Yosaku Shiomi

Sound-induced activation of auditory cortices in cochlear implant users with post- and prelingual deafness demonstrated by Positron Emission Tomography

Changes of regional cerebral blood flow (rCBF) in the auditory cortices induced by sound stimulation were examined in nine postlingually and five prelingually deaf cochlear implant (CI) users by 15O-labeled water Positron Emission Tomography, and the results were compared with those of eight normal volunteers. Speech stimulation caused significantly greater rCBF increase compared with noise stimulation in the auditory association area in normal and postlingually deaf subjects. In prelingually deaf subjects, however, speech activation of the auditory association area was much less than that found in either of the other two groups. Neuronal networks for speech sound processing in the auditory association area in postlingually deaf individuals are thought be similar to those in normal subjects, while those in prelingually deaf patients who received CI after the speech acquisition period may not develop completely.

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.

Cortical activation with sound stimulation in cochlear implant users demonstrated by positron emission tomography

Six postlingually deaf patients using multi-channel cochlear implants were examined by positron emission tomography (PET) using 15O-labeled water. Changes in regional cerebral blood flow (rCBF) were measured during different sound stimuli. The stimulation paradigms employed consisted of two sets of three different conditions; (1) no sound stimulation with the speech processor of the cochlear implant system switched off, (2) hearing white noise and (3) hearing sequential Japanese sentences. In the primary auditory area, the mean rCBF increase during noise stimulation was significantly greater on the side contralateral to the implant than on the ipsilateral side. Speech stimulation caused significantly greater rCBF increase compared with noise stimulation in the left immediate auditory association area (P < 0.01), the bilateral auditory association areas (P < 0.01), the posterior part of the bilateral inferior frontal gyri; the Brocas area (P < 0.01) and its right hemisphere homologue (P < 0.05). Activation of cortices related to verbal and non-verbal sound recognition was clearly demonstrated in the current subjects probably because complete silence was attained in the control condition.

Influence of unilateral deafness on auditory evoked magnetic field.

TO investigate the effect of unilateral deafness on central auditory mechanisms, we examined patients with unilateral deafness of various durations. Auditory evoked magnetic fields (AEF) were recorded using a whole-head neuromagnetometer. In patients who had unilateral deafness for more than 3 weeks, the average N100m latency in the ipsilateral hemisphere did not differ from that in the contralateral hemisphere. In addition, in some patients with congenital or early onset deafness, the equivalent current dipole (ECD) moment was larger in the ipsilateral hemisphere than in the contralateral hemisphere. These findings suggest that unilateral deafness may cause reorganization of the central auditory pathway. They also suggest that central auditory pathway in adults has some plasticity, though not as much as in childhood.

Efficacy of transmeatal low power laser irradiation on tinnitus: a preliminary report

Thirty-eight patients suffering from tinnitus resistant to several medical therapies for more than 6 months were treated by low power laser irradiation. A 40 mW laser with a wavelength of 830 nm was irradiated via their external auditory meatus toward the cochlea for 9 min once a week, 10 times or more. Patients were asked to score their symptoms on a 5 point scale before and after the treatment for a subjective evaluation of the effect. The results were estimated by the change of the loudness and duration of tinnitus, and the degree of annoyance due to tinnitus. Although only 26% of the patients had improved duration, loudness and degree of annoyance were relieved in up to 58 and 55%, respectively, without major complication. Laser therapy seemed to be worth trying on patients with intractable tinnitus.

Correlation between rCBF and speech perception in cochlear implant users.

OBJECTIVE Although cochlear implants (CIs) have provided the opportunity for bilaterally deaf individuals to recover their hearing abilities, the speech perception performances of the CI users varies considerably. To elucidate the cortical mechanisms of processing speech signals coded by CIs, we evaluated the correlation between the brain activity during speech activation and speech perception in CI users by PET. METHODS Fourteen postlingually deaf CI users were examined. CI used in the patients was a 22-channel system and its speech-coding strategy was the Nucleus spectral peak (SPEAK) strategy. To evaluate the speech perception performances, we examined vowel perception, consonant perception and speech tracking performances in the Japanese language. Regional cerebral blood flow (rCBF) was measured during no sound stimulation and speech sound stimulation. PET data of the silent condition was subtracted from that of speech stimulation to determine changes in rCBF. In the search for changes in rCBF in the areas for auditory processing, three regions of interest (ROI) were selected; primary auditory area, auditory association area and Brocas area. The correlation between the rCBF changes in the ROIs and the speech perception performances was analyzed using Pearsons correlation coefficient. RESULTS The patients speech perception performances ranged widely. Although there were no significant correlations between the speech perception and the rCBF increases in the primary auditory area and Brocas area, there were positive correlations in the auditory association area. In the left auditory association area, the correlation coefficient of the vowel perception performance was 0.546 (P <0.05) and that of the speech-tracking test was 0.657 (P < 0.05). Regarding the consonant perception performance, the correlation coefficient was 0.743 (P < 0.01). There was a positive correlation only between the consonant perception performance and the rCBF increase (R = 0.576, P < 0.05) in the right auditory association area. These correlations are stronger in the left hemisphere than in the right hemisphere. CONCLUSIONS It is suggested that the improvement of the auditory processing of speech in CI users with SPEAK strategy is accompanied by the recruitment of more neurons in the auditory association areas. The adult auditory cortices may still have plasticity or

Cochlear implant in patients with residual hearing

OBJECTIVE The postoperative speech perception abilities of severely hearing-impaired patients with multi-channel cochlear implant were compared with preoperative speech perception performance with conventional hearing aids. METHODS Cochlear implantation was performed in six severely to profoundly hearing-impaired patients. They had unaided pure-tone thresholds of 70-100-dB HL and aided thresholds of 35-90-dB HL in the better ear, but were not able to perceive speech sounds well with hearing aids. RESULTS Postoperatively, all the patients had significantly improved speech perception performance, exceeded the average skills of profoundly deaf cochlear implant users, and were able to communicate without writing. CONCLUSION These results imply that cochlear implant may be indicated for severely to profoundly deaf subjects, if they receive little or no benefit from conventional hearing aids.

Tinnitus remission by lidocaine demonstrated by auditory-evoked magnetoencephalogram : A preliminary report

An auditory-evoked magnetic field was recorded before and during tinnitus remission induced by an intravenous lidocaine injection. One and 4 kHz probe tones were presented monaurally in four tinnitus patients, and the responses were recorded using a 122-channel magnetometer. Three normal volunteers were also examined as controls. In tinnitus patients, the N100 m peak became sharper, while there was no marked change except for slight reduction in amplitude in normal subjects. Tinnitus remission by lidocaine may be related to attenuation of a masking-like effect of tinnitus on the sound-evoked responses.

Hyperviscoelasticity of Epipharyngeal Mucus May Induce Globus Pharyngis

Detailed observation reveals a lump of translucent sticky mucus standing in the epipharynx of most globus patients, suggesting that the mucus adherent to the epipharynx causes a globus sensation. The epipharyngeal mucus of 70 consecutive globus patients was sampled via the nasal cavity. Fucose and sialic acid, the determinants of the viscoelasticity of mucus, were measured. Twenty-three patients were also asked to complete the Throat Questionnaire so we could evaluate the correlation between the degree of globus sensation and the viscoelasticity of the mucus. The mucus of 10 healthy subjects was sampled, analyzed, and compared with the data of the patients. The fucose and sialic acid concentrations found in the patients with globus pharyngis were significantly higher than those in the control subjects (Mann-Whitney U test, p < .01). The fucose concentrations correlated significantly with the globus pharyngis scores (Spearman correlation, p < .05). We conclude that there is a close association between stagnant mucus in the epipharynx and globus sensation.

Surface-Coil Magnetic Resonance Imaging of the Internal Auditory Canal and the Inner Ear Preliminary Report

Parasagittal surface-coil magnetic resonance imaging of the internal auditory canal and the inner ear was performed. We used T2-weighted fast spin-echo sequences to visualize the inner ear and the individual nerves in the internal auditory canal with high contrast in a short acquisition time. Computer-assisted quantitative measurement of the nerves was performed to estimate the cross-sectional areas and the diameters of the nerves. The average diameters of the facial nerve, the cochlear nerve, and the vestibular nerve of normal-hearing individuals were, respectively, 1.1 ± 0.2 mm (mean ± SD), 1.2 ± 0.2 mm, and 1.5 ± 0.2 mm. In the cerebellopontine angle, the average diameter of the eighth nerve was 1.8 ± 0.2 mm. Two patients with unilateral and bilateral hearing loss were also presented. In the patient with unilateral deafness, the cochlear nerve of the diseased side was not identified and the eighth cranial nerve diameter was smaller than that of the normal side. In the patient with bilateral deafness, fibrosis of the inner ear and atrophy of the eighth nerve were demonstrated in the ear with posttraumatic deafness. The present method may represent a new approach to the assessment of pathologic processes involving the inner ear and the nerves in the internal auditory canal.