Tetsushi Sakashita

Evoked otoacoustic emissions from ears with idiopathic sudden deafness.

Evoked otoacoustic emissions (EOEs) were examined in ears with idiopathic sudden deafness (ISD) at an early stage after onset and were compared with those in ears with long-standing sensorineural hearing losses of unknown etiology (SHLUE). In ears with SHLUE, EOEs were not recordable from ears with a hearing loss exceeding 35 dB at minimum hearing level of 4 audiometric frequencies: 500, 1,000, 2,000 and 4,000 Hz (4 MHL). On the other hand, although 4 MHLs were greater than 35 dB in most of the ears, EOEs could be detected in about one-half of the ears with ISD, and, moreover, the majority of these EOE detectable ears showed a good hearing prognosis in spite of the degree of hearing loss. There was, however, no correlation between EOE threshold and degree of hearing recovery. From these results it seems that EOE testing might be clinically applicable for predicting whether or not hearing loss due to ISD can be recovered.

Sound Lateralization and Speech Discrimination in Patients with Sensorineural Hearing Loss

Sound lateralization and speech discrimination abilities are both closely related to central auditory system function. In this study, we investigated the relationship between sound lateralization and speech discrimination in patients with sensorineural hearing loss (SNHL) of unknown aetiology or presbycusis. Interaural intensity difference (IID) and interaural time difference (ITD) discriminations were measured using a self-recording apparatus for dichotic sound presentation, and the means of bilateral maximum scores in speech discrimination tests were calculated. Subjects with normal sound lateralization had good speech discrimination scores above 70%, while those with abnormal sound lateralization had poor scores below 70%. Some patients, however, had good speech discrimination but abnormal sound lateralization. These findings were obtained in both IID and ITD discrimination tests. Furthermore, some subjects could not discriminate ITD, although all could discriminate IID. These findings suggest that sound lateralization ability may be affected more than speech discrimination in SNHL of unknown aetiology or in presbycusis.

Patterns of change in growth function of distortion product otoacoustic emissions in Meniere's disease

The patterns of change in the growth function of distortion product otoacoustic emissions (DPOAEs) associated with hearing improvement in six patients with Menières disease were investigated. The growth functions of 2F1-F2 DPOAEs at F2 frequencies of 1001, 2002 and 4004 Hz (DP-1, DP-2 and DP-4, respectively) were measured with F2 intensities ranging from 70 to 37 dBSPL in 3-dB steps. The F1 intensity was maintained 10 dB higher than the F2 intensity. The growth function was paired with the hearing threshold at the corresponding F2 frequency, and the relationships between changes in DP-1, DP-2 and DP-4 and those in hearing thresholds at 1, 2 and 4 kHz, respectively, were also investigated. The patterns of change in the growth function associated with hearing improvement could be classified into five types. In the first type, the DPOAE growth function became detectable, while the remaining four types were distinguished by combinations of changes in DPOAE amplitudes for lower and higher primary intensities. Multiple parameters, such as maximum amplitude and detection threshold of the growth function, appeared to be required for simple detection and discrimination of these patterns of change. It was also found that the DPOAE growth functions clearly changed in some cases even though the hearing thresholds did not change significantly at the corresponding F2 frequencies. This finding suggests that DPOAE growth function measurement can detect small changes in cochlear function which do not lead to changes in hearing threshold, and has higher sensitivity than pure tone audiometry in monitoring of cochlear function. In conclusion, our findings suggest that measurement of the DPOAE growth function is useful for monitoring cochlear function, and that information on its patterns of change is clinically important and useful.

Evaluation of Radiological Examination for Sensorineural Hearing Loss

The accuracy of radiological examinations has improved and their diagnostic ability has markedly increased. However, the cost of such examinations has also recently become an issue. In this study, the clinical significance of radiological examinations for sensorineural hearing loss (SNHL) was evaluated and the value of their utilization was reconsidered. A total of 1,276 ears of 724 patients who demonstrated unilateral or bilateral SNHL was studied retrospectively. Findings of radiological examinations such as plain X-ray (X-p), computed tomography (CT) and magnetic resonance imaging (MRI) of the brain or the temporal bone were investigated. Temporal bone X-p was usually performed to rule out acoustic tumors (AT). CT was further performed in 119 patients (16.4%) and MRI in 84 patients (11.6%) in total. The reasons or symptoms for further examination such as CT or MRI were X-p findings or auditory symptoms suspicious for AT or vertigo/dizziness suspicious for intracranial disease. Of five cases with AT, two with a small tumor exhibited normal findings for the internal auditory canal on temporal bone X-p. These small ATs were finally confirmed by MRI. MRI could also detect lacunar infarctions, cerebral atrophy and high jugular bulb which might be related to SNHL. These findings confirmed that MRI is very useful for detecting small ATs and suggested that MRI also reveals cerebral vascular insufficiency in patients with SNHL.The accuracy of radiological examinations has improved and their diagnostic ability has markedly increased. However, the cost of such examinations has also recently become an issue. In this study, the clinical significance of radiological examinations for sensorineural hearing loss (SNHL) was evaluated and the value of their utilization was reconsidered. A total of 1,276 ears of 724 patients who demonstrated unilateral or bilateral SNHL was studied retrospectively. Findings of radiological examinations such as plain X-ray (X-p), computed tomography (CT) and magnetic resonance imaging (MRI) of the brain or the temporal bone were investigated. Temporal bone X-p was usually performed to rule out acoustic tumors (AT). CT was further performed in 119 patients (16.4%) and MRI in 84 patients (11.6%) in total. The reasons or symptoms for further examination such as CT or MRI were X-p findings or auditory symptoms suspicious for AT or vertigo/dizziness suspicious for intracranial disease. Of five causes with AT, two with a small tumor exhibited normal findings for the internal auditory canal on temporal bone X-p. These small ATs were finally confirmed by MRI. MRI could also detect lacunar infarctions, cerebral atrophy and high jugular bulb which might be related to SNHL. These findings confirmed that MRI is very useful for detecting small ATs and suggested that MRI also reveals cerebral vascular insufficiency in patients with SNHL.

Neural mechanisms of phonemic restoration for speech comprehension revealed by magnetoencephalography.

In daily communication, we can usually still hear the spoken words as if they had not been masked and can comprehend the speech when spoken words are masked by background noise. This phenomenon is known as phonemic restoration. Since little is known about the neural mechanisms underlying phonemic restoration for speech comprehension, we aimed to identify the neural mechanisms using magnetoencephalography (MEG). Twelve healthy male volunteers with normal hearing participated in the study. Participants were requested to carefully listen to and understand recorded spoken Japanese stories, which were either played forward (forward condition) or in reverse (reverse condition), with their eyes closed. Several syllables of spoken words were replaced by 300-ms white-noise stimuli with an inter-stimulus interval of 1.6-20.3s. We compared MEG responses to white-noise stimuli during the forward condition with those during the reverse condition using time-frequency analyses. Increased 3-5 Hz band power in the forward condition compared with the reverse condition was continuously observed in the left inferior frontal gyrus [Brodmanns areas (BAs) 45, 46, and 47] and decreased 18-22 Hz band powers caused by white-noise stimuli were seen in the left transverse temporal gyrus (BA 42) and superior temporal gyrus (BA 22). These results suggest that the left inferior frontal gyrus and left transverse and superior temporal gyri are involved in phonemic restoration for speech comprehension. Our findings may help clarify the neural mechanisms of phonemic restoration as well as develop innovative treatment methods for individuals suffering from impaired speech comprehension, particularly in noisy environments.

Temporal resolution and speech recognition ability of patients with retrocochlear auditory dysfunction

Objective To study the effect of temporal resolution measured by gap detection tasks on the speech recognition ability of patients with retrocochlear auditory dysfunction. Material and Methods The gap detection thresholds (GDTs) for dichotic stimuli were measured for 23 patients with retrocochlear auditory dysfunction confirmed by abnormal auditory brainstem responses the relationship between GDTs and maximum speech recognition scores (max. SRSs) in quiet was examined. In gap detection testing, narrow-band noises of the five center frequencies of 0.25, 0.5, 1.0, 2.0, 4.0 kHz were used as leading and trailing markers. Each of these two marker sounds was presented to the opposite ear at 20 dBSL with various gap durations between them. Results Abnormal GDTs were observed at one or more test frequencies in 17 of 23 patients. In 12 patients, abnormal GDTs were found at four or five test frequencies. These 12 patients included 4 patients with poor max. SRS less than 30%. However, no tendency was found for max. SRSs to be poorer as abnormal GDTs were observed for more test frequencies. Conclusion Temporal resolution measured by gap detection for dichotic stimuli was frequently reduced in patients with retrocochlear auditory dysfunction, and this reduction appeared to spread over a wide frequency range when speech recognition had markedly deteriorated. However, it also appeared that reduced temporal resolution for dichotic stimuli might not necessarily imply poor speech recognition in quiet.

Frequency Analysis of Evoked Otoacoustic Emissions

Evoked otoacoustic emissions (EOEs) were examined in 8 normal hearing ears without spontaneous otoacoustic emissions (SOEs), and the frequency of the first 10 ms after appearance of the EOE response wave was analyzed, dividing it into the first 5 ms half (First half A) and the last 5 ms half (Last half B). In the First half A, the peak frequency of the power spectrum tended to match the stimulus frequency, but in the Last half B, the peak frequency tended to be constant and moreover, it tended to match the frequency at which EOE can best be recorded. These findings suggest that each ear has its own characteristic EOE frequency.

A psychometric validation of the Japanese versions of new questionnaires on tinnitus (THI-12, TRS, TRSw, TSS, and TSSw)

Abstract Conclusion: The Japanese version of the Tinnitus Handicap Inventory-12 (THI-12), Tinnitus Rating Scale (TRS), TRS 1-week version (TRSw), Tinnitus Severity Scale (TSS), and TSS 1-week version (TSSw), which were developed in this study, showed high reliability and validity, suggesting their usefulness in clinical practice. Based on the THI severity grades, we propose that the severity grades of THI-12 (draft) are categorized into four groups: 0–4 points, 5–9 points, 10–14 points, and 15–24 points. Objectives: We developed Japanese versions of new questionnaires for evaluating the level of psychological distress and difficulty in activities of daily living due to tinnitus, and performed their psychometric validation to determine the reliability and validity. The THI-12 is an assessment consisting of 12 items, each of which is rated on a 3-point scale that was created by reducing the number of questions from the 25 items of the THI. The TRS, TRSw, TSS, and TSSw, which were self-evaluation questionnaires of tinnitus on an 11-grade integer Likert scale from 0 to10 points, were used as additional instruments to assess tinnitus severity and distress. Methods: The subjects were healthy adults, and patients with subjective tinnitus who were examined at the Otolaryngology Department of Keio University Hospital, Osaka City University Hospital, or Nagoya City University Hospital with a chief complaint of tinnitus between September 2010 and January 2011. In all, 38 healthy adult subjects and 113 patients with subjective tinnitus were included. We examined the reproducibility and the internal consistency for reliability. We also examined the relationship with the available scales (THI and Hospital Anxiety and Depression Scale, HADS) and group divergence for validity. Results: The psychometric validation showed high reliability and validity of the THI-12, TRS, TRSw, TSS, and TSSw.

Changes in input/output function of distortion product otoacoustic emissions during the glycerol test in Ménière's disease

Objective To investigate the manner of change in the input/output (I/O) function of distortion product otoacoustic emissions (DPOAEs) during the glycerol test in patients with Ménières disease. Material and Methods The DPOAE I/O functions at three F2 frequencies of 1001, 1501, and 2002 Hz were measured before and after the glycerol test following pure-tone audiometry for 16 ears of 16 patients with unilateral Ménières disease. Changes in DPOAE I/O function during the glycerol test were analyzed using maximum level of DPOAEs (max. DP level) and the detection threshold of DPOAEs (DP threshold) in the I/O function as parameters. Results Significant changes in I/O function during the glycerol test were observed for at least one of three F2 frequencies in all 8 ears and 6 of 8 ears with and without positive test results, respectively, regardless of change in pure-tone thresholds at 1000 and 2000 Hz. A total of 12 ears exhibited two findings of significant change in parameters indicating improvement of cochlear function, increase in max. DP level and lowering of DP threshold, and 2 ears exhibited decrease in max. DP level, a finding indicative of deterioration of cochlear function. Neither of the two parameters exhibited significant change simultaneously, except in one I/O function. Moreover, there appeared to be no clear relationship between the parameter exhibiting significant change and F2 frequencies or changes in pure-tone threshold. Conclusion Subtle changes in cochlear function during the glycerol test can be detected with higher sensitivity by measurement of the DPOAE I/O function than by conventional audiometry. However, multiple parameters should be used in analysis of change in the I/O function since it is difficult to predict how the I/O function will change prior to the glycerol test. Furthermore, the high sensitivity of DPOAEs in detecting change in cochlear function may provide useful information on inner ear status in Ménières disease.

Usefulness of Otoacoustic Emissions in Diagnosis of Pseudohypacusis with Organic Hearing Loss; A Report of Two Cases

We report two cases of pseudohypacusis with organic hearing loss in which useful diagnostic information could be obtained from otoacoustic emission (OAE) testing.Case 1 was a 12-year-old female who had complained of fluctuating hearing loss for a few years. Although her initial pure-tone audiogram indicated moderate hearing loss in both ears, speech audiometry strongly suggested that the hearing of her left ear was considerably better than anticipated based on the pure-tone testing. Since the wave V thresholds of auditory brainstem response (ABR) were 70 and 20dBnHL in the right and left ear, respectively, it was suspected that she had moderate hearing loss in the right ear and normal hearing sensitivity in the left ear. However, OAE testing subsequently performed revealed moderate to severe hearing loss in all frequency regions except between 1.5 and 5kHz in her left ear, and this finding was also confirmed by follow-up pure-tone audiometry.Case 2 was a 54-year-old male whose complaints were left-sided hearing loss and tinnitus developing after a traffic accident. His initial pure-tone audiogram showed moderate to severe hearing loss in the left ear. However, his speech discrimination score for the left ear suggested much better hearing than expected from the pure-tone testing results, and mild hearing loss in the left ear was suspected based on ABR examined later. OAE testing was subsequently performed and revealed moderate to severe hearing loss in the frequency region above 3kHz in the left ear, a finding subsequently confirmed by pure-tone audiometry.The diagnosis of pseudohypacusis is sometimes difficult in patients with organic hearing loss, as in the two cases presented here. In such cases, frequency-specific information about cochlear function provided by OAE might be helpful for assessment of true hearing loss. From this perspective, OAE testing is considered useful as a diagnostic tool for pseudohypacusis.