T. Jauhiainen

Hearing Preservation in Acoustic Neurinoma Surgery

In a series of 120 patients with acoustic neurinoma, hearing preservation at removal of the tumour via the suboccipital approach was attempted in 30 ears. Hearing was preserved in 13 ears (43%), but in two, hearing was lost entirely in 3 to 4 years; thus the success rate was 36%. In 9 of the remaining 11 ears useful speech discrimination was present. Audiological tests showed increased retrocochlear loss after surgery. A surgical team should master the methods of both translabyrinthine and suboccipital surgery in order to choose the best approach for each patient.

Combined Effect of Noise and Neomycin on the Cochlea

The study was designed to examine the combined harmful effect of intensive noise and neo-mycin on the cochlea in three groups of guinea pigs; one receiving neomycin alone, one exposed to noise alone, and one exposed to both factors. Electrophysi-ologically and microscopically, the harmful effects were shown, when the two factors were combined, to increase more than predicted by simple addition of the two effects. The correlation between the percentage of destroyed outer hair cells and the micro-phonic potential amplitude loss was calculated.

The Prognostic Value of Eustachian Tube Function Measurements in Tympanoplastic Surgery

The Eustachian tube function was tested preoperatively by sonotubometry and by the negative pressure equalization test in 87 ears subjected to simple myringoplasty, tympanoplasty alone, or tympanoplasty combined with mastoid surgery. The relations between tubal function test results and healing were analysed on average 10 months after the operation. The results indicating absent or partial pressure equalization ability were poorly correlated with the successful outcome of surgery, while sonotubometry showed a good correlation. Pressure equalization may produce such an unphysiological underpressure that many test results are erroneously negative. Sonotubometry is an entirely physiological method and has in this Department replaced the pressure equalization test for routine evaluation of the Eustachian tube function.

Noise sensitivity and hearing disability.

The aim of this study was to investigate the association of noise sensitivity with self-reported hearing disability and hearing levels, with consideration of the role of self-reported history of noise exposure and use of hearing protectors. The study is based on the Finnish Twin Cohort. In 1988, a noise questionnaire was sent to 1005 twin pairs, 1495 individuals (688 men, 807 women) replied. The age range was 31-88 years. Information on some potential confounders was obtained from the questionnaire in 1981 for the same individuals. A subsample of thirty-eight elderly women with noise sensitivity response from 1988 had audiometry data from 2000 to 2001. Noise sensitivity was associated with self-reported hearing disability among all subjects [odds ratio (OR) 1.55, 95% confidence interval (CI) 1.14-2.12] and among women (OR 1.90, 95% CI 1.19-3.04), but no-more significantly among men (OR 1.31, 95% CI 0.86-1.98). The association was primarily seen among younger subjects (50 years or less). The difference between noise sensitive and non-noise sensitive elderly women in the average of thresholds at frequencies of 0.5-4 kHz in the better ear was not significant (Pr = 0.18). Noise sensitivity did not modify the association of hearing disability with the self-reported history of occupational noise exposure. Noise sensitivity was associated with the use of hearing protectors at work. The study shows the importance of recognizing the noise sensitive in noise effect studies, since sensitivity in annoyance has implications in most of the effect categories.

Diagnosis and Surgery of Acoustic Tumours

In the diagnosis of acoustic neuromata the stapedial reflex test, the forward vs reverse Békésy test, the loudness balance test, and the adaptation test have all been found superior among the special tests used in predicting a tumour diagnosis. Conventional X-ray studies of the internal acoustic meati are always performed, followed by tomograms and in suspected cases by meatocisternography. In the present series translabyrinthine total removal was performed in 21 cases, a planned decompression in 5, while in 2 the removal was subtotal. Only two permanent facial paralyses arose, one corrected by masseteric plasty and the other by facial-hypoglossal lateral perceptive hearing impairment as being caused by a tumour until proven otherwise.

Comparison of Pure Tones and Noise Stimuli in Sonotubometry

Sonometric data on the Eustachian tube opening response to swallowing and to pressing the mandible down were evaluated in 51 normal ears and 62 ears with chronic disease. Testing with a narrow-band noise which was centered on 7 and 8 kHz gave the best results. The limit for a positive response was set at 3 dB, and of the normal ears, 80% showed a positive response in a short routine test. The data correlated reasonably well with surgical results. If test results point to tubal insufficiency, measures should be taken to prevent the formation of retraction pockets.

VESTIBULAR NEURECTOMY AND SACCUS DECOMPRESSION SURGERY IN MENIERE'S DISEASE

Results of vestibular neurectomy, total eighth nerve section, and saccus decompression in 42 patients with Menieres disease are reported. Vestibular nerve section was found in isolated cases to be a very effective method of abolishing the symptom of vertigo. Hearing is not affected but may be lost owing to opening of the vertical canal or disruption of blood supply. Saccus surgery might be the surgical treatment of choice in early cases with good hearing but in patients with fixed non-fluctuating hearing loss, rehabilitation can be effected only by vestibular neurectomy. In bilateral cases either sac surgery or the use of vestibulotoxic drugs is advised.

Experimental Deafness Caused by Etachrynic Acid

A single large intravenous dose of etachrynic acid (20–40 mg/kg body weight) causes a rapid significant diminution in the voltages of cochlear microphonic potentials in the guinea pig. No permanent functional or morphologic alterations can be demonstrated 3 weeks following a single large intravenous dose (30 mg/kg body weight) of the drug.

Behavioural Observation Audiometry in Testing Young Hearing-Impaired Children

The aim was to examine the accuracy of unconditioned behavioural observation audiometry (BOA) in predicting hearing acuity in children and the validity of test results at various frequencies. The study was designed to longitudinally compare each childs best BOA response level (at the age >12 months) with the conclusive pure-tone threshold of the better ear. The subjects were 119 children derived from a material of 353 children fitted with a hearing aid at Helsinki University Central Hospital. BOA was carried out on 119 children, 19 of whom did not respond to frequency-specific stimuli. The predictive power of BOA depended on the severity of hearing loss. At the hearing level of 30-39 dB, BOA registered 10-15 dB poorer levels than the pure-tone audiometry. The pure-tone averages (0.5, 1, 2 kHz) of 50-69 dB agreed best with the BOA responses. In severe impairments (more than 70 dB HL), the BOA registered too good hearing. Correlation of the results from the two modes to measure hearing level was highly significant (r = 0.71, p = 0.000), and the pure-tone hearing level agreed with that of BOA at the frequencies 0.5 to 4 kHz. Our results show that BOA averages < or =30 dB rarely indicate hearing loss demanding fitting of a hearing aid.

Cochlear Implants, Vibrators and Hearing Aids in the Rehabilitation of Postlingual Deafness

Three groups of postlingually deaf adults were formed by non-random selection. The subjects with some residual hearing were fitted with a powerful hearing aid (HA group, n = 10). The others received either a single-channel vibrotactile aid (V group, n = 8) or a single-channel intracochlear implant (CI group, n = 10). Training containing individual counselling and rehearsal in small groups was arranged. During the follow-up (CI group 2.0 yrs, V group 1.8 yrs, HA group 2.6 yrs), the subjects achievement was assessed by a repetition of audiological testing and written questionnaires. Whereas the HA group obtained the highest scores in the audiological tests, the CI group found the implant most beneficial in everyday life. No significant improvement in the test scores was observed during the follow-up. The extent of personal training, after an initial training period and motivation of the user, did not affect the test scores or the subjective evaluation.