Loss of temperature and pain sensation as risk marker of neurological complications in surgical correction of severe spinal deformity

Background. Treatment of severe spinal deformity remains a challenging surgical problem, with an iatrogenic injury to the spinal cord being a critical complication. There is a high risk of neurological deficit following surgical correction of a severe spinal deformity. Aim. To determine the relationship between the extent of disturbed thermal and pain sensations at Th1-S2 dermatomas and the intensity of the spinal cord pathways’ responses to surgical correction of the severe spinal deformity. Material and methods. We reviewed 58 patients with severe spinal deformities of different etiologies (mean age, 15.7±0.8 years). All patients underwent surgical deformity correction followed by thoracic/thoracolumbar spine fixation by using a variety of internal transpedicular fixations. Intraoperative neurophysiological monitoring (IONM) with transcranial motor-evoked potentials (MEPs) was used during operative interventions. Preoperative and postoperative thermal and pain sensations were assessed in Th1-S2 dermatomas to the right and left by using an electrical aesthesiometer. Results. The extent of disturbed preoperative and postoperative thermal and pain sensations in Th1-S2 dermatomas before and after correction of spinal deformities correlated with the response type scale (I–V) of the spinal cord pathways to the surgical correction we offered. Correlation between the response type and characteristics of thermal and pain sensations was mostly revealed by the test results for the thermal pain threshold (thermal analgesia). The incidence of postoperative thermal analgesia increased monotonically from patients with response type I (persistent MEP form and amplitude-time parameters close to the baseline) to patients with response type V (higher risk of neurological complications). The overall rate of thermal analgesia increased after surgical correction of the spinal deformity relative to the baseline and was higher (≤8%) in patients with response type V. Conclusions. Surgeons and neurophysiologists who perform IONM should give careful attention to patients with severe spinal deformity who exhibit marked postoperative thermal analgesia.