Utility of Motor and Somatosensory Evoked Potentials for Neural Thermoprotection in Ablations of Musculoskeletal Tumors

Purpose: To characterize the utility of monitoring transcranial electrical motor evoked potentials (TCeMEPs) and somatosensory evoked potentials (SSEPs) for neural thermoprotection during musculoskeletal tumor ablations. Materials and Methods: Retrospective review of 29 patients (16 male; median age, 46 y; range, 7–77 y) who underwent musculoskeletal tumor radiofrequency ablation (n = 8) or cryoablation (n = 22) with intraprocedural TCeMEP and SSEP monitoring was performed. The most common tumor histologies were osteoid osteoma (n = 6), venous malformation (n = 5), sarcoma (n = 5), renal cell carcinoma (n = 4), and non–small-cell lung cancer (n = 3). The most common tumor sites were spine (n = 22) and lower extremities (n = 4). Abnormal TCeMEP change was defined by 100-V increase above baseline threshold activation for a given myotome; abnormal SSEP change was defined by 60% reduction in baseline amplitude and/or 10% increase in latency. Results: Abnormal changes in TCeMEP (n = 9; 30%) and/or SSEP (n = 5; 17%) occurred in 12 procedures (40%) and did not recover in 5 patients. Patients with unchanged TCeMEP/SSEP activities throughout the procedure (n = 18) did not have motor or sensory symptoms after the procedure; 3 (60%) with unrecovered activity changes and 2 (29%) with transient activity changes had new motor (n = 1) or sensory (n = 4) symptoms. Relative risk for neurologic sequelae for patients with unrecovered TCeMEP/SSEP changes vs those with transient or no changes was 7.50 (95% confidence interval, 1.66–33.9; P = .009). Conclusions: Abnormal activity changes of TCeMEP or SSEP during percutaneous ablative procedures correlate with postprocedural neurologic sequelae.