Patients with phantogeusia show increased expression of T2R taste receptor genes in their tongues.

OBJECTIVES: The taste receptor gene family T2R has been implicated in the sensation of bitter taste. Phantogeusia is a spontaneous abnormal taste with no external stimulus. We analyzed the expression of T2R taste receptor genes in the tongues of patients with phantogeusia to assess their role in the pathogenesis of phantogeusia. METHODS: We obtained specimens from 43 patients with phantogeusia and 24 normal volunteers by scraping the foliate papillae and examined these specimens for the expression of 10 T2R taste receptor genes using reverse transcription-polymerase chain reaction and electrophoresis. RESULTS: The expression rate (subjects with detectable expression) of the 10 taste receptor genes in the healthy subjects ranged from 16.7% to 100%; 3 receptor genes were found in 50% or fewer of these subjects. In the patients with phantogeusia, the expression rate was increased significantly compared to that in the healthy control subjects for 3 of the 10 receptor genes examined. CONCLUSIONS: Our results show that the expression rate of some of the T2R taste receptor genes was increased significantly in patients with phantogeusia. These results suggest that increased expression of taste receptor genes is involved in the pathogenesis of phantogeusia; this finding may contribute to elucidation of the mechanism of this disorder.

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.

Patients with hypogeusia show changes in expression of T2R taste receptor genes in their tongues.

OBJECTIVES/HYPOTHESIS: Taste receptor genes associated with bitterness belong to the T2R gene family. In this study, we compared the expression of genes of the T2R family in the tongues of patients with hypogeusia to those in healthy subjects and examined the possibility that T2R genes are involved in the pathogenesis of hypogeusia. STUDY DESIGN: Prospective clinical and basic study. METHODS: The control group consisted of 24 healthy people. The patient group consisted of 40 subjects with hypogeusia who were confirmed to have abnormally elevated taste thresholds including that of bitter taste. A tissue sample was collected from each individual by scraping the mucosa on the foliate papillae of the tongue. Total RNA was extracted from each sample and reverse transcribed. The expression of 10 T2R genes (TAS2R40, -R42, -R43, and -R48, and T2R3, -R8, -R9, -R10, -R13, and -R16) was evaluated by reverse transcriptase-polymerase chain reaction. RESULTS: Comparison of the frequency of gene expression between the control group and patients with hypogeusia showed that the frequency of expression of six receptor genes were significantly reduced in the hypogeusia patients. In particular, TAS2R40 showed a significant and marked decrease in the frequency of expression regardless of the cause or severity of hypogeusia. CONCLUSIONS: Our results suggest that decreased expression of taste-associated genes may be involved in hypogeusia in humans. In addition, the evaluation of taste receptor gene expression may be useful clinically for an objective diagnosis of hypogeusia or to evaluate the severity of the disorder.

Facial nerve paralysis caused by middle ear cholesteatoma and effects of surgical intervention.

CONCLUSIONS: The clinical and surgical findings of this study indicated advanced cholesteatoma in many patients with facial paralysis. The outcome of facial paralysis was good. Poor outcomes were observed in cases with petrosal cholesteatoma and in those who underwent surgery > or = 2 months after the onset of paralysis. OBJECTIVE: To investigate clinical features of cholesteatoma associated with facial paralysis. MATERIAL AND METHODS: Sixteen patients with facial paralysis due to middle ear cholesteatoma were reviewed. After removal of the cholesteatoma lesion, a limited area of the fallopian canal, that in which facial nerve edema or redness was evident, was opened. Incision of the epineural sheath for nerve decompression was not performed. RESULTS: Initial paralysis was incomplete in 11 patients (69%). The onset of paralysis was sudden in 12 patients (75%). Labyrinthine fistulae (n = 9; 56%) and bone destruction in the cranial fossa (n = 10; 63%) were frequently observed. Six patients (38%) were totally deaf due to labyrinthitis. The outcome of facial paralysis was good in 13 patients (81%). Patients who underwent surgery > or = 2 months after the onset of paralysis frequently had a poor outcome. Paralysis was not improved in two cases with petrosal cholesteatoma.

Laterality of human primary gustatory cortex studied by MEG.

We examined the laterality of the human gustatory neural pathway by measuring gustatory-evoked magnetic fields (GEMfs) and demonstrating the activation of the human primary gustatory cortex (PGC). In patients whose chorda tympani nerve had been severed unilaterally on the right side, we stimulated the normal side (i.e., left side) of the chorda tympani nerve with NaCl solution using a device developed for measuring GEMfs. We used the whole-head magnetoencephalography system for recording GEMfs and analyzed the frequency and latency of PGC activation in each hemisphere. "The transitional cortex between the insula and the parietal operculum" was identified as PGC with the base of the central sulcus in this experiment. Significant difference was found in frequencies among bilateral, only-ipsilateral, and only-contralateral responses by the Friedman test (P < 0.05), and more frequent bilateral responses were observed than only-ipsilateral (P < 0.05) or only-contralateral responses (P < 0.01) by the multiple comparison tests. In the bilateral responses, the averaged activation latencies of the transitional cortex between the insula and the parietal operculum were not significantly different in both hemispheres. These results suggest that unilateral gustatory stimulation will activate the transitional cortex between the insula and the parietal operculum bilaterally in humans.