Table 2

Alien limb differential diagnosis

DisorderDefinition/distinguishing feature
Grasp reflexSimple frontal release sign.
Utilisation behaviourInvoluntary (and inappropriate) use of a presented object for its usual purpose.
HemineglectLoss of awareness of limb as belonging to the person.
Mirror movementsOne hand involuntarily mimics the movement of the other.
PseudoathetosisInvoluntary movement of extremities due to proprioceptive loss.
Task specific limb dystoniaProvoked task specific abnormal limb posturing (eg, writer’s cramp).
Focal dystoniaAbnormal limb posturing that may increase with distraction or as overflow from movement of other limbs.
HemiballismusUnilateral large amplitude ballistic movements of limbs -exaggeration of chorea.
Clonic perseverationRhythmic, stereotyped and repetitive movements.
HemiataxiaClumsy ataxic limb with no involuntary movements.
  • Neurological phenomena that should be distinguished from alien limb. Note that for the motor phenomena in this table there is preserved sense of limb ownership and no sense of the affected limb(s) being ‘foreign’. Adapted with permission from: Hassan and Josephs.72