Vestibular caloric stimulation evokes phantom limb illusions in patients with paraplegia

Abstract

Study design: Prospective study. Objectives: To determine the mechanisms of body illusions in paraplegia patients as compared with the amputee phantom phenomena. Methods: A vestibular caloric stimulation was performed in 10 consecutive patients with complete section of the spinal cord. Perception of body, before and after stimulation, was classed as illusion of a normal body (lower limbs with normal morphological, postural and kinetic characteristics perceived as before spinal injury), normal phantom (overly vivid perception of all or part of the lower limbs), deformed phantom (perception of all or part of the limbs below the injury level as abnormal in shape, posture, movement or even number), or painful phantom. Results: After vestibular caloric stimulation, nine out of 10 patients stated their perception of body segments below the injury level had changed to normal phantoms or to deformed phantoms (morphological, pastural or kinetic changes). Among the four patients who initially had painful limbs, two stated the stimulation greatly relieved their pain. Conclusion: The normal or deformed phantom evoked by vestibular stimulation would result from use of identity data or instantaneous data as is observed in amputees. Cerebral remapping following deafferentatian could be the origin of the deformed phantoms. Illusions corresponding to phenomena perceived at the time of the accident corresponding to autobiographical engrammes do not appear to be evoked by vestibular stimulation, as is also the case in amputees.