Abstract
Dear Sir Raieli et al. present the case of a 13-year-old girl who experienced ‘unwilling grasping and rotating movements of the left hand, with fear and the feeling that the hand did not function under her control’ during her second ever episode of migraine (1).
The explanation they propose, that this is alien hand syndrome as part of a migrainous aura, is plausible, but they do not discuss an important alternative diagnosis—dissociative loss of control of the hand. The presence of ‘great fear’ raises the possibility that the sequence of events was a migrainous aura with hemisensory symptoms leading to fear about the possible diagnosis which in itself produced dissociative symptoms related to the affected limb. This would be supported by the way in which symptoms reappeared during the EEG (although we are not told at what point the patient became afraid). The presence of mild anxiety and lack of ‘hysterical personality’ does not make this diagnosis any less likely since transient, and even more serious dissociative symptoms can arise in otherwise healthy people, particularly in response to threatening physical symptoms. Alternatively, dissociation severe enough to produce an out of body experience may appear as a symptom of migrainous aura even without fear (2).
Dissociative experiences can affect all aspects of brain function including memory, identity and motor and sensory symptoms. The report of ‘feeling as if it were someone else's hand’ and even of autonomy of movement are common in dissociative states involving limbs (3). For example, the stage hypnotist's victim may carry out movements against their will for the amusement of the audience.
It may be that, once we understand alien hand syndrome better, it will turn out to have a similar neurophysiological substrate to that of dissociative motor symptoms. In the mean time the distinction is important because it keeps open the possibility that the mechanism for symptoms such as these may be as dependent as much on the cognitive and emotional impact of the attack as the migrainous aura itself.