HOW IONM WORKS
A biomedical computer is used to record impulses generated by electrical stimulation of peripheral nerves and the dermatomes of nerve roots. Using the International EEG 10-20 electrode placement system, needle electrodes are precisely placed into the scalp, at specific locations associated with the spinal column and along the course of related peripheral nerves.

Needle electrodes are inserted into associated muscle groups to monitor spontaneous and electrically evoked myogenic activity. The neurotechnologist (NT) will monitor all structures that are placed at risk as a result of the surgical procedure, patient positioning or physiological variations.

Data generated by intraoperative neurophysiological monitoring (IONM) provides a measurement of latency (time it takes for a nerve impulse to travel from a specific point of stimulation to a specific recording site), amplitude (strength of that impulse), and wave form definition.

These recordings are called somatosensory and dermatome evoked potentials.

Additional intraoperative modalities may include:

• Motor evoked potentials (monitoring of the motor tracts)
• Electromyography (motor response testing)
• Nerve conduction studies (a segmental motor component)
• Electroencephalography (brain wave recording)
• Motor strip mapping of the brain (determines location of sensory and motor cortex)

Knowledge of changes reflected in these recordings or the existence of a response in the case of EMG activity may help the surgeon protect the spinal cord and related neural structures, thereby reducing the possibility of a neurological deficit.

« back to top