Continuous dynamic subcortical mapping of corticospinal tract: A systematic review and meta-analysis

Background: This systematic review and meta-analysis aimed to assess neurological outcomes at different thresholds and identify a cutoff associated with safer resections. Methods: Following Preferred Reporting Items for Systematic Reviews Incorporating Network Meta-analyses guidelines, we included case series reporting the use of continuous dynamic mapping during tumor resection near the corticospinal tract. Outcomes included temporary and permanent post-operative motor deficits. Risk ratios (RRs) with 95% confidence intervals (CIs) were calculated; heterogeneity was assessed using the I 2 statistic. Results: Seven studies involving 301 patients were included in this study. Patients with thresholds of 1–5 mA had a significantly higher risk of temporary motor deficits compared to those with thresholds >5 mA (43% vs. 11%; RR 3.14, 95% CI: 1.96–5.03; P < 0.00001). A post hoc analysis showed all permanent deficits occurred in patients with thresholds ≤3 mA, with a significantly higher risk than those with thresholds >3 mA (6% vs. 0%; RR: 16.40, 95% CI: 2.13–126.26; P = 0.007). No significant difference in permanent deficits was found between the 1–5 mA and >5 mA groups. Conclusion: Extending resection beyond the minimal stimulation threshold of 5mA increases the risk of transient neurological deficits. Going beyond ≤3 mA will additionally increase the risk of permanent motor deficits. These exponential risks should be carefully counterweighted with the potential oncological benefit of higher EOR in each patient. These findings emphasize the need for prospective multicenter studies with standardized stimulation parameters to establish evidence-based guidelines for safe resection near eloquent motor pathways.