Electrodiagnostics is an important field of medicine that is used by physiatrists to help in the diagnosis of nerve and muscle disorders. What is electrodiagnostic medicine? How do I prepare for the exam? What conditions do NCS/EMG test for?
What is Electrodiagnostic Medicine? Electrodiagnostics is the field of medicine that is used by physiatrists and neurologists to search for the cause of nerve and muscle disorders. It consists of two parts: nerve conduction studies (NCS) and electromyography (EMG). Both parts give different important information, which when correlated with the clinical exam, can tell the physician if a neurologic process exists, and often how long it's been present and to what severity. The goal is to learn about the health of the nerve and muscle by studying their physiology. NCS requires placement of electrodes on the skin, and then stimulation applied to various nerves. The speed the nerve conducts electricity is calculated, and the physician can comment on whether this speed is normal or too slow. EMG involves placement of a special needle under the skin into multiple muscles. Normally, muscles send out certain electric sounds and patterns that can be seen on a computer screen. A muscle which is damaged will cause irregular sounds and images on the screen, and the physician can interpret these and formulate a diagnosis. Nothing is injected during the exam.
NCS requires the physician to shock the nerves, so it can feel anywhere from a little bothersome to very irritating. The shocks generally are very brief and do not cause any residual discomfort. EMG, on the other hand, involves needle insertion into several muscles and can be painful. The use of Tylenol before the exam, and ice afterwards, can minimize discomfort.
How Do I Prepare for the Exam? Dr. Marlowe asks his patients to take Tylenol an hour before the test to reduce soreness. Since aspirin and blood thinners can lead to bruising, patients should advise the physician about their use, and expect more than average bruising afterwards. Otherwise, patients may do their routne activities before and after. Do not put any lotion on the parts to be tested, since tape will not stick over lotion.
What Conditions Do NCS/EMG Test For? NCS is used to test conditions that cause weakness and numbness, particularly if the problem is arising in the extremity (arm or leg). While it can help pinpoint the source of pain, it generally does not tell the physician why something hurts. Disorders that can be detected include: Carpal tunnel syndrome Ulnar neuropathy Tarsal tunnel syndrome Peroneal nerve injury EMG tests the health of muscles, and can reflect nerve damage that is causing muscle damage. It can be useful to map out which muscles are affected in the setting of a pinched nerve, and collectively point to a specific nerve. It is not used for low back pain or neck pain, but can be useful if a pinched nerve in the back or neck is suspected. EMG is used to detect: Cervical radiculopathy (pinched nerve in the neck) Lumbar radiculopathy (pinched nerve in the back) Myopathy (muscle disease) While EMG can test the physiology of a pinched nerve, MRI is often used to study the anatomy in the neck or back. Both tests bring different information into the work-up.
Although most insurance companies will permit patients to receive testing when medically indicated, authorization is generally sought in advance either by the referring physician or The Marlowe Institute. Every plan differs regarding the patient's financial responsibility. Dr. Marlowe conducts only the necessary parts of the exam, which tends to keep the cost down.
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