title: Extraoperative electrical cortical stimulation:  characteristics of motor responses and correlation with precentral gyrus.
abstract: OBJECTIVE
  To characterize properties and stimulation thresholds of extraoperative cortical stimulation with respect to the anatomic area stimulated.
  
  
  METHODS
  Analysis of 1,496 bipolar extraoperative cortical stimulations with respect to stimulation threshold, anatomic area stimulated, afterdischarges (ADs), and latencies to observe a clinical sign on video analysis.
  
  
  RESULTS
  Cortical stimulation mapping stimulus thresholds to induce clinical motor responses are lower when compared with stimulus thresholds to induce nonmotor responses (P < 0.01). Motor thresholds vary depending on the anatomic area stimulated with the precentral gyrus, showing lower stimulation thresholds when compared with cortex outside the precentral gyrus (P < 0.001). Afterdischarges are more likely to occur with motor stimulations outside the precentral gyrus (χ = 1; n = 123; P < 0.05), and those stimulations show longer latencies to observe an arm motor response on video analysis when compared with precentral gyrus stimulations (P < 0.05). Within the precentral gyrus, stimulation of the hand knob was achieved with lower stimulation intensities compared with stimulation outside the hand knob (P < 0.001).
  
  
  CONCLUSIONS
  Clinical response thresholds, afterdischarge occurrence, and latencies to observe clinical signs during extraoperative cortical stimulation vary depending on the cortex stimulated. Findings provide information about motor cortex organization and might aid interpreting results from extraoperative cortical stimulation in a clinical setting.
authors.affiliation: Institute of Neurology, National Hospital for Neurology and Neurosurgery, Queen Square, London, UK stjepana.kovac@gmail.com
authors.forename: Stjepana
authors.initials: S
authors.lastname: Kovac
authors.forename: Catherine A
authors.initials: CA
authors.lastname: Scott
authors.forename: Vesela
authors.initials: V
authors.lastname: Maglajlija
authors.forename: Roman
authors.initials: R
authors.lastname: Rodionov
authors.forename: Andrew W
authors.initials: AW
authors.lastname: McEvoy
authors.forename: Beate
authors.initials: B
authors.lastname: Diehl
mesh_terms: D000328:Adult; D055592:Biophysical Phenomena / Q000502:physiology; D001931:Brain Mapping; D016009:Chi-Square Distribution; D004558:Electric Stimulation; D004566:Electrodes; D005260:Female; D005625:Frontal Lobe / Q000601:surgery; D006179:Gyrus Cinguli / Q000033:anatomy & histology / Q000502:physiology*; D006801:Humans; D008297:Male; D016343:Monitoring, Intraoperative; D009044:Motor Cortex / Q000502:physiology*; D009068:Movement / Q000502:physiology*; D011930:Reaction Time; D012189:Retrospective Studies; D012684:Sensory Thresholds; D014741:Video Recording