RESUMO
PURPOSE: To demonstrate the utility of intraoperative neuromonitoring (IONM) as an effective method of passive thermoprotection against cryogenic injury of neural structures during musculoskeletal and lymph node cryoablation. MATERIAL AND METHODS: 29 patients (16 male, mean age and range, M: 68.6 and 45-90, F: 62.6 and 28-88) underwent 33 cryoablations of musculoskeletal and lymph node lesions. Transcranial electrical motor evoked potentials (MEPs) and somatosensory evoked potentials (SSEPs) of target nerves were recorded throughout the ablations. Significant change was defined as waveform amplitude reduction greater than 30% (MEP) and 50% (SSEP). The primary outcomes of this study were immediate post-procedural neurological deficits and frequency of significant MEP and SSEP amplitude reductions. RESULTS: Significant amplitude reductions were detected in 54.5% (18/33) of MEP tracings and 0% (0/33) of SSEP tracings. Following each occurrence of significant amplitude reductions, freeze cycles were promptly terminated. Intra-procedurally, 13 patients had full recovery of amplitudes to baseline, 11 of which had additional freeze cycles completed. In 5/33 (15.2%) of cryoablations, there were immediate post-procedure neurological deficits (Moderate Adverse Events). Unrecovered MEPs conferred a relative risk for neurological sequela of 23.2 (95% confidence interval [CI], 3.22-167.21; P=0.0009) vs. those with recovered MEPs. All five patients had complete neurologic recovery by twelve months. CONCLUSION: IONM is a reliable, safe method of passive thermoprotection of neurological structures during cryoablation. It provides early detection of changes in nerve conduction, which when addressed quickly, may result in complete restoration of MEP signals within the procedure and minimize risk of cryogenic neural injury.
