Why It Is Done
An EMG is done to:
Find problems that damage muscle tissue, nerves, or the spots where nerves and muscles join. These problems may include a herniated disc, amyotrophic lateral sclerosis (ALS), or myasthenia gravis (MG).
Find the cause of weakness, paralysis, or muscle twitching. Problems in a muscle or the nerves going to a muscle can cause these symptoms. So can problems in the spinal cord or the area of the brain that controls a muscle. The EMG does not show brain or spinal cord diseases.
A nerve conduction study is done to:
Find damage to the peripheral nervous system. This includes all the nerves that lead away from the brain and spinal cord. It also includes the smaller nerves that branch out from those nerves. This test is often used to help find nerve problems such as carpal tunnel syndrome or Guillain-Barré syndrome.
An electromyogram (EMG) measures the electrical activity of muscles when they're at rest and when they're being used. Nerve conduction studies measure how well and how fast the nerves can send electrical signals.
Nerves control the muscles in the body with electrical signals called impulses. These impulses make the muscles react in certain ways. Nerve and muscle problems cause the muscles to react in ways that aren't normal.
If you have leg pain or numbness, you may have these tests to find out which nerves are being affected and how much they are affected. These tests check how well your spinal nerves are working. They also check the nerves in your arms and legs.