Hitoshi Yamane

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.

Clinical Evaluation of the Auditory Evoked Brain Stem Response

A clinical evaluation of the auditory evoked brain stem response (BSR) has been performed in eleven artificial, and twelve pathological cases of conductive hearing loss, and also in seven patients with deafness from Menieres disease. The latency of wave V of the BSR was plotted as a function of auditory stimulus intensity (of clicks from 10 dB to 85 dBHL) to produce latency-intensity (L-I) curves for subjects with hearing losses, and compared to those from a normal population. L-I curves from conductive hearing losses of both artificial, and pathological cases showed characteristic horizontal shifts to the right (in dBHL); thresholds determined by BSR audiometry were within 15 dB of the thresholds obtained by standard audiometry (4 kHz) in 83 f of these cases. L-I curves from Menieres patients were within the normal range at high stimulus intensities but showed a marked deviation from normal at low intensities; thresholds estimated by BSR audiometry in Menieres disease were usually lower than those determined by standard audiometry (4 kHz). The results indicate that BSR audiometry can be useful in the evaluation, differentiation, and threshold determination of peripheral auditory pathologies.

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.

THE CHOICE OF STIMULUS IN THE AUDITORY BRAINSTEM RESPONSE TEST FOR NEUROLOGICAL AND AUDIOLOGICAL EXAMINATIONS

In Japan, the auditory brainstem response (ABR) has already been established as a useful test. Most of the ear, nose, and throat clinics in university hospitals are equipped with the ABR system. Neurologists, neurosurgeons, and pediatricians are also interested in the ABR. However, most of them are not familiar enough with the test yet. In our ENT department, there are two groups of patients. One is comprised of patients with neurological disorders and the other of infants and young children with suspected hearing impairment. The purpose of the ABR test is apparently different for each group of patients. According to the data requested from the test, appropriate stimuli were studied and established in my department. Consequently, clicks are utilized for neurological examination and tone pips with a 5 msec rise and fall were selected for audiological examination. It does yet not seem to be commonly recognized that the appropriate choice of stimulus helps to increase the data from the ABR test. FIGURE I shows the ABR to a click stimulus (left) and that to a tone pip (right). The click-evoked ABR delineates clearly separated waves that represent the sequential activities in the brainstem auditory pathways. On the other hand, response to the tone pip may seem unfamiliar to those who have been utilizing the click stimulus only. The separated five waves are missing in the tone-pip-evoked ABR and the slow component of the ABR is enhanced. The difference of wave form is due not only to the difference of stimulus sound, but is also related to differences in the stimulating and recording system. TABLE 1 summarizes the arrangement of the ABR system for neurological examination and audiological examination. In addition to the choice of stimulus, the important role of the high-pass filter and the time base of the display should be emphasized. The high-pass filter, which is common for neurological and audiological examinations, has a slope of 5 dB/octave and its 3 dB roll-off point is set a t 48 Hz. This filter was selected empirically for the purpose of maintaining the slow component of the ABR. The slow component, which rises positively toward the peak of wave V and falls negatively afterwards, is essential for audiological examination because it is the indicator of the threshold of ABR. The time base of the display also influences the ABR threshold. By using a 10 msec time base, details of the response configuration are clearly visible and accurate measurement of latency is possible. Use of a 30 msec time base results in loss of the detail. However, it enhances the slow component and makes threshold measurement easier. In addition, the peak latency of wave five is sometimes much longer than 10 msec when the intensity of the stimulus is close to the threshold. 7 3 1

Cochlear Initiation Site of the Frequency-Following Response: a Study of Patients with Sensorineural Hearing Loss

The cochlear initiation of the frequency-following response (FFR) was assessed by comparing the FFR thresholds to the pure-tone thresholds in four groups of patients suffering from different forms of sensorineural hearing loss. The groups consisted of patients suffering from (1) pure high-frequency hearing losses; (2) high-frequency hearing losses mixed with moderate low-frequency losses; (3) flat hearing losses, and (4)low-frequency hearing losses. Across groups, the pattern of thresholds of the FFR evoked by 500-Hz tome bursts paralleled the pattern of pure-tone thresholds only for the low frequencies- not the high frequencies. In order to clarify the interpretation of this result, a high-pass masking experiment was performed on patients with low-frequency hearing losses. High-pass masking noise did not affect the FFR thresholds to 500-Hz tone burst, but it produced a phase shift of the FFR at stronger intensity levels. The data are interpreted as strongly supporting the view that the FFR at low levels is initiated primarily by activity in the apical portion of the cochlea.

Effects of number and interstimulus interval of tone pips on fast responses.

Effects of stimulus number and interstimulus interval on auditory-evoked fast responses (BSR: Jewetts V, and middle-latency components: Na, Pa and Nb) were studied by using 1000- and 500-Hz tone pips in 6 normal human adults. At a stimulus intensity of 50 dB SL, 500 stimuli evoked BSRs and the middle-latency components in all cases. At a stimulus intensity of 30 dB SL, 1000 stimuli were necessary to evoke BSRs and Na in all 6 subjects. Even 4000 stimuli were not sufficient for identifying Pa in 1 subject and Nb in 3 subjects. The largest mean peak-to-peak amplitude was the Na-Pa amplitude, but, differences across subjects were large. On the other hand, the BSR-Na amplitude showed relatively small differences across subjects. The BSR latencies were highly stable across subjects. These characteristics indicate that the BSR-Na component is more suitable as an indicator for objective audiometry than either the Na-Pa or Pa-Nb component. The BSR-Na amplitude did not show a decrease as the interstimulus interval was decreased from 104 to 32 ms. On the other hand, the Na-Pa amplitude significantly decreased as the interstimulus interval was decreased from 104 to 42 ms, and the Pa-Nb amplitude also significantly decreased as the interstimulus interval was decreased from 104 to 73 ms. Therefore, because of its resistance to the effects of high rates of stimulation, the BSR-Na component appears to be a suitable audiometric index in the clinical situation where time constraints are a consideration.

Tympanoplasty for cholesteatoma in relation to the patient's age.

The relationship between age and three different pathological conditions of cholesteatoma (epitympanic, posteriorsuperior quadrant and mesotympanic) was analyzed in 88 patients. The middle ear pathology and pre- and post-operative hearing levels were examined.For posterior-superior quadrant and mesotympanic cholesteatomas, there were no age differences in the air conduction thresholds of speech frequencies or in middle ear pathology before tympanoplasty. For the epitympanic type, however, the air conduction thresholds were better and the middle ear pathology milder before age 40.The air conduction threshold after tympanoplasty was better in the epitympanic cholesteatoma group than in the other two groups and in younger patients in all three groups.