Microvascular Brainstem Ischemia After Vestibular Schwannoma Surgery: A Clinical and Microanatomic Study

To identify a potential microvascular etiology in patients who underwent vestibular schwannoma surgery (VSS) complicated by postoperative microvascular brainstem ischemia.

Charts were retrospectively reviewed of all patients who had an MRI within 14 days of VSS in years 2005-2016. Patient characteristics, preoperative and postoperative imaging features, clinical course and potential predictors of brainstem ischemia were recorded. Cadaveric dissections of 4 cerebellopontine angle (CPA) cisterns with focus on the anterior inferior cerebellar artery (AICA) microvascular were also performed to identify candidate vessels and potential etiology.

Fifty-four of 258 patients had an MRI within 14 days of VSS. Retrosigmoid approach was used in 61.1% of patients, translabyrinthine approach in 25.9%, and middle fossa approach in 13.0%. Four patients (7.4%) had acute microvascular ischemia involving the middle cerebellar peduncle (MCP) adjacent to the cranial nerve (CN) VII-VIII complex demonstrated on postoperative MRI. A statistically significant association was found between the translabyrinthine approach and acute brainstem ischemia (odds ratio, 10.6; 95% confidence interval, 1.004-112.7). Dissection of CPAs revealed 10-20 perforating arteries per specimen originating from the lateral pontine and the flocculopeduncular segments of the AICA. Most microvessels travelled in retrograde fashion along the anteroinferior surface of the CN VII-VIII complex to perforate the cisternal surface of the MCP. No patient had residual or delayed neurologic deficits related to brainstem ischemia at final follow-up.

While effort should be made to preserve perforating vessels, microvascular brainstem ischemia is often asymptomatic and did not lead to permanent neurologic deficits in our series.