Biometric Analysis of Simulation of Sylvian Fissure Dissection and Cerebrovascular Bypass under Subarachnoid Hemorrhage Conditions

Introduction: Sylvian fissure dissection and microvascular anastomosis/repair of intraoperative vascular injury are core skills in skull base, cerebrovascular, and other areas of complex cranial surgery. Additionally, the technique is frequently required under subarachnoid hemorrhage (SAH) conditions, which are more technically demanding, unpredictable, and potentially stress-inducing. We previously described and validated a rodent model for simulation of Sylvian fissure dissection and cerebrovascular bypass (e.g., microvascular anastomosis), which was demonstrated by subject self-reporting and blinded video assessment to be a realistic, challenging, and high-fidelity model system. In the present study, we sought to expand our validation of the model to formal biometric analyses, to confirm that the experimental condition constitutes a meaningful physiologic stressor for the subject.

Methods: Rat femoral artery and vein end-to-end microvascular anastomoses were used for control model and experimental framework. In the experimental protocol, following vessel exposure, we completed an extensive, 1- to 2-mm soft tissue debridement, and hematoma initiation, followed by wound closure and delayed re-exploration at intervals of 7 to 14 days. Three resident subjects dissected one rat each under control and experimental conditions (total n = 6 rats), during which heart rate (HR), hand tremor, and axial EMG were monitored.

Results: All dissections and anastomoses were successfully completed, with an overall patency rate of 100%. HR monitoring demonstrated a significant mean difference, with an increase of 10 to 20 bmp in the experimental condition, as compared with the control condition, for each subject (p = 0.01). Hand tremor demonstrated an inconsistent but statistically significant increase in incidence of 5 to 15 Hz during the experimental condition, as compared with control (2/36 vs. 14/36, p = 0.001). Axial EMG did not show a significant difference between the conditions.

Conclusion: To our knowledge, ours is the unique and novel model of SAH simulation for microsurgical training, particularly in a live animal system. The current study provides objective, biometric data in support of the experimental condition in our simulation system as a significant physiologic stressor that appears to reproduce the impact of SAH conditions, with respect to technical, physiologic, and potentially psychological difficulty-of-dissection. These data have motivated a randomized, controlled study, which is presently underway at our institution; pending those results, the simulation system may have broad utility in skull base training programs.