Paresthesia (paraesthesia in British) is a sensation of tingling, pricking, or numbness of the skin with no apparent physical cause, more generally known as the feeling of pins and needles. Transient paresthesia is usually caused by inadvertent pressure on a superficial nerve, and disappears gradually as the pressure is relieved. Other kinds of paresthesia, however, can be chronic and painful, and can come from a wide variety of sources.

Chronic paresthesia indicates a problem with the functioning of nerve cells, or neurons, in the central nervous system. This malfunction, which is especially common in older individuals, is often the result of poor circulation in the limbs, or may be caused by atherosclerosis—the build up of plaque on artery walls. Without a proper supply of blood and nutrients, nerve cells can no longer adequately send signals to the brain. Because of this, paresthesia is also a symptom of vitamin deficiency and malnutrition, as well as metabolic disorders like diabetes and hypothyroidism.

Irritation to the nerve can also come from inflammation to the surrounding tissue. Joint conditions such as rheumatoid arthritis and carpal tunnel syndrome are common sources of paresthesia.

Another cause of paresthesia, however, may be direct damage to the nerves themselves, or neuropathy, which can stem from injury or infection, or which may be indicative of a current neurological disorder. Chronic paresthesia can sometimes be symptomatic of serious conditions, such as a transient ischemic attack, a brain tumor, motor neurone disease, or autoimmune disorders like multiple sclerosis or lupus erythematosus. A diagnostic evaluation by a doctor is necessary to rule these out.

Paresthesiae of the mouth, hands and feet are common, transient symptoms of the related conditions of hyperventilation syndrome and panic attacks.

Other known causes of paresthesia:

• Alcoholism
• Anticonvulsant drugs such as topiramate, sulthiame, and acetazolamide
• Heavy metal poisoning
• Migraine headaches

External links

• National Institute of Neurological Disorders Paresthesia Information Page (http://www.ninds.nih.gov/health_and_medical/disorders/paresthesia.htm)