Cochlear Loss Research Articles

Auditory brainstem response (ABR) to rarefaction and condensation clicks in normal and abnormal ears.

The shift in latency of wave V in ABR upon the reversal of stimulus phase was investigated in a normal-hearing reference material (65 ears) and in 20 ears of conductive hearing loss, 29 ears of steep high-frequency hearing loss and 17 ears of acoustic neurinoma or cerebellopontine angle tumor. In addition, reproducibility was studied in the reference material. The stimulus was a 2.0-kHz haversine wave at 75 or 35 dB nHL delivered at the rate of 20 Hz. 2000 responses were averaged for each stimulus phase. Electrodes were placed on the vertex and on ipsilateral mastoid. Stimulus wave form was determined in a 6-cc coupler and in a few cases with a miniature electrete microphone in the ear canal. In the reference material, a significant difference of the wave V latency between the condensation (C) and rarefaction (R) stimulus was observed. When taking the absolute difference, the mean value was 0.15 ms at 75 dB nHL. This time difference corresponds to a frequency of 3-4 kHz. In high frequency cochlear loss, the C-R difference increased in proportion to the downward shift in frequency of the high frequency slope of the audiogram. In conductive hearing loss, the C-R difference was similar to that of the reference material. In retrocochlear cases, the C-R difference was unpredictable, but was remarkably often small compared with the V latency. It was concluded that the difference in wave V latency between C and R clicks provides information about the excitation pattern in the inner ear but it is not reliable enough to give more than a rough estimate of the individual frequency of generation of ABR. The results are arguments against the use of the alternating stimulus phase as a routine procedure.

Obliterative pathology in otosclerosis

A retrospective study was done in 176 stapedectomy patients where there was obliterative pathology of the footplate. The technique and care during stapes surgery in order to obtain satisfactory results and minimise the risk of cochlear losses is emphasized. Revision surgery should be avoided.

On the use of click-evoked electric brainstem responses in audiological diagnosis. IV. Interaural latency differences (wave V) in cochlear hearing loss.

Interaural latency differences (ILDs) of wave V of the brainstem electric response (BSER) were studied (1) in 20 normal-hearing subjects at 90, 80, 60 and 40 dB HL click level, (2) in 22 patients with symmetrical cochlear hearing loss at 90 dB HL, corresponding to 45-80 dB SL, and (3) in 45 patients with asymetrical cochlear hearing loss with interaural recruitment, at 90 dB HL on one hand and at a click sensation level corresponding to 90 dB HL in the poorer ear (range 10-75 dB SL) on the other hand. In the normal hearing group the ILDs did not exceed 0.2 ms except in one case at 40 dB HL (0.3 ms). In the symmetrical cochlear loss group the ILD did not exceed 0.2 ms in any patient. In the asymmetrical cochlear loss group the ILD at 90 dB HL exceeded 0.2 ms in 12 cases, but only in four cases after correction for pure tone hearing loss at 4 kHz by 0.1 for each 10 dB above 50 dB HL; at equal sensation levels the ILDs were all zero or negative meaning that the wave V latency was shorter on stimulation of the poorer ear. Assuming ILD to be a valid discriminator between cochlear and retrocochlear lesions, the corrected ILD at equal click hearing levels (90 dB HL), with the critical value set at 0.2 ms, thus gave a 9% false-positive rate whereas the ILS at equal sensation levels, with the critical value set at zero, gave no false-positives. It still remains to be shown that the latter criterion will not increase the number of false-negative results in retrocochlear lesions.

The approximation of audiometric thresholds by auditory brain stem responses.

Auditory brain stem response (ABR) thresholds for tone pip stimuli were compared with audiometric thresholds for 63 ears to assess the feasibility of deriving audiograms with ABR techniques. Correlations between the two measures were highly significant, indicating a high degree of accuracy in assessing degree and configuration of hearing loss with ABR. Patients with conductive losses showed a simple one-to-one relationship between ABR and audiometric thresholds, while patients with cochlear losses did not. Possibly this is due to the effects of abnormal temporal integration or poor frequency selectivity in this latter group.

Evidence for sound perception with the labyrinth.

A report is presented of experiments on guinea pigs and pigeons concerning behavioural and electrophysiological responses of the labyrinth to sound. In the guinea pigs the cochlea was destroyed on both sides by CO2 laser radiation and fenestration of the lateral semicircular canal was done. In the pigeons the cochlea was removed before fenestration. On account of the results obtained, fenestration of the lateral canal in patients with bilateral total cochlear loss can be considered as an alternative to monopolar cochlear implants.

Narrow-band AP latencies in normal and recruiting human ears.

Derived narrow-band action potential latencies increase monotonically with decreasing central frequency, and can be interpreted as reflecting the traveling wave delay in the cochlea. It was found that, for recruiting human ears with average flat hearing losses around 40 dB, this accumulating latency increase was smaller than for normal ears. A comparison of 15 normal ears and 37 recruiting ears showed, however, that in only half of the recruiting ears this difference was significant. These recruiting ears were therefore divided in two groups based on the waveform of the narrow-band action potential AP, which correlated well with the subdivision according to latency. The findings have been explained on the basis that latency of the narrow-band APs is not determined solely by the mechanical traveling-wave delay, but also by the response time of the (second?) cochlear filter. When this filter broadens, one expects a decrease in its impulse response time. Since this impulse response time. Since this impulse response depends on the sum of the high- and low-frequency slope values of the cochlear filter, one expects only a latency decrease when the steep high-frequency slope also becomes more shallow. A support for the influence of the response times of the cochlear filter is found in the narrow-band AP latencies for restricted cochlear losses (e.g., in a 4-kHz noise dip). It appears that the latency in that area actually is shorter than for the higher central frequencies, a fact which cannot be explained solely on the basis of a traveling wave phenomenon.

Human Auditory Nerve Action Potentials and Brain Stem Evoked Responses: Latency-Intensity Functions in Detection of Cochlear and Retrocochlear Abnormality

Latency-intensity (L-i) functions for (1) the auditory nerve action potential (AP) N1 peak, (2) the brain stem evoked response (BER) V peak, and (3) the N1-V interval were related to hearing level and lesion location. The AP L-l curves tended to steepen with increasing 4 to 8 kHz hearing level. This relationship was identical for cochlear and retrocochlear ears, except for a few retrocochlear ears with "inappropriate AP perservation." Both high-frequency cochlear loss and retrocochlear abnormality prolonged peak V latency, but retrocochlear abnormality generally prolonged it more. Among cochlear-loss ears, as 4 to 8 kHz hearing levels increased, N1-V intervals decreased and L-i curve slopes increased. In contrast, retrocochlear abnormality greatly prolonged N1-V intervals. As a retrocochlear sign, N1-V prolongation was slightly more reliable than V prolongation.

Use of low-pass noise in word-recognition testing.

This study attempted to determine whether word-recognition scores obtained in noise were more sensitive to the presence of a hearing loss than recognition scores obtained in quiet. Subjects with normal hearing, high-frequency cochlear hearing loss, and flat cochlear hearing loss were tested in quiet and in the presence of a 500-Hz low-pass noise. Two signal-to-noise conditions were employed, -4 dB and -12 dB. Words were presented at 40dB SL in one experiment and at 96 dB SPL for normal-hearing subjects in a second experiment. The results indicated that, while the word-recognition scores of groups were similar in quiet, the more negative the signal-to-noise ratio, the greater the separation of group scores, with hearing-impaired subjects having poorer recognition scores than normal-hearing subjects. When the speech and noise were presented at high SPLs, however, the normal-hearing subjects had poorer word recognition than those with flat cochlear losses. The results are interpreted as indicating greater spread of masking in normal-hearing than hearing-impaired subjects at high sound pressure levels.

Brief-Tone Audiometry with Normal and Deaf School-Age Children

Ten normal children and 10 deaf children with cochlear losses were tested on a brief-tone audiometric task at 500, 1000, 2000, and 4000 Hz using a modified method of limits. The normal children yielded similar values of temporal integration at all test frequencies, and the results approached closely the theoretical values anticipated on the basis of Zwislocki’s theory. With the exception of the data obtained at 500 Hz, the mean values of temporal integration associated with the deaf group were only about one-third the magnitude of those yielded by their normal counterparts. The results conformed neatly to what is considered to be typical of the performance of a group of individuals exhibiting cochlear pathology. There was little or no overlap between the distributions of the individual values of temporal integration recorded for the normal and the deaf groups. A possible future application of brief-tone audiometry is suggested.

Problème des Réinterventions Dans la Chirurgie de l'otospongiose

The authors have studied the problems of re-operating in otosclerosis surgery and emphasize the risks of cochlear losses which are very great in these cases.After studying general diagnostic and operative problems, the authors deal with the difficulties of re-operating fenestrations, mobilizations, Fowler, and stapedectomies, with or without interpositions. For each of these cases, the technique is first demonstrated with animated pictures, then with film sequences showing a concrete example. Their personal ‘teflon-interposition’ technique which allows safer operations is also explained.Finally, the treatments of failures due to causes other than otosclerosis or the techniques themselves are described.This study, based on more than 1000 re-operations and more than 10 000 stapedectomies, teflon-pistons and teflon-interpositions, ends with a chart showing the percentage successes which may be expected in each type by re-operating.

Brief-tone audiometry in patients with 8th nerve tumor.

Brief-tone audiometry, the determination of temporal auditory integration of power, has been proposed as a diagnostic procedure on the assumption that the results identify the ear with cochlear pathology. Previous studies have shown a clear distinction between the normal ear and the ear with cochlear impairment but have not included results for the ear with sensory-neural loss from Vlllth nerve lesion. In this study, temporal integration functions were obtained for 10 normal hearers, 10 patients with cochlear pathology and 3 patients with surgically confirmed Vlllth nerve tumors. The cochlear loss patients were clearly distinguished from the normals by abnormality in integration function. Results for the Vlllth nerve tumor patients fell well within the range of normal on the brief-tone test.

Vestibule exposure during surgery. Clinical observations in three cases of cholesteatoma.

A review of the literature to determine the fate of the inner ear when the footplate has been removed during surgery for chronic otitis media revealed 48 cases of stapes extraction that were reported during the 19th century and in no patient did total cochlear loss develop in a one-year follow-up. In four clinical cases of chronic otitis media, there was visibly definite exposure of the vestibule during surgery, but no significant cochlear loss developed postoperatively. The prompt recognition of exposure and coverage of the oval window, with immediate parenteral administration of antibiotics would appear to be indicated when the vestibule is opened during surgery for cholesteatoma or chronic otitis media.

Six years experience with the Robinson stainless steel stapedial prosthesis and vein craft

In summarv, all the delayed hearing losses, both conductive and cochlear, consisted of 1.4% of the 1336 cases. There were no total delayed cochlear losses (“dead ears”) and interestingly enough there were. 0.3% transient cochlear losses and 0.3% transient conductive losses, all of which returned to normal. What appears most interesting in this series is that the delayed cochlear losses (0.8%) are almost equalized by the delayed conductive losses (0.6%) and that very little emphasis has been placed on the delayed conductive losses, their causes, and their treatment, despite the fact that the hearing in most of these can be successfully restored by revision surgery.

Labyrinth irritation after otosclerosis operations.

The appearance of positional nystagmus was examined in 63 patients during the first postoperative week. In six cases nystagmus was found preoperatively, in 3 cases of these it disappeared in 7 days after the operation. In only 5 cases (7, 9%) nystagmus was not postoperatively registered. In all the others it existed in different forms and types. In 76% of the cases nystagmus decreased during the first 7 days.Positional nystagmus of Nylén's type II was most frequent. Only in 3 cases nystagmus of Nylén's type III was found. In most cases the type of nystagmus remaind unchanged until its disappearance.Only 2 patients had cochlear loss in the postoperative hearing, in one of them it confined to 4 000 cps, and in the other the ear became totally deaf. The latter case is reported more accurately, because in this case the patient had both Menière's disease and otosclerosis in the operated ear.The results show that the operative technique which was used, above all, the fascia interposition, does not lead to more serious labyrinthine disturbances than other techniques.

Postauricular sulcus approach in middle ear surgery.

MIDDLE ear surgery, especially stapedectomy, is usually performed through an incision in the skin of the external meatus which creates a tympanomeatal flap which is then lifted forward to expose the middle ear (tympanotomy). The external auditory meatus is deep and covered by thin skin that is easily traumatized on cleaning and disinfection. It contains ceruminal glands and hair follicles which harbor infection so deep that it cannot be completely eradicated. Shea says 1 : Sterilization of the ear canal for surgery is difficult, and I agree with House, who has recently pointed out that even with the most vigorous efforts the ear canal cannot always be sterilized and cultures taken will demonstrate some organisms after the sterilization is completed in about 25% of patients. He believes that the multiplication of these organisms may be the cause of some of the early cochlear losses that occur after surgery from an inapparent

Inner ear pathology after experimental stapedectomy.

SEVERE sensorineural deafness after stapedectomy is still a problem in otosclerosis surgery. Permanent cochlear losses may occur immediately after surgery or may have a delayed onset of weeks or months following an initial good result. It is especially difficult to understand the profound delayed cochlear loss which can sometimes follow an uncomplicated stapedectomy. The incidence of this complication varies somewhat according to the different reports as well as, probably, to interpretation of cases which qualify for selection. An incidence of 2.6% has been reported by Schuknecht,¹2.4% by House,²and 2.5% by Portmann.³ Cochlear lesions may occur twice as often in stapedectomy revisions (not mobilization) and three times as often in fenestration revisions,⁴so that apparently the more often the inner ear is opened in otosclerosis surgery the greater the possibility of developing irreversible pathological cochlear changes. Shambaugh and Takahara⁵have evaluated both early and

Preoperative sterilization technique of the external ear canal.

Bacterial infection following stapedectomy is an undesirable feature. Although such infection happens infrequently, it may cause some of the unexplained cochlear losses. Postoperative occurrence of external otitis, and especially otitis media, have caused perforations of the tympanic membrane and thus have caused failure to close the airbone gap. It is reasonable to assume that most of the postoperative infections could be prevented if the ear canal were to be adequately sterilized prior to surgery. Previous investigators have found that the sterilization technique of the external ear canal prior to stapes surgery resulted only in 40% to 50% effective sterilization, no matter what technique was used. 1,2 These figures were substantiated by our own experiences using the solutions recommended for preoperative sterilization. Because the ear canal cannot be scrubbed effectively, preoperative sterilization is very difficult to obtain. The techniques, using different solutions and methods in scrubbing, cleansing, and irrigating have not

The Effect of Trauma in Causing Cochlear Losses After Stapedectomy

Trauma undoubtedly may play an important role in causing sensori neural deafness after stapedectomy. In stapedectomy, trauma may be considered indirect (stimulation of the intact ossicles) or direct (disturbance of the vestibular contents). In evaluating indirect trauma the ossicular chain was stimulated in trained cats resulting in acoustic trauma lesions of the basal turn. Direct trauma was evaluated by making sac-cular lesions through the oval window in the squirrel monkey and cat. This resulted in normal cochlear findings. These findings indicate that acoustic trauma more likely results from a massive volume displacement of perilymph beneath an intact footplate. Although trauma sometimes explains severe cochlear deafness immediately following stapedectomy it does not explain the delayed deafness which may follow an initial good result.Stapedektomie spielt zweifellos eine wichtige Rolle in der Verursachung von Nervenschwerhorigkeit. Trauma bei Stapedektomie kann auf zwei Arten erfolgen. Auf indirektem ...

TRAUMATIZED OVAL WINDOW FAT GRAFTS.

AS OVAL window surgery has become prominent in the field of otology, the untoward inner ear reactions of this surgery (eg, cochlear losses, persisting vertigo) have received much serious consideration. 1-3,6,10,12,13 Various authors have suggested possible etiologic factors including intralabyrinthine injury from manipulation, 6,11 drilling, 12,13 compression of perilymph (pumping), 2,6,10 bleeding into the vestibule or the technical difficulties resulting therefrom, 2,3,12 infection, 2,12 drill trauma, 12,13 foreign protein in the vestibule, 12,13 and severe otosclerotic disease. 3 Harris and Weiss 4 reported six granulomas of oval window fat grafts and concluded that they represented minor variations upon a common theme of healing by cicatrization of injured, devascularized adipose tissue. With the wide diversity of procedures, replacement materials, and the surgeon's individual skills, it is difficult to evaluate the differences in these techniques in terms of possible causes of inner ear reactions. This experiment was designed as a histopathologic study

IRRIGATION OF OPEN VESTIBULE IN STAPES SURGERY. A CLINICAL AND EXPERIMENTAL STUDY.

Postoperative cochlear loss and recession of hearing due to bony closure of the oval window are the two major problems in stapes surgery today, just as they were in the days of classical fenestration. Although most authors report a higher incidence of cochlear problems in total stapedectomy procedures than in those in which the vestibule is opened less widely, there is little agreement as to other factors responsible for cochlear losses in stapes surgery. Shambaugh and Takahara, 1 in a study in 1955 of cochlear pathology after fenestration, found a significantly higher incidence when bleeding into the fenestra was greater and when infection of the postoperative cavity was noted. House 2 noted an increase in the incidence of cochlear losses after stapes operations when organisms were cultured from the middle ear during surgery. He also suggested that the use of Gelfoam rather than tissue grafts to close the oval window