Alien hand syndrome: symptoms, causes and treatment

Also known as alien hand syndrome, this phenomenon generates surprising symptoms.

Our brain is made up of two hemispheres linked by a bundle of nerve fibers that make up the corpus callosum. that make up the corpus callosum. Thanks to this structure, both hemispheres can exchange information and, together with the action of other brain areas, we can be aware of our own body.

However, when this structure fails or is injured, a strange disorder known as corpus callosum a strange disorder known as foreign hand syndrome can appear, whereby the person is whereby the person is unable to control the movements of his or her own arm and hand, which can be experienced as alien or even possessed.

What is alien hand syndrome?

Also known as "strange hand syndrome", "alien hand syndrome" or "Dr. Strangelove's syndrome", this strange disorder of neurological origin is distinguished by causing in the person who suffers from it all kinds of involuntary and uncontrolled movements in one of the upper extremities of the body..

In addition, another of the peculiarities of the foreign hand syndrome is the sensation of strangeness that the person feels with respect to that limb. In other words, the patient experiences a personification of the arm and hand, which seem to have a life of their own..

This syndrome was first described in 1908. The famous German physician Kurt Goldstein discovered these strange symptoms in patients who had undergone commissurotomy. This intervention consists of making a cut in the corpus callosum and was typical of treatments for very severe epilepsies, in order to prevent seizures from spreading from one cerebral hemisphere to another.

Clinical classification

There are two different types of foreign hand syndrome, which differ in relation to the causes and anatomical correlates of this syndrome.

Acute variant of the syndrome

One of the forms in which the syndrome manifests itself is the acute variant, which is due to damage to the corpus callosum causing temporary changes in the motor area. temporary changes in the supplementary motor area.. It is hypothesized that this damage is due to hemispheric retraction during commissurotomy.

This acute variant is characterized by more intense and exaggerated movements, but of short duration.

Chronic variant

The second form of foreign hand syndrome is the chronic variant. It is caused by a lesion in the corpus callosum, as well as lesions in the supplementary motor area, which is located in the medial frontal lobe.

What symptoms appear?

The clinical picture of the foreign hand syndrome has two main symptoms. These symptoms are:

Dissociation

Sensation of dissociation of the affected extremity. The person firmly believes that this arm is not part of his or her body and that, therefore, he or she cannot and therefore cannot exercise any control over its movements. However, tactile sensitivity is preserved so that, although the person cannot control it, he/she can feel everything that happens to the limb.

Absence of control of movements

The patient is not aware of the actions performed by the affected arm and hand.. That is, the person does not realize when the limb is performing any type of movement, regardless of how complicated or exaggerated it is.

In many cases, the movements performed by the limb considered to be foreign cause interference with the movements or actions carried out by the healthy limb. In addition, this neurological alteration dissociates the intention from the action so that the impulses of the foreign hand are totally opposite to those of the healthy hand.

Context influences

After observation of cases, it has been found that these "foreign limbs" tend to react in response to stimuli of the healthy hand. tend to react in response to nearby stimuli such as conspicuous objects within reach. objects within reach. Hence, it is hypothesized that the behavior of these limbs is guided by contextual stimuli.

The intensity of the symptoms may vary in a fluctuating manner. In highly stressful or highly anxious situations, the clinical picture of foreign hand syndrome tends to increase in both quantity and intensity.In highly stressful or anxious situations, the clinical picture of foreign hand syndrome tends to increase in both quantity and intensity.

Finally, these symptoms can lead to a large number of psychological and emotional side effects. This associated symptomatology can range from feelings of confusion and anxiety, to the experience of fear and fear crises. to experiencing fear and panic attacks.. However, the psychological consequences can vary greatly among patients as many of them learn to live with this type of disorder.

What causes it?

As mentioned above, the origin of foreign hand syndrome is to be found in a lesion of the corpus callosum. This structure is responsible for linking and transmitting information between both cerebral hemispheres, as well as ensuring that both work in a coordinated manner.

However, there is much research that points to the idea that this syndrome cannot be explained by this type of lesion alone, but is most likely also due to some type of cortical damage or frontal lobe lesion.

This brain damage may be due to numerous incidents, such as tumor masses, aneurysmssuch as tumor masses, cerebral aneurysms, cranioencephalic trauma or brain surgeries such as the aforementioned commissurotomy.

What is the diagnosis?

Because the foreign hand syndrome has exclusively organic causes, its diagnosis is based almost exclusively on the elaboration of a clinical history and an exhaustive physical examination..

The tests that the clinician must perform for an effective diagnosis of this disorder include neuroimaging testssuch as computerized axial tomography (CT) or nuclear magnetic resonance imaging (MRI). These techniques make it possible to assess the state of the nervous system and the severity of brain lesions.

Is there a treatment?

At present, no effective treatment protocol has been developed for foreign hand syndrome. When this condition is caused by brain lesions associated with tumors or aneurysms, treatment of these should reduce the symptomatology of this syndrome..

However, symptomatologic treatment for the psychological symptoms can be performed. In addition, the patient can undergo training by which he or she can keep the affected limb occupied and thereby reduce the amount of unwanted movements.