Paresthesia
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Paresthesia (
paraesthesia in
British English) is a sensation of tingling, pricking, or numbness of the skin with no apparent long-term physical effect, more generally known as the feeling of
pins and needles.
Most people have felt the sensation of an extremity "falling asleep". This lack of sensation is caused by a temporary impedance of blood flow to the extremity which results in nerve cells being starved of
oxygen and
glucose. Additionally, the impedance of blood flow is usually due to pressure on the limb which in turn compresses the nerve cells, making transmission of neural impulses more difficult. Transient paresthesia is the familiar sensation of "pins and needles" felt when oxygen and glucose-rich blood return to the nerve cells which in turn fire at an accelerated rate until they establish their regular transmission rate.
Chronic paresthesia indicates a problem with the functioning of nerve cells, or
neurons. This malfunction, which is especially common in older individuals, is often the result of poor
circulation in the limbs (such as in peripheral vascular disease), 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 such as
Lyme disease, 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 (aside from pressure on the affected area):
*
Alcoholism*
Anticonvulsant drugs such as
topiramate,
sulthiame, and
acetazolamide*
Dehydration*
Fibromyalgia*
Heavy metals*
Migraines
*
Radiation poisoning*
Lidocaine poisoning
* Withdrawal from certain
SSRIs, such as
Paroxetine*
National Institute of Neurological Disorders and Stroke: Paresthesia Information Page
