Electromyography (EMG) is a diagnostic procedure to assess the health of muscles and the nerve cells that control them. These cells are called motor neurons. They transmit electrical signals that cause muscles to contract and relax. An EMG translates these signals into graphs or numbers, helping doctors to make a diagnosis. EMG results can reveal nerve dysfunction, muscle dysfunction, or problems with nerve-to-muscle signal transmission.
Motor neurons transmit electrical signals that cause muscles to contract. An EMG uses tiny devices called electrodes to translate these signals into graphs, sounds or numerical values that are then interpreted by a specialist.
Why EMG is Done
Your doctor may order electromyography if you have signs or symptoms that may indicate a nerve or muscle disorder. Such symptoms may include:
- Muscle weakness
- Muscle pain or cramping
- Certain types of limb pain
EMG results are often necessary to help diagnose or rule out a number of conditions such as:
- Muscle disorders, such as muscular dystrophy or polymyositis
- Diseases affecting the connection between the nerve and the muscle, such as myasthenia gravis
- Disorders of nerves outside the spinal cord (peripheral nerves), such as carpal tunnel syndrome or peripheral neuropathies
- Disorders that affect the motor neurons in the brain or spinal cord, such as amyotrophic lateral sclerosis or polio
- Disorders that affect the nerve root, such as a herniated disk in the spine
What to Expect
Your doctor or a technician places surface electrodes at various locations on your skin depending on where you’re experiencing symptoms. Or the doctor may insert needle electrodes at different sites depending on your symptoms (needle EMG).
They will give you instructions on resting and contracting a muscle at appropriate times. Depending on what muscles and nerves the specialist is examining, he or she may ask you to change positions during the exam.
Nerve Conduction Study
A nerve conduction study uses electrode stickers applied to the skin (surface electrodes) to measure the speed and strength of signals traveling between two or more points.
During a needle EMG, a needle electrode inserted directly into a muscle records the electrical activity in that muscle. The doctor will assess whether there is any spontaneous electrical activity when the muscle is at rest (activity that isn’t present in healthy muscle tissue) and the degree of activity when you slightly contract the muscle.
Electromyography at South Shore Orthopedics
South Shore Orthopedics is fortunate to offer electromyography with the addition of Dr. Sandra Maguire to our practice. If you have symptoms of a muscular condition and believe you’d benefit from diagnostic testing with EMG, call our office at (781) 337-5555 to make an appointment