A case of supernumerary phantom limb induced by intention to move the left plegic limb

Abstract

  The term “phantom limb” is used to denote a dissociation between the perceived position of an intact body part and its actual position, and the patient experiences a vivid illusion involving paralyzed limbs.
  The presence of a phantom limb resulting from a cerebral vascular lesion has been reported to be a rare event. We experienced a case of supernumerary phantom limb (SPL) that was evoked only with motor intent directed to the paralytic anesthetic upper limb. A 40ʼs right-handed male was admitted for rehabilitation to our hospital after right putaminal hemorrhage. He showed complete left sensorimotor hemiplegia. On day 57 during rehabilitation he reported a SPL involving his right arm, originating at the level of the elbow. The most striking finding of his SPL was its motor character. Exerting intent to move the paralytic arm at the same time of the trainerʼs facilitative action was sufficient to trigger the illusion, whereas its passive movement had no effect. His SPL was not associated with anosognosia, asomatognosia or somatoparaphrenia except for mild left hemi neglect.
  A brain magnetic resonance imaging (MRI) revealed right putaminal hemorrhage involving right subcortical temporal and frontal lobe, thalamus, and cerebral peduncle. However, the premotor cortex, including supplementary motor area, was not involved.
  The mechanism by which phantom limb is induced has not been clarified. Regarding intentional phantom limb, Staub et al (.2006) reported a similar case. Within the striato-thalamo- cortical circuits subserving the motor functions, the premotor cortex of the motor loop, which interconnects the supplementary motor area (SMA) , primary motor cortex, putamen, globus pallidus, and ventrolateral thalamus, has been shown to be critically involved in generating intentional movements. Abnormal activation of the basal ganglia-thalamus-cortex loops as a cause of the illusion may be contributed to inducing SPL under the intact premotor cortex function.