Intraoperative Transit Time Flowmetry for Unruptured Middle Cerebral Artery Aneurysms.

Abstract

Aim of the study: Clipping of the middle cerebral artery (MCA) aneurysms presents significant anatomical challenges, requiring precise occlusion while preserving the integrity of adjacent vessels. Narrowing or occlusion of MCA branches can lead to strokes and severe neurological deficits. Intraoperative transit time flowmetry (ITTF) provides quantitative real-time measurements of cerebral blood flow, potentially reducing ischemic complications. This study evaluates whether ITTF monitoring during unruptured MCA aneurysm clipping improves postoperative outcomes compared to a control group without ITTF.

Material and methods: A retrospective review of a prospectively maintained institutional database was performed. A retrospective cohort study was conducted involving two groups of patients who underwent clipping for unruptured MCA aneurysms between 2010 and 2019. The monitored group (n = 34) received intraoperative ITTF monitoring, while the control group (n = = 20) did not. Intraoperative flow measurements were performed before and after clip placement, allowing for real-time clip adjustment if flow restriction exceeded 25%. All patients were monitored using motor-evoked potentials and indocyanine green video angiography. Postoperative outcomes were assessed using the modified Rankin Scale (mRS) at 30 and 90 days.

Results: In the ITTF-monitored group, postoperative morbidity was 3% compared to 5% in the non-monitored group. Clip repositioning was required in two ITTF-monitored cases to restore blood flow, despite normal indocyanine green video angiography and motor evoked potential findings. The odds ratio for postoperative neurological deficits was 5.05 when comparing the ITTF-monitored group to a hypothetical non-monitored scenario (13.6% morbidity); however, this difference was not statistically significant.

Conclusions: Despite the lack of statistical significance, ITTF monitoring may still play a valuable role in enhancing surgical safety, as it enabled clip repositioning in two cases where standard modalities (ICG and MEPs) showed no abnormalities. Further research is needed to confirm its clinical benefit and define its role in intraoperative decision-making.