Atypical Supernumerary Phantom Limb and Phantom Limb Pain in a Patient With Spinal Cord Injury: Case Report
A 43-year-old man was admitted to our hospital for intensive rehabilitation 115 days after a traffic accident. Cervical computed tomography (CT) and magnetic resonance imaging (MRI) on the day of the injury had shown a C6 vertebral body fracture as well as a cervical cord signal change on T2-weighted MRI images (). He had undergone a C5-6-7 lateral mass fusion on the day of the injury. Six days after injury, he was transferred to the rehabilitation department. A subsequent C5-6-7-T1 anterior and posterior fusion was additionally performed 35 days after injury due to spinal instability detected on follow-up cervical spine X-ray (). There was no concomitant brain injury on brain CT scans and all cognitive evaluations including cognitive score subsets of the Functional Independence Measure showed intact cognition. Other than a past history of type 2 diabetes mellitus, no other significant medical history including psychiatric history existed. The patient also had no history of drug or alcohol misuse.\nAccording to the International Standards for Neurological Classification of Spinal Cord Injury, the patient had a complete lesion (American Spinal Injury Association impairment scale A [ASIA A]) with a C6 neurologic level of injury. According to neurologic exams performed 6 days after injury, the initial upper extremity motor score was 27 and the lower extremity motor score was 0. These scores improved to 31 and 0, respectively, at 115 days after injury when he was transferred to our hospital. Total light touch scores were initially 21 for the right side and 21 for left side and improved to 28 and 29, respectively, at 115 days follow-up. Total pin prick scores were initially 23 for the right side and 24 for the left side, but improved to 27 and 27, respectively on follow-up. There was no interval change in the neurologic exam at 6 months follow-up. Electrodiagnostic studies performed 2 months after injury revealed complete myelopathy and bilateral symmetric peripheral sensorimotor polyneuropathy. Due to concurrent diabetes related peripheral polyneuropathy, sensory nerve conduction studies were done, which showed low amplitudes in bilateral ulnar, superficial peroneal, and sural nerves. However, conduction velocities of all examined nerves and bulbocavernosus reflex latencies were within normal range. Median somatosensory evoked potentials (SEP) stimulating the median nerves at the wrist bilaterally showed prolonged N20 latency in both sides. Tibial and pudendal SEPs were un-evoked with stimulations to the tibial nerves at the ankle and pudendal nerve at penile shaft.\nSPL sensations appeared 6 days after trauma onset. The patient felt the presence of an additional pair of legs that originated at the hip joints and extended medially, at equal lengths to the paralyzed legs (). The patient described the presence of both knee and ankle joints in an extended position. SPL perceptions persisted throughout the day but its intensity fluctuated with more vividness during the afternoon and evening. Body posture also altered the intensity of SPL sensations with more prominence in the supine position and waning during sitting. The patient reported that he could feel but could not see the additional limbs and was aware that this feeling was an illusion. Visualization of his legs did not diminish or alter the intensity of SPL sensations. The supernumerary legs were also associated with severe lancinating pain that measured 8 points on the numeric rating scale. The patient also complained of severe neuropathic pain of the paralyzed legs that worsened when the SPLs were in the flexed position. However, he reported that he had no voluntary control over the phantom limbs and the movements of the SPLs were unintentional. Psychiatric evaluation showed no evidence of delusion, hallucination or any other specific psychiatric abnormality, and the patient showed good insight regarding his various clinical status related to his SCI. The intensity of the SPLs was equal to his paralyzed limbs.\nCombinations of oral gabapentin, pregabalin, baclofen, tramadol, and duloxetine improved the neuropathic pain in both the real and supernumerary limbs that measured 6 points on the numeric rating scale, but failed to affect changes in the intensity of the SPLs.\nThe patient underwent visual-tactile stimulation treatment where he would first visually identify his paralyzed limbs and then gently tap his legs with a wooden stick (). Although his legs were anesthetic to both pain and light touch, tactile stimulation evoked painful tingling sensations in his paralyzed legs. Thus, he was able to receive both visual and sensory feedback and reconfirm the existence of his paralyzed legs. Wooden stick stimulation also evoked painful tingling in the SPLs but visually he was able to recognize the absence of the SPLs and thus differentiate the sense as erroneous. Visual-tactile stimulation was performed three times daily for 10-15 minutes per session with approximately one tap per second. The patient was then asked to rate the intensity of the SPLs on a 10-point numeric analog scale relative to the paralyzed real limb. The presence of the SPLs were felt at an equal intensity to the real limbs initially but improved to half the intensity of the real paralyzed limbs after 8 days of daily visual-tactile stimulation. This improvement continued over the 2 months of inpatient treatment at our hospital and the presence of the SPLs was reduced to 20% of the real paralyzed legs.\nNine months after the SCI, the patient reported persistence of the illusory limb sensations, but the sensations had improved to an extent where it no longer affected the patient's quality of life. Through a telephone interview conducted 13 months post-trauma, the patient reported a telescoping pattern of the SPL with total length shortening to levels half of the original. However, although shorter in length, the knee and ankle joints were still present and the limb continued to remain in the extended position. Although SPL sensation and subsequent total motor and sensory scores at 6 months follow-up improved, motor and sensory scores pertaining to the lower extremities as well as the ASIA A neurologically complete injury state remained unchanged. Additional lower limb SEP studies and imaging studies were not preformed due to patient refusal. However, considering the lack of change in both motor and sensory scores as well as ASIA grades, these studies did not appear to be clinically significant or essential.