Nerve conduction studies (NCS) measure how well and how fast nerves can send electrical impulses. An electromyogram (EMG) measures the electrical activity of muscles both at rest and during contraction.
During an exam, a doctor may find a weakness in a specific muscle of the arm or leg. Back and neck NCS/EMG studies help to identify why this muscle may be weak and pinpoint where a nerve blockage may be occurring. Muscles cannot contract well if they do not have full nerve flow, and this may limit your ability to function normally. The test is based on placing needles into the arm or leg and measuring the length of time required for an electrical signal to pass down the nerve root.
Nerve conduction studies are most commonly performed for conditions that cause symptoms in the arms or legs. Some of the diagnoses include radicular symptoms, herniated disc, stenosis and nerve root compression. Testing can also evaluate for non-spinal causes of limb pain and weakness such as carpal tunnel syndrome and peripheral neuropathy.