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.