Retrocochlear hearing disorders

The diagnosis of retrocochlear hearing impairment is mainly based on threshold tone decay, absence of the stapedius reflex, abnormal dichotic speech discrimination and ERA findings. A relatively poor discrimination for monosyllables with regressive understanding at high intensities can also indicate a neural or central lesion provided that the unaffected side has been correctly masked. ERA results mainly show a synchronisation disorder within the brain-stem, i.e. the J V-response is prolonged or cannot be recorded at all. The cortical response N1, however, corresponds to the subjective threshold except that in impairments of the cortex, the N1-response is worse than expected from the pure tone threshold. Representative examples are given.     

Functional hearing loss.

Functional hearing loss is a rather common entity, although it probably is overlooked more often than not. In most instances, the services of an experienced audiologist are necessary if one is to detect these cases. First, one must consider carefully the patient's behavior before and during the otologic and audiologic examination, and note the referral source, if any, since patients with certain backgrounds are more apt to exhibit functional hearing loss than others. Second, careful attention is given to certain aspects of the initial basic audiometric examination. Discrepancies here often stand out and point clearly toward functional loss. A so-called "modified approach" to conventional audiometry has enabled us to detect almost all cases of functional hearing loss without resort to the special audiometric tests designed for that purpose.     

Genes related to hearing disorders

The inner ear is a highly specialized organ and the mechanisms of its function are complex and have not yet fully been elucidated. For example, there are questions such as how the stereocilia characteristics of hair cells are regularly arranged, how the reactions of stereocilia and ion channels of hair cells to sound are controlled, and how the ion environment is maintained in the internal ear. The mechanisms of inner ear function are being elucidated by analysis of human hereditary hearing disorders and genetic and molecular biological techniques using mouse hearing disorder models. Understanding of the mechanism of inner ear function provides important information for treatment of the inner ear. This review outlines several findings obtained from humans with hereditary hearing disorders and mouse hearing disorder models.     

Functional hearing loss in children

The cases of children diagnosed with pseudohypacusis in the Department of Pediatric Otolaryngology were presented. Probable mechanism of its pathogenesis was described. The main stress was put on its correct diagnosis particularly in children with co-existing organic changes. Diagnosis of pseudohypacusis in children is not problematic provided that the occurence of this disease is taken into consideration during diagnostic procedures.     

Functional hearing loss in children

This report reviewed 39 school-age children diagnosed as having a functional hearing loss utilizing auditory brainstem response (ABR) audiometry during the past 5 years at the Department of Otolaryngology, Kyushu University Hospital in Japan. Twenty-seven cases were females and 12 were males. Seven cases had a hearing loss unilaterally and 32 bilaterally. Although pure-tone audiometry revealed a variety of audiogram shapes, two-thirds of the cases had a flat or saucer-shaped audiogram with a mild to moderately severe hearing loss. ABR audiometry for the frequencies of 1, 2 and 4 kHz indicated a normal hearing threshold in 65 ears of 35 patients, and mild threshold elevations of at least one frequency in the remaining 6 ears of 4 patients. Three illustrative cases were demonstrated, and a discussion was held regarding the features in audiometric tests, and environmental factors surrounding the children with this condition. We emphasized that the physiological hearing measurement such as ABR audiometry should be performed when any discrepancy was noted between the patient's history and results of pure-tone audiometry, because of not infrequent occurrence of functional hearing loss.     

Rehabilitation of patients with hearing disorders using hearing aids and tactical hearing measures

After a brief summary of the problems of rehabilitation of hearing-impaired subjects, the optimal conditions for rehabilitation with hearing aids are presented: a) The right timing is crucial. b) Optimal provision of hearing aids must be carried out in close co-operation between the patient, the hearing aid technician and the otolaryngologist. c) Easy handling of the hearing aid and the use of attachments must be guaranteed. d) The hearing-impaired person must be fully informed as to the extent and type of hearing loss. He/she must accept the affliction and know about the possibilities of rehabilitation. The patient's motivation is a pre-requisite for all further steps. e) The patients must learn tactical measures to make optimal use of their hearing ability in relation to their environment. Hearing tactics consist of hearing training and a change in the attitude of the hearing-impaired patients themselves and their attitude towards their surroundings.     

Functional hearing loss and its relationship to resolved hearing levels

The nature of functional hearing loss was retrospectively studied with respect to hearing sensitivity after resolution of the nonorganic components in 63 adults with bilateral exaggerated losses (126 ears). The configuration of the functional components (difference between the functional and resolved thresholds) was found to be related to that of the resolved hearing levels. The size of the functional overlay was essentially the same across the audiometric frequency range when the hearing was actually normal or if there was only mild loss. In cases of precipitously sloping high-frequency losses, the magnitude of the functional overlay became dramatically smaller for the impaired frequencies than for lower frequencies where hearing was normal or only mildly impaired. Moderate and severe losses represented a transitional situation, in which the functional components became gradually smaller with increasing frequency. Subjects with different resolved hearing in each ear (e.g., mild loss in one ear and a precipitous loss in the other) demonstrated nonorganic overlays that were consistent with the actual hearing levels for each respective ear. The findings suggest the use of an internalized, loudness level-based anchor by subjects with functional losses: the test signal must sound as loud as the anchor at each frequency in order for an exaggerated threshold response to be volunteered at that respective frequency. The pure-tone audiometric configuration and amount of functional loss at least in bilateral cases is thus consistently accounted for on the basis of known and explainable auditory factors.