Peripheral Neuropathy - Questions and Answers Print E-mail

Question: What is a peripheral neuropathy?
Answer: Peripheral neuropathy is a term that is used for disorders of the peripheral nerves.

Question: How is peripheral neuropathy classified?
Answer: There are many ways to classify peripheral neuropathy. Topographically, if the neuropathy affects a single nerve, it is called mononeuropathy, such as carpal tunnel syndrome and Bell’s palsy. If the neuropathy affects two or more nerves in separate areas, it is called mononeuropathy multiplex. When many nerves are affected simultaneously, it is called polyneuropathy.

Another classification follows the pathological involvement. If the axons are predominantly affected, it is called axonal neuropathy, such as most of the diabetic and uremic neuropathies. If the myelin sheath (the insulator) is affected, it is called demyelinating neuropathy, such as Guillain-Barré syndrome or chronic demyelinating inflammatory polyneuropathy (CIDP).

Another classification depends on the modality of involvement. When the sensory fibers are primarily affected, it is called sensory neuropathy, while if the motor fibers are predominantly affected, it is called motor neuropathy. The sensory neuropathy can be divided into small fiber neuropathy when the damage is mainly in the small nerve fibers that convey pain sensation, and large fiber neuropathy when the damage involves primarily the large fibers that convey proprioceptive and vibratory sensation. Autonomic neuropathy is a term that is used when the main system that is affected is the autonomic nervous system, which controls the autonomic functions, such as the heart rate, temperature control, sweating etc.

Neuropathy can also be divided according to the temporal evaluation, such as acute or chronic. The prototype of acute neuropathy is Guillain-Barré syndrome and the prototype of chronic neuropathy is diabetic neuropathy and chronic demyelinating neuropathy.

Question: What are the causes of peripheral neuropathy?
Answer: The etiology all depends on the specific type of neuropathy. Trauma is a common cause of localized nerve injury. Exposure to chemicals, infection, medications, drug abuse, alcohol abuse and diabetes mellitus are all causes of neuropathy. The most common cause of peripheral neuropathy is diabetes mellitus.

There are at least 212 identified causes for peripheral neuropathy, such as: Connective tissue diseases, such as systemic lupus erythematosus; Sjögren syndrome etc; infections, such as HIV infection and Lyme disease; internal malignancies, such as lung cancer; hereditary factors; immunizations; nutritional deficiencies; thyroid dysfunctions; renal failure; etc.

Question: How is the diagnosis of peripheral neuropathy made?
Answer: Clinical history and exam are the most important tools to diagnose neuropathy and identify its type and severity. EMG is very helpful, but it is considered to be an extension of the clinical examination. Blood workup, to identify some of the mentioned causes such as hyperthyroidism, vitamin deficiency, infection, etc., can be very helpful. Genetic testing for hereditary neuropathy is also available. Spinal tap may be needed in some inflammatory neuropathies to look for evidence of increased protein or cells in the spinal fluid. A nerve biopsy can be a useful tool, in particular, to diagnose disorders such amyloidosis, leprosy and vasculitis.

Question: Is neuropathy treatable?
Answer: It all depends on the type of neuropathy. Some neuropathies are curable, other neuropathies are arrestable, and some neuropathies are neither..

Question: What drugs can cause peripheral neuropathy?
Answer: Chloroquine; displatin; colchicine; dapsone; ethambutol; isoniazid; metronidazole; nitrous oxide; nitrofurantoin; procainamide; phenytoin; excessive pyridoxine; suramin; thalidomide; vincristine; and amidarone.
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