title: Intraoperative electrocortical stimulation of Brodman area 4: a 10-year analysis of 255 cases.
abstract: BACKGROUND
  Brain tumor surgery is limited by the risk of postoperative neurological deficits. Intraoperative neurophysiological examination techniques, which are based on the electrical excitability of the human brain cortex, are thus still indispensable for surgery in eloquent areas such as the primary motor cortex (Brodman Area 4).
  
  
  METHODS
  This study analyzed the data obtained from a total of 255 cerebral interventions for lesions with direct contact to (121) or immediately adjacent to (134) Brodman Area 4 in order to optimize stimulation parameters and to search for direct correlation between intraoperative potential changes and specific surgical maneuvers when using monopolar cortex stimulation (MCS) for electrocortical mapping and continuous intraoperative neurophysiological monitoring.
  
  
  RESULTS
  Compound muscle action potentials (CMAPs) were recorded from the thenar muscles and forearm flexors in accordance with the large representational area of the hand and forearm in Brodman Area 4. By optimizing the stimulation parameters in two steps (step 1: stimulation frequency and step 2: train sequence) MCS was successful in 91% (232/255) of the cases. Statistical analysis of the parameters latency, potential width and amplitude showed spontaneous latency prolongations and abrupt amplitude reductions as a reliable warning signal for direct involvement of the motor cortex or motor pathways.
  
  
  CONCLUSIONS
  MCS must be considered a stimulation technique that enables reliable qualitative analysis of the recorded potentials, which may thus be regarded as directly predictive. Nevertheless, like other intraoperative neurophysiological examination techniques, MCS has technical, anatomical and neurophysiological limitations. A variety of surgical and non-surgical influences can be reason for false positive or false negative measurements.
authors.affiliation: Department of Neurosurgery, Charité-Universitaetsmedizin Berlin, Campus Benjamin Franklin, Berlin, Germany. olaf.suess@charite.de
authors.forename: Olaf
authors.initials: O
authors.lastname: Suess
authors.forename: Silke
authors.initials: S
authors.lastname: Suess
authors.forename: Mario
authors.initials: M
authors.lastname: Brock
authors.forename: Theodoros
authors.initials: T
authors.lastname: Kombos
mesh_terms: D000200:Action Potentials / Q000502:physiology; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001931:Brain Mapping / Q000379:methods*; D001932:Brain Neoplasms / Q000601:surgery*; D002540:Cerebral Cortex / Q000503:physiopathology* / Q000601:surgery; D003287:Contrast Media; D004558:Electric Stimulation / Q000379:methods*; D005260:Female; D006801:Humans; D007431:Intraoperative Complications / Q000175:diagnosis* / Q000503:physiopathology; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic; D019635:Neurosurgical Procedures
chemical_list: D003287:Contrast Media