To evaluate the application of neurophysiological monitoring in the second modified Foerster-Dandy's operation for the treatment of spasmodic torticollis during perioperative period.

Forty patients with severe spasmodic torticollis treated with the second modified Foerster-Dandy's operation were enrolled retrospectively. Direct electrical stimulation of anterior and posterior roots of spinal nerves was performed during the operation. The proportion of rhizotomy was selected according to the results of electromyography (EMG). Intraoperative somatosensory evoked potential (SEP) was used to monitor the integrity of spinal transduction pathway function. The efficacy was determined according to the EMG results of sternocleidomastoid, trapezius, and splenius capitis before and after surgery.

EMG showed that the turning numbers and amplitudes of sternocleidomastoid, trapezius, and splenius capitis after surgery were decreased compared with before surgery (P<0.01). The decreased degree of sternocleidomastoid was more significantly; the ratios of the turning number and amplitude of sternocleidomastoid were decreased (P<0.01), whereas the ratios of trapezius and splenius capitis did not change obviously. According to the results of intraoperative monitoring, the proportion of bilateral accessory neurectomy was 100%, anterior roots of C₁ was 80%-90%, anterior roots of C₂ was 60%-75%, posterior roots of C₂ was 10%-15%, anterior roots of C₃ was 45%-60%, and posterior roots of C₃ was 50%-70%. The intraoperative SEP amplitude and latency in 2 patients were decreased compared with the warning reference potential. They recovered after adjusting surgical operation mode or stopping operation. No postoperative spinal cord function injury was observed. The patients were followed up for 0.5-2.5 years. The remission rate was 92.5% (37/40) during follow-up period. The spasticity recurred in varying degrees in 3 cases.

The differences of EMG related parameters of the same spastic guilty muscle before and after surgery may objectively assess the efficacy of surgery. The intraoperative electrophysiological monitoring quantifies the proportion of neurectomy and avoids nerve injury. The intraoperative SEP monitoring may effectively reduce the possibility of high cervical cord injury.

Spasmodic torticollis; Monitoring, physiologic; Electromyography; Foerster-Dandy's operation