Measurement of optic nerve blood flow during dissection of parasellar tumors

Abstract

The authors describe direct measurement of optic nerve blood flow (ONBF) and examine the application of such monitoring to detecting optic nerve ischemia during parasellar tumor surgery. Prospective evaluation was performed for 26 patients requiring surgery for parasellar tumors. Ophthalmologic examination was performed pre- and postoperatively. ONBF was measured using laser Doppler flowmetry before tumor dissection (initial ONBF) and after tumor removal (final ONBF). The waveform was analyzed using a data acquisition system. Initial ONBF could be measured in 16 patients (22 nerves; 8.9 +/- 0.9 ml/100 g/min). Final ONBF could be determined in all 26 patients (42 nerves; 10.8 +/- 0.7 ml/100 g/min). In the 22 nerves with initial measurements, final ONBF (11.3 +/- 0.6 ml/100 g/min) was significantly increased (p < 0.01). In six patients whose optic canal was unroofed, ONBF did not change immediately; nonetheless, an increase was prominent in the final phase (p < 0.05). In another six patients, a small vessel adjacent to the optic nerve was temporarily occluded. ONBF was demonstrably reduced in three patients and recovered quickly after reperfusion. Intraoperative ONBF measurement may be useful as real-time monitoring for prediction and prevention of intraoperative optic nerve ischemia.