The use of intraoperative neurophysiological monitoring in dorsal resection of hemivertebrae

BACKGROUND: Congenital disorders of vertebrae formation are a common pathology in children. Intraoperative neurophysiological monitoring is a mandatory procedure, although it may not be effective enough due to the immature neural structures and the use of inhalation anesthetics in young children.

AIM: To study aims to investigate the characteristic features of intraoperative neurophysiological monitoring in children with a congenital deformity of the spine during dorsal resection of the hemivertebrae.

MATERIALS AND METHODS: 42 patients aged 1–17 years with a congenital deformity of the spine underwent 46 resections of the abnormal vertebra from an isolated dorsal approach (egg-shell technique). Intraoperative neurophysiological monitoring at the stages of the operation included a muscle relaxant test (TOF), transcranial electrical stimulation of the motor cortex (TCeMEP), control of the approach to the nerve (N. Proxy), correct placement of the pedicle screw (Screw Integrity), and EMG recording of the electromyogram. The accuracy of the screw placement was assessed by the Gerzbien method, and the presence of neurological disorders was tested by the Frenkel scale. The effect of inhalation anesthetic (sevoran) on motor evoked potentials was monitored by regulating its delivery, and the dependence on the age of patients was evaluated.

RESULTS: The average age of patients was 7.7 ± 4.5 years, and the TOF value was 80.5 ± 17%. In 41 patients, the N. Proxy test was unremarkable, while in one patient, the 8–12 mA value did not require a change in the trajectory of the screws. From the beginning of sevoran and intraoperatively, motor evoked potentials from all tested muscles were recorded in 54.8% of patients; in children over 8 years old, this was observed in 92.8%, in children under 8 years old — in 35.7% of cases in their age groups. In other patients, motor evoked potentials were most often not recorded from the muscles of the thigh and lower leg after sevoran administration. In children over 8 years old in 7.2%, under 8 years old — in 83.3% of patients; Interestingly, in 7.2% of patients who are under 8 years of age, motor evoked potentials were not initially recorded from any muscle. Withdrawal of sevorane in 30.9% of patients allowed intraoperative motor evoked potentials to be obtained from all tested muscles in 100% of cases. For adequate management of anesthesia, 5 patients (50%) 1–4 years old and one patient 6 years old (5.6%) did not receive sevoran, and motor evoked potentials were recorded from the abdominal muscles. This allowed to assess the conduction only at the thoracic level and are required increased vigilance of surgeons when carrying out any corrective manipulations.

CONCLUSIONS: Intraoperative neurophysiological monitoring with dorsal hemivertebra resection is an effective method that allows controlling the neurological complications during manipulations on the spine.