What is Somatosensory evoked potential (SSEP)?
An evoked potential brought on by a physical stimulus—typically a brief electric pulse—is known as a somatosensory evoked potential, or SSEP. Electrodes placed over specific body parts capture the SSEP responses, subsequently shown as a readout on an electroencephalogram (EEG). The most typical SSEPs involve stimulating the posterior tibial nerve at the ankle or the median nerve at the wrist. Thus, even if the stimuli are non-physiologic, this study examines the route taken by the sensory nerves to reach the brain's sensory regions.
When is the SSEP used?
If you have been experiencing numbness or weakness in your arms or legs, which could be related to issues affecting the somatosensory nerve system, your doctor can advise you to have an SSEP test. These feelings are frequently mild and difficult to detect during a standard clinical evaluation.
What does the SSEP detect?
A neurologist can ascertain the duration required for nerve fibres to transmit a stimulus from the wrist or ankle, the point of stimulation, to a detection site on the skull, neck, or back based on the results of the SSEP. The SSEP pattern analysis allows the neurologist to assess the function of these sensory nerves. For instance, a condition known as demyelination caused by multiple sclerosis (MS) can harm the myelin sheath that protects the nerve fibres of the brain and spinal cords. Changes in the SSEP ensue from the injury, which causes signals to travel along neural pathways more slowly or perhaps get blocked.
How to prepare for SSEP tests
If you have a pacemaker, you should inform the person conducting the test before beginning.
- Consuming a meal before the procedure is fine
- Please bring your medication list with you. Sedatives and medications that can make you drowsy should be avoided.
- Arrive at the test on time and try to relax.
- No additional preparation should be required.
What happens during an SSEP test?
The SSEP procedure is non-invasive and risk-free. You may be required to remove your shoes and outer upper garments for electrodes to be placed.
- Detection electrodes will be adhered to specific areas of the skull, neck, and back.
- Tiny electrical impulses are produced by a generator and used to stimulate nerves in the wrist or the ankle. It is usual for the notions, which are typically painless, to cause your thumb or toe to twitch slightly.
- For the test to be accurate, it is crucial that you pay close attention to the test administrator, obey their instructions, and try to relax as much as possible.
- Using a specialized apparatus, responses to electrical stimulation are recorded through electrodes.
- After the procedure, the electrodes will be removed, and you can put on your clothing and footwear again.
- Unless otherwise instructed, you should be able to return home immediately after the procedure.
- After the test results have been analysed, your doctor may discuss them with you; if not, the referring doctor will.
Side effects and risks
The SSEP testing procedure is typically non-painful, as the electrical impulses used as a stimulus are minute. You may experience minimal skin irritation from the electrodes, but these side effects are uncommon. If you are sufficiently healthy, you should be able to drive yourself home after the procedure.
Factors that impact SSEPs
SSEP readings can be affected by your age, gender, height, limb length, and body temperature. Some drugs may affect the SSEP.
What the results of the SSEP may show
SSEPs can be helpful in diagnosing:
- Trauma: Any physical injuries that impact the nerves and nerve pathways of the somatosensory system constitute trauma.
- Tumours: They can affect the nerves involved in transmitting somatosensory signals.
- Multiple sclerosis (MS): Nerve fibre damage is a prevalent symptom of MS. SSEP analysis can aid in confirming and locating disease-affected regions.
- Myoclonus refers to the quivering of a muscle or group of muscles. Myoclonus can develop in response to a physical injury or stroke but is often a symptom associated with another neurological condition.
- Dystonia: It is a condition that is characterized by sustained involuntary muscle contractions.
- Vitamin B12 deficiency: It can cause SSEP variations
- Various neurological conditions can influence the SSEP.
- Hereditary neuropathies such as Charcot-Marie tooth disease and Friedreich ataxia
