めまいリハビリテーションのエビデンスと神経機構

抄録

　After an acute unilateral loss of peripheral vestibular function, numerous oculomotor and postural deficits appear; these deficits can be subdivided into static and dynamic categories. Static signs are present without head movement, while dynamic signs are present only during head movement. Static signs include vigorous spontaneous nystagmus, which is mainly horizontal with a quick phase directed away from the affected ear, and postural symptoms such as falling to the affected side and difficulty standing and walking. These symptoms usually diminish or disappear entirely with no medical intervention. This recovery of normal function is due to the plasticity inherent in the central vestibular system even if the vestibular function on the affected side does not recover (vestibular compensation). In humans, vestibular compensation takes 3 to 5 days to begin and a month or more to reach a functionally useful level. Dynamic signs include depressed and asymmetrical vestibule-ocular reflex (VOR) and diminished VOR. Vestibular rehabilitation is known to be useful for the alleviation of dynamic signs after unilateral vestibular loss. The aim of vestibular rehabilitation is to promote vestibular compensation and sensory substitution by visual and somatosensory input. Moderate to strong evidence exists supporting the safety and efficacy of vestibular rehabilitation in managing unilateral peripheral vestibular dysfunction based on a number of high-quality randomized controlled trials. Moderate evidence also exists supporting the ability of vestibular rehabilitation to resolve symptoms and improve function within the mid-term. In this article, evidence for vestibular rehabilitation and the underlying mechanism of vestibular compensation, which is processed mainly by the commissural fibers connecting the vestibular nuclei on both sides of the medulla oblongata and by the vestibular cerebellum, will be introduced. The role of somatosensory input, which is processed in the spinal cerebellum, as a promoting factor for vestibular compensation will also be discussed.