Objective : To characterize the utility of monitoring motor evoked potentials (MEPs) and somatosensory evoked potentials (SSEPs) for neural thermoprotection during ablation of musculoskeletal lesions.
Methods : Patients from 2015 to 2018 who underwent either tumor cryoablation or radiofrequency ablation procedures with intraprocedural transcranial electrical stimulation MEP and SSEP monitoring were retrospectively identified. Data regarding demographics, tumor characteristics, pain, ablation technical details, and MEP/SSEP activity was reviewed. For procedures in which an abnormality in MEPs or SSEPs was identified, the characteristics and duration of the diminished or lost activity, associated sensory and/or motor deficits, and symptom duration and/or recovery were also reviewed.
Results : 30 procedures, including cryoablation (n=20) and radiofrequency ablation (n=10), were identified in 29 patients. Median patient age was 46, ranging from seven to 77. Ten different tumor types were identified, most commonly osteoid osteoma (n=6), venous malformation (n=5), sarcoma (n=5), and renal cell carcinoma (n=4). Tumors involved the spine (n=22), lower extremities (n=4), scapula (n=2), pelvis (n=1), and trapezius (n=1). In 12 (40%) of the procedures, an activity loss in MEPs (n=9) and/or SSEPs (n=5) was charted, and in five cases the activity loss did not recover intraprocedure. Three patients (60%) with unrecovered activity losses and two patients with recovered activity losses (29%) had charted new motor (n=1) or sensory symptoms (n=4) post-procedure (RR 2.10, 95%CI 0.53-8.29). No patients without activity losses (n=17) had new motor or sensory symptoms post-procedure. SSEP activity losses were 75% (95%CI 19-99%) sensitive for new post-procedure sensory symptoms and 92% specific (95%CI 74-99%). MEP activity losses were 100% (95%CI 2.5-100%) sensitive for new post-procedure motor symptoms and 71% (95%CI 51-87%) specific.
Conclusions : Activity losses of MEPs or SSEPs during ablative procedures can be predicative of post-procedural neurological sequelae. Its use should be considered in musculoskeletal ablations in which there is concern for neural thermal injury.