Hiroaki Nakatani

Hormonal Aspects of Ménière’s Disease on the Basis of Clinical and Experimental Studies

Conclusions: Endolymph homeostasis is thought to be mediated by the vasopressin-aquaporin-2 (VP-AQP2) system in the inner ear. Endolymphatic hydrops, the morphological characteristics of Ménière’s disease (MD), seems to reflect the malregulation of the VP-AQP2 system in inner ear fluid. The elevation of plasma vasopressin (p-VP) level, which is often observed in MD and its related diseases, might be one of the causative factors underlying these diseases. Purpose of Review: Review of the role of the VP-AQP2 system in the inner ear fluid homeostasis and in the formation and development of endolymphatic hydrops. Recent Clinical and Experimental Findings: A clinical survey has revealed that the p-VP level is often elevated in MD and its related diseases and that the increase in the p-VP level was closely linked to vertigo attacks in MD. Experimental studies have revealed that proteins and mRNAs of aquaporin-2 and vasopressin type 2 receptor were expressed in the stria vascularis of the cochlea and the epithelium of the endolymphatic sac, and that the volume of the endolymphatic compartment was mediated by the activity of the VP-AQP2 system in the inner ear.

Sensorineural Hearing Loss of Suspected Autoimmune Etiology: A Report of Three Cases

The present paper reports three cases of sensorineural hearing loss of suspected autoimmune origin. Cases 1 and 2 were bilateral sensorineural hearing loss which responded to steroid therapy. Case 3 was bilateral fluctuant sensorineural hearing loss in conjunction with systemic lupus erythematosus. The pathogenesis of autoimmune sensorineural hearing loss is not yet fully understood. In two patients, hearing levels improved or stabilized following the use of osmotic expanders. The clinical results suggest that endolymphatic hydrops may participate in autoimmune sensorineural hearing loss.

Primary aspergillosis of the larynx associated with CD4+ T lymphocytopenia

The purpose of this study was to report the first case (to our knowlege) of primary laryngeal aspergillosis in a patient with underlying CD4(+) T lymphocytopenia. Laryngeal involvement of Aspergillus is more commonly seen as a part of a wider infection involving the respiratory system in an immunocompromised host. However, primary infection of the larynx is extremely rare. Although there were 12 cases of primary laryngeal aspergillosis previously reported in healthy subjects, there is no known study describing immunological findings in detail. We report a case of primary laryngeal aspergillosis in a healthy 79-year-old male. The examination of his immunity subsequently revealed that there was a marked decline in the number of CD4(+) T lymphocytes and a decrease in the ratio of CD4(+) to CD8(+). It is suggested that it is essential to examine the defence mechanisms, specifically cell-mediated immunity in a patient showing primary laryngeal aspergillosis.

Diagnostic value of plasma antidiuretic hormone, electrocochleography, and glycerol test in patients with endolymphatic hydrops.

Objective: To investigate the relationship between the plasma antidiuretic hormone (p-ADH) level, electrocochleogram (ECoG), and the glycerol test in patients with endolymphatic hydrops (ELH). Patients and Methods: The subjects were 60 patients, including 51 with Ménière’s disease (except for cochlear Ménière’s disease), 7 with delayed ELH, and 2 with syphilitic ELH. The time period for measurements of the p-ADH level, ECoG and the glycerol test was within 4 weeks. Results: 13 patients showed positive results for all tests. 58 patients showed positive results for at least one of three tests. Only 2 patients showed negative results for all tests. Conclusion: The p-ADH level, ECoG and the glycerol test show different selectivity of ELH detection. It is useful to perform all three tests to diagnose ELH.

Stapedial electromyograms recorded by electrocochleography.

The stapedial reflex (SR) can be obtained by the impedance method only when the middle ear is intact. In order to examine the function of the stapedius muscle in diseased ears, the recording of the stapedial electromyogram by an electrocochleographic (ECoG) method was considered. The SR was recorded simultaneously by the impedance method in ten normal subjects for comparison. The outputs of ECoC were averaged by a signal processor up to 200 times under a longer sweep time, and a large biphasic wave with a latency of about 11 ms was obtained on the ECoC records. The amplitude increase of the biphasic wave caused by raising the intensity of the acoustic stimulation paralleled that of the SR. This means that the biphasic wave obtained by ECoC with a latency of about 11 ms originated from the stapedius muscle.

An Animal Model of Ischemic Facial Palsy

We investigated facial palsy which was induced by the interruption of the petrosal artery in guinea pigs. Forty animals were observed for 2 months regarding their behavioral facial nerve function and assessed by the blink reflex. Morphological changes in the intratemporal portion were observed with transmission electron microscopy in 20 animals with an interrupted petrosal artery. Facial palsy developed in 85.0% within 3 days after the interruption. The degree of palsy varied from mild to severe. Remission of palsy required 2–3 months in severe cases, 3 weeks or less in mild/moderate cases. Histological studies revealed a striking difference in the degree of degenerative changes between severe cases and mild/moderate cases. Animals with severe palsy showed extensive axonal atrophy and myelin disruption from the early stage. Meanwhile, degenerative changes were slight in cases with mild/moderate palsy. Regenerating unmyelinated fibers appeared 1 week after the interruption, but diminished in number 4 weeks later. Thereafter, new myelin was reformed on fibers. In cases of severe nerve damage, however, this regeneration process did not always seem to work well. A decrease in number and an irregular shape of the fibers were noted in animals with incomplete recovery. This animal model may be helpful for understanding the pathophysiology of ischemic facial palsy.

Protective effect of edaravone against endolymphatic hydrops

Conclusion. Our findings suggest that edaravone prevented the production of reactive oxygen species (ROS). Edaravone also delayed the formation of endolymphatic hydrops in guinea pigs, but had no effect on endolymphatic hydrops. Objective. To analyse the protective effect of a free radical scavenger, edaravone, on endolymphatic hydrops. Materials and methods. Guinea pigs were subjected to surgical obliteration of the endolymphatic duct (ED). For the detection of ROS, group 1 received intraperitoneal injections of edaravone (3 mg/kg/day) for 2 days, group 2 received edaravone for 2 weeks, group 3 saline for 2 days, and group 4 saline for 2 weeks. ROS production by the organ of Corti and stria vascularis was examined by using dihydrotetramethylrosamine. For the morphological analysis, guinea pigs were divided into five groups, i.e. 2 or 4 weeks after ED obliteration, 2 weeks with edaravone, first or last 2 weeks with edaravone and sacrificed 4 weeks after ED obliteration. Increases in the ratios of the cross-sectional area of scala media were analysed quantitatively to assess the degree of endolymphatic hydrops among the above-mentioned five groups of the hydropic cochlea. Results. ROS was detected both in the organ of Corti and in the lateral wall of cochleae 2 days after ED obliteration. Edaravone prevented the production of ROS and also attenuated the formation of endolymphatic hydrops in the acute hydrops group.

Waveform changes in antidromic facial nerve responses in patients with Bell's palsy.

We repeatedly tested the antidromic facial nerve response within 7 days after onset of paralysis in patients with Bells palsy. None of 109 patients showed the triphasic waveform that reflects normal conduction of the facial nerve action potential. The waves recorded from patients showed biphasic, monophasic, or flat waveforms. Eighty-two of 88 patients with complete recovery showed biphasic waves, whereas half of the patients with nerve degeneration had monophasic or flat waves. Most patients with complete recovery maintained biphasic waves, but in patients with incomplete recovery, the waveforms changed to monophasic or flat, except in 1 case. The presence of monophasic or flat waves with a low facial score strongly suggests nerve degeneration. The antidromic facial nerve response is recommended as a method of diagnosing paralysis and monitoring the progression of intratemporal facial nerve damage during its early stages.

Initial Lesions in Bell’s Palsy and Ramsay-Hunt Syndrome

Conclusion: The antidromic facial nerve response (AFNR) revealed that the initial lesion in both Bell’s palsy and Hunt syndrome was mainly located around the geniculate ganglion within 1 week after onset of paralysis. The preoperative AFNR reflected the response near the initial lesion. Objectives: To review the initial lesion in Bell’s palsy and Ramsay-Hunt syndrome using intraoperative monitoring of the AFNR. Methods: 15 patients, including 8 with Bell’s palsy and 7 with Ramsay-Hunt syndrome, were checked for the AFNR before and during transmastoid decompression surgery within 1 week after onset of paralysis. The AFNR monitoring was performed at the posterosuperior part of the anulus tympanicus preoperatively and at 4 points of the facial nerve during surgery. The nerve conduction block sites were diagnosed by the AFNR waveform. Results: The monophasic wave revealing the block site was mainly observed at the geniculate ganglion in both diseases. The latencies of the preoperative responses corresponded to those recorded intraoperatively around the pyramidal segment of the facial nerve.

Facial Nerve Stimulation Through Stensen's Duct

We report on a new method of stimulating the facial nerve through Stensens duct. Electrical resistance of the skin and subcutaneous tissue is one of the major problems of neurophysiological facial nerve testing. To overcome this disadvantage, the authors show that the facial nerve can be stimulated with far less current through Stensens duct. The NET, ENoG, and antidromic facial nerve responses are recordable at less than a third of the current required for conventional percutaneous stimulation. It is our belief that nerve stimulation through Stensens duct will be a new and useful method for assessing facial nerve dysfunction in the early stage of palsy.