Alien Hand Syndrome

Alien hand syndrome is a rare neurological syndrome. With uniquely unusual clinical symptomatology, alien hand syndrome may be produced by a number of etiologies of cerebral damage and more than one specific region of cerebral damage.

Symptoms and diagnosis of alien hand syndrome 

A lack of hand control is the most prominent symptom of alien hand. Yet alien hand syndrome involves more than just a lack of hand control. The affected hand is not weak, instead, the hand maintains normal strength, but it may move involuntarily, without cognitive control or awareness. The hand movements are not spastic or convulsive, but are purposeful and coordinated. Individuals who suffer from alien hand syndrome typically explain that the hand seems to be controlled by ‘someone else.’ Normal movements such as picking up objects, touching the face, and even dressing or undressing, are all characteristics of alien hand syndrome. The distinctive feature of alien hand syndrome is the sufferer’s complaint that these ‘regular’ hand actions are unintentional, unwanted, and unexpected.

Diagnosis can be a challenge because alien hand syndrome, according to the case reports in the medical literature, is truly a neurological disorder without a psychiatric component. This can be confusing during the diagnostic stage, particularly because true psychiatric disorders and behavioral issues are much more prevalent among patients than is alien hand syndrome, making complaints of a ‘hand moving on its own,’ far more likely to be accurately explained by something other than alien hand syndrome based on statistics alone. Therefore, careful observation and evaluation is required for the diagnosis of alien hand syndrome vs. any of the other condition in the differential diagnosis of these symptoms. 

Causes of alien hand syndrome 

The causes of alien hand syndrome are varied. The condition is not associated with a characteristic vascular stroke syndrome, although stroke is one of the causes. Alien hand syndrome may occur after neurosurgical procedures, particularly when there is an incision involving the corpus callosum. There is an unexpected association between alien hand syndrome and neurodegenerative disease. Other lesions such as trauma and cancer may cause alien hand syndrome.

Besides the corpus callosum, other regions of the brain associated with alien hand syndrome include:

Brain lesions in alien hand syndrome

In general, it would make sense for visual, sensory, or motor dissociation such as hemiagnosia to be associated with alien hand syndrome. Yet, hemiagnosia is not associated with alien hand syndrome. Interestingly, case reports of alien hand syndrome are not consistent with respect to neuroimaging correlates. Lesions of the corpus callosum are well documented. But other lesions, including areas of the motor cortex or supplementary motor cortex, have also been identified, making it impossible to identify one specific location of brain injury with alien hand syndrome.

Is there a treatment for alien hand syndrome?

Some methods that have been successfully used in the treatment of alien hand syndrome include therapies directed at muscle control, such as botulinum toxin and neuromuscular blocking agents. Cognitive therapy techniques have been used with cooperation from the majority of patients with moderate efficacy. 

References:

Sarva H, et al. Pathophysiology and treatment of alien hand syndrome. Tremor Other Hyperkinet Mov (N Y). 2014 Dec 5;4:241.

Hassan A, et al. Alien hand syndrome. Curr Neurol Neurosci Rep. 2016 Aug;16(8):73.