Paresthesia is a sensation of tingling, 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 being "asleep" (although this is not directly related to the phenomenon of sleep). The manifestation of paresthesia may be transient or chronic.
Paresthesias of the hands and feet are common, transient symptoms of the related conditions of hyperventilation syndrome, often open mouth, and panic attacks.
Other common examples occur when sustained pressure has been applied over a nerve-inhibiting/stimulating function. Removing the pressure will typically result in gradual relief of these paresthesias, often described as a "pins and needles" feeling.
Paraesthesia is also a very frequently occuring withdrawal symptom after stopping the intake of some medicinal drugs, like paroxetine and—to smaller extent—fluoxetine (kinds of SSRIs—see: SSRI discontinuation syndrome).
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.
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. Nerves below the head may be compressed where chronic neck and spine problems exist and can be caused by, amongst other things, muscle cramps which may be a result of clinical anxiety or excessive mental stress, bone disease, bad posture, unsafe heavy lifting practices or physical trauma such as whiplash. Paresthesia can also be caused simply by blocking of the blood stream to a limb by applying weight [or pressure] on 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 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, motor neurone disease, or autoimmune disorders like multiple sclerosis or lupus erythematosus. The herpes zoster virus can attack nerves causing numbness instead of pain commonly associated with shingles. A diagnostic evaluation by a doctor is necessary to rule these out. Demyelination diseases may also cause cross-talk between adjacent axons and lead to parasthesia. 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-Barre Syndrome.
Treatment should be decided by a neurologist. 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, amongst others, according to the underlying cause.
In some cases, rocking the head from side to side will painlessly remove the "pins and needles" sensation in less than a minute. A tingly hand or arm is often the result of compression in the bundle of nerves in the neck. Loosening the neck muscles releases the pressure. Compressed nerves lower in the body govern the feet, and standing up and walking around will typically relieve the sensation. An arm that has "fallen asleep" may also be "awoken" more quickly by clenching and unclenching the fist several times; the muscle movement increases blood flow and helps the limb return to normal. However, in some cases this clenching action simply exacerbates the discomfort. More rapid relief can sometimes be obtained by gently and systematically massaging the affected area of the body.
Manipulation of the neck won't apply to facial paresthesia, such as early stages of Bell's palsy, as nerves of the face and scalp don't pass through the neck.
Paresthesia caused by shingles is treated with appropriate antiviral medication.