Nerve Conduction Study (NCS)
Nerve conduction studies (NCS) provide information about how well and how fast the nerves in your body send electrical impulses. This test can be used to check for various types of problems with the peripheral nervous system, which includes all the nerves in your body apart from those in your brain and within the spinal cord itself. Nerves in the brain and spinal cord make up the central nervous system.
Nerves are like electrical cables that transmit impulses to allow communication between the brain and all the other parts of the body.
These nerves (or cables) send information from the brain to the tissues of the body and also carry information from the body back to the brain. Peripheral nerves connect the outside of the body to the spinal cord and the spinal cord transmits signals to and from the brain. The median nerve is an example of a peripheral nerve that runs through the arm into the wrist (carpal tunnel) and is one part of the connection between the thumb and the spinal cord.
What are nerve conduction studies used for?
If nerves are damaged the electrical signal often moves slower through the nerve fiber. By measuring the speed (velocity) and the amount (amplitude or voltage) of the impulse that travels from one point in the nerve to another, NCS allows us to assess:
- The degree of nerve damage following an injury.
- For damage to nerves caused by conditions such as diabetes.
- For conditions affecting the nervous system.
- 'Trapped' nerves - conditions such as carpal tunnel syndrome.
How do nerve conduction studies work?
Small electrical pulses are delivered to the nerves of the body to mimic the electrical signals made by nerves. Our technician will place electrodes (small devices that detect and supply electricity) against the skin to send impulses from one point along the course of a nerve and record from another point. If the nerve is attached to a muscle, the muscle will contract in response to the electrical signal and this response is measured by the electrodes on the skin.
Similarly, to test sensory nerves, the electrodes are usually attached to the fingers or toes with another electrode either at the ankle or wrist. When the electrical pulse is applied to the fingers or toes, the sensory nerve carries the electrical signal away from the arm or leg. The electrode at the wrist or ankle detects the electrical impulse when it reaches that point.
Our machine receives the signals from these electrodes and measures the voltage of the response and the time taken for the impulse to travel in the nerve from the first electrode to the second. This information computes the speed at which the impulse is travelling along the nerve. This is referred to as the conduction velocity. Nerve conduction tests may take from 15 minutes to 1 hour or more, depending on how many nerves and muscles are studied.