Jun Tsuji

Characteristics of DPOAE audiogram in tinnitus patients

To investigate cochlear activity in tinnitus, the DPOAE (distortion product otoacoustic emission) audiograms (DP-gram) of tinnitus patients were measured. Nine tinnitus patients (15 ears) with normal hearing and 55 tinnitus patients (75 ears) with hearing impairment were included in this study. Significant decreases in DPOAE amplitude over a limited frequency range were observed in 93.3% of the normal hearing tinnitus group and in 96% of the hearing-impaired tinnitus group. The averaged DP-gram of the normal hearing tinnitus group was significantly different from that of the normal subject (repeated-measures ANOVA, P < 0.01). These results imply that tinnitus may be evaluated objectively by DPOAE.

Clinical features of sudden hearing loss associated with a high signal in the labyrinth on unenhanced T1-weighted magnetic resonance imaging

Abstract We report on five patients with high signals in the labyrinth on unenhanced magnetic resonance imaging who developed sudden hearing loss and vertigo. Weissman et al. (1992) suggested the possibility that such high signals were caused by hemorrhage. We assessed these patients using audiograms, caloric tests, and auditory brainstem responses to investigate the possibility of inner ear hemorrhage. Most of the patients were found to have severe and irreversible impairment of both cochlear and vestibular function. These findings were consistent with the hypothesis that their symptoms were caused by inner ear hemorrhage.

Relationship between cochlear implant outcome and the diameter of the cochlear nerve depicted on MRI

This study aimed to evaluate the relationship between the diameters of the auditory and eighth cranial nerves and improvements in post-implant performance. Twenty prelingually deafened children (aged from 2.0 to 6.0 years) who received the Nucleus 24 cochlear implant participated in this study. All subjects had used their implant for at least 1 year after device connection. The diameters of cochlear and eighth cranial nerves were retrospectively measured on preoperative T2-weighted axial magnetic resonance image (MRI). In 17 of 20 subjects, the cochlear and eighth cranial nerves could be identified on MRI. The mean diameter of the cochlear and eighth cranial nerves were 0.9±0.2 mm and 1.2±0.3 mm, respectively. In the remaining three subjects, the cochlear and eighth cranial nerves could not be identified on MRI. These three subjects had significantly lower scores in the Infant–Toddler-Meaningful Auditory Integration Scale (IT-MAIS) than the other 17 subjects at 12 months post-implant. There was no significant correlation among the maximal diameters of the nerves and age, ECAP thresholds and IT-MAIS scores. A sufficient outcome from cochlear implantation can be expected when cochlear and eighth cranial nerves are depicted on MRI, regardless of the nerve diameters.

Vestibular compensation in glutamate receptor delta-2 subunit knockout mice: dynamic property of vestibulo-ocular reflex

The delta-2 subunit of the glutamate receptor delta subfamily is selectively localised in cerebellar Purkinje cells. Delta-2 knock-out mice have defects in Purkinje cell synapse formation, as well as cerebellar long- term depression. In order to elucidate the roles of neural transmission around Purkinje cells in vestibular compensation, the gain and phase of the vestibulo-ocular reflex were measured before and after unilateral vestibular deafferentiation in delta-2 knock-out mice. After unilateral injury of the inner ear, gain decreased and then recovered in both knock-out mice and wild-type mice. However, recovery of VOR gain after unilateral vestibular deafferentiation was slower in knock-out mice than in wild-type mice. The knock-out mice displayed lower VOR gain than wild-type mice during the period between the 1st and the 2nd postoperative weeks. The results suggest that the cerebellum is necessary for augmentation of vestibulo-ocular reflex gain during the partially compensated stage of vestibular compensation after unilateral vestibular deafferentiation.

Non-organic hearing loss.

Conclusion. Most non-organic hearing loss (NOHL) patients were young females. The discrepancy between the results of pure tone audiometry and objective auditory testing suggests NOHL. The diagnostic problem is that objective audiometry is not included in routine examinations and we have to suspect NOHL in order to perform further examination. The correct diagnosis can be difficult in patients who present with unilateral sudden hearing loss or who also have moderate to profound organic hearing loss. Objective. Symptoms and results of auditory tests for NOHL patients were reviewed. Patients and methods. This study comprised 31 patients with NOHL. Age, symptoms, and the results of subjective and objective audiometry were collected. Results. Twenty-four patients were female and 7 were male. The age at attendance ranged from 7 to 39 years old, with an average age of 16.6 years. Eight patients received steroids before the correct diagnosis was made. Six of them presented with unilateral sudden hearing loss, and the other two patients had accompanying bilateral organic hearing loss.

Cochlear implants in post-lingually deafened patients

Conclusion. Post-lingually deafened patients had good speech intelligibility scores with cochlear implantation. The age at the operation, duration of deafness, and the number of electrodes outside the cochlea showed only weak correlation with the postoperative performance, which warrants cochlear implantation in elderly patients and patients with a long history of deafness and leaving dummy electrodes outside the cochlea. Patients with cochlear obstruction showed comparable performance to patients with an open cochlea. Objective. To evaluate the background and performance of post-lingually deafened cochlear implantation recipients. Patients and methods. Preoperative and intraoperative factors were collected for 109 cochlear implant subjects. Speech intelligibility scores were obtained and the effects of preoperative and intraoperative factors on postoperative performance were evaluated. Results. The average speech intelligibility score was 85.1% for vowels, 41.1% for consonant-vowel (CV) syllables, and 80.4% for phrases. The correlation coefficient between the age at the operation, the duration of deafness, and the number of electrodes outside the cochlea and the postoperative performance was between 0.03 and −0.27. Patients with cochlear obstruction and patients with open cochlea did not show significant differences in speech intelligibility tests. The onset of deafness (progressive vs sudden) did not have an effect on the speech intelligibility test.

The influence of middle ear pressure on the otolith system in cats

SummaryThe influence of varying middle ear pressure on the otolith system was investigated in anesthetized cats. Extra-axonal recordings of action potentials were performed in the vestibular nerve fibers and in the neurons in the lateral vestibular nucleus that responded to lateral or anteroposterior steadystate tilt. Positive or negative pressure was applied to the ipsilateral middle ear during the recordings. Seventy-three percent of the fibers and 63% of the neurons responded to changes in the middle ear pressure. These response rates were higher than those previously reported on the units innervating semicircular canals. Findings suggest that the otolith organs are more sensitive to changes in the middle ear pressure than are the semicircular canals. The units responding to lateral tilt were more sensitive to middle ear pressure than those that responded to anteroposterior tilt. Displacement of endolymph caused by pressure changes in the middle ear was considered to have affected the activities of hair cells in otolith organs.

The influence of caloric stimulation on the otolith organs in the cat.

SummaryThe influence of caloric stimulation on the otolith organs was investigated in cats by recording the firing rate of the single vestibular nerve fiber originating from each otolith organ. Sixty-six percent of the vestibular nerve fibers originating from the otolith organs responded to the caloric stimulation. The caloric nystagmus occurred not only by the activities of the semicircular canal system but also by those of the otolith system.

Clinical characteristics of delayed endolymphatic hydrops: long-term results of hearing and efficacy of hyperbaric oxygenation therapy

Conclusion. Diuretics significantly improved hearing in patients with contralateral-type DEH, whereas they did not inpatients with ipsilateral-type DEH. Objective. We report a review of 26 cases of DEH treated in recent 6 years. Patients and methods. The study group comprised 22 contralateral and 4 ipsilateral types of DEH. The efficacy of diuretics on the improvement in hearing was examined quantitatively. The efficacy of hyperbaric oxygenation therapy (HBO) on hearing was examined in six patients. Results. The general properties of these cases were similar to those reported previously, except for the high proportion of patients with contralateral-type DEH. Diuretics significantly improved the hearing of patients with contralateral-type DEH. In contrast, no significant improvement by diuretics was noted in ipsilateral-type DEH.

Chronological changes of stimulation levels in prelingually deafened children with cochlear implant.

This study investigated changes in long-term cochlear implant MAPs (values of the program to stimulate electrodes) in children, and examined whether there were significant differences between children and adults. Ten prelingually deafened children (aged from 2.7 to 7.8 years) who received the Nucleus 22 cochlear implant at Kyoto University between 1996 and 1998 participated in this study. Behavioral thresholds (T levels) and maximal comfortable levels (C levels) were evaluated at 3 months post-implant, and then every 6 months up to 4 years. Ten adult cochlear implant users were also evaluated as a control group. All subjects had used their implant for at least 4 years after device connection. All prelingually deafened children demonstrated slower but continuous improvements in speech perception and production abilities during the test period. T levels became stable at 30 months post-implant in children and at 24 months post-implant in adults. C levels became stable at 6 months post-implant in children and within 3 months post-implant in adults. In conclusion, T levels of prelingually deafened children became stabilized 30 months post-implant, while C levels stabilized 6 months post-implant. MAPs of prelingually deafened children were stabilized 30 months post-implant, which was longer than that in adult cochlear implant users.