What is intraoperative monitoring?

Intraoperative Neurophysiologic Monitoring (IONM) uses special equipment to monitor the integrity of the nervous system during complex surgeries that may place neural structures at risk for injury.  It's role is to provide the surgeon with immediate feedback and warning before permanent nerve injury occurs.  This has been shown to increase safety and improve outcomes in surgery.

Intraoperative Neurophysiologic monitoring (IONM)) began with the use of somatosensory evoked potentials (SSEPs). This measures the conduction of sensation above and below the area of surgery. During spinal surgery, electrodes are placed on limbs that could be affected by the surgery. Electrodes are also placed on the surface of the skull over the area of the brain where the impulse from the limb is received. A machine is used to monitor the electrical activity in the brain just like an electroencephalogram (EEG). The electrical activity is recorded as waves. When the limb is stimulated with an electrical current by the surgeon or technician, there should be a response in the brain. This checks the function of the sensory portion of the nerves and spinal cord.

Somatosensory evoked potentials (SSEPs) are the most widely used intraoperative neurophysiological monitoring during surgery. However, SSEP monitoring may not detect injuries to individual nerve roots.

In the 1980'€™s surgeons began using electromyography (EMG) to monitor the motor portion of the nerves during spinal surgery. It is becoming more commonly used. During surgery, while the patient is asleep, needle electrodes are placed in the muscle groups that correspond to the area where the surgeon will be working. Electrical activity from the muscle can be monitored by a machine. The activity is recorded as waves, similar to the SSEP monitor. It is also similar to the waves that are recorded from the heart muscle during an electrocardiogram (ECG). Baseline recordings are taken before the surgery begins. Recordings are then repeated throughout the procedure. A significant change in the wave alerts the surgeon or technician that the nerve in the area could be damaged. The surgeon can then take action to prevent permanent damage.

EMG seems to be more accurate in identifying potential neurological damage than other methods of monitoring that have been used. However, it is not useful when muscle paralyzing agents are used for anesthesia. It is also not useful if a nerve root has been cut completely.

Studies show that the use of both SSEPs and EMG monitoring during spinal surgery is most ideal but not always available.

Other monitoring modalities available include electroencephalography (EEG), individual nerve monitoring, rectal and urinary sphincter...." Eliminate "spinal" mapping and end and close the paragraph with "cortical mapping.

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