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Extracranial internal carotid artery aneurysm presenting as symptomatic hypoglossal and glossopharyngeal nerve paralysis.

Aneurysms of the extracranial portion of the internal carotid artery are rare, particularly in young patients. They usually develop following trauma, or secondary to infection involving the parapharyngeal space that extends to the vessel wall. This is a case of an internal carotid artery aneurysm presenting acutely following chiropractic neck manipulation with hypoglossal and glossopharyngeal nerve palsy. The imaging findings and subsequent operative management are described.

Aneurysm↗

Amiloride blocks salt taste transduction of the glossopharyngeal nerve in metamorphosed salamanders.

Studies in the last two decades have shown that amiloride-sensitive Na(+) channels play a role in NaCl transduction in rat taste receptors. However, this role is not readily generalized for salt taste transduction in vertebrates, because functional expression of these channels varies across species and also in development in a species. Glossopharyngeal nerve responses to sodium and potassium salts were recorded in larval and metamorphosed salamanders and compared before and after the oral floor was exposed to amiloride, a blocker of Na(+) channels known to be responsible for epithelial ion transport. Pre-exposure to amiloride (100 microM) did not affect salt taste responses in both axolotls (Ambystoma mexicanum) and larval Ezo salamanders (Hynobius retardatus). In contrast, in metamorphosed Ezo salamanders the nerve responses to NaCl were significantly reduced by amiloride. In amphibians amiloride-sensitive components in salt taste transduction seem to develop during metamorphosis.

Ambystoma↗

Taste responses to electrolytes in the frog glossopharyngeal nerve: initial process of taste reception.

In taste reception, it has been proposed that changes in surface potential on the apical membrane of taste cells bring about activation of taste cells during chemical stimulation. To ascertain whether changes in the surface potential are involved in taste reception of electrolytes, unitary discharges were recorded from single water fibers of the frog glossopharyngeal nerve with a suction electrode. The surface potential is a function of both the charge density of the membrane surface and the ionic strength of the medium. Low concentrations of CaCl2 (less than 1 mM) were very effective stimuli. However, 0.01-1 mM LaCl3 and HCl (pH 3.0-4.5), which alter the surface potential in the positive direction, had no excitatory effect. Transition metal cations, such as Mn2+, Co2 and Ni2+, had an excitatory effect, but the responses to these cations appeared at relatively high concentrations (greater than 5 mM), in spite of the high affinity of the receptor membrane for these cations. The results suggest that the surface charge of the apical membrane is not associated with the excitation caused by electrolytes. MgCl2 (greater than 5 mM) and NaCl (greater than 100 mM) were also effective stimuli, whereas choline Cl (100-1000 mM) had no excitatory effect. An increase in the ionic strength was achieved by the addition of 100-300 mM choline Cl to stimulating solutions of MgCl2 or NaCl. The responses to Mg2+ and Na+ were not affected by the increase in the ionic strength. The results obtained here indicate that changes in the surface potential on the surface of the apical membrane are not involved in taste reception of electrolytes. Alteration of the surface potential of the membrane in the positive direction would bring about a reduction in the local concentration of cations in the vicinity of the membrane. Hence, the presence of divalent cations in the medium may affect the response to monovalent cations. However, addition of 100 mM MgCl2 to the stimulating solution of NaCl did not affect the concentration-response curve for NaCl. This result suggests that the surface charge density of the apical membrane is very low and hence the magnitude of the surface potential is very small. The results also suggest that Mg2+ and Na+ activate the taste cells by two separate, non-interacting processes. The present study suggests that, in the initial process of taste reception, only the binding of each separate cation to its appropriate receptor site (specific receptor site) leads to activation of the receptor.

Animals↗

Differential taste responses of mouse chorda tympani and glossopharyngeal nerves to sugars and amino acids.

The differential taste responses of the chorda tympani (CT) and the glossopharyngeal (GL) nerves in preweanling and adult mice were examined by comparing magnitudes of responses to six sugars and 10 amino acids. The results indicate that for sugars the responses of the CT nerve are greater than those of the GL nerve while for umami and essential amino acids the responses of the GL nerve are greater than those of the CT nerve. Such differential taste responses of the CT and GL nerves does not prominently change during development.

Aging↗

Effects of glossopharyngeal nerve section on the expression of neurotrophins and their receptors in lingual taste buds of adult mice.

The expression of neurotrophins and neurotrophin receptors is essential for the proper establishment and function of many sensory systems. To determine which neurotrophins and neurotrophin receptors are expressed in taste buds, and in taste buds of mice following denervation, antibodies directed against the neurotrophins and their receptors were applied to adult mouse gustatory tissue. Immunohistochemistry reveals that nerve growth factor (NGF)-like immunoreactive (LIR), tyrosine kinase (trk) A-LIR, trkB-LIR, and p75-LIR elongated, differentiated taste cells are present within all lingual taste buds, whereas neither neurotrophin (NT)-3- nor trkC-LIR was detected in taste cells. Double-label immunohistochemistry using markers of different taste cell types in brain-derived neurotrophic factor (BDNF)LacZ mice reveals that BDNF (beta-gal) and trkB colocalize, mainly in type III taste cells. NGF, pro-NGF, and trkA coexist in type II taste cells, i.e., those expressing phospholipase Cbeta2 (PLCbeta2). p75-LIR also is present in both BDNF and NGF taste cell populations. To determine the neural dependence of neurotrophin expression in adult taste buds, glossopharyngeal nerves were cut unilaterally. During the period of denervation (10 days to 3 weeks), taste buds largely disappear, and few neurotrophin-expressing cells are present. Three weeks after nerve transection, nerve fascicles on the operated side of the tongue exhibit BDNF-LIR, NGF-LIR, and ubiquitin carboxyl terminal hydrolase (PGP 9.5)-LIR. However, BDNF-LIR staining intensity but not NGF-LIR or PGP 9.5-LIR is increased in nerve fascicles on the operated compared with the unoperated side. Five weeks following nerve transection, NT and NT receptor expression resumes and appears normal in taste buds and nerves. These results indicate that neurotrophin expression in taste buds is dependent on gustatory innervation, but expression in nerves is not dependent on contact with taste buds.

Animals↗

Eagle syndrome: entrapment of the glossopharyngeal nerve? Case report and review of the literature.

Eagle syndrome is characterized by unilateral pain in the oropharynx, the side of the face, and the earlobe. It is caused by an elongated styloid process; resection of the elongated process eliminates the pain. Although quite rare, this syndrome is well represented in the oral, ear, nose, and throat surgery literature. In the neurosurgical literature, on the other hand, there is little if any mention of Eagle syndrome. The author presents a case of a woman who suffered from severe pain in the throat, the side of the face, and the ear. After the diagnosis of Eagle syndrome was made based on radiographic findings and was confirmed using a local anesthetic block, resection of the elongated styloid process was performed, resulting in complete and lasting pain relief. Eagle syndrome, which is caused by compression of the glossopharyngeal nerve as it passes the elongated styloid process, may be classified as an entrapment syndrome deserving of neurosurgical attention. The goal of this report is to familiarize neurosurgeons with Eagle syndrome and its diagnostic work up and treatment.

Adult↗

Glossopharyngeal nerve schwannoma: report of a case operated on by the far-lateral transcondylar approach.

Complete resection with conservation of cranial nerves is the primary goal of contemporary surgery for lower cranial nerve tumors. We describe the case of a patient with a schwannoma of the left glossopharyngeal nerve, operated on in our Neurosurgical Unit. The far lateral approach combined with laminectomy of the posterior arch of C1 was done in two steps. The procedure allowed total tumor resection and was found to be better than classic unilateral suboccipital or combined supra- and infratentorial approaches. The advantages and disadvantages of the far lateral transcondylar approach, compared to the other more common approaches, are discussed.

Case Reports↗

Sense of taste in a new world monkey, the common marmoset: recordings from the chorda tympani and glossopharyngeal nerves.

Whole nerve, as well as single fiber, responses in the chorda tympani proper (CT) and glossopharyngeal (NG) nerves of common marmosets were recorded during taste stimulation with three salts, four acids, six bitter compounds and more than 30 sweeteners. We recorded responses of 49 CT and 41 NG taste fibers. The hierarchical cluster analysis distinguished three major clusters in both CT and NG: S, Q, and H. The S(CT) fibers, 38% of all CT fibers, responded only to sweeteners. The S(CT) fibers did not respond during stimulation with salts, acids, and bitter compounds but exhibited OFF responses after citric and ascorbic acids, quinine hydrochloride (QHCl), and salts (in 80% of S(CT) fibers). S(NG) fibers, 50% of all NG fibers, also responded to sweeteners but not to stimuli of other taste qualities (except for citric acid, which stimulated 70% of the S(NG) fibers). Some sweeteners, including natural (the sweet proteins brazzein, monellin) and artificial [cyclamate, neohesperidin dihydrochalcone (NHDHC), N-3,5-dichlorophenyl-N'-(S)-alpha-methylbenzylguanidineacetate (DMGA), N-4-cyanophenylcarbamoyl-(R,S)-3-amino-3-(3,4-methylenedioxyphenyl) propionic acid (CAMPA)] did not elicit responses in the S fibers. In general, the response profiles of the S(CT) and S(NG) clusters were very similar, the correlation coefficient between the responses to sweeteners in these clusters was 0.94. Both the Q(CT) and the Q(NG) fibers (40 and 46% of all fibers) were predominantly responsive to bitter compounds, although their responses to the same set of bitter compounds were quite different. Sweeteners with sweet/bitter taste for humans also stimulated the Q clusters. The H clusters (22 and 3% of all fibers) were predominantly responsive to acids and did not respond to stimuli of other taste qualities. However, bitter stimuli, mainly QHCl, inhibited activity in 70% of H(CT) fibers. Among a total of 90 fibers from both nerves there was only 1 NaCl-best fiber in CT. We found, however, that 35% of the CT fibers reacted to salts with inhibition of activity during stimulation, followed by an OFF response. This OFF response was diminished or eliminated by amiloride. These characteristics indicate that amiloride-sensitive sodium channels are involved in salt transduction in marmosets. In the two NG fibers responding to NaCl, we recorded neither suppression by amiloride nor OFF responses. Comparison of marmoset data with those of other nonhuman primates studied, rhesus and chimpanzee, demonstrates phylogenetic trends in the organization of taste system. This can help to uncover pathways of primate evolution.

Animals↗

Traumatic dissection of the internal maxillary artery associated with isolated glossopharyngeal nerve palsy: case report.

OBJECTIVE AND IMPORTANCE: Spontaneous or traumatic dissection of the internal carotid artery with resultant lower cranial nerve palsies is well documented. However, dissection of the external carotid artery with lower cranial palsies has not been reported previously. CLINICAL PRESENTATION: A 42-year-old man experienced an epidural hematoma as the result of a fall and underwent a craniotomy and hematoma removal. Subsequently, he developed dysgeusia and difficulty in swallowing. Brain magnetic resonance imaging showed a dilated linear structure, with isosignal intensity on T1-weighted images and hyperintense signal intensity on T2-weighted images. Strong enhancement was seen on postcontrast T1-weighted images, indicating a dissected internal maxillary artery. This was confirmed on selective angiography of the left common carotid artery. INTERVENTION: Guglielmi detachable coils were introduced into the false lumen of the dissected artery. Subsequently, 0.5 ml of glue mixed with Lipiodol (Lafayette Pharmacal, Lafayette, IN) was packed into the remnant of the false lumen. Repeat angiograms demonstrated complete occlusion of the dissected vessel. The patient's postoperative course was uneventful, and the neurological deficits gradually improved. CONCLUSION: We describe the first reported case of internal maxillary artery dissection and pseudoaneurysm presenting with isolated glossopharyngeal nerve palsy. The association between cranial nerve palsy and dissection of the external carotid artery branch may be the result of a compressive mechanism, as suggested by its anatomic relationships, the characteristics of the dissection, and the good prognosis. Endovascular embolization of the external carotid artery dissection and pseudoaneurysm is suggested as an effective therapeutic method for improving or alleviating neurological deficits produced by mass effect.

Accidental Falls↗

Neural responses of the glossopharyngeal nerve to several bitter stimuli in mice.

The neural reaction to bitter stimuli was tested in the glossopharyngeal (GL) and chorda tympani (CT) nerves of mice. Relative responses to several bitter stimuli (quinine, iso-alpha-acids, L-tryptophan and L-phenylalanine) were greater in the GL nerve than in the CT nerve. Strain variability for taste sensitivity to bitter stimuli existed between two strains (C57BL and BALB/C). The GL nerve response to caffeine, iso-alpha-acids and L-phenylalanine in the BALB/C strain was greater than the response in the C57BL strain.

Amino Acids↗

Responses of cerebellar cortex to electrical stimulation of the glossopharyngeal nerve in the frog.

In the frog cerebellar cortex, electrical stimulation of the glossopharyngeal (IXth) nerve induced negative field potentials with a peak latency of 57 ms whose distribution was bilateral with ipsilateral predominance. The site where the maximum negativity was induced by IXth nerve stimulation was histologically located within the molecular layer near the Purkinje cell layer. In extracellular recording, electrical stimulation of the IXth nerve induced complex and/or simple spike discharges of Purkinje cells. Such evoked potentials and unitary spikes in the cerebellum were attributed to the excitation of the IXth nerve afferents of higher threshold which are mainly composed of fibers sensitive to taste stimulation. These results suggest that gustatory information projects to the cerebellum, as well as those of other kinds of senses, such as touch, visual and auditory sensation.

Animals↗