TMC4 is a novel chloride channel involved in high-concentration salt taste sensation

Abstract“Salty taste” sensation is evoked when sodium and chloride ions are present together in the oral cavity. The presence of an epithelial cation channel that receives Na+ has previously been reported. However, no molecular entity involving Cl− receptors has been elucidated. We report the strong expression of transmembrane channel-like 4 (TMC4) in the circumvallate and foliate papillae projected to the glossopharyngeal nerve, mediating a high-concentration of NaCl. Electrophysiological analysis using HEK293T cells revealed that TMC4 was a voltage-dependent Cl− channel and the consequent currents were completely inhibited by NPPB, an anion channel blocker. TMC4 allowed permeation of organic anions including gluconate, but their current amplitudes at positive potentials were less than that of Cl−. Tmc4-deficient mice showed significantly weaker glossopharyngeal nerve response to high-concentration of NaCl than the wild-type littermates. These results indicated that TMC4 is a novel chloride channel that responds to high-concentration of NaCl.

Recurrent syncope from parapharyngeal cancer

The glossopharyngeal nerve is a cause of reflex bradycardia and syncope in patients with head and neck cancer. These clinical syndromes are rare but can be debilitating with variation in clinical presentation. The underlying mechanism is often incorrectly assumed to be carotid sinus hypersensitivity due to the cancerous lesion; however, examples in the literature also report the effect on the glossopharyngeal nerve or its branches by parapharyngeal lesions. We report two such cases known to a palliative care service. The symptomatic treatment options were limited due to patients’ frailty. Both patients experienced some reduction in their syncopal symptoms with anticholinergic agents.

Vascular decompression with videoendoscopy as a treatment for glossopharyngeal nerve neuralgia: clinical case and literature review

The objective is to demonstrate the effectiveness of the vascular decompression with videoendoscopy in the treatment of classical glossopharyngeal nerve neuralgia by a clinical case and to summarize the literature data on this subject. Clinical case. In February 2020, a 56-year-old patient with a clinical picture of glossopharyngeal nerve neuralgia was admitted to the Research Clinical Center of Specialized Medical Care and Medical Technologies. The pain syndrome bothered about 3 years, constantly took carbamazepine at a dose of 1200 mg per day, amitriptyline 75 mg per day, clonazepam 2 mg per day without effect. After further examination and differential diagnosis of causal neuralgia of the glossopharyngeal nerve, a neurovascular conflict appeared between the glossopharyngeal nerve, the posterior inferior cerebellar and vertebral arteries. A good postoperative clinical result was obtained. An analysis of the available scientific literature on this problem is carried out.Results. After performing vascular decompression of the root of the glossopharyngeal and vagus nerves, pain completely regressed (BNI - I, VAS - 0). 6 months after surgery, there is no pain, the patient does not receive drug therapy. In the course of the analysis of available literature, the effectiveness of vascular decompression in the treatment of patients with classical neuralgia reaches 98 %.Conclusion. Given the low incidence of glossopharyngeal neuralgia, the correct diagnosis and the choice of an appropriate treatment method determine the outcome of the disease. The performed operation in the volume of vascular decompression of the glossopharyngeal nerve root with the use of videoendoscopy allowed to completely stop the pain syndrome.

Glossopharyngeal neuralgia due to exposed glossopharyngeal nerve post tonsillectomy and transoral styloidectomy

<p>Glossopharyngeal neuralgia (GN) is a rare facial pain syndrome, characterized by paroxysm of excruciating radiating pain in the sensory distribution of the auricular and pharyngeal branches of glossopharyngeal and vagus nerves. In relation to the tonsil, the glossopharyngeal nerve passes deep to the styloid process and related muscles attaching to styloid process. The lingual branch of the glossopharyngeal nerve provides sensation to the posterior tongue and enters the tongue base by traveling through the constrictor muscles in the area of the lingulotonsillar sulcus. Post tonsillectomy fossa with exposed nerve causing intractable pain is a rare entity. We report a case of 64 year male patient, post tonsillectomy and transoral styloidectomy, with complaint of severe throat pain on left side for 2 years, radiating upwards to the ipsilateral ear, face and eye. Glossopharyngeal nerve and its branches were found exposed in the posterior and inferior aspect of tonsillar bed. Surgical resection of exposed glossopharyngeal nerve and its branches was carried out in view of failure to respond to oral carbamazepine. Patient was symptom free during 10 months of follow up visit. GN is a rare condition following tonsillectomy and styloidectomy. Radical dissection of tonsillar bed during tonsillectomy and not suturing tonsillar bed properly after styloidectomy can lead to exposure of glossopharyngeal nerve and its branches, resulting in intractable GN.</p>