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Clinical significance and disorders of the Somatosensory system

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A somatosensory deficiency may be caused by a peripheral neuropathy involving peripheral nerves of the somatosensory system.

This may present as numbness or paresthesia.

Certain types of seizures are associated with the somatosensory system.

Cortical injury may lead to loss of thermal sensation or the ability to discriminate pain. An aura involving thermal and painful sensations is a phenomenon known to precede the onset of an epileptic seizure or focal seizure. Another type of seizure, called a sensory Jacksonian seizure involves an abnormal, localizable, cutaneous sensation but does not have apparent stimulus. This sensation may progress along a limb or to adjacent cutaneous body areas, reflecting abnormal neuronal firing in the postcentral gyrus where an epileptic discharge is propagated. These episodes in which patients are consciously aware during a seizure have been useful for identifying problems associated with the somatosensory cortex. Patients can describe the nature of the seizure and how they feel during it.[19]

The absence of proprioception or two-point tactile discrimination on one side of the body suggests injury to the contralateral side of the primary somatosensory cortex. However, depending on the extent of the injury, damage can range in loss of proprioception of an individual limb or the entire body. A deficit known as cortical astereognosis of the receptive type describes an inability to make use of tactile sensory information for identifying objects placed in the hand.

Tactile illusion. Tactile illusions are illusions that exploit the sense of touch.

Tactile illusion

Some touch illusions require active touch (e.g., movement of the fingers or hands), whereas others can be evoked passively (e.g., with external stimuli that press against the skin). Examples[edit] References[edit] Further reading[edit] Flanagan, J.R., Lederman, S.J. (2001). Phantom limb. A cat attempting to use its left forearm to scoop litter several months after it has been amputated.

Phantom limb

Although not all phantom limbs are painful, patients will sometimes feel as if they are gesturing, feel itches, twitch, or even try to pick things up. For example, Ramachandran and Blakeslee describe that some people's representations of their limbs do not actually match what they should be, for example, one patient reported that her phantom arm was about "6 inches too short".[6] A slightly different sensation known as phantom pain can also occur in people who are born without limbs, and people who are paralyzed.[7] Phantom pains occur when nerves that would normally innervate the missing limb cause pain. It is often described as a burning or similarly strange sensation and can be extremely agonizing for some people, but the exact sensation differs widely for individuals.

Somatosensory rehabilitation of pain. The Somatosensory Rehabilitation of Pain, is a method whose aim is to treat conditions of a reduced sense of touch or sensation (hypoesthesia) in order to decrease neuropathic pain.

Somatosensory rehabilitation of pain

Neuropathic pain, with a prevalency of 6.9% of the general population, represents an important public health problem.[1] e.g. Carpal Tunnel Syndrome (CTS) concerns 2.7% of the general population.;[2] i.e. Complex Regional Pain Syndrome (CRPS) concerns 26/100,000 person-years of the general population.[3] Patients with chronic pain need every possible therapy to battle the pain. Chronic pain is not a symptom but a syndrome in its own right, and requires therapists from a wide range of disciplines.So too, transcutaneous electrical nerve stimulation and other physical therapy procedures emerged rapidly, bringing substantial pain relief to large numbers of people.[4] History[edit] The Somatosensory Rehabilitation Method[edit] The presence of mechanical allodynia,[31] hinders other physical treatments.

Allochiria. Allochiria (from the Greek meaning "other hand") is a neurological disorder in which the patient responds to stimuli presented to one side of their body as if the stimuli had been presented at the opposite side.[1] It is associated with spatial transpositions, usually symmetrical, of stimuli from one side of the body (or of the space) to the opposite one.

Allochiria

Thus a touch to the left arm will be reported as a touch to the right arm, which is also known as somatosensory allochiria.[2] If the auditory or visual senses are affected, sounds (a person's voice for instance) will be reported as being heard on the opposite side to that on which they occur and objects presented visually will be reported as having been presented on the opposite side. Often patients may express allochiria in their drawing while copying an image.

Allochiria often co-occurs with unilateral neglect and, like hemispatial neglect, the disorder arises commonly from damage to the right parietal lobe.[1] Animation. Paresthesia. Paresthesia (/ˌpærɨsˈθiːziə/ or /ˌpærɨsˈθiːʒə/), is a sensation of tingling, tickling, pricking, or burning of a person's skin with no apparent long-term physical effect.

Paresthesia

The manifestation of a paresthesia may be transient or chronic. The most familiar kind of paresthesia is the sensation known as "pins and needles" or of a limb "falling asleep". A less well-known but still fairly common paresthesia is formication. Etymology[edit] Peripheral neuropathy. Peripheral neuropathy (PN) is damage or disease affecting nerves, which may impair sensation, movement, gland or organ function, or other aspects of health, depending on the type of nerve affected.

Peripheral neuropathy

Common causes include systemic diseases (such as diabetes or leprosy), vitamin deficiency, medication (e.g., chemotherapy), traumatic injury, excessive alcohol consumption, immune system disease, or infection, or it may be inherited (present from birth).[1][2][3] In conventional medical usage, the word neuropathy (neuro-, "nervous system" and -pathy, "disease of")[4] without modifier usually means peripheral neuropathy. Neuropathy affecting just one nerve is called "mononeuropathy" and neuropathy involving multiple nerves in roughly the same areas on both sides of the body is called "symmetrical polyneuropathy" or simply "polyneuropathy. " Neuropathy may cause painful cramps, fasciculations (fine muscle twitching), muscle loss, bone degeneration, and changes in the skin, hair, and nails.

Hypoesthesia.