Let’s imagine Patient X. After multiple pharmacological treatments for her severe epilepsy proved ineffective, last-resort, radical surgery was performed. Initially, the surgery seemed to have worked: the seizures had stopped. However, some bizarre symptoms became apparent regarding her left hand. She began to complain that it was acting under someone else’s control, and had “a mind of its own”. As she tried to open a drawer with her right hand, the left would slam it shut. As she lit a cigarette with her right hand, her left stubbed it out. More alarmingly, Patient X reported that her left hand would slap her own face, and that on numerous occasions it had tried to strangle her. She insisted she was not controlling the movements of her left hand, but that it acted of its own accord.  

Patient X was probably suffering from ‘Alien Hand Syndrome’ – a rare neurological disorder characterised by unwilled, uncontrollable, but seemingly purposeful movements of an upper limb. To be diagnosed, patients must verbally complain of a ‘foreign limb’ (for example, by expressing feelings that the movements are not controllable) and the hand must make complex, autonomous and involuntary movements.

The syndrome can arise through brain lesions – in the case of Patient X, through surgery. It has been known to occur after strokes, brain tumours and aneurysms, all of which can damage brain tissue. 

In Dr Strangelove – Stanley Kubrick’s famous film – the main character has a right hand which sometimes clutches his own throat, and sometimes performs the Nazi salute. The hand is driven by a will of its own, performing undesirable and even embarrassing movements. This is scarily close to the real disorder. The wayward limb can only be restrained by the ‘normal’ hand, which can be physically difficult. Many patients fear and even personify the disobedient limb, calling it ‘him’.

Several areas of the brain have been implicated in this disorder. In many cases, damage to the corpus callosum – a band of nervous fibres which keeps the two halves of the brain in constant contact – is thought to be responsible. Damage to the frontal lobes of the brain might also play a part – such damage can result in reaching and grasping movements, to the point where grasped objects often cannot be released, and the other hand must physically peel back the fingers to prise the object free.

This condition can be debilitating, preventing patients from going out in public and leading a normal life. Although there is no cure, many strategies and treatments exist to manage symptoms: wedging the disobedient hand between the legs, applying warm water to it, ‘training’ the patient to override the alien behaviour, or even attempting to ‘muffle’ the action of the alien limb by an oven glove or oversized foam glove. Alien Hand Syndrome sufferers often report great frustration – even if they can eventually manage the condition, they remain powerless over the alien limb itself.