Clinical study of central taste disorders and discussion of the central gustatory pathway

The aim of this work is to examine the clinical findings of patients with taste disorders due to central lesions and also to study the central gustatory pathway in humans. We conducted a retrospective review of 13 patients with central taste disorders that visited Nihon University Itabashi Hospital. An additional 25 cases with central taste disorders previously reported in the literature were assessed in the study. We examined 38 patients with taste disorders due to central lesions. The sites of the central lesions and their frequencies, the laterality of taste disorders relative to the central lesions, and prognosis of taste disorders were studied. We identified the following taste-related regions in the central nervous system: the medulla, pons, midbrain, thalamus, internal capsule, putamen, corona radiata, and cerebral cortex. As for the laterality of the taste disorders, we observed more ipsilateral cases for lesions located from the medulla to the pons. We observed ipsilateral, contralateral, and bilateral cases for lesions located above the midbrain, but bilateral cases were more frequently detected. Taste disorders of 80% of the patients improved by 24 weeks. The prognoses of central taste disorders appeared to be good. We identified eight central regions supposed to be relate to taste disorders. From the laterality of the taste disorders relative to the central lesions, it was suggested that the central gustatory pathway ascends ipsilaterally from the medulla to the pons, branches at the upper pons, and then ascends bilaterally from the midbrain to the cerebral cortex.