If you have pain, pins and needles, numbness, or muscle weaknesses in your arm, your doctor may refer you to a neurologist, who is a nerve specialist. These doctors are trained to perform and interpret tests that look at individual nerves for signs of damage. Why are these tests important? With nerve injuries, the location of the symptoms may not be the location of the damage. For instance, the nerves in your arms emerge from your spinal cord at the level of your neck, called the cervical region. So if you experience symptoms in your hand or forearm, the damage could be in your hand or forearm but it also could be coming from the neck. These tests are invaluable in determining where the damage is occurring to make sure a patient receives the correct diagnosis. This is especially important if surgery is being considered.
An electrical wire consists of the wire itself and a protective outer covering. The same is true for a nerve. The axon, which transmits electrical impulses, is the actual wire, while the myelin sheath is outer covering. If only the outer covering is damaged, a nerve can be expected to heal easily. But if the axon itself is damaged, healing can be slower and less certain.
A nerve lending study helps to determine the pattern of a nerve injury. The severity of the symptoms a person is experiencing usually correlates with the severity of damage shown on a nerve conduction study and electromyography, but not always. It is possible for a person to have classic symptoms but normal nerve lending studies.
A nerve conduction study looks at both the nerves that make your muscles work and the nerves that provide sensation. The test measures how fast the nerve sends a signal from one point to another, called the construction velocity. This determinates if there's damage in the myelin sheath, or outer covering of the nerve. The study also measures the size of the nerve response, which tests the axon.
An electromyography, or EMG, is a test that shows the neurologist how long nerve damage has been occurring. During this test, an acupuncture-like needle is placed in a muscle to act like an amplifier. The neurologist is trained to recognize minor differences in the sound, as well as in the amplitude of the muscle response to determine if the damage is still occurring. If the damage is no longer occurring, the test indicates how recently it had occurred. The muscles are tested at rest and during an active contracting to look at recruitment. This information tells how much damage is going on in the specific muscle that is tested.
If you have numbness and tingling in your hand or forearm, be sure to see your doctor. Early detection of syndromes like carpal tunnel and cubital tunnel is important to prevent progress of symptoms. If your nerve conduct study and EMG suggest moderate to severe damage, you can expect a referral to a surgeon to further discuss your options. If, on the other hand, the injury is mild to moderate, conservative treatments such as occupational therapy, splinting, or anti-inflammatory medications may be recommended.