clinical article J neurosurg 126:266–273, 2017 C ortiCal spreading depressions (CSDs) are waves of near-complete cellular depolarization that spread slowly across the cortical surface at a rate of 2–5 mm/min and result in transient loss of cell signaling capa- bilities. This results in the observed “depression” of elec- trocorticographic (ECoG) activity. 13 While CSD has been thought to represent the physiological underpinnings of brain dysfunction during migraine aura for many years, 15 the signifcance of these events for brain injury and stroke has become apparent only relatively recently. Cooperative abbreviations AVM = arteriovenous malformation; CSD = cortical spreading depression; ECoG = electrocorticographic; ICU = intensive care unit; OR = operating room. sUbMitteD August 14, 2015. accePteD November 25, 2015. inclUDe when citing Published online March 11, 2016; DOI: 10.3171/2015.11.JNS151871. Cortical spreading depression occurs during elective neurosurgical procedures andrew P. carlson, MD, Mscr, 1 c. william shuttleworth, PhD, 2 brittany Mead, bs, 1 brittany burlbaw, bs, 1 Mark Krasberg, PhD, 1 and howard Yonas, MD 1 Departments of 1 Neurological Surgery and 2 Neurosciences, University of New Mexico School of Medicine, Albuquerque, New Mexico obJective Cortical spreading depression (CSD) has been observed with relatively high frequency in the period fol- lowing human brain injury, including traumatic brain injury and ischemic/hemorrhagic stroke. These events are character- ized by loss of ionic gradients through massive cellular depolarization, neuronal dysfunction (depression of electrocorti- cographic [ECoG] activity) and slow spread (2–5 mm/min) across the cortical surface. Previous data obtained in animals have suggested that even in the absence of underlying injury, neurosurgical manipulation can induce CSD and could potentially be a modifable factor in neurosurgical injury. The authors report their initial experience with direct intraopera- tive ECoG monitoring for CSD. MethoDs The authors prospectively enrolled patients undergoing elective craniotomy for supratentorial lesions in cases in which the surgical procedure was expected to last > 2 hours. These patients were monitored for CSD from the time of dural opening through the time of dural closure, using a standard 1 × 6 platinum electrode coupled with an AC or full-spectrum DC amplifer. The data were processed using standard techniques to evaluate for slow potential changes coupled with suppression of high-frequency ECoG propagating across the electrodes. Data were compared with CSD validated in previous intensive care unit (ICU) studies, to evaluate recording conditions most likely to permit CSD detec- tion, and identify likely events during the course of neurosurgical procedures using standard criteria. resUlts Eleven patients underwent ECoG monitoring during elective neurosurgical procedures. During the periods of monitoring, 2 defnite CSDs were observed to occur in 1 patient and 8 suspicious events were detected in 4 patients. In other patients, either no events were observed or artifact limited interpretation of the data. The DC-coupled amplifer system represented an improvement in stability of data compared with AC-coupled systems. Compared with more widely used postoperative ICU monitoring, there were additional challenges with artifact from saturation during bipolar cautery as well as additional noise peaks detected. conclUsions CSD can occur during elective neurosurgical procedures even in brain regions distant from the im- mediate operative site. ECoG monitoring with a DC-coupled full-spectrum amplifer seemed to provide the most stable signal despite signifcant challenges to the operating room environment. CSD may be responsible for some cases of secondary surgical injury. Though further studies on outcome related to the occurrence of these events is needed, ef- forts to decrease the occurrence of CSD by modifcation of anesthetic regimen may represent a novel target for study to increase the safety of neurosurgical procedures. http://thejns.org/doi/abs/10.3171/2015.11.JNS151871 KeY worDs neurosurgical procedures; intraoperative monitoring; cortical spreading depolarization; cortical spreading depression; diagnostic and operative techniques ©AANS, 2017 J neurosurg Volume 126 • January 2017 266 Unauthenticated | Downloaded 06/08/20 10:42 AM UTC