Abstract
BACKGROUND: Severe spinal deformity corrections requiring VCRs are associated with high incidence of neuromonitoring losses intraoperatively, particularly during correction of rigid curves. TcMEPs are commonly used to monitor spinal cord integrity during these high-risk procedures. This study aimed to analyse the patterns of TcMEP signal losses in these rigid curves in relation to their neurological outcomes. MATERIALS AND METHODS: A retrospective study was conducted on 42 consecutive cases of VCRs performed above the D8-D9 level, with a preoperative Cobb's angle greater than 80°. These surgeries were carried out between October 2019 and June 2024. Abdominal TcMEP monitoring was performed and we studied its association with the lower limb signal losses and postoperative neurology. RESULTS: After excluding four cases, TcMEP data from 38 thoracic VCR procedures were analyzed. The mean preoperative Cobb's angle was 103.4° (80-145°). The average intraoperative blood loss was 1678 ml (700-3500 ml), and the mean operative time was 185 min (120-270min). Lower limb TcMEP signal loss occurred in 18 of 38 cases (47.4 %). In Group 1 (n = 12): Abdominal muscle signals remained stable throughout the procedure. In Group 2 (n = 3): Abdominal signals were transiently lost but recovered during surgery. Group 1 and 2 demonstrated normal postoperative neurology. In Group 3 (n = 3): Abdominal signals were lost and did not recover, along with lower limb signal loss. All three patients developed new postoperative neurological deficits, with full recovery observed within 1-3 months. CONCLUSION: In thoracic VCRs, the presence of abdominal TcMEP signals - despite lower limb signal loss - was not associated with significant postoperative neurological deficits. Loss of both abdominal and lower limb signals, however, correlated with fresh neurological deficits. Abdominal TcMEP monitoring may serve as a useful intraoperative indicator for predicting postoperative neurological outcomes in high-risk spinal deformity surgeries.