Sunday, August 25, 2013

Peripheral Neuropathy

The term peripheral neuropathy is used to refer to many different types of neuropathy, from those involving only a single nerve, such as Bell’s palsy,
to those producing profound generalized paralysis, such as Guillain-Barre syndrome. There are also many different causes, ranging from heritary neuropathies to toxic ones caused by heavy metal poisoning.
A neuropathy is any abnormal state (pathy) of a nerve or nerves (neuro). The peripheral nerves are those that are outside the central nervous system, running from the brain or spinal cord to our muscles, organs, skin, etc. The peripheral nerves are usually divided into three types; motor nerves which go to muscles and control their contractions, sensory nerves which run from sensory organs to the spinal cord, and autonomic nerves which regulate many of our automatic functions such as controlling blood pressure, movement of the intestines, sweating, etc. A peripheral neuropathy may involve exclusively one type of nerve, or all three.
Some common conditions are actually neuropathies. I mentioned Bell’s palsy above; in addition there is carpal tunnel syndrome, which occurs when pressure at the wrist causes the nerves running through the wrist not to conduct correctly; trigeminal neuralgia, a painful neuropathy of the nerve going to the face; and shingles, an infection of the nerves by varicella-zoster virus. Some conditions are experienced by many people temporarily — for example, the numbness that can occur in the little finger and side of the hand during sleep when the elbow is bent to its maximum, which stretches the ulnar nerve in the elbow. But when most people, and most doctors, refer to peripheral neuropathy they are talking about numbness, tingling and pain, usually in the feet and legs.
Diabetes is a common cause of neuropathy, as is kidney failure. Maximum control of these underlying diseases may improve the neuropathy. There is an ancient disease, beri-beri, caused by thiamine deficiency, which causes such a neuropathy. No one eating a regular diet will develop beri-beri, and it is therefore seen in this country exclusively in alcoholics. For others, supplementing B complex vitamins will probably not help but won’t hurt, although megadoses should not be taken. (Megadoses of Vitamin B6, pyridoxine, have been shown to cause a neuropathy.)
Some cases of slowly developing neuropathies are hereditary, and usually inherited in a recessive fashion, meaning the parents and siblings will probably not have the disease. A careful family history that includes grandparents, aunts, uncles and cousins may give a clue.
Many drugs may cause a neuropathy, including some used in cancer chemotherapy, in the treatment of HIV infection, isoniazid used to treat tuberculosis, and others less commonly used. Severe alcoholism can cause a neuropathy that is not beri-beri and that will not respond to doses of thiamine. Infections that can cause it include HIV, Lyme disease, leprosy, polio, diptheria, and syphilis. Treatment of the underlying infection will often reduce the symptoms of neuropathy.

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Nasal spray made from ‘hot pepper’ eases shingles pain

A NASAL spray made from a compound found in hot peppers could be a new way to treat the severe pain associated with shingles.

  Now United States researchers have developed a spray to tackle this when it occurs in the face. The spray is designed to block pain signals in the trigeminal nerve, which is responsible for facial sensation.

  Shingles is caused by the reactivation of the chicken pox virus (the varicella-zoster virus). After causing chickenpox, the virus lies inactive in the nerves, where it is kept in check by a healthy immune system.

  But if this is weakened - because of advancing age, stress or disease - the virus ‘wakes up’. This can happen years, even decades, after the initial chickenpox infection.

  The virus then causes inflammation and damage to the nerves, triggering a rash and pain in the affected area - usually the chest or abdomen, though sometimes the face.

  A bout of shingles lasts two to four weeks, but up to one in five people will develop postherpetic neuralgia - severe chronic pain that persists for at least three months. In some cases, it can last ten years or more.

  The pain is variously described as a burning, stabbing, shooting, aching or throbbing sensation; the area can also feel itchy. It is not clear why some people develop pain after shingles.

  But the risk increases with age - postherpetic neuralgia affects one third of people aged over 80 at some time.

 Conventional treatments include low-dose anti-depressants and epilepsy drugs, which dampen down pain messages.

  The new spray, developed by U.S.-based Winston Laboratories, is based on capsaicin, the compound that makes chilli peppers hot. When eaten, capsaicin triggers a burning sensation by activating nerve cells - it’s thought that it tackles pain by desensitising the nerves.

  In a trial at the California Headache Centre, 40 patients with moderate to severe daily pain with postherpetic neuralgia will use the spray or placebo twice a day.

  The researchers say administering the drug, as a spray will be more effective than existing treatments at targeting the trigeminal nerve.

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