← Back to Previous Page

 

S116: THERMAL DYNAMICS OF ENDOSCOPIC ENDONASAL OPTIC CANAL DECOMPRESSION: CADAVERIC STUDY WITH INTRANEURAL MICROPROBE MONITORING
Guilherme Gago, MD¹; Yousef Odeibat, MD¹; Martin Côté, MD¹; Joel Lavinsky, MD, PhD²; Pierre-Olivier Champagne, MD, PhD¹; ¹Université Laval; ²Universidade Federal do Rio Grande do Sul

Introduction: Thermal injury is a common concern when drilling near cranial nerves. During optic canal decompression, heat accumulation may potentially endanger the optic nerve, although the magnitude of this risk remains poorly defined. Surgeons frequently apply irrigation during drilling as an intuitive measure, but its specific influence on intraneural temperatures has not been systematically evaluated. We designed a cadaveric study to directly monitor intraneural thermal dynamics during endoscopic endonasal optic canal drilling and to assess the protective role of room-temperature saline irrigation.

Methods: Six cadaveric heads underwent standardized endoscopic endonasal optic canal drilling with a 3 mm diamond burr at 75,000 rpm. Ultra-fine microthermometer probes were inserted intraneurally via a transcranial route, enabling direct measurement at preforaminal, foraminal, and postforaminal segments. Temperature was continuously monitored throughout drilling. Continuous drilling was performed without irrigation (n=3) or with irrigation using room-temperature saline at a flow rate of 20 mL/min (n=3). Derived metrics included mean, maximum, cumulative temperature, heating slope, and time to reach the 43 °C threshold. To approximate physiological conditions, results were adjusted with a conservative ×5 correction factor based on conductivity ratios (air vs CSF) and bioheat perfusion models.

Results: Without irrigation, corrected mean intraneural temperatures rose to 35–40 °C, with peaks up to 86 °C. The foraminal and postforaminal segments heated most rapidly, consistently crossing the 43 °C threshold within 6–48 s. With irrigation, mean corrected values remained near 25 °C, maximum temperatures did not exceed 44 °C, and heating slopes were reduced by ~60% (p<0.001). No segment reached the injury threshold under irrigation. Mixed-effects ANOVA confirmed significant effects of irrigation and segment (p<0.01).

Conclusion: Intraneural microthermometer monitoring in a cadaveric model shows that continuous high-speed drilling without irrigation can rapidly elevate optic nerve temperature to potentially concerning levels, while irrigation with room-temperature saline markedly limits this rise. Although cadaveric conditions differ from living physiology, these findings provide experimental insight into the thermal dynamics of optic nerve decompression and highlight irrigation as an important protective measure. This work establishes a foundation for future translational and in vivo studies on thermal safety in skull base surgery.

 

← Back to Previous Page