title: Limiting the current density during localization of the primary motor cortex by using a tangential-radial cortical somatosensory evoked potentials model, direct electrical cortical stimulation, and electrocorticography.
abstract: BACKGROUND
  Traditionally, the dual-radial model, which requires high cortical stimulation intensities and may evoke intraoperative seizures, is used for mapping during resection of lesions within or near the central sulcus.
  
  
  OBJECTIVE
  To examine the potential utility of using the multimodal tangential-radial triphasic model, which may increase the accuracy and reliability of cortical mapping at lower stimulation intensities.
  
  
  METHODS
  We performed a retrospective review of intracranial neuromonitoring cases at the University of Virginia. The tangential-radial triphasic model used direct electrical cortical stimulation (DECS), electrocorticography, and somatosensory evoked potentials with an additional P25 peak for waveform interpretation, instead of the older dual-radial model with N20 and P30 peaks alone. The central sulcus and sensory cortex were localized by generating multiple sensory maps. DECS with 50-Hz frequency was applied. Electrocorticography was used for detection of afterdischarges.
  
  
  RESULTS
  Fifteen consecutive intracranial cases were identified. The patients consisted of 8 males and 7 females ranging in age from 12 to 74 years (median, 53 years). Fourteen patients had an intra-axial cortical mass, and 1 patient had a cortical arteriovenous malformation. The DECS thresholds ranged from 3.7 to 12 mA (median, 6.2 mA). Localization of motor and sensory cortices was accurately performed at low thresholds with bipolar DECS in all patients. Intraoperative seizures occurred in 1 patient (7%), and new permanent postoperative functional deficits occurred in 1 patient (7%).
  
  
  CONCLUSIONS
  Our mapping technique appears safe and reliable for resection near the central sulcus. The tangential-radial triphasic model allows for lower stimulation intensities, reducing the risk of intraoperative seizures.
authors.affiliation: Impulse Monitoring Inc, Columbia, MD, USA.
authors.forename: Faisal R
authors.initials: FR
authors.lastname: Jahangiri
authors.forename: Jonathan H
authors.initials: JH
authors.lastname: Sherman
authors.forename: Jason
authors.initials: J
authors.lastname: Sheehan
authors.forename: Mark
authors.initials: M
authors.lastname: Shaffrey
authors.forename: Aaron S
authors.initials: AS
authors.lastname: Dumont
authors.forename: Michael
authors.initials: M
authors.lastname: Vengrow
authors.forename: Francisco
authors.initials: F
authors.lastname: Vega-Bermudez
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001931:Brain Mapping / Q000379:methods*; D001932:Brain Neoplasms / Q000601:surgery*; D004558:Electric Stimulation / Q000379:methods; D004562:Electrocardiography / Q000379:methods; D005073:Evoked Potentials, Somatosensory; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative / Q000379:methods*; D019635:Neurosurgical Procedures; D012189:Retrospective Studies; D055815:Young Adult