Are flash-evoked visual potentials useful for intraoperative monitoring of visual pathway function?
Flash-evoked visual potentials (VEPs) recorded from the scalp were used in a series of 35 patients with tumors along the visual pathway: 3 orbital tumors, 25 perisellar tumors, 4 intraventricular tumors, and 3 occipital lesions. Preoperatively, various combinations of impaired visual fields and visual acuity were observed in over 90% of the patients. A postoperative decrease in visual function was observed in 3 cases. Of the 25 perisellar lesions, 13 were operated through a standard frontotemporal craniotomy and 12 were operated through a transnasal-transsphenoidal approach. VEPs were highly susceptible to volatile anesthetics, and there was a significant incidence of spontaneous latency increases and amplitude decreases in a large number of patients. There was an unacceptably high number of cases with significant VEP alteration occurring without concomitant visual function change. During trepanation or the transnasal approach, a reversible potential loss was observed in 11 patients, a profoundly altered wave form was seen in 8 cases, and a loss of single peaks was observed in 15 patients. During dissection of the tumor, a reversible potential loss or a potential with unidentifiable peaks was found in 25 cases; however, the VEPs recovered during closure or in the recovery room. There was no correlation between intraoperative VEP changes and the postoperative changes in visual function. In only 1 patient with an insignificant postoperative decrease in visual acuity from 0.4 to 0.3 was there a concomitant intraoperative potential loss. The major conclusion of our findings is that light-emitting diode flash-evoked VEPs demonstrate intraoperative changes that appear too early and too prominently to be caused solely by manipulation of the optic pathways.(ABSTRACT TRUNCATED AT 250 WORDS)
Department of Neurosurgery, University of Erlangen-Nürnberg, West Germany.
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Cedzich
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Schramm
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R
Fahlbusch
D000293:Adolescent; D000328:Adult; D000368:Aged; D001932:Brain Neoplasms / Q000601:surgery*; D002551:Cerebral Ventricle Neoplasms / Q000601:surgery; D002648:Child; D005074:Evoked Potentials, Visual; D005260:Female; D006423:Hemianopsia / Q000503:physiopathology; D006801:Humans; D007431:Intraoperative Complications / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D009918:Orbital Neoplasms / Q000601:surgery; D010911:Pituitary Neoplasms / Q000601:surgery; D011183:Postoperative Complications / Q000503:physiopathology; D011930:Reaction Time / Q000502:physiology; D012307:Risk Factors; D014794:Visual Fields; D014795:Visual Pathways / Q000503:physiopathology / Q000601:surgery*