The terminal of the sympathetic nerve fibers in the facial nerve.

OBJECTIVE: The terminal of the sympathetic nerve fibers of the rat facial nerve in the temporal bone region was investigated. MATERIAL AND METHODS: We used tyrosine hydroxylase (TH) and the synaptophysin antibody as markers of the sympathetic nerve fiber and the membrane of the synaptic vesicle, respectively. Using immunohistochemistry, we determined whether and where the synapse exists in the facial nerve of the Sprague-Dawley rat. RESULTS: TH-immunoreactive fibers were confirmed as being present in both the epineurium and the nerve fascicle of the facial nerve. A synaptophysin immunoreaction was found in the facial nerve in a region of the temporal bone. These reaction products looked like varicosities. Most TH-positive fibers in the facial nerve disappeared after superior cervical ganglionectomy. CONCLUSIONS: As the synaptophysin immunoreaction indicates the existence of a synapse, we speculate that the sympathetic fibers affect the facial nerve in the region of the temporal bone. Further studies may be needed to elucidate the function of the sympathetic system in the facial nerve.

Inhibitory effect of cyclosporin A on p-glycoprotein function in peripheral nerves of mice treated with doxorubicin and vinblastine.

OBJECTIVE: To investigate the inhibitory effect of cyclosporin A on p-glycoprotein function in peripheral nerves (VIIth, VIIIth and sciatic nerves). MATERIAL AND METHODS: Male mdr1a(-/-) and mdr1a(+/+) FVB mice were used. Doxorubicin (30 mg/kg) was administered intravenously with or without i.p. administration of cyclosporin A (200 mg/kg). Vinblastine (5 mg/kg) was also administered intravenously with or without i.p. administration of cyclosporin A (200 mg/kg). RESULTS: Tissue concentrations of doxorubicin and vinblastine in peripheral nerves of the mdr1a(+/+) mice pretreated with 200 mg/kg cyclosporin A were significantly higher than those in the mdr1a(+/+) mice administered doxorubicin or vinblastine alone, suggesting that cyclosporin A inhibited the efflux pump function of p-glycoprotein in the peripheral nerves. In the mdr1a(-/-) mice, tissue concentrations of doxorubicin and vinblastine in peripheral nerves were also significantly higher than those in the mdr1a(+/+) mice administered doxorubicin or vinblastine alone. Based on these results, it is suggested that p-glycoprotein plays an important role in blood-nerve barrier function by preventing side-effects induced by neurotoxic drugs. CONCLUSION: When doxorubicin and vinblastine are co-administered with cyclosporin A, the patient should be carefully monitored because peripheral nerve disorders may be induced.

Cochlear nerve demyelination causes prolongation of wave I latency in ABR of the myelin deficient (md) rat.

In this study, we examined the auditory brainstem responses (ABRs), distortion product of otoacoustic emissions (DPOAEs) and cochlear morphology of the myelin deficient (md) rat, which completely lacks central myelin but not peripheral myelin. ABRs showed a marked prolongation not only wave II-IV latencies but also wave I latency. Cochlear nerve fibers near the modiolus lost their myelin halfway into the internal auditory canal. DPOAEs also decreased at a lower frequency of the combined tone. Since nerve fibers ending at the apical turn of the cochlea passed through central portion of the cochlear nerve, wave I prolongation of ABRs and decrease of DPOAEs at a lower frequency might originate mainly from the demyelinated CNS part of the cochlear nerve and efferent olivocochlear bundle in the internal auditory canal.

Tracheoesophageal shunt method with omohyoid muscle loop for voice restoration.

OBJECTIVE: To decrease the aspiration rate of the previously reported simple mucodermal tracheoesophageal (TE) shunt method for voice restoration after total laryngectomy with the use of omohyoid muscle loop. DESIGN: Retrospective clinical analysis. SETTING: Department of Otorhinolaryngology, Fukui Medical University, Fukui, Japan. PATIENTS: Ten male patients underwent total laryngectomy and received TE shunt by the omohyoid muscle loop method for voice restoration. There were 5 patients with glottic laryngeal cancer, 2 with supraglottic laryngeal cancer, and 3 with hypopharyngeal cancer. Patients' age ranged from 46 to 66 years. INTERVENTION: The dermal incision on the neck was U-shaped with a superiorly pedicled, small U-shaped dermal flap. This small flap was used to form the anterior wall of the shunt. Bilateral omohyoid muscles were preserved at the total laryngectomy site with or without neck dissection. After creating a TE shunt directly on the posterior wall of the tracheal stump, the bilateral omohyoid muscles were looped through each other beneath the TE shunt. MAIN OUTCOME MEASUREMENTS: Maximum phonation time, maximum phonation intensity, and rating scales of shunt voice, aspiration rate, and survival time. RESULTS: Mean maximum phonation time was 20 seconds, while mean maximum phonation intensity was 83 dB. The first voice was obtained on postoperative day 29 on average. Of the 10 patients, 9 could phonate, with 1 case (10%) of slight aspiration 3 months after the surgery. CONCLUSIONS: Although this omohyoid muscle loop method needs to preserve the hyoid bone with those muscles, aspiration was prevented more effectively compared with the former, direct mucodermal TE shunt method. The indication for this method is preferably glottic laryngeal cancer.

Incidence of regeneration of the chorda tympani nerve after middle ear surgery.

We retrospectively reviewed 52 patients who underwent middle ear surgery during which the chorda tympani nerves were severed and who then underwent secondary surgery 1 to 5 years later. In 22 patients (42.3%), regenerated chorda tympani nerves (entire length of the tympanic segment) were detected in the submucosal layer of the reconstructed eardrum during the secondary surgery. Before the secondary surgery, 16 patients (30.8%) showed threshold recovery on electrogustometry. When 5 regenerated nerves were observed by transmission electron microscopy, myelinated nerve fibers were detected in a small fascicle or connective tissue, but the number of myelinated axons was significantly decreased (7.4% to 84.6%; p = .01) compared with that in normal subjects (1,911 +/- 324; n = 4). There was a significant difference in the incidence of regeneration between the group with end-to-end anastomosis (5/5 or 100%) and that with nerve gap defects (17/47 or 36.2%; p <.05); this finding suggests that repair of the sectioned nerve produces a better incidence of regeneration than leaving the nerve unrepaired.