Diagnosing Nerve Pain with EMG and NCV Testing
Electromyography (EMG) and nerve conduction velocity (NCV) tests help to determine if the source of pain is an injured muscle or nerve. The two separate tests, which are generally conducted during the same appointment, are used to measure the electrical activity of muscles and nerves. By pinpointing the source of the pain, doctors can then devise an appropriate plan of treatment.
An EMG measures muscle response to nerve stimulation in order to differentiate between a muscle or nerve disorder or find diseases that damage muscle tissue or nerves. It can also detect conditions such as pinched nerves or inflammation of muscles. NCV tests find damage to the peripheral nervous system, which includes all the nerves leading away from the brain and spinal cord and the smaller nerves branching out from them. The test measures the speed and strength of electrical activity in a nerve and can be used to diagnose a number of disorders, including Guillain-Barre and carpal tunnel syndrome.
The examinations may be conducted in a hospital, clinic, or doctor’s office, usually in a room that prevents any outside electrical interference. Before undergoing EMG and NCV testing, patients should alert their doctors to any medications they are taking, as certain medications can affect the nervous system. They should also inform their doctors if they have a pacemaker. Patients who smoke should avoid doing so for three hours before the test, and they should also avoid any foods or drinks that contain caffeine, such as coffee, soda, or chocolate. They should also wash off any body lotion and remove metal jewelry. Some patients may be required to wear a gown.
During the examination, patients will be asked to lie on a table or sit in a reclining chair to help the muscles relax. If both tests are being conducted, the NCV test will be conducted first. The NCV testing consists of placing flat metal disc electrodes on the skin, one to stimulate the nerve and one to record the stimulation. Several quick electrical pulses are given, which may cause a mild, tingling feeling. The test takes about thirty minutes.
For the EMG testing, a needle electrode attached to a recording machine is inserted into a muscle. The doctor may ask the patient to contract and relax the muscle in order to record the electrical activity, or the electrode may be moved to different locations. The entire procedure takes approximately thirty to sixty minutes. However, the results are immediately available for evaluation.
Both tests are extremely safe, although they can be somewhat painful or uncomfortable. Some patients experience bruising or swelling at the injection sites, but there is little risk of infection from an EMG. NCV testing requires no injection, and the voltage of electrical pulses is too low to cause an injury. Patients may feel some tingling or soreness after the procedure, but this should subside after about two hours.
It can be difficult to differentiate between muscle and nerve pain. At Masri Sports Medicine, EMG and NCV tests allow us to detect the true source of pain in order to determine the necessary treatment.
Electromyogram (EMG) and Nerve Conduction Studies: Healthwise Medical Information on eMedicineHealth. eMedicineHealth. https://www.emedicinehealth.com/electromyogram_emg_and_nerve_conduction_studies-health/article_em.htm. Published November 30, 2011. Accessed January 21, 2018.
Nerve Conduction Velocity: Purpose, Procedure & Results. Healthline. https://www.healthline.com/health/nerve-conduction-velocity. Accessed January 21, 2018.
Nerve Conduction Studies. Nerve Conduction Studies | Johns Hopkins Medicine Health Library. https://www.hopkinsmedicine.org/healthlibrary/test_procedures/neurological/nerve_conduction_velocity_92,P07657. Accessed January 21, 2018.