The diagnosis of a peripheral nerve problem proceeds in a fairly straightforward fashion.
A detailed history provides information about the symptoms experienced by the patient, how long they have been present, and how they have progressed. Mechanism and timing of injury, muscle weakness, numbness, and pain are all important components of the history.
The peripheral nerve examination tests motor and sensory function to help localize the region of injury. Muscle atrophy and changes in the skin and nails can be helpful as well.
The most important diagnostic study in the evaluation of peripheral nerve problems is electromyography (EMG) with nerve conduction studies (NCS). This study provides accurate, quantitative information on the function of nerves and muscles and helps to more precisely localize the region of injury, and to pick up more subtle signs of injury and/or recovery that are otherwise undetectable to the examiner.. Sometimes it is the only way to reliably localize a lesion, quite crucial if surgery is being contemplated. Unfortunately, this study can make some patients uncomfortable, as it involves placement of tiny needles into the muscles. Most patients, however, tolerate the procedure just fine.
Sometimes intraoperative nerve action potential recordings (NAPs), which measure the function of nerves during surgery, are necessary to establish whether a nerve must undergo repair or if it can heal on its own.
Imaging studies can be quite helpful in patients with peripheral nerve problems. For example, patients who have peripheral nerve tumors almost invariably require an MRI. This study uses harmless magnets (NOT ionizing radiation) to create highly detailed pictures of the relevant anatomy, including the tumor. Such detailed pictures facilitate the planning of surgery to treat peripheral nerve tumors.
CT myelography is used to evaluate brachial plexus traumatic injuries. The brachial plexus represents the network of neural structures that connects the nerve roots exiting the spinal cord in the neck to the individual nerves in the shoulder and arm. Patients who have suffered severe brachial plexus trauma may actually have one or more avulsion injuries, in which the nerve roots are actually pulled out from the spinal cord in the neck. A CT myelogram is really the only way to reliably document this type of injury. To perform a CT myelogram, contrast dye is injected along into the spinal canal. Then spinal X-rays and a spine CT are performed.