Three arms: a case study of supernumerary phantom limb after right hemisphere stroke.

A case of supernumerary phantom limb is described after a haematoma within the right basal ganglia. The phantom, which persisted for many months, occurred in the context of severe left hemiplegia, sensory loss, hemianopia, and neglect. The subjective reality of this "third arm" caused the patient considerable distress, which was not ameliorated by his attempts to rationalise its existence. Although deeply confused by the phantom, the patient was otherwise fully oriented, with a high verbal IQ, and normal cognition. Two distinct formal interpretations of the phenomenon are discussed.