Intraoperative Evaluation of Sigmoid Sinus Velocity in Translabyrinthine Craniotomies for Vestibular Schwannomas using Doppler Ultrasound

Introduction: Sigmoid sinus (SS) occlusion or compression is a known complication of the translabyrinthine approach. Velocity changes in the SS measured by intra-operative Doppler ultrasound, may help in identifying patients at risk for sinus occlusion.

Methods: SS velocity was measured using Doppler ultrasound prior to opening dura and again prior to placement of the abdominal fat graft. Data collected included patient age, side of surgery, sigmoid sinus dominance, tumor volume, intra-operative Doppler ultrasound measurements, postoperative venous sinus imaging, use of anticoagulation, morbidities and mortalities. Statistical analysis was performed using Wilcoxon signed rank test (IBM SPSS Statistics 24).

Results: A total of eight patients were included for analysis. Age ranged from 22 to 69 years old. Four had left-sided and four had right-sided craniotomies. Sigmoid sinuses were either right-side dominant or co-dominant. The mean velocity + SD prior to dura opening and abdominal fat packing was 23.2 + 11.3 and 25.5 + 13.9 cm/s, respectively, p = 0.575. Postoperative MRV imaging showed four sigmoid sinus occlusions; seven patients showed sigmoid sinus compression, and one internal jugular vein occlusion. One patient only had postoperative CTV. On the four patients with MRV occlusions, CTVs were performed with three showing occlusion and all four showing compression. There were no occluded internal jugular veins on CTV. The one patient with internal jugular vein occlusion on MRV received warfarin anticoagulation. There was one CSF leak requiring ear closure and one small cerebellar infarct.

Conclusions: SS velocity changes before and after tumor resection were not predictive of sinus occlusion. We hypothesize that sinus occlusion may be caused by related factors other than thrombosis, such as external compression of the sinus secondary to abdominal fat grafting.