I. W. S. Mair

High-Frequency Audiometry Normative Studies and Preliminary Experiences

A new, commercial high-frequency audiometer, Demlar 20K, for measuring hearing thresholds between 8 and 20 kHz has been used routinely in different patient groups and in a control population over the past 3 years. Test-retest studies have shown that this instrument can be used in the clinic with approximately the same degree of reproducibility as in conventional audiometry. While inter-subject variation is comparatively large, repeated evaluations can be performed in individual cases with an acceptable degree of reliability. This techniques can be helpful in differentiating between noise damage and presbycusis. Pre- and post-operative high-frequency audiometry may prove to be of value in the assessment of middle ear surgical techniques.

Recurrent facial palsy

SummaryDuring a 9-year period a total of 447 peripheral facial palsies was seen. Of the 377 cases of acute idiopathic facial palsy (AIFP) for which information was available, 41 (10.9%) were recurrent attacks. The final outcome is known for 346 (92%) of AIFPs. All patients were subjected to an extensive investigation protocol. No prognostic differences were found between primary and recurrent attacks of AIFP and complete recovery occurred just as frequently after recurrent palsies irrespective of whether these were ipsilateral or contralateral to the first attack. The incidence of recurrent AIFP was 2.03/100,000/year.

High-Frequency Audiometry: Comparison of Electric Bone-Conduction and Air-Conduction Thresholds

Thresholds have been measured with two commercially available high-frequency (HF) audiometers providing respectively air-conduction (AC) and electric bone-conduction (EBC) stimulation. Normative values for the latter have been obtained, and the reduction of HF sensitivity with both stimulus modes documented in two groups aged 50-59 and 70-79 years. EBC reproducibility is of the same order of magnitude as the AC signal through 14 kHz, while the dynamic range is limited to 50 dB. Lateralization of the EBC signal occurs up to at least 17 kHz. The logarithmic conversion factor of Tonndorf and Kurman [Ann. Otol. Rhinol. Lar. 93: 576-582, 1984] does not result in equivalent AC and EBC thresholds at all frequencies, but does provide similar loudness sensation increases. The 40 log (i) re 1 mA conversion factor must be adjusted with a frequency-dependent additive correction.

Frequency Specificity of the Auditory Brainstem Responses A Derived-Band Study

Auditory brainstem responses evoked by both clicks and 0.5 kHz tone-bursts were recorded using the derived-band paradigm in 10 normal-hearing subjects. The derived-band analyses showed a similar distribution of activity with both stimuli, the largest contributions coming from the 2-4 and 4-8 kHz bands. Neither the click nor the 0.5 kHz tone-burst is a frequency-specific stimulus, and both would appear to be unsuitable for brainstem response audiometric evaluation of the apical cochlea.

Basal cell adenomatosis of minor salivary glands of the upper lip.

SummaryThe basal cell adenoma is one of the more commonly occurring types of salivary tumors in the upper lip. A case with multiple (five) tumors is presented and the literature reviewed. This lesion would be more correctly designated as an adenomatosis. In spite of its frequent multicentricity, recurrence is unusual following surgical removal.

Auditory Brain-Stem Electric Responses Evoked with Suprathreshold Tone-Bursts

The brain-stem electric responses elicited by tone-bursts with central frequency at octave intervals from 0.5 to 4 kHz and at 80--100 dB HL stimulus levels have been studied in normally hearing subjects and patients with sensorineural hearing loss. Jewett V latencies were considerably prolonged in patients with retrocochlear or central pathology. Latencies from normal and cochlear hearing loss ears were largely independent of thresholds at both the stimulus and other frequencies. The interpretation of response latencies at suprathreshold stimulus levels is discussed. Stimulus frequency should be selected in accordance with the pure-tone audiogram, and ears with prolonged latencies investigated at more than one frequency.

High-frequency audiometry: Air- and electric bone-conduction

Normative values have been obtained for high-frequency air- and electric bone-conduction thresholds in different age groups. Reproducibility with both methods is of the same order of magnitude as with conventional audiometry. The two thresholds can be compared and the air-conduction/electric bone-conduction gap obtained by transforming the electric bone-conduction values to a dB notation by means of a formula containing a frequency-dependent constant.

Development of surface-recorded cochlear and early neural potentials in the cat

ZusammenfassungDie Entwicklung der an der Oberfläche registrierten cochlearen und frühen neuralen Potentiale wurde bei der Katze von der Geburt bis zur 8. Woche studiert.CM, SP und jeder der neuralen Wellen haben ein charakteristisches altersbedingtes Entwicklungsmuster und eine Responsschwelle.Welle IV wird am wenigsten von einer Reduktion in der Stimulusintensität beeinflußt. Die Schwelle der beiden cochlearen Potentiale sind dagegen erhöht. Tiere mit angeborener einseitiger Taubheit sind bestens geeignet für das Studium der funktionellen Reifung der Gehörbahnen, besonders in bezug auf die exakten Latenzzeitmessungen.SummaryThe development of the surface-recorded cochlear and early neural potentials has been studied in the cat from birth to the 8th post-natal week. CM, SP, and each of the neural waves has a characteristic temporal developmental pattern and mature threshold. Wave IV is the most resistant to reduction in stimulus intensity levels, while the thresholds of both cochlear potentials are high. Animals with hereditary unilateral deafness constitute a most convenient model for the study of functional maturation in the auditory pathways, particularly with regard to precise latency estimations.

Brain-stem responses of the cat and interaural attenuation

SummaryThe early auditory evoked responses have been studied in bilaterally hearing cats, and in animals with hereditary unilateral anacusis. Cross-over stimulation of the hearing ear occurs at an interaural attenuation of 50-50 dB, and all six waves of the responsare present at supra-threshold stimulus levels.

Screening for Retrocochlear Pathology

In 1982, 135 patients were screened for possible retrocochlear pathology, by means of an investigation protocol consisting of caloric test, impedance audiometry and brainstem response audiometry (BRA). A combination of the first two of these procedures had an unacceptably low prognostic accuracy. BRA indicated retrocochlear pathology in 8 and was inconclusive in 4 cases. Enhanced computer tomography revealed an intracranial tumour in 4 of the former, while no space-occupying lesion could be demonstrated in the remainder nor in the 4 patients with inconclusive BRA. BRA is the best single test for screening of this patient category.