Somatosensory evoked potentials evaluate the nerve pathway from the arms and legs through the spinal cord to the brain.
Somatosensory evoked potentials are used to:
- Identify spinal cord injuries or diseases
- Identify neuromuscular disease and demyelineating diseases
- Monitor patients during surgery on the spine at the neck and chest levels
Before having a somatosensory evoked potential, avoid drinking coffee or tea for four hours.
When the test is done, electrodes (small metal discs that receive electrical currents) will be taped or pasted to your scalp and along the nerve pathway on your neck and shoulders. A small electrical current is sent through a probe to the skin near a nerve on your wrist or ankle. This may be done several times. This makes a twitching or pulsating feeling in your wrist and ankle. Your thumb or big toe may twitch during the test. While the sensation may be unusual or slightly uncomfortable, most people don't consider this test painful. Each arm and leg is tested separately.
A somatosensory evoked potential takes two to three hours.
If the spinal cord is pinched, the electrical signals sent during the somatosensory evoked potential will travel slower than usual.