A somatosensory evoked potential test checks the ability of the spinal nerves and spinal cord to send sensory signals from the body to the brain. The entire nerve pathway is evaluated for transmission of sensations such as pain, touch, and temperature, starting from the arms and legs, going through the spinal nerves, into the spinal cord, and finally terminating in the brain. The test checks for the speed and strength of transmission of sensory signals.
When SSEP May Be Useful for Back or Neck Pain
SSEPs are useful in determining the health of the spinal nerves or spinal cord and evaluating the extent of nervous tissue injury. In diagnosing neck and back pain, SSEP may help:
- Identify conditions affecting the spinal nerves or the spinal cord, such as demyelination (damage to the outer covering of the nerves)
- Detect compression of the spinal cord or spinal nerves
- Monitor spinal nerves and the spinal cord during a surgical procedure
If a nerve or spinal cord problem is present, the electrical signals sent during the SSEP test will travel at a slower rate than usual.
An SSEP test does not ascertain why the nerve or spinal cord isn’t functioning appropriately. The underlying cause of the spinal problem is typically identified through other tests, such as imaging studies. The results of those tests can be correlated with SSEP findings and the patient’s medical history to arrive at a comprehensive diagnosis.
An SSEP test is done on an outpatient basis in a clinic or a hospital and may take 2 to 3 hours. A neurologist or physiatrist trained in performing the procedure conducts the test.
- Patients usually change into a hospital gown after removing personal clothing, jewelry, and metal objects that may interfere with the test.
- Caffeinated drinks are avoided a few hours before the test to avoid caffeine-induced variations in the test results.
- During the test, the patient lies down, and small metallic electrodes are taped to the patient’s body on the scalp, arm, and shoulder. A probe is placed near the wrist or ankle (depending on the spinal nerves being assessed), through which small, mild bursts of electrical current are passed.
- Each side of the body is tested separately in an SSEP procedure.
Slight discomfort and mild twitching in the fingers and/or toes may be experienced when the electrical current is passed, but the test is generally not considered painful.
SSEPS are used for a wide range of applications, including but not limited to confirming sensory abnormality, identifying nerve problems that are not visible externally, and monitoring nerve responses during surgical procedures.
Read more about Getting an Accurate Back Pain Diagnosis