title: Application of multichannel near-infrared spectroscopic topography to physiological monitoring of the cortex during cortical mapping: technical case report.
abstract: BACKGROUND
  Cortical stimulation via a subdural grid electrode (SGE) is one of the most reliable methods for identifying eloquent areas before surgery. However, the physiological conditions of the cortex during stimulation cannot be monitored electrophysiologically because of electrical artifacts. In the present case, we tested whether or not multichannel near-infrared spectroscopy (NIRS) topography, a noninvasive optical imaging technique, is applicable for monitoring the physiological conditions of the stimulated cortex.
  
  
  METHODS
  The patient (a 27-year-old right-handed man) suffered from glioma in the left frontal lobe. For preoperative cortical mapping, SGEs were implanted over the left motor cortex before tumor resection. Employing NIRS topography, we undertook 2 dimensional imaging of the changes in oxyhemoglobin (Oxy-Hb) and deoxyhemoglobin (Deoxy-Hb) concentration during electrical stimulation. Five-hertz stimulation with 5 mA at the left-hand area produced a localized increase in Oxy-Hb and a decrease in Deoxy-Hb, associated with slight twitching of the right hand. In contrast, 50-Hz stimulation produced significant increases in both Oxy-Hb and Deoxy-Hb at the stimulation site, and the area with such cerebral blood oxygenation (CBO) changes propagated beyond the hand area associated with prominent muscle contractions of the right upper extremity, suggesting that 50-Hz stimulation caused epileptic discharge.
  
  
  CONCLUSIONS
  Near-infrared spectroscopy topography may represent a useful tool for imaging the degree and extent of the physiological effects of electrical stimulation on the cortex, and permits safe and accurate cortical mapping.
authors.affiliation: Department of Neurological Surgery, Nihon University School of Medicine, Tokyo 173-8610, Japan.
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Hoshino
authors.forename: Kaoru
authors.initials: K
authors.lastname: Sakatani
authors.forename: Yoichi
authors.initials: Y
authors.lastname: Katayama
authors.forename: Norio
authors.initials: N
authors.lastname: Fujiwara
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Murata
authors.forename: Kazutaka
authors.initials: K
authors.lastname: Kobayashi
authors.forename: Chikashi
authors.initials: C
authors.lastname: Fukaya
authors.forename: Takamitsu
authors.initials: T
authors.lastname: Yamamoto
mesh_terms: D000328:Adult; D001254:Astrocytoma / Q000378:metabolism / Q000503:physiopathology*; D001931:Brain Mapping / Q000379:methods*; D001932:Brain Neoplasms / Q000378:metabolism / Q000503:physiopathology*; D002540:Cerebral Cortex / Q000378:metabolism / Q000503:physiopathology*; D004558:Electric Stimulation; D006801:Humans; D008297:Male; D010101:Oxygen Consumption / Q000502:physiology; D019265:Spectroscopy, Near-Infrared