Supernumerary phantom limb appearing in association with motor intention or pain in the paralyzed upper limb: a case report

We describe a case of supernumerary phantom limb (SPL) persisting into the chronic phase of a right putaminal hemorrhage. The individual, a forced right-handed female in her 40's, was admitted to the hospital 9 months after onset with clear consciousness, well-preserved cognitive function, severe left hemiparesis, and deep sensory impairment. When attempting to move the paralyzed upper limb, she perceived an SPL and felt as if it assisted the motion. Subsequently, the perceived SPL became associated with pain in the paralyzed upper limb. She reported that the SPL wrapped and tightened around her left arm. In another situation, she described the SPL as protruding from the back of her left shoulder and hurting when she lay on her back. Previous reports noted that hemiparesis and deep sensory impairment may be necessary for SPL's to appear. Staub et al. (2006) associated SPL to motor intention, suggesting that motor imagery triggers the feeling of movement in SPL. Our case shares these conditions with the previous reports. Pain and deep sensory impairment may contribute to SPL development. This case is interesting because SPL's with different triggers emerged at various times during the long-term course after cerebral hemorrhage onset.