Imaging Study Shines Light on Phantom Limbs

Post-stroke patient reported sensing extra limb attached to her left arm

WEDNESDAY, April 1 (HealthDay News) -- The case of a patient who perceived a supernumerary phantom limb (SPL) that she could see, feel, and move following a stroke offers insight into brain structures involved in such phenomena, according to research published online March 20 in the Annals of Neurology.

Asaid Khateb, Ph.D., of the Geneva University Hospitals and Faculty of Medicine in Switzerland, and colleagues discuss the case of a 64-year-old woman with a subcortical capsulo-lenticular hemorrhage. The SPL appeared to start from the elbow of her left plegic arm. She claimed she could see it and touch herself with it. She underwent functional MRI at three weeks post-stroke.

When she imagined scratching her left cheek with her left plegic hand, imaging revealed that her right premotor and motor regions were engaged, the researchers report. Performing this movement with the SPL resulted in the recruitment of more left middle occipital areas. When she "scratched" her left cheek with the SPL, the sensory response indicated that she did experience the sensation of the movement, the investigators found.

"Although rare, previous studies have assessed the neural correlates of the presence, or of the intentional movements, of stroke-induced SPL, the present investigation is the first to demonstrate the multimodal aspects of this phenomenon. Particularly, visual activation accompanying SPL movements has never been observed either in amputation, or post-stroke phantoms. Also, the activation of somesthesic areas fits with the patient's reported conscious experience of feeling and seeing her SPL," the authors write.

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