6. Neurosurgery

Background:Meningiomas are the most common intracranial tumors, and while gross total resection (GTR) of meningiomas including their dural attachments is the primary treatment of choice, recurrence rates are highly variable and remain a persistent clinical challenge.The grading of extent of resection (EOR) in meningioma surgery currently relies on the surgeon's macroscopic assessment utilizing tools like white light microscopy, MRI-based neuronavigation, ultrasound or fluorescence-guided surgery, all of which fail to reliably detect microscopic tumor cell remnants beyond visible tumor margins.Given that recurrences presumably arise from such residual microscopic tumor infiltration within the primary arachnoid resection bed and the dural infiltration zone (dural tail), there is need for more precise methods of microscopic resection control.This study aims to evaluate the feasibility of emerging Stimulated Raman Histology (SRH) for rapid intraoperative visualization of residual tumor and characterization of dural infiltration patterns. Material and methods:In this monocentric prospective observational study, patients with primary or recurring convexityassociated meningiomas with a neurooncological indication for complete resection were included.For SRH image generation, up to 4 tissue samples (<3mm 3 ) were obtained from the dural resection margins, which had been assessed as tumor-free by the surgeon, as well as samples from the tumor core serving as tumor reference.These tissue specimens were then imaged with a portable stimulated raman scattering microscope.Additionally, preoperative MRI images were integrated into the neuronavigation system to enable spatial localization of the resection margin samples.Subsequent histopathological processing with conventional H&E staining of the samples served as the ground truth for later assessment of the diagnostic accuracy of SRH imaging and AI-based analysis algorithms. Results:Currently, 36 patients have been enrolled, including 18 conventionally diagnosed with CNS WHO grade 1 meningiomas, 17 with CNS WHO grade 2 and 1 with CNS WHO grade 3. Of these, 29 were female and 7 male.9 of the 36 patients (25%) intended for complete resection showed microscopic tumor infiltration in Open Access.