Clinical applications and mechanism of intravenous taste tests

Posttonsillectomy Taste Distortion: A Significant Complication

OBJECTIVE/HYPOTHESIS

Tonsillectomy is among the most commonly performed procedures. As with any surgery, head and neck surgeons must be aware of possible complications and their potential affects. At our smell and taste center, we have been referred several patients in a 6-month period with the complaint of taste distortion after tonsillectomy. We report in this article a patient that complains of taste distortion after a right tonsillectomy for unilateral tonsillar hypertrophy.

STUDY DESIGN

A prospective study documenting taste distortion after tonsillectomy using clinical, subjective, and objective evaluation.

METHODS

The clinical course of a patient with taste distortion after a tonsillectomy is described. The gustatory function was investigated by conducting electrogustometry and spatial taste testing. Threshold measurements were determined at three left- and three right-side tongue regions: 1) the tongue tip region (innervated by the chorda tympani branch of the facial nerve), 2) the lateral margin of the tongue (anterior to the foliate papillae), and 3) the posterior tongue region (innervated by the lingual branch of the glossopharyngeal nerve).

RESULTS

After a complete clinical evaluation and taste testing, it was found that the patient suffered an injury to the right lingual branch of the glossopharyngeal nerve. The close anatomic relationship between the palatine tonsil and lingual branch of the glossopharyngeal nerve makes the nerve vulnerable during tonsillectomy. This injury has caused the patient to suffer ageusia to the right posterior one third of the tongue, compensated by a contralateral phantogeusia (phantom taste) with clinical dysgeusia. The phantogeusia was abolished by application of anesthetic to the area where the phantom was perceived. We propose that the phantogeusia is the result of release-of-inhibition in the contralateral glossopharyngeal nerve.

CONCLUSION

Taste distortion (including, phantogeusia and dysgeusia) after tonsillectomy is rarely reported as a complication but has a significant impact on quality of life. This article examines the taste distortion presence as a complication after tonsillectomy to make head and neck surgeons aware of this serious complication and the pathophysiology of taste distortion.

Taste disturbance in two patients after dental anesthesia by inferior alveolar nerve block

We report two cases of temporary taste disturbance after inferior alveolar nerve block. The first patient to present with this rare complication of anesthesia for dental surgery was a 41-year-old woman. She lost the sense of taste on the left side of her tongue after local anesthesia for treatment of a left mandibular molar and first visited our outpatient clinic complaining of taste disorder 3 months later. Electrogustometry (EGM) and filter paper disk (FPD) testing revealed a taste disturbance in the innervation area of the left chorda tympani nerve and atrophy of the fungiform papillae on the left side of the tongue was observed. Eleven months after the dental treatment, the fungiform papillae and the results of EGM were normal. The second patient, a 22-year-old woman, received local anesthetic for extraction of a right mandibular molar and subsequently developed loss of taste on the right side of the tongue. When she visited our outpatient clinic 3 months later, atrophy of the fungiform papillae on the right side was observed. Her gustatory sense began to improve 4 months after the dental surgery and was normal at 13 months. From these findings we conclude that taste disturbance on the same side as the inferior alveolar nerve block in each case was due to direct injury to the chorda tympani and lingual nerves during administration of the local anesthetic. The results of EGM and FPD testing were diagnostic: atrophy of the fungiform papillae on the same side and disappearance of taste on the same side in the intravenous taste test provided complementary diagnostic information. The outcome was satisfactory in both cases.

Effect of tricyclic antidepressants on taste responses in humans and gerbils

One of the side effects of antidepressant pharmacotherapy reported clinically is impairment of the sense of taste. In this study, the taste effects of four tricyclic antidepressant compounds (clomipramine HCl, desipramine HCl, doxepin HCl, and imipramine HCl) were evaluated experimentally by topical application of the drugs to the tongue. Taste detection threshold concentrations for all four medications ranged from 0.1 mM to 0.2 mM in young persons but were elevated by as much as 7.71 times that in elderly individuals who were taking no concurrent medications. Each compound had a predominantly bitter taste with other qualities including metallic, sour, and sharp-pungent. In addition, each tricyclic antidepressant at concentrations from 1 mM to 5 mM blocked responses to a wide range of taste stimuli in both humans and gerbils. The differential suppression of other tastes by tricyclic antidepressants at the level of the taste receptors may contribute to the clinical reports of dysgeusia and hypogeusia.

Identification and characterization of dehydrocholic acid reductase system in the cytosol of human red blood cells

We conducted in vivo and in vitro studies of the reductive metabolism of the cholagogue, dehydrocholic acid (DHCA). Immediately after the intravenous administration of 1 g of DHCA in normal subjects (n = 6), the concentration of the reductive metabolite, 3 alpha-hydroxy-7,12-dioxo-cholanoic acid (unconjugated form), increased sharply in the systemic circulation, rising to 95.8 microM 10 min after administration. The results of in vitro experiments with DHCA and whole blood showed that 3 alpha-hydroxy-7,12-dioxocholanoic acid were produced from DHCA. In vitro experiments using DHCA and the red blood cell fraction, and DHCA and the red blood cell cytoplasmic fraction gave similar results to those described above with whole blood. However, a reductive metabolite was not formed by the incubation of DHCA and the red blood cell membrane fraction. These findings indicated that, contrary to the conventional theory that intravenously administered DHCA is subjected to reductive metabolism only in the liver, reduction also occurs in the systemic circulation, and the mechanism for this reductive metabolism is present in the cytoplasmic fraction of red blood cells. Further investigation to characterize this reductive metabolic system revealed an optimum temperature of 37 degrees C, an optimum pH of 7.4, a Km value of 2.0 x 10(-3) M, and inactivation by heat treatment (70 degrees C for 2 min).