Brainstem Surface Mapping for Identification of Entry Zone in Cavernous Malformation Resection

Objective: Surgery for deep brainstem cavernous malformations (BCMs) is challenging. The value of brainstem surface mapping in surgery for BCMs remains unclear. The objective of this study was to evaluate the impact of direct surface mapping on surgical strategy and modification of planned entry point intraoperatively.

Methods: A retrospective review of all patients with BCM operated between January 2014 and August 2024 was performed. All lesions with no surface representation necessitating an entry through normal brainstem parenchyma were selected. In addition to all preoperative workup including, MRI diffusion tensor imaging and augmented reality ([Fig. 1]), direct surface mapping of brainstem was performed in all patients upon exposure of the brainstem surface. Reliability of mapping was determined in each case. The presumed entry zone before mapping and the entry zone used to access the BCM were compared. Outcomes, including neurological exam, were compared in the group with reliable surface mapping and change in presumed entry zone, compared to those with no change in entry zone or unreliable mapping.

Results: A total of 43 patients with deep BCM met the inclusion criteria. Reliable brainstem mapping was obtained in 40 patients (93.0%). In 34 patients, the preplanned entry point based on safe entry zone and preoperative planning was modified based on the area of least stimulation ([Fig. 2]). In nine patients, there were no adjustments in the entry zone or there was unreliable intraoperative mapping. There was no significant difference in surgical approach or location of the BCM and modification of entry zone. Four patients (11.8%) in the modified group had new or worsened neurological deficit compared to 6/9 (66.7%) patients with no change in entry zone or unreliable mapping had new or worsened neurological deficit. There were 3 occurrences of change in intraoperative neuromonitoring from baseline which did not return, 2 out of 3 (66.7%) of these were in patients where no modification in entry zone was made and both had postoperative neurologic deficits. Complete resection was achieved in 40 patients (93.0%). A good outcome (defined as mRS ≤2) was observed in 40 patients (93.0%). There was no rehemorrhage or mortality.

Conclusion: Intraoperative modalities such as fiber tracking and direct surface mapping of the brainstem can enhance the safety of BCM surgery. The addition of brainstem mappings adds another layer of security to surgical resection and should be considered in surgical management of BCMs which do not have surface representation.

Publikationsverlauf

Artikel online veröffentlicht:
07. Februar 2025