Alien hand syndrome

The alien hand syndrome ( AHS ) is a hitherto been rarely described neurological disorder in which affected people in one of two hands no longer subject to voluntary control. It is best documented in humans, where in the brain, the corpus callosum (bar ) is severed ( split-brain patient). However, the disorder can also occur after a stroke or infection. First described it in 1908 by German neurologist Kurt Goldstein. The term alien hand syndrome comes from a paper from the year 1972, in the three cases of patients have been described with a tumor on the corpus callosum, showed the corresponding disturbances in the control of a hand.

Impact

The affected patients have no or very little control of a hand, the so-called alien hand. They feel that hand as alien and not belonging to her body. This hand often works against the other. This can for example cause the affected person wants something to eat with your right hand and his left hand prevents him or in extreme cases, attempts to strangle him.

Since the affected hand and to enable the competent hemisphere has no contact with the other, no information can be captured and processed through a palpated object even in times of conscious control. For example, can not be known whether an object is round or square.

Causes

The exact causes are, apart from references to the spatial location of a corresponding functional disorders in the brain is not yet known. It is assumed that two different forms can be distinguished.

When a form is it damaging to the corpus callosum, in some cases, the frontal lobe. In these patients, usually the left hand is concerned. A severance or other damage to the corpus callosum leads to disruption of communication between the brain's two halves. Since each half of the brain is responsible for the control of the respective opposite side of the body, subject 's left hand, in such a case, only the control by the right side of the brain. However, the left side of the brain is also responsible by the exchange of information with the right hemisphere via the corpus callosum, generally for logical and analytical thinking processes and for the control of complex fine motor movements in addition to controlling the right half of the body. This function of the left hemisphere of the brain is then subject the left hand in these patients no longer. Characteristic of this form is often that the affected hand is especially active when the unaffected hand performs movements.

In a second form of the frontal lobe damage only occurs during the corpus callosum is not affected. The frontal lobes are the brain areas that are important for the planning and execution of voluntary movements. In affected patients typically the dominant hand of the side of the body is affected, in most cases the right. A striking feature of this form is often a compulsive reaching for objects located in the visual field of the patient.

Treatment

There is currently no treatment options available for the alien hand syndrome, but there is often after a certain period of only one improvement.