What Is an EMG?
Summit Orthopedics electrodiagnostic medicine specialist David Rippe, M.D., explains the basics of EMGs.
What is an EMG?
An EMG, which is short for electromyography, is a muscle and nerve test that evaluates the peripheral nervous system. The peripheral nervous system includes all of the body’s nerves that are outside of the brain and spinal cord.
For example, an EMG could look at the nerves leading out of the neck to the shoulder, then down the arm, into the hand, and all the way to the fingertips. Or, if the problem is in the lower body, it could evaluate nerves from the nerve roots in the back all the way down to the toes. Its goal is to evaluate how well the nerves and muscles are functioning and to pinpoint problems with the nerves or muscles that might be causing a person’s symptoms.
An EMG can diagnose many problems caused by pinched, inflamed, or damaged nerves. When it comes to muscles, the process can diagnose muscle diseases like myopathies or muscular dystrophy. An EMG is not used to diagnose the cause of sore muscles or arthritis.
Why might I need an EMG?
“Patients may be referred for an EMG because they are having any of a range of symptoms, including numbness, tingling, pain, weakness, and sometimes also muscle twitching or cramping,” Dr. Rippe said.
EMG are most often ordered for one of the following reasons:
- To determine the cause of a patient’s symptoms
- To determine how severe a specific nerve injury is and whether or not more permanent nerve damage is occurring
- To determine whether or not a nerve injury is old or new
“The age of a nerve injury guides treatment plans, because an old nerve injury is treated differently than a new nerve injury is,” Dr. Rippe said.
The most common orthopedic conditions that might need an EMG are:
- Carpal tunnel syndrome — “This is the most common reason,” Dr. Rippe said.
- A pinched nerve at the elbow
- Pinched nerves at the knee, which could cause foot drop
- A pinched nerve in the spine
- Peripheral neuropathy from diabetes or other causes
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