Published papers

Acetylcholine (Ach) has been considered a major neurotransmitter in the inner ear efferent nerve endings. A bioassay analysis has shown that the electrical stimulation of the crossed olivocochlear bundle increased the Ach-like activity in the perilymph. Applying in vivo microdialysis techniques and high-performance liquid chromatography to the perilymph, the change of Ach level was thus measured before and after α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA), a glutamate receptor agonist, was added to the perfusate. Ach was only detectable when the perfusate contained an acetylcholinesterase inhibitor. The level of Ach increased 2-3-fold immediately after AMPA was administered. Our data suggest that the afferent stimulation, such as the administration of AMPA, may therefore induce the release of Ach from the efferent nerve endings.

An experimental model of cochlear ischemia using the photosensitization reaction of rose bengal (RB) is reported. Ischemia was induced by the systemic administration of RB solution and localized irradiation of the cochlea with a green light of specific wavelength for RB activation. After the RB solution was administered, the cochlear blood flow was temporarily increased and then decreased, and the latency of wave I of the auditory brainstem response increased and the amplitude of wave I decreased after RB injection and finally wave I disappeared completely. A histological study revealed thrombus formation in the vessels of the irradiated cochlea not only in the stria vascularis and the spiral ligament, but also in the modiolus. L-Histidine, a scavenger of singlet oxygen (1O2) and hydroxyl radical (·OH), significantly prolonged cochlear dysfunction, but D-mannitol, a specific scavenger of ·OH did not, suggesting that 1O2 has an important role in this reaction.

A grading system for sudden deafness has been established by the Research Group on Sudden Deafness of the Japanese Ministry of Health and Welfare. According to this grading system, sudden deafness cases are classified according to the initial hearing level and the vestibular symptoms. Few clinical analyses of sudden deafness cases have been made using this grading system. In this study, 263 sudden deafness cases were classified into 6 groups based on the grading system. All of the cases presented with an initial hearing level of more than 40 dB and underwent treatment within 1 week of the onset of symptoms. The relationship between the grading system and hearing recovery is discussed. Fixed hearing levels with a good prognosis were grades 2b, 2a, 3b, 3a, 4b and 4a. To quantitatively evaluate hearing recovery, the average hearing recovery rate and the percentage of the complete recovery cases were analyzed for each group. Average hearing recovery was ranked into five levels, regardless of the evaluation method. Grades 2b and 3b were the best, and grade 4a was the worst. After grades 2b and 3b, grade 2a was the second best, grade 3a was the third, and grade 4b was the fourth. The cases included in grades 2 and 3 were more strongly effected by whether the cases had vestibular symptoms or not than by their initial hearing levels. When grade 4 cases were classified by their initial hearing level, a large difference existed among grade 4a cases with regard to whether they presented with an initial hearing level of under or more than 100 dB. The hearing recovery of grade 4a cases with an initial hearing level of less than 100 dB was almost the same as that of grade 3a. However, the hearing recovery of grade 4b cases varied only slightly. Consequently, some ranges of initial hearing level exhibited similar degrees of hearing recovery. In cases without vestibular symptoms, the range of initial hearing levels was 40-89 dB. These cases had a 60% chance of complete recovery, and the hearing recovery rate was 80% on average. In cases with vestibular symptoms, the range of initial hearing levels was 60-99 dB. These cases had a 40% possibility of complete recovery, with an average hearing recovery rate of 60%. After comparing the initial grades and the final grades using the same grading system, the majority of grade 2 and 3 cases attained a grade 1 fixed hearing level. However, most grade 4 cases had a grade 3 fixed hearing level.

To clarify the mechanism underlying ear fullness in otosclerosis, we studied the relationship between clinical features and examinations. Subjects were 116 otosclerosis patients (140 ears). The presence or absence of ear fullness was judged from a questionnaire in initial diagnosis or a chart description. Ear fullness was observed in 44 ears (31%) and absent in 96. The averaged air and bone conduction hearing levels (500 Hz-4 k Hz) in initial diagnosis were significantly lower in the group with ear fullness. The difference in averaged hearing was mainly apparent at 2 k Hz and 4 k Hz. The difference in hearing at lower frequencies (125 Hz, 250 Hz, and 500 Hz) and higher frequencies (2 k Hz, 4 k Hz, and 8 k Hz) was significantly larger in the group of ear fullness. From these results, we postulated that ear fullness in otosclerosis is caused by fixation of the stapes. The psychoacoustic abnormal sensation caused by lower input of lower-frequency sound or incomplete fixation of the stapes may cause ear fullness. Further study is needed to clarify the pathogenesis of ear fullness in different ear pathologies.

The diagnosis procedure combination/prospective payment system (DPC/PPS) that was begun in university hospitals in fiscal 2003 is outlined. The DPC in the 2004 version concerning head and neck cancer was analyzed, and the handling of local complications in postoperative head and neck surgery patients in the DPC/PPS was examined. If major surgery of the head and neck cancer was performed, it often turned out to fall outside the scope of the inclusive evaluation. Moreover, it is understood that the presence of complication is not reflected in the classification in head and neck cancer even though it is common in other diseases to subdivide the diagnosis group classification by the presence of complication. The problem of local complication was examined in the case of oral cancer treatment by our department in 2004. It was clarified that the decision on whether complication was a negative factor of the DPC/PPS depended on the medical treatment expense concerning complication and the balance of the hospitalization period. Moreover, it seemed that cases which did not have complication and were quickly discharged from hospital were a minus in the DPC/PPS, and so improvement plans are necessary.

After treatments, several patients with sudden deafness (SD) continued to have symptoms, including hearing loss, tinnitus and dizziness. These unresolved symptoms and their effect on the quality of life (QOL) in SD patients have not been studied. We evaluated QOL using the Hearing handicap inventory (HHIA) and an original questionnaire in SD patients who had been treated more than 6 months prior to the study. Compared to results in bilateral sensorineural hearing were significantly lower in SD patients (p<0.01). In bil-SNHL, this score peaked two to K) years after onset of disease and decreased thereafter. The score peaked more than 10 years after onset of disease in patients with SD. While hearing and test scores were correlated in bil-SNHL, this was not observed in SD. About half of patients were embarrassed by hearing loss and tinnitus after treatment. Among patients who scored more than 44 points on HHIA, all reported hearing loss and tinnitus. When asked about subjective changes in hearing after treatment, 27% believed their hearing had improved, 60% believed there was no change, and 13% believed their hearing had deteriorated. Cases believing deterioration in hearing also had high scores on HHIA. Sequelae of SD may worsen QOL, driving embarrassed patients to visit other medical facilities in to improve their QOL. Even though hearing may not improve after initial treatment in ears affected by SD, informed consent about the clinical course and audiological follow-up should be done.

Drop attacks are sudden falls without concurrent vertigo whose etiology may be unknown. Drop attacks are also associated with cardiac, cerebrovascular, psychogenic, and vestibular disorders, in addition to seizures. Vestibular-based drop attacks without loss of consciousness can occur in patients with Meniere's disease. We present 2 cases of drop attack in patients with Meniere's disease. Case 1, a 65-year-old man, experienced 4 such attacks and case 2, a 55-year-old woman, experienced 20 within 2 years of Meniere's disease onset. Case 1 enjoyed spontaneous remission. In case 2, selective serotonin reuptake inhibitor (SSRI) administration suppressed attack frequency. Anxiety may predispose individuals to drop attack. Etiologically, inadequate stimulation of otolith organs may induce a sudden vestibule spinal reflex that, in turn, causes sudden falls. To correctly diagnose drop attacks, the patient must exhibit sudden falls, and transient ischemic attack should be carefully ruled out.

Congenital cholesteatoma of the middle ear is frequently seen in younger children including infant. By contrast, that of the petrous bone is rarely seen in younger children. We report an exceptional case occurring in 23-month-old infant who presented with unilateral facial nerve paralysis at about 18-month-old. Computed tomography and magnetic resonance imaging revealed congenital cholesteatoma measuring approximately 2 cm in the area of the right geniculate ganglion. The mass was completely eradicated via the middle fossa approach, which allowed for preservation of hearing. The facial nerve maintained intact during surgery and paralysis showed partial recovery after the operation. To our knowledge, the present case seems to be the youngest case of congenital petrosal cholesteatoma reported, and also demonstrates congenital petrosal cholesteatoma could exhibit facial nerve paralysis in early childhood.

Mitochondrial dysfunction in the cochlea is thought to be an important cause of sensorineural hearing loss. Recently, we have established a novel rat model with acute hearing impairment caused by exposure to the mitochondrial toxin 3-nitropropionic acid (3-NP) to analyze the mechanism of cochlear mitochondrial dysfunction. Both permanent and temporary threshold shifts were observed in this model depending on the amount of 3-NP used to induce hearing impairment. In this study, we demonstrate cochlear morphological changes in the permanent threshold shift model. Marked degeneration was detected in type 2 fibrocytes in the spiral prominence, type 4 fibrocytes in the spiral ligament, marginal cells and intermediate cells in the stria vascularis 3 h after 3-NP administration; these changes were progressive for at least 14 days. Less prominent degeneration was detected in type 1 and type 3 fibrocytes in the spiral ligament. These results indicate that permanent threshold shift caused by acute cochlear mitochondrial dysfunction is primarily mediated by cellular degeneration in the lateral wall of the cochlea, and suggest that therapy of cochlear hearing loss due to acute energy failure may be achieved through protection and regeneration of the cochlear lateral wall.

Previous experiments have established that visual stimulation in the roll plane causes people to feel roll vection. However, few experiments have been aimed at characterizing the relationship between changes in the subjective visual vertical (SVV) and the generation of vection. In this experiment we investigate the relationship between SVV, a quasi-subjective parameter, and vection, the visually induced perception of self-motion. We observed three different patterns of change in SVV. Even with fixed visual stimuli, in many cases SVV changed continuously. These results suggest that conflicts among different sensory inputs produce dynamic changes in the priority of these sensory inputs. The longer vection is perceived, the more predominant the visual sensory input becomes.

The origin of vertigo is difficult to identify since a similar symptom occurs in either central or peripheral impairment. An initial evaluation of the patient's clinical history, as well as his clinical manifestations are important for correct diagnosis. Final diagnosis typically depends on conventional imaging techniques, such as CT and MRI. Here, we describe a patients whose functional examination was quite helpful to identify the lesion. The patient was case a 44-year-old man with cavernous hemangioma in the brainstem presenting acute hearing loss with vertigo. Initially he was diagnosed as having peripheral vertigo by neurological examinations together with CT images. Later a rare cavernous hemangioma was identified by head MRI. In the process of diagnosis, the result of auditory brainstem response (ABR) strongly suggested brainstem impairment. This case reveals that conventional imaging procedures, such as CT, are inadequate for diagnosis, whereas functional exams, such as the auditory brain stem response (ABR), are quite helpful for clinical evaluation. ABR can work as a screening examination for patients with vertigo to rule out brainstem lesion even in patients with normal hearing.

Pulmonary embolism (PE) is a prominent cause of morbidity and mortality in surgical patients. Here, we report two cases of PE following head and neck surgery: (1) in case 1, the patient underwent endoscopic sinus surgery (ESS), and (2) in case 2, the patient was suspected PE after resection of the parotid gland and radical neck dissection. Prophylactic compression devices were used during the operation in both cases. In case 1, PE was diagnosed 3 days following surgery after the patient complained of dyspnea while walking. PE was successfully treated by intravenous administration of heparin. In case 2, PE was strongly suspected 13 days following surgery after the patient experienced syncope and chest pain and exhibited abnormal findings on a cardiac echogram. This patient died 18 h after the onset of cardiac symptoms. Despite prophylactic measures taken during surgery, the prognosis was poor for this patient due to numerous high-risk factors (e.g., advanced age, obesity, prolonged immobilization). Although the incidence of postoperative PE in our department during the last 7 years is very low (0.04%), the frequency of postoperative PE in Japan has steadily increased in recent years. PE still is one of the most significant complications leading to morbidity and mortality following surgery. Given the gaining prominence of PE, we conclude that otolaryngologists including those in Japan should be reminded of high-risk factors associated with PE and be made aware of prophylactic treatments newly aimed at reducing the frequency of PE.

Intramuscular myxoma is a benign mesenchymal tumor that commonly occurs in the larger skeletal muscles, and is rare in the head and neck. A case of intramuscular myxoma in the scalene muscle is described. This is the first report of this tumor arising in that muscle. It is difficult to diagnose pre-operatively from clinical features, CT scan and ultrasonography of the neck because of the lack of characteristic manifestation or radiographic features. Intramuscular myxoma has an infiltrative tendency, so there are several reports of recurrence because of incomplete excision or enucleation. In our case no recurrence was observed for 4 years, since the tumor was removed with the muscle adherent to it.

We reported a case of Paget's disease presenting fluctuating hearing loss together with repeated dizziness and vertigo attacks. Pure tone audiometry in this patient was performed successively during follow-up periods. She visited our hospital 13 years ago with slight low tone sensorineural hearing loss in her left ear. Sensorineural hearing loss in her right ear and sensorineural and conductive hearing loss in left side deteriorated. Results of her latest examinations were as follows. Glycerol test was positive and inverted reflex was recorded in her right ear. CT showed severe calcification in skull bone and stenos of bilateral internal auditory canal. Endolymphatic hydrops, compression of VIII nerve in internal auditory canal, damage of cochlear hair cell and changes in middle ear conductive system were possible etiology of hearing loss and vertigo. Oral bisphosphonate is used to prevent deterioration of these symptoms. Evaluation of auditory and vestibular function should be continued.

We describe the case history of a 70-year-old female patient presenting with bilateral hearing disturbance, facial paralysis, and vertigo. Radiological tests of temporal bone revealed soft tissue in the mastoid and tympanic cavities, and T1 weighted MRI revealed prominent Gd enhancement of the middle skull basal meninges. Middle ear inflammation appeared to induce pachymeningitis and to exacerbate associated symptoms, leading to a decline in the patient's overall condition. Bilateral mastoidectomies were effective in improving her general condition. Her hearing improved only on the right side because ossiculoplasty was performed only on that side. Her facial movement progressively improved and pachymeningitis diminished over time. We speculate that removal of the infectious granulation within the middle ears and mastoids ameliorated the acute inflammation. The etiology remains unknown in this case.

We used social and emotional approaches to psychologically evaluate hearing disorders, translating the Hearing Handicap Inventory for Adults (HHIA) into Japanese and using it to evaluate Japanese adults with sensorineural hearing loss. The HHIA is a 25-item self-assessment scale composed of 2 subscales, emotional and social/situational, which has been used to evaluate adult patients with hearing disorders in Europe and North America. The test-retest reliability of the Japanese version and its screening version (HHIA-S) were excellent (kappa coefficients were 0.912 and 0.842). Due to the limitation of social/situational items, test-retest reliability was only good (0.6 < kappa coefficient < 0.8), possibly because of problems in translating these items. We discovered that the average of scores of the HHIA Japanese version was higher in bilateral hearing disorder patients than in those with unilateral hearing disorder. This score peaked in 2 to 10 years after onset and decreased thereafter in bilateral hearing disorder patients. The correlation coefficient between the average hearing level of 7 frequencies and scores of the test was highest among the 4 audiological evaluations. The HHIA Japanese version is thus useful for following up patients with hearing disorders.