Pure Sensory Lacunar Infarction in the Thalamus Presented as Bilateral Hypogeusia: A Case Report.

PURPOSE: While the gustatory pathway of animals has been well-researched, that of humans is still a mystery. Several theories have been established, and some earlier reports hypothesized the relation to laterality. However, some cases could not be fully explained by the laterality theory (1). To clarify the gustatory pathway, we reported a case with bilateral hypogeusia after right thalamic infarction. CASE: This 55-year-old, right-handed man suffered from sudden decreased sensitivity of taste. He was unable to differentiate sweetness and saltiness at bilateral anterior parts of tongue. Additionally, there was numbness at the upper palate and the lips. Neurological examination revealed decreased taste sense at both sides of his anterior tongue and decreased pin-prick sensation of the left part of his lips. Brain magnetic resonance imaging (MRI) revealed acute ischemic stroke at the right ventral posteromedial nucleus (VPM). Thus, single antiplatelet therapy was administered. Two weeks later, the symptoms improved significantly and completely recovered without sequelae. CONCLUSION: The exact gustatory pathway in humans remains uncertain nowadays. First, there were few reports about dysgeusia, which might be related to clinical neglect of taste deficits. Second, our knowledge of the human gustatory pathway depends solely on sporadic cases of taste-involved brain lesions. We reported a case of bilateral hypogeusia after right thalamic infarction. This finding indicates that, although there might be laterality of gustatory fibers to the left hemisphere, anatomical variations may exist in the human gustatory system. More research is needed to elucidate the understanding of the gustatory pathway in humans.

Photobiomodulation therapy for treatment olfactory and taste dysfunction COVID-19-related: A case report.

It is postulated that the inflammatory process resulting from SARS-CoV-2 infection is the main cause of smell and taste dysfunctions in patients. In view of this, photobiomodulation, due to its anti-inflammatory and antioxidant effects, may be a promising therapeutic modality to treat these disorders. In the present case report, we observed clinical improvement in the symptoms of anosmia and ageusia related to COVID-19 after treatment with photobiomodulation. Due to the inflammatory nature of COVID-19 and the anti-inflammatory effects, photobiomodulation antioxidants already proven in the literature make it a promising therapeutic modality, especially sequela COVID-related, including olfactory (anosmia) and taste (ageusia) dysfunction. In the present case report, the patient's olfactory and gustatory functions were re-established after 10 treatment sessions with photobiomodulation.

Autonomic Brain Centers and Pathophysiology of COVID-19.

Accumulating data have now shown strong evidence that COVID-19 infection leads to the occurrence of neurological signs with different injury severity. Anosmia and agueusia are now well documented and included in the criteria list for diagnosis, and specialists have stressed that doctors screen COVID-19 patients for these two signs. The eventual brainstem dysregulation, due to the invasion of SARS CoV-2, as a cause of respiratory problems linked to COVID-19, has also been extensively discussed. All these findings lead to an implication of the central nervous system in the pathophysiology of COVID-19. Here we provide additional elements that could explain other described signs like appetite loss, vomiting, and nausea. For this, we investigated the role of brainstem structures located in the medulla oblongata involved in food intake and vomiting control. We also discussed the possible pathways the virus uses to reach the brainstem, i.e., neurotropic and hematogenous (with its two variants) routes.

[Gustatory loss: causes, consequences and treatment]. / Smaakverlies: oorzaken, gevolgen en behandeling.

The loss of taste is a common symptom and may have serious somatic and psychological consequences. Little attention is paid to the condition in doctors' practices, however, and the topic is also hardly mentioned in scientific publications. It is important to distinguish between isolated gustatory loss and gustatory loss in combination with other neurological symptoms. Isolated gustatory loss can be the result of a laesion of the chorda tympani of the facial nerve caused by otitis media or damage to the taste buds, for example. Treatment is aimed at removing the cause, e.g. medication or chronic otitis media, but the treatment options are often limited. Zinc supplementation in patients with zinc deficiency has not been proven to be effective. Gustatory loss in combination with other neurological symptoms is caused by damage to one or more cranial nerves, to the brain stem or cerebral cortex, and is an indication for referral to a neurologist. Early detection of the loss of taste, good patient counselling, diagnostics and possible treatment may limit the negative consequences of this condition.

[Bilateral ageusia caused by right thalamic infarction].

A 58-year-old man noticed left hemiparesis at 01:00 pm on a particular day in March 2006. Because his symptoms developed gradually, he was referred to the emergency room of our hospital at 05:00 pm and was admitted with the diagnosis of cerebral infarction. While he presented slight left hemiparesis involving the face, impairment of sensation was not apparent. Diffusion-weighted magnetic resonance imaging of the head showed a high-intensity area in the ventromedial area in the right thalamus. The patient was treated with anticoagulant and edaravone, and his symptoms resolved on hospital day 3. When he began eating, he noticed that he was unable to distinguish tastes. On day 5, we performed taste examination using a commercial kit. The taste sensation on both sides of his tongue was severely affected, while the touch sensations in the mouth and olfaction were preserved. His symptoms improved spontaneously and resolved on hospital day 15. This is the second case report of bilateral ageusia caused by right thalamic infarction. Our study indicates the importance of the right thalamus in taste sensation involving both sides of the tongue.

The accuracy of the Zinc Taste Test method.

BACKGROUND: Diminished taste acuity (hypogeusia) has been linked to zinc deficiency in humans and animals. This phenomenon has been exploited in the Zinc Taste Test (ZTT), a taste acuity test commonly employed by Australian naturopaths. However, its validity has not yet been firmly established. METHODS: A systematic search of several key databases was conducted. Only studies in which there were full reports of clinical trials comparing the ZTT to at least one other zinc test within the same sample population were included. RESULTS: Three (3) studies matched the criteria for inclusion. Study I compared the ZTT with sweat zinc in patients with food intolerance, reporting moderate correlation. Study II recruited pregnant women using the ZTT and serum zinc to assess zinc status, with above 70% congruence between the two tests at the start of the trial and 100% congruence at the end. Study III also recruited pregnant women at three stages during gestation, assessing ZTT and leukocyte zinc initially, later adding dietary zinc intake and at delivery cord blood zinc. No significant correlation was found between the results of these different methods; however, statistically significant differences in the ZTT responders (tasters and nontasters) were found for pregnancy outcomes. DISCUSSION: The methodology of the three studies is critically discussed. Although depletion of zinc leads to decreased taste acuity, it does not explain all cases of hypogeusia. Various other influences on taste perception are discussed in relation to the validity of the ZTT. Stringent exclusion criteria are therefore mandatory to increase specificity. Large variations from the original test design have been identified. The laboratory assays of zinc in these studies are also lacking sensitivity to accurately assess zinc status. CONCLUSIONS: To date, there are no tests that are both sensitive and specific that accurately assess marginal zinc status in humans. The ZTT, albeit widely used, does not fill this void, and further research is needed.

Evaluation of taste acuity by the filter-paper disc in Japanese young women: the relationship with micronutrients status.

The aim of the present study is to investigate the taste acuity in Japanese young women in relation to their micronutrient status. Thirty-eight healthy young women (mean age; 21.3, range; 19-27 years) were enrolled. Gustatory thresholds were estimated for four basic tastes: sweet (sucrose), salty (sodium chloride), sour (tartaric acid), and bitter (quinine hydrochloride) by a filter-paper disk method. Various concentrations at each taste were serially scored from disc number 1 (lowest) to number 5 (highest). The lowest concentration at which the quality of the taste was correctly identified was defined as the recognition threshold. The mean of three measurements for each test on three different days was calculated. We divided our participants into normal taste and hypogeusia groups based on the mean threshold disc numbers, <=3.5 and >3.5, respectively, according to previous literature using the same method. We also measured serum concentrations and dietary intakes of micronutrients including zinc, iron, copper, and selenium. The numbers of participants belonging to the hypogeusia group were 24 (63.2%) for sweet, 19 (50.0%) for sour, 17 (44.7%) for bitter, and 16 (42.1%) for salty taste. Although the hypogeusia group exhibited significantly lower serum iron concentrations, except for the salty taste, the other three micronutrients concentrations did not show any association with the four taste acuities. Dietary micronutrient intake did not show any association with the four taste acuities. This study indicates that in addition to zinc status, iron status should be considered in the study of taste acuity.

Recurrent hypogeusia in a patient with chronic inflammatory demyelinating polyradiculoneuropathy (CIDP).

Hypogeusia, a condition with diminished sense of taste, is caused by several conditions, including zinc deficiency and as a side-effect of drugs, but is not common in neurological disorders. A 55-year-old Japanese man with a 30-year history of chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) presented with hypogeusia during hospitalization for a recurrence of CIDP. The hypogeusia improved after treatment with high-dose intravenous methylprednisolone (HIMP). Two years later, hypogeusia developed again. A complete taste deficit was revealed by a filter paper test. Brain MRI showed enhancement of the bilateral facial nerve ganglia. Hypogeusia was partially ameliorated after extensive immunosuppressive therapy with repeated HIMP and plasma exchange. Improvement was more prominent in the area innervated by the chorda tympani nerve than that innervated by the glossopharyngeal nerve. To our knowledge, this is the first report of recurrent hypogeusia, which might be caused by cranial nerve injury associated with CIDP.

Bilateral ageusia caused by a unilateral midbrain and thalamic infarction.

BACKGROUND: Based upon scarce clinical data in humans and experimental findings in animal studies, it has been postulated that the ascending gustatory projection from the nucleus tractus solitarii courses ipsilaterally through the pons and midbrain to the ipsilateral ventral posteromedial nucleus. Thus, it has been assumed that ischemic lesions affecting the secondary projection gustatory fibers would cause ipsilateral taste disorders. DESCRIPTION OF CASE: We report a case of bilateral ageusia following an acute right midbrain and thalamic infarction affecting the ipsilateral central trigeminal tract and ventral posteromedial nucleus in a right-handed man. CONCLUSION: The present case indicates that, in contrast to animal data, some secondary projection gustatory fibers may cross in humans and consequently unilateral right-sided posterior circulation ischemic lesions can cause bilateral gustatory deficits.

[Gustatory disorders during multiple sclerosis relapse]. / Les troubles du goût au cours de poussées de sclérose en plaques.

Gustatory dysfunction is a known but uncommon element in the course of multiple sclerosis. Gustatory dysfunction has been described during the chronic progressive phase and during the relapse phase. We report five patients with clinically definite multiple sclerosis who developed transient gustatory disorders during the relapse phase of their disease. Agueusia occurred as one of the first symptoms in three patients, revealing the disease. Symptoms generally improved with remission or corticosteroid administration. These disorders are due to demyelinating lesions of the gustatory pathways in the thalamus or brainstem. MRI studies were not performed during the relapse phase and no clinical neuroimaging correlations could be established. Agueusia may be accompanied by olfactory dysfunction which is due to plaque demyelinization of the olfactory pathways, particularly in the temporal and inferior frontal lobes. Taste anomalies can also be observed in other diseases, including systemic diseases such as sarcoidosis or Sjogrën's syndrome. Drug-induced gustatory disorders are also reported.

Chorda tympani nerve injury following inferior alveolar injection: a review of two cases.

Permanent nerve injury following the injection of local anesthetic during dental procedures is rare. Two cases of chorda tympani nerve injury shown by ageusia are presented.

Ageusia associated with thalamic plaque in multiple sclerosis.

Ageusia and the cheirooral syndrome developed in a patient with a relapse of multiple sclerosis. Magnetic resonance imaging revealed an area of demyelination in the thalamus. This lesion presumably affected the most medial part of the ventralis posterior nucleus, where taste information is located. Given the proximity of the taste area and somatosensory representation of the hand and oral cavity in the ventralis posterior nucleus, we propose that a diagnosis of thalamic lesion should be considered when ageusia occurs with the cheirooral syndrome.