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- Main article: Somatosensory disorders
Paresthesia (// or //), spelled paraesthesia in British English, is a sensation of tickling, tingling, burning, pricking, or numbness of a person's skin with no apparent long-term physical effect. It is more generally known as the feeling of "pins and needles" or of a limb "falling asleep". The manifestation of paresthesia may be transient or chronic.
Greek para ("beside", i.e., abnormal) and aisthesia ("sensation").
Other common examples occur when sustained pressure has been applied over a nerve, inhibiting/stimulating its function. Removing the pressure will typically result in gradual relief of these paresthesias.
Chronic paresthesia indicates a problem with the functioning of neurons.
In older individuals, paresthesia is often the result of poor circulation in the limbs (such as in peripheral vascular disease, also referred to by physicians as PVD or PAD), most often caused by atherosclerosis, the build up of plaque within artery walls, over decades, with eventual plaque ruptures, internal clots over the ruptures and subsequent clot healing but leaving behind narrowing of the artery openings or closure, both locally and in downstream smaller branches. Without a proper supply of blood and nutrients, nerve cells can no longer adequately send signals to the brain. Because of this, paresthesia can also be a symptom of vitamin deficiency and malnutrition, as well as metabolic disorders like diabetes, hypothyroidism, and hypoparathyroidism. It can also be a symptom of mercury poisoning.
Irritation to the nerve can also come from inflammation to the tissue. Joint conditions such as rheumatoid arthritis, psoriatic arthritis, and carpal tunnel syndrome are common sources of paresthesia. Nerves below the head may be compressed where chronic neck and spine problems exist and can be caused by, among other things, muscle cramps that may be a result of clinical anxiety or excessive mental stress, bone disease, poor posture, unsafe heavy-lifting practices or physical trauma such as whiplash. Paresthesia can also be caused simply by putting pressure on a nerve by applying weight (or pressure) to the limb for extended periods of time.
Another cause of paresthesia, however, may be direct damage to the nerves themselves, i.e., neuropathy, which itself can stem from injury or infection such as frostbite or Lyme disease, or which may be indicative of a current neurological disorder. Neuropathy is also a side effect of some chemotherapies. Benzodiazepine withdrawal may also cause paresthesia as the drug removal leaves the GABA receptors stripped bare and possibly malformed. Chronic paresthesia can sometimes be symptomatic of serious conditions, such as a transient ischemic attack, or autoimmune diseases like multiple sclerosis or lupus erythematosus.The herpes zoster disease (shingles) can attack nerves causing numbness instead of pain commonly associated with shingles. A diagnostic evaluation by a medical doctor is necessary to rule these out.
Demyelinating diseases may also cause cross-talk between adjacent axons and lead to paresthesia. During impulse conduction some aberrant current that escaped a demyelinated axon can circulate in the exterior and depolarize an adjacent demyelinated, hyperexcitable axon. This can generate impulses conducted in both directions along this axon since no part of the axon is in a refractory state. This becomes very serious in conditions such as multiple sclerosis and Guillain–Barré syndrome.
Other causes may include:
The nerve conduction study usually provides useful information for making diagnosis. A CT scan is sometimes used to rule out some causes from the central nervous system.
Medications offered can include the immunosuppressant prednisone, intravenous gamma globulin (IVIG), anticonvulsants such as gabapentin or Gabitril and antiviral medication, among others, according to the underlying cause.
In addition to treatment of the underlying disorder, palliative care can include the use of topical numbing creams, such as lidocaine or prilocaine. Care must be take to apply only the necessary amount, as excess can contribute to the condition. Otherwise, these products offer extremely effective, but short-lasting, relief from the condition.
Paresthesia caused by shingles is treated with appropriate antiviral medication.
- ↑ Paresthesia Information Page: National Institute of Neurological Disorders and Stroke. (NINDS)
- ↑ Chemotherapy-induced Peripheral Neuropathy. National Cancer Institute. URL accessed on 1 December 2011.
- ↑ Marks, Dawn B.;Swanson, Todd; Kim, Sandra I.;Glucksman, Marc (2007). Biochemistry and Molecular biology, Philadelphia: Wolters Kluwer Health/Lippincott Williams & Wilkins.
- ↑ Ietsugu, T, Sukigara, M, Furukawa, TA (Dec 2007). Evaluation of diagnostic criteria for panic attack using item response theory: findings from the National Comorbidity Survey in USA.. Journal of Affective Disorders 104 (1-3): 197–201.
- ↑ Nitrous Oxide
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