm for arm muscle representation areas. In all patients the representation areas defined with nTMS and ECS were located on the same gyrus, also in patients with abundant interictal epileptic activity on the motor gyrus.
  
  
  CONCLUSIONS
  nTMS can reliably locate the hand motor cortical representation area with the accuracy needed for pre-surgical evaluation in patients with epilepsy.
authors: Department of Radiology, HUS Medical Imaging Center, Helsinki University Central Hospital and University of Helsinki, P.O. Box 340, 00029, Helsinki, Finland. anne-mari.vitikainen@hus.fi
authors: Anne-Mari
authors: AM
authors: Vitikainen
authors: Eero
authors: E
authors: Salli
authors: Pantelis
authors: P
authors: Lioumis
authors: Jyrki P
authors: JP
authors: Mäkelä
authors: Liisa
authors: L
authors: Metsähonkala
mesh_terms: D000293:Adolescent; D000328:Adult; D001132:Arm / Q000294:innervation; D001931:Brain Mapping / Q000379:methods*; D001932:Brain Neoplasms / Q000503:physiopathology* / Q000601:surgery*; D002648:Child; D004558:Electric Stimulation; D004576:Electromyography; D004828:Epilepsies, Partial / Q000503:physiopathology* / Q000601:surgery*; D017034:Epilepsy, Frontal Lobe / Q000503:physiopathology / Q000601:surgery; D020938:Epilepsy, Partial, Motor / Q000503:physiopathology / Q000601:surgery; D006225:Hand / Q000294:innervation; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D021621:Imaging, Three-Dimensional; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D009044:Motor Cortex / Q000503:physiopathology*; D018482:Muscle, Skeletal / Q000294:innervation; D011300:Preoperative Care / Q000379:methods*; D012189:Retrospective Studies; D013003:Somatosensory Cortex / Q000503:physiopathology; D014057:Tomography, X-Ray Computed / Q000379:methods; D050781:Transcranial Magnetic Stimulation / Q000379:methods*; D055815:Young Adult