Intraoperative Flow Measurement by Microflow Probe During Spinal Dural Arteriovenous Fistula Surgery.

Objective: Flow measurement by microvascular ultrasonic flow probe is an established procedure in intracranial vascular surgery. This study tested the application of this procedure in spinal dural arteriovenous fistula (SDAVF) treatment. Methods: Data from 12 SDAVF patients who consecutively underwent microsurgical resection with the assistance of both microflow probe and indocyanine green videoangiography (ICG-VA) were retrospectively analyzed. Flowmetry was performed on a dilated perimedullary venous plexus at different distances from the fistula point (FP). In addition, measurements were made at different phases of surgery to address specific issues: at the beginning, to identify the fistula; after temporary clipping, to evaluate proper disconnection; and after section, to exclude residual filling. Results: Flowmetry was reliable in assessing both the value and direction of flow in all cases, thereby aiding fistula localization and confirming its disconnection. Indeed, fistula localization was helped by detection of increasing flow values approaching the FP (mean flow: 11 mL/min <10 mm vs. 3 mL/min >20 mm), while fistula disconnection was confirmed by a flow value lower than 1 mL/min (0-1 mL/min). Data from microflow probe measurements were concordant with ICG-VA data in all cases. In 3 cases, ICG-VA findings on fistula disconnection uncertain due to residual ICG dye were clarified by flowmetry. Conclusions: With the limits of our small series, multistage intraoperative quantitative flow measurement is a feasible, safe, and reliable adjunct in the surgical treatment of SDAVFs. The procedure provides data helpful in guiding the surgical strategy or clarifying ICG-VA data when necessary.