# Microvascular Cortical Dynamics in Minimal Invasive Deep-Seated Brain Tumour Surgery

## TL;DR

This study shows that changes in microvascular flow during a minimally invasive brain tumor surgery technique are linked to worse patient outcomes.

## Contribution

The paper introduces the first assessment of microvascular dynamics during a specific brain tumor surgery technique and links it to neurological outcomes.

## Key findings

- Increased speed and cerebral blood flow index correlate with worse neurological outcomes.
- Findings were consistent across multiple regions of interest and patient-level analyses.
- The study confirms the clinical relevance of microvascular changes during surgery.

## Abstract

The minimally invasive parafascicular approach for the removal of deep-seated brain tumours represents a challenge in neurosurgical oncology. The use of tubular retractors with a transsulcal cannulation is the safest technique to reach those lesions minimizing the risk of brain injury and postoperative neurological deficit. As far as we know, no reports in the literature are present concerning the impact on cortical vascularization, its dynamics and the clinical consequences in terms of the patient’s outcome. Therefore, we assess the impact of tubular retractors in the microvascular dynamics on the surrounding brain using a quantitative indocyanine green (ICG)-based module in the operative microscopes and we correlate these measurements with neurological outcome and postoperative MRI restriction to diffusion areas. Our study demonstrates an increase in speed and cerebral blood flow index related with worse neurological presentation and postoperative neurological outcome in both pre-cannulation and pre–post-cannulation analysis, making it a strong predictor of worse outcome.

Background: The tubular retractor-assisted minimally invasive parafascicular approach (trMIPS) is a transsulcal approach to deep-seated brain tumours. It is a safe surgical approach but its impact on the microvascular dynamics of the retracted cortex and its clinical implications are unknown. Methods: This was a single-centre prospective study including patients with deep-seated brain tumours operated on with a trMIPS (BrainPath Nico System©). All patients underwent pre- and post-cannulation indocyanine green study using a FLOW 800 module in a KINEVO Zeiss© microscope. Speed, delay, time-to-peak (TtP) rise-in-time and cerebral blood flow index (CBFI) metrics were assessed. Results: Thirty-five patients were included, with 144 regions-of-interest (ROIs) selected. The majority of patients were diagnosed with glioblastoma (51.43%), and 37.14% of patients had a preoperative focal neurological deficit (FND) at presentation. A ROI-based analysis concluded that an increase in speed and CBFI was related with a worse neurological outcome when comparing the pre- and post-brain cannulation assessments (speed: deterioration = 43.12 ± 80.60% versus stable = −14.51 ± 57.80% versus improvement = 6.93 ± 31.33%, p < 0.0001; CBFI: deterioration = 50.40 ± 88.17% versus stable = −2.70 ± 67.54% versus improvement = −38.98 ± 26.17%, p = 0.0005). These findings were reproducible in a combined-ROI per patient analysis and confirmed after adjustment for confounding. Conclusion: Microvascular flow dynamics impact trMIPS outcomes as an increase in the speed and CBFI after decannulation was related with worse neurological outcome.