前庭・平衡機能のイメージング研究の現状

抄録

The control of extraocular and neck movements relies on the information from the vestibular organs. The brainstem and cerebellum are in charge of these processes. Further, the higher-order processing of vestibular information is mediated by the posterolateral part of the thalamus (“vestibular thalamus”), which in turn projects to multiple cortical areas including the parieto-insular vestibular cortex and thus constitutes the “thalamo-cortical vestibular system”. Recent advances in neuroimaging techniques have enabled researchers to visualize brain activity changes in the thalamo-cortical vestibular system in response to unilateral vestibular perturbation by means of electric or caloric stimulation. Clinically, neuroimging studies on peripheral vestibular disorders have shown abnormal responses of the thalamo-cortical vestibular system to vestibular perturbation. Studies have also revealed anatomo-functional reorganization of non-vestibular cortical areas (such as visual or somatosensory cortices) in peripheral vestibular disorders. Moreover, such reorganization may be correlated with functional recovery after peripheral vestibular disorders. Studies on cerebrovascular disorders involving the vestibular thalamus support the importance of this area for controlling posture. These imaging studies have begun to cast light on the otherwise unknown pathophysiology and compensatory mechanisms of vestibular disorders, although many issues still remain to be answered.