Measurement of optic nerve blood flow during dissection of parasellar tumors

Abstract

The authors describe direct measurement of optic nerve blood flow and examine application of such monitoring to detect optic nerve ischemia during parasellar tumor surgery. Twenty-six patients requiring surgery for parasellar tumors were evaluated prospectively. Ophthalmologic examination was performed before and after surgery.The optic nerve blood flow was measured using a laser Doppler flowmeter before tumor dissection (initial ONBF) and after tumor removal (final ONBF). The waveform was analyzed by a data acquisition system. In 16 patients, initial ONBF could be measured (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 6 patients whose optic canal was unroofed, the optic nerve blood flow did not change immediately; nonetheless, an increase was prominent in the final phase (p<0.05). In another 6 patients, a small vessel adjacent to the optic nerve was temporarily occluded. The optic nerve blood flow was reduced demonstrably in 3 and recovered quickly after reperfusion. Intraoperative optic nerve blood flow measurement may be useful as a real-time monitoring for prediction and prevention of intraoperative optic nerve ischemia.

Post-Operative Vision Loss (POVL) following Surgical Procedures

“…ION will result in a reduction in the amplitude and a slight increase in the latency of the monitored waveform [11]. In addition, the blood flow to the optic nerve head may also be measured intraoperatively through the use of invasive or noninvasive flowmeters [12,13].…”