DOI: 10.1097/bn9.0000000000000135 ISSN: 3066-8905

Somatosensory Evoked Potentials and Motor Functional Recovery: A Clinical Correlation Following Pedicle Subtraction Osteotomy

Lane McCoy, Dillon Stone, Leah Rakers, Mark Lambrechts
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Introduction:

Intraoperative somatosensory evoked potentials (SSEPs) are routinely monitored during spine surgery to detect neural compromise in pedicle subtraction osteotomy (PSO), yet their relationship to postoperative functional outcomes remains incompletely understood. Establishing a link between intraoperative SSEP changes and both neurological recovery and patient-reported outcomes could bridge the gap between surgical monitoring and meaningful clinical endpoints. We aimed to evaluate whether intraoperative changes in SSEPs predict postoperative lower extremity motor strength, sensation, and patient-reported function and pain.

Materials and Methods:

Adult spinal deformity patients undergoing a single-stage procedure involving fusion of >6 levels and one lumbar PSO with intraoperative neuromonitoring were included. Neuromonitoring records were reviewed to identify baseline and post-PSO tibial somatosensory evoked potentials and amplitudes, from which delta values were calculated. Changes in somatosensory evoked potentials and amplitudes were correlated with the most recent postoperative assessments of lower extremity motor strength (graded 1–5) and sensation (intact vs . deficient). The Youden index was used to calculate optimal cutoffs in significant variables. Associations with patient-reported functional and pain outcomes, as well as 90-day complications, were also evaluated. Spearman and Pearson correlation analyses were performed, and logistic regression models were used to estimate odds ratios (OR). Significance was defined as P <0.05.

Results:

Ninety-six patients who met the inclusion criteria were included. Changes in SSEPs were not significantly correlated with patient-reported functional outcomes ( r =0.182, P =0.13) or pain scores ( r =0.162, P =0.18). No association was observed between delta SSEP and 90-day complication rates (OR=0.97, P =0.15). Delta SSEP demonstrated a modest but statistically significant association with poorer postoperative lower extremity motor strength (ρ=−0.24, P =0.033), which remained significant in logistic regression analysis (OR=0.91 [0.85–0.98]; P =0.025). Receiver-operator characteristic analysis identified a 0.45 SSEP decrease as the optimal Youden cutoff for motor strength deficit (AUC=0.56, sensitivity=0.46, specificity=0.68). Delta SSEP and postoperative lower extremity sensation trended towards association without statistical significance (ρ=0.20, P =0.082). Changes in amplitude were not significantly associated with patient-reported function ( r =−0.07, P =0.55), pain ( r =−0.05, P =0.70), complication rates (OR=0.98, P =0.85), postoperative lower extremity motor strength (ρ=0.106, P =0.35), or sensation (ρ=0.13, P =0.26).

Conclusion:

Intraoperative changes in SSEPs are modestly associated with postoperative lower extremity motor strength but not with patient-reported functional or pain outcomes, suggesting that neuromonitoring findings primarily reflect objective neurological recovery rather than perceived clinical improvement.

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