Objective. A quantitative evaluation of the relationship between the level of postoperative motor deficit and the intensity of reaction of pyramidal tract to the correction of spinal deformity. Material and methods. The correction of spinal deformities of different etiology was performed under neurophysiological control for 87 patients (30 men, 57 women), aged 15.6±0.6 years. Reaction intensity of pyramidal tract was evaluated using the scale developed by the authors. Results. The relationship between the intensity of intraoperative reaction of somatic motor system and EMG-signs of postoperative subclinical motor deficit in temperature-and-pain sensitivity disorders was shown. Conclusion. EMG evaluation of the level of intensity of subclinical motor deficit in combination with changes in temperature-and-pain sensitivity after the spinal deformity correction complies the reaction intensity of somatic motor system to surgical aggression. Neurologists should pay more attention to the patients with V type reaction not only during postoperative period, but before the next stage of surgery.