Kazuoki Kodera

Effects of Rise Time on Simultaneously Recorded Auditory-Evoked Potentials from the Early, Middle and Late Ranges

The view that the effects of stimulus rise time are qualitatively different for early brain stem components, middle latency components and late vertex components of the auditory-evoked responses was reexamined. The amplitudes and latencies of the brain stem response (Jewetts wave V), middle latency components Na and Pa, and vertex potentials P1, N1 and P2, evoked by tone burts of various rise times, were analyzed. Increases in rise time were associated with smaller peak amplitudes and longer peak latencies for all of the components measured. These effects were comparable in magnitude for all the components. The results are interpreted in terms of a delayed and less synchronized neural discharge from the cochlea as rise time is extended.

Brain stem response audiometry at speech frequencies.

Auditory-evoked brain stem response (BSR; wave V) was studied, using tone pips at three speech frequencies (500, 1 000 and 2 000 Hz) as stimuli. The tone pips consisted of 5-ms rise-decay times without a plateau. BSR recordings were made in 10 normal subjects and in 16 subjects with impaired hearing. In the normal subjects, BSR thresholds ranged from 10 to 20 dB SL at these three frequencies. In the subjects with impaired hearing, BSR thresholds corresponded well to conventional pure-tone thresholds at each frequency in cases of low- as well as high-frequency hearing loss. In all subjects with impaired hearing, the BSR thresholds were higher by as much as 25 dB than the pure-tone thresholds. The mean differences between these two thresholds at 500, 1 000 and 2 000 Hz were 11.3 +/- 8.0, 10.9 +/- 6.2 and 10.9 +/- 7.3 dB, respectively. Thus, we conclude that the BSR is useful for objective assessment of hearing thresholds at each of these speech frequencies.

Three-dimensional Morphological Analyses of Positional Dependence in Patients with Obstructive Sleep Apnea Syndrome

Background:It is generally considered that patients with obstructive sleep apnea syndrome (OSAS) at increased perioperative risk should be placed in nonsupine positions throughout the recovery process; however, not all patients with OSAS show positional dependence. The authors hypothesized that morphological differences exist in three-dimensional (3D) soft tissue and craniofacial structures of the pharyngeal airway between positional and nonpositional OSAS. Methods:The subjects of the study were body mass index–matched, age–matched, and apnea hypopnea index–matched positional (n = 10) and nonpositional (n = 10) Japanese OSAS patients and body mass index–matched Japanese control subjects (n = 10). Pharyngeal magnetic resonance imaging and cephalometric radiography were performed during wakefulness. Results:The patients with positional OSAS had a smaller volume of the pharyngeal lateral wall soft tissues, larger maxilla-nasion-mandible angle, and smaller lower facial height than the nonpositional OSAS and the control subjects. The patients with positional OSAS showed a significantly steeper sella-nasion-mandible angle and smaller craniofacial volume than the control subjects. There were no significant differences in tongue volume and 3D pharyngeal anatomical balance between positional and nonpositional OSAS. Multivariate stepwise regression for positional dependence showed that the dominant determinant was the volume of the lateral pharyngeal wall, followed by lower facial height and maxilla-nasion-mandible angle. Conclusions:Patients with positional OSAS have wider airways in the lateral parts, lower facial height, and more backward position of the lower jaw, which may explain differences in the maintenance of pharyngeal airway patency in the lateral sleep position.

The effect of onset, offset and rise-decay times of tone bursts on brain stem response.

Auditory-evoked brain stem responses (BSRs) were recorded from the scalp in 4 cats and 10 human subjects. Auditory stimuli consisted of 1 kHz tone bursts and their duration, intensity and rise--decay time were varied. The BSR evoked by the tone bursts consisted of on- and off-responses. The off-responses showed different intensity--amplitude and different intensity--latency functions from the on-responses. In the feline subjects, an increase in rise time as an input resulted in an increase in the number of recorded sharp waves of the on-responses, indicating that several cycles of tone bursts during the rise time take part in generating on-responses. In both the feline and human subjects, BSRs were evoked by tone bursts with a rise time of as long as 10 msec; an increase in the rise time resulted in an increased latency and broadened waveforms of the on-responses. These demonstrated properties of BSR may provide useful information in determining input parameters, such as rise--decay time, appropriate for audiometric assessment.

Simultaneous recordings of the brain stem response and the frequency-following response to low-frequency tone ☆

Abstract The brain stem response (BSR) and the frequency-following response (FFR) evoked by 500 c/sec tone bursts were simultaneously recorded from the twenty normal hearing and twenty-eight hearing-impaired subjects. By reversing the stimulus phase and the polarity of the recordings, the BSR and FFR could also be recorded in isolation from one another. In normal hearing subjects the FFR could be recorded at intensities of 30 dB HL or 40 dB HL, while the BSR could be discerned at even lower stimulus levels. In cases of severe high frequency hearing loss, both the BSR and the FFR could be recorded at normally low stimulus levels which is inconsistent with the view that BSR and FFR originate from the basal turn of cochlea. In cases of flat conductive hearing loss, the discrepancies between the BSR thresholds and the FFR thresholds were in the normal range (20–30 dB), but in cases of flat sensorineural hearing loss, these discrepancies were absent or very small (within 10 dB). We attribute this to recruiting.

Cochlear Processes Affecting Wave V Latency of the Auditory Evoked Brain Stem Response: A Study of Patients with Sensory Hearing Loss

The effects of inner ear pathologies on wave V latency of the auditory evoked brain stem response (BSR) were studied in 12 selected patients with flat, low-frequency, severe high-frequency, and gradual high-frequency sensory hearing loss. In patients with flat and low-frequency sensory hearing loss (Menieres disease), the latencies of wave V at intensities 4--10 dB greater than their response thresholds were roughly the same as those in normal-hearing subjects. In patients with severe high-frequency sensory hearing loss (sharp cut-off at about 2 or 3 kHz), the latencies of wave V were always delayed, compared with those in normal-hearing subjects. In patients with gradual high-frequency sensory hearing loss, the latency of wave V was delayed according to the degree of hearing loss (as determined by pure tone audiometry) above 2 kHz. The data are interpreted as showing that the wave V latency is sensitive to a kind of recruiting phenomenon in the transduction process as well as being an index of the pressure wave travel time to the cochlear portion responsible for the elicitation of the BSR.

P300 response to tones and speech sounds after cochlear implant: A case report

P300 potentials evoked by tones and spoken words were recorded from a 20‐year‐old man with a House‐3M® single‐channel cochlear implant. Three months after cochlear implantation, there was a slight appearance of P300 response to both pure‐tone stimuli and spoken‐word stimuli; 6 months later, clearly identifiable P300 response to both pure‐tone stimuli and spoken‐word stimuli were obtained. These results are consistent with an encoding improvement for re‐establishment of information processing after auditory rehabilitation.

Binaural Interaction of a Beating Frequency-Following Response

Frequency-following responses to 500-Hz tone bursts presented to the left ear and 540-Hz tone bursts presented to the right ear were recorded from human subjects. Recordings were made both under monaural and binaural conditions. The responses summed over monaural conditions (for left and right ear stimulation) were larger than the responses obtained in the binaural condition. This binaural interaction shows that the frequency-following response reflects binaural processing probably occurring at or below the level of the inferior colliculi.

Pathological findings in the temporal bone of newborn infants with neonatal asphyxia.

Conclusions Hypoxia in adults frequently causes damage to the brain, but not the inner ear. However, hypoxia in neonates with inadequate blood–inner ear barrier function causes damage to the inner ear, leading to hearing loss and equilibration disorder. Objective Clinically, asphyxiated neonates sometimes have the complication of sensorineural hearing impairment at high frequencies. Many reports suggest that this problem is caused by hypoxic encephalopathy. However, it is not clear whether inner ear disorders are present. In this report we examined the inner ear pathology of four asphyxiated neonates using serial sections of temporal bone. Material and methods The subjects (n=4) were 1–13-day-old neonates with pregnancy periods of 24–36 weeks. Their fetal growth curves were within the normal range. There was one case each of twin pregnancy, placental abruption, placenta previa and meconium aspiration syndrome. Results For the case of severe neonatal asphyxia, damage to the inner ear included the degeneration and disappearance of outer hair cells of the organ of Corti and edematous changes in the stria vascularis. Degeneration of spiral ganglion and vestibular ganglion cells was observed in two of the other cases.

A new mutation in the POU3F4 gene in a Japanese family with X-linked mixed deafness (DFN3)

Objective: The molecular defect in patients with X‐linked mixed deafness showing a perilymphatic gusher at stapedectomy (DFN3) has been attributed to mutations in the POU3F4 gene. This study aimed to clarify an allelic variant of this gene. Study Design: This was a genetic study of a single Japanese family with DFN3. Methods: Products of a polymerase chain reaction (PCR) were subjected to single‐strand conformation polymorphism (SSCP) analysis. Direct sequencing of PCR products from patients and carriers showing SSCP variants was performed using the fluorescent dideoxy termination method and a sequencer. Results: Sequencing of the PCR product revealed a 6‐base deletion (TTCAAA) at nucleotides 601 to 606, resulting in a two‐amino‐acid deletion in the POU3F4 protein, (phenylalanine and lysine at amino acid residues 201 and 202). The deletion was adjacent to the site of a nonsense mutation previously described. Conclusion: Microdeletions at a previously undescribed location account for some clinically important POU3F4 mutations. Laryngoscope, 108:1544–1547, 1998