[Transient improvement in motor function and hemineglect by vestibular stimulation in a patient with right middle...

A 62-year-old Japanese man presented left hemiparesis and left visuospatial hemineglect following a right hemispheric stroke. His CTs and MRIs of the brain revealed a large embolic infarction of the middle cerebral artery territory. A month after the cerebrovascular event, his weakness of the left lower limb almost recovered fully. However, his upper limb motor function was still disabled; in particular, his ability of finger flexion in the left hand was almost lost. Then, vestibular stimulation using either a cold caloric stimulation to the left ear or a warm caloric stimulation to the right ear was performed, and the effect on the hemineglect symptoms were assessed by a line bisection task. After vestibular stimulation, not only his hemineglect symptoms but also his motor functions of left upper limb transiently improved; he became able to make a fist. The improvement of his hemineglect symptoms was obtained by vestibular stimulation using either a cold or a warm caloric stimulation. However, the effect on the motor function was obtained only by the cold caloric stimulation applied to the left ear. Based on the effect of the vestibular stimulation, we postulates that the impairment of the motor function in the present patient is not only a paresis caused by the pyramidal tract lesion but also symptoms related to the hemineglect syndrome.