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

Abstract

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.

Functional MRI cortical activations from unilateral tactile-taste stimulations of the tongue

“…According to recent data of Onoda et al [39], based on taste disturbances from unilateral central nervous lesions from the medulla to the cortex in humans, the taste pathways ascend ipsilaterally from the medulla to the pons and then bilaterally from the upper pons to the thalamus and the cortex. Bilateral gustatory losses following unilateral CNS lesions suggest that the branching of the ascending taste pathways into crossed and uncrossed components can occur at different levels, from the mesencephalon [20,62], to the pons [39] or the thalamus [33,62], but, contrary to rodents, in primates the ascending taste pathway from the nucleus of the solitary tract does not synapse in the parabrachial nucleus of the pons, but bypasses it to terminate in the thalamus [46,48,55]. Bilateral cerebral activation from unilateral taste stimulation of the tongue has been verified using gustatory magnetic field recording by Murayama et al [32] and confirmed with electrogustatory lingual stimulation [31,66].…”

“…The somatosensory and motor representations of the tongue in the inferior perirolandic cortex and in the Rolandic operculum have been previously implicated in taste and flavor processing by the clinical and experimental literature [e.g. 16,39,46,54,55] and these cortical areas are assumed to take part in the natural multisensory processing of the intraoral content during feeding [48,54,55,64]. To the extent that our stimulations involved a constant tactile and thermal component from the pad, regardless of whether the added component was salt or water, we could compare the responses to the two latter components.…”

“…There is a consensus that both sides of the tongue in both the somatosensory and the gustatory modalities are represented in the cortex of both hemispheres [1,2,10,22,[38][39][40]59], most likely with a predominance of contralateral over ipsilateral representations in the somatosensory modality and an opposite predominance of ipsilateral over contralateral representation in the taste modality [3,10,22]. There are also reports of a comparatively greater reactivity of the right hemisphere to both somatosensory [50] and gustatory lingual stimuli [52].…”

Greater Insula White Matter Fiber Connectivity in Women Recovered from Anorexia Nervosa

“…For instance, the corona radiata, a collection of fiber bundles that extend from the internal capsule to cerebral cortex (Schmahmann et al, 2008) basal ganglia, and spinal cord, has been associated with altered taste perception when lesioned (Onoda et al, 2012), and lesions in the anterior corpus callosum were associated with altered taste signal transmission (Fabri et al, 2011). The external capsule lies between putamen medially and claustrum laterally, connecting ventral and medial prefrontal cortices with limbic regions via fibers from the uncinate fasciculus and inferior fronto-occipital fasciculus (Schmahmann et al, 2008), and white matter FA in these pathways predicted in the past brain reward activation (Olson et al, 2009).…”

Cortical and Subcortical Substrates of Cranial Nerve Function

“…26 However, clinical data from other studies have shown ipsilateral, contralateral, and bilateral ageusia after lesions of the primary gustatory cortex, suggesting that branching at the level of pons is probably variable and may not be equal. The variability in clinical manifestations has also spurred research on hemispheric lateralization.…”