L.N.'s somatosensory evoked potentials (SSEPs) were monitored throughout her spinal fusion surgery to provide continuous information on the functional state of her sensory pathways from the median and posterior tibial nerves through the dorsal column to the primary somatosensory cortex. Before surgery, needle electrodes were inserted into L.N.'s right and left quadriceps muscles to determine nerve conduction through L2 to L4, into the anterior tibialis muscles to measure passage through L5, and into the gastrocnemius muscles to measure S1 to S2. Electrodes were placed in her rectus abdominus to monitor S1 to S2. All electrodes were taped in place, and the wires were plugged into a transformer box with feed-back to a computer. A neuromonitoring technologist placed the electrodes and attended the computer monitor throughout the case. During the procedure, selected muscle groups were stimulated with 15 to 40 milliamps (mA) of current to test the nerves and muscles. Feedback data into the computer confirmed the neuromuscular integrity and status of the spinal fixation of the instrumentation and implants.

After the pedicle screws, hooks, and wires were in place and the spinal rods were cinched down to straighten the spine, L.N. was permitted to emerge temporarily from anesthesia and muscle paralysis medication to a lightly sedated but pain-free state. She was given commands to move her feet, straighten her legs, and wiggle her toes to test all neuromuscular groups that could be affected by misplaced or compressed spinal fixation devices. Her feet were watched, and movement was announced to the team. Dorsiflexion cleared the tibialis anterior muscles; plantar flexion cleared the gastrocnemius muscles. Knee flexion cleared the hamstring muscle group, and knee extension determined function of the quadriceps group. L.N. had a successful "wake-up" test. She was put back into deep anesthesia, and her incision was closed. A postoperative "wake-up" test was repeated after she was moved to her bed. The surgical instruments and tables were kept sterile until after all of the monitored muscle groups were tested and showed voluntary movement. The electrodes were removed, and she was taken to PACU for recovery.

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