A 17-year-old white adolescent boy with kyphosis and normal neurological function underwent an anterior release from T8 to T12 followed by posterior spinal fusion from T3 to L1. The intraoperative left posterior tibial somatosensory evoked potential became significantly attenuated during the procedure (Figure 1).
Because of these neurophysiological monitoring changes, the patient was awakened from anesthesia and noted to have left leg weakness. The surgeon removed the rods and left the pedicle screws in place, but the asymmetry of the posterior tibial somatosensory evoked potentials and the left leg weakness remained. The patient underwent computed tomography of the thoracic and lumbar spine, which showed the pedicle screw entering the spinal canal from the left at the T4 level (Figure 2). He was taken back to the operating room, where the screw at T4 was removed and replaced with pedicle hooks. The kyphosis was successfully corrected and fusion completed, and the somatosensory evoked potentials remained stable after screw removal. His neurological status returned to normal.
Haffey S, Quinlivan L, O’Donovan CA. Intraoperative Monitoring. Arch Neurol. 2005;62(10):1636-1637. doi:10.1001/archneur.62.10.1636