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Intraoperative Neurophysiological Monitoring (IOM)

Intraoperative Neurophysiological Monitoring, or Spinal Cord Monitoring, is a field of electroneurodiagnostics devoted to the recording and study of the electric activity of the brain and nervous system during surgery. Technologists use a variety of techniques and instruments to record electric activity arising from the brain, spinal cord and peripheral nerves. These recordings are reported to the surgeon and supervising electrodiagnostic physician.

Spinal-cord monitoring involves putting sensors on the patient to monitor changes in electric signals. It can spot changes in brain, spinal-cord and peripheral-nerve function before there is any irreversible damage. Monitoring of nerves can guide the surgeon through dissection and alert him or her of a stimulated nerve. It can show nerve stress or damage and pinpoint the location of the irritation. Your physician will provide information to you regarding intraoperative spinal cord monitoring prior to your surgery.

Spinal cord monitoring is often conducted during the following procedures:

  • Electroencephalogram (EEG) - EEG testing records brain activity and allows physicians to diagnose brain disorders. During surgery, surgeons can also use an EEG to make sure the patient is receiving enough oxygen.

  • Electromyography - Electromyography studies assess the electric potentials of both spinal nerve roots and peripheral nerves. Electrodes are placed on a patient's arms and legs to monitor muscle activity during surgery. Testing these nerves allows surgeons to make sure they have not caused damage during surgery.

  • Evoked potential (EP) - Evoked potential studies use external stimuli to record the electric activity in a patient's brain, spine and peripheral nerves. My monitoring the waveforms produced by these studies, surgeons can better avoid causing any nerve damage.

  • Nerve-conduction studies - Nerve-conduction studies involve stimulating nerves with an electric current and measure how long the resulting nerve impulse takes to the reach the muscle.

  • Pedicle-screw testing – These studies allow surgeons deliver a low electric current to the pedicle screw during spine fusion procedures. By monitoring the current, surgeons can verify that no breach or crack in the bone occurred during screw placement.