Takehiko Harada

Ototoxicity of neomycin and its penetration through the round window membrane into the perilymph.

The ototoxicity of neomycin and its concentration in the perilymph after direct application on the round window membrane were studied. After placing 5 mg of neomycin on the round window membrane of guinea pigs for various time intervals, concentration of the drug in the perilymph was determined by high performance liquid chromatography, and the cochlea was examined by light microscopy. Neomycin penetrated the round window membrane quite easily, and its concentration in the perilymph became extremely high in a short time and then decreased gradually. This indicates that high concentration of neomycin in the perilymph can be attained by application of a small amount of the drug on the round window membrane. Ototoxicity of neomycin was observed after application for 4 hours. Cochlear damage increased as neomycin application time became longer, but no consistent relationship was noted between the concentration of neomycin and the amount of damage. This result is discussed from the point of concentration and persistence of the drug in the inner ear fluids.

Temporal bone histopathology in deafness due to cryptococcal meningitis.

This paper reports on a patient who survived an attack of cryptococcal meningitis eight years prior to his death. A bilateral sensorineural hearing loss had been noted a short time before the patient was admitted to the hospital, and was the only complication after he recovered from the disease. Histopathologic study of the temporal bones showed a similar pattern of pathology in both ears, the most striking finding being a severe loss of spiral ganglion cells in Rosenthals canal, and of cochlear nerve fibers in the osseous spiral lamina and internal auditory meatus. The vestibular nerve was mostly free from pathology. The organ of Corti was atrophic but the hair cell population appeared to be almost normal. A slight number of cryp-tococci were observed in limited areas of the cochlear and the saccular nerves in the internal auditory meatus. The severe pathology of the cochlear nerve was compatible with audiologic evaluations, which pointed to a retrocochlear lesion. Thus, this case demonstrates some characteristic aspects of cryptococcal infection of the temporal bone: The primary site of invasion was the cochlear nerve in the internal auditory meatus and the modiolus, leading to the loss of ganglion cells and nerve fibers, while the vestibular nerve appears to have been resistant to infection.

An Electrocochleographic Study of Acute Low-Tone Sensorineural Hearing Loss

SummaryTwenty-four patients with acute low-tone sensorineural hearing loss (ALHL) were examined using electrocochleography. The negative summating potential (SP) amplitude and the summating potential/action potential (AP) ratio were significantly greater in the ALHL patients than in normals. The SP/AP ratio was smaller in the ALHL patients than in patients with known Menieres disease and moderate hearing loss, although the SP amplitude was somewhat greater in the former. An abnormal increase in the SP amplitude following click stimuli was found in 54% of the ALHL patients, while the SP/AP ratio was increased abnormally in 63% of these patients. These findings suggest that the pathophysiology of ALHL may be similar to that for endolymphatic hydrops.

Sudden Deafness and Asymptomatic Mumps

Adult patients who had experienced sudden deafness were examined for possible presence of subclinical mumps infection, using a new method of detecting mumps IgM antibody. Three of 53 patients demonstrated a positive reaction, indicating a strong correlation of sudden deafness with recent mumps infection. Mumps vaccination is recommended for those who have one deaf ear, in order to protect the better ear from mumps infection.

Sensorineural hearing loss associated with otitis media with effusion.

The clinical records of 1,372 cases of otitis media with effusion (OME) treated during the past 10 years were reviewed in search of associations with sensorineural hearing loss (SNHL). In 14 cases (1.0%), the development of SNHL was considered to be etiologically related to OME. These 14 cases were classified into two groups. In group A, which consisted of 5 cases, the clinical feature was acute onset of SNHL and gradual improvement. In group B of 9 cases, SNHL progressed gradually or insidiously and did not improve. Different pathophysiology may be assumed to underlie these two groups. The results of this study demonstrate that we have to pay attention to a possible development of SNHL during the course of OME.

Temporal Bone Histopathologic Findings in Congenital Anomalies of the Oval Window

The histopathologic findings in five temporal bones from three cases showing various stages of oval window development arrest are presented. The anomalies ranged from complete absence of the oval window to congenital cartilaginous fixation of the stapedial footplate. Surgical approaches for establishment of a new oval window must take into consideration the frequent association of facial nerve anomalies with anomalies of the oval window.

Labyrinthine Anomalies with Normal Cochlear Function

Three cases of labyrinthine anomaly confirmed by polytomography and CT scan are reported. They showed similar dysplasia of the bony labyrinth: dilation and fusion of the lateral semicircular canal (SCC) and of the vestibule with a normally shaped cochlea and other SCCs. One side was involved in 2 cases and both sides in 1 case. The 1st case showed normal hearing levels with markedly reduced response to caloric stimulation in the affected ear. The 2nd case showed conductive hearing loss due to cholesteatoma with normal bone conduction hearing levels and normal caloric response. The 3rd case showed bilateral conductive hearing loss of unknown cause. The classification of labyrinthine anomalies and labyrinthine functions is discussed. Labyrinthine anomaly detected by CT scan and polytomography can be present in patients with normal cochlear and/or vestibular function.

Osteogenesis Imperfecta Tarda and Otosclerosis a Temporal Bone Histopathology Report

The histopathology of the temporal bones in a 59-year-old female with osteogenesis imperfecta tarda (OIT), complicated by otosclerosis, is presented. Advanced conduction and sensorineural deafness in the left ear and absence of a response to sound in the right ear had been recorded before she died and the temporal bones were acquired for histological study. Histopathological examination revealed a marked degree of porosity of the labyrinthine capsule, enlarged vascular spaces, and a deficiency in number and size of bony trabeculae in the marrow of the petrous apex. All layers of the otic capsule had been extensively replaced by otosclerotic material including the bony semicircular canals and the cochlear and vestibular walls. In the right ear, which had a profound hearing loss, the outline of the space which had been occupied by a piston prosthesis in the oval window was evident; in addition, a layer of new bone (labyrinthitis ossificans was present in the scala tympani in the region of the round window. In the left ear the stapedial footplate was otosclerotic with the base of the crura slightly displaced but fixed in the window. The severity of the OIT in this case was demonstrated by the patients history of repeated fractures, marked porosity of the nonotosclerotic areas of the labyrinthine capsule, and possibly by the females relatively early death at age 59. The unique features of the otosclerosis in this case were the extensive replacement of all layers of the cochlear and vestibular capsules and the relatively large areas of an osteoporotic type of degeneration in the more central areas of the otosclerotic bone While the etiology of otosclerosis remains unknown it is apparent that both the incidence and severity of the disorder as it occurs in association with OIT bear some as yet unknown but definite relationship to the pathologies occurring with OIT.

Audiological Characteristics of Hearing Loss Following Meningitis

Meningitis is one of the leading causes of acquired sensorineural hearing loss in childhood, and many retrospective and prospective studies and case reports have been published. However, they have seldom discussed the nature of postmeningitic hearing loss from the audiological point of view. This study reports the results of audiological examinations performed on 5 patients suffering from hearing loss following meningitis. Extremely poor word discrimination scores as compared with pure-tone audiograms were common in all 5 cases. Type IV Békésy tracings were observed in 2 cases. Discrepancies between pure-tone audiograms and subjective hearing sensation and between pure-tone audiograms and ABR recordings were noted in 2 cases. These results suggest that varying degrees of retrocochlear involvement complicating the inner ear damage are the audiological characteristics of hearing loss following meningitis.

Audiological findings in glomus tumours.

Glomus tumours of the skull base are rare, but as they present with symptoms of hearing loss and tinnitus they are a clinical entity of which audiologists should be aware. This paper describes the findings of the major series of skull base glomus tumours found in the literature, and notes that the contribution of conductive and sensorineural components varies with tumour classification. The reported incidence of hearing loss and tinnitus in glomus tympanicum and glomus jugulare is reviewed and compared with the Cambridge series, in which two tumours were Fisch type A, four type B, two type C and five type D. In each case a mixed hearing loss was found, though the extent of sensorineural impairment was variable. The length of history of tumours limited to the middle-ear was far shorter (mean 8 months) than for more extensive lesions (type B, mean 64 months; C, 48 months; and D, 23 months). Eleven patients (85%) reported the symptom of hearing loss, and 12 (92.5%) of tinnitus, and some patients had experienced these symptoms for some time without seeking the advice of an otologist. It may be concluded that the presence of subjective pulsatile tinnitus or a retrotympanic mass should be considered an indication for an otological opinion, wherein the use of high resolution imaging techniques and arteriography will be considered in conjunction with detailed audiological assessment. Audiologists should be aware of the possibility of glomus tumour in such cases.