Unoperated Ear Research Articles

Hearing Loss in the Unoperated Ear After High-Speed Drilling in Otologic and Skull Base Surgery.

To evaluate if permanent hearing loss occurred in the unoperated ear of patients undergoing otologic and skull base surgery with high-speed otologic drilling. We retrospectively studied 250 patients (mean age 57.8 yr; 120 males, and 130 females) undergoing otologic or skull base surgery with high-speed drilling between 2013 and 2019. The University of Pittsburgh Medical Center. We evaluated preoperative and postoperative audiograms for patients undergoing surgery for cochlear implantation (95 patients, 38.0%), cholesteatoma or chronic ear disease (88 patients, 35.2%), repair of lateral skull base encephalocele (26 patients, 10.4%), resection of vestibular schwannoma or meningioma of the cerebellopontine angle (23 patients, 9.2%), lateral temporal bone resection (8 patients, 3.2%), microvascular decompression (7 patients, 2.8%), or other operations involving a high-speed otologic drill (3 patients, 1.2%). Hearing threshold shift, measured as the difference between postoperative threshold and preoperative threshold for each frequency. The association of age, gender, tested frequency, and surgery type with hearing threshold shift was investigated with analysis of covariance. A total of 102 patients (40.8%) had a 10-dB or greater worsening of their hearing in at least one frequency on their postoperative audiogram in the contralateral, unoperated ear. One hundred six subjects (42.4%) had no change in hearing of 10 dB or greater at any frequency. Among patients with longitudinal postoperative audiograms, accelerated age-related hearing loss was observed in low frequencies. A significant number of patients demonstrated poorer hearing thresholds in the contralateral, unoperated ear after otologic and skull base surgery.

Stability of computed tomography densitometry in patients with otosclerosis:a two-year follow-up

ObjectivesTo quantify the progression of otosclerosis in the unoperated ear between two stapedotomy procedures for patients with bilateral otosclerosis which can help to determine whether a HRCT scan should be re-performed before the second surgery for patients who already received HRCT imaging before the initial surgery. Methods35 patients who underwent bilateral stapedotomy were included. Two rounds of HRCT examination and audiometry were performed at the time of the first surgery and second surgery on the ear that was not operated on during the initial surgery. The relationship between the changes in HRCT densitometry and audiometry over time was analyzed. ResultsThe second round of HRCT did not add significant information about the changes to the otosclerosis lesions in either the imaging diagnosis or the HRCT density values except for small changes in the HRCT densitometry readings at the area anterior to the inner auditory (P = 0.01). While the changes in HRCT manifestation are small, changes near the fissula ante fenestram (FAF) were still positively correlated with the air bone gap (ABG) of patients (p = 0.031, r = 0.388). ConclusionsThe progression of lesions in otosclerosis is slow resulting in small and insignificant changes to the HRCT features. Therefore, a repeat HRCT evaluations prior to surgery is not necessary for patients who have had a previous HRCT evaluation within 2 years of the operation. The small changes in HRCT manifestation near the FAF were still correlated with negative effects on the ABG which could cause worsened hearing thresholds over this timeframe.

The Impact of Superior Canal Dehiscence on Power Absorbance, Otoacoustic Emissions, and Hearing in Fat Sand Rats.

Superior Semicircular Canal Dehiscence (SSCD) may lead to vestibular and auditory impairments. To study the effects of power absorbance (PA), Distortion Product Otoacoustic emissions (DPOAE), and hearing thresholds in normal ears of fat sand rats, after a bullotomy, creation and patching. SSCD was performed unilaterally in eight normal hearing animals while the contra-lateral un-operated ear was used as a control. Measures included auditory brain stem responses thresholds for air and bone conduction stimuli, DPOAEs and PA at peak pressure. The normal PA pattern of the animals grossly resembled that of human ears. A bullotomy generated specific, large and significant (p < 0.0001) changes in PA without altering hearing thresholds. SSCD significantly decreased PA at low (p < 0.02) and increased at high frequencies (p < 0.03), but on a smaller scale than the bullotomy. SSCD, induced a mean air-bone gaps of 24.3 for clicks, and 31.2 dB for 1 kHz TB. SSCD also increased the DPOAEs levels by mean of 10.1 dB SPL (p < 0.03). Patching the dehiscence, reversed partially the PA changes, the auditory threshold shifts, and the DPOAEs levels to pre-SSCD values. SSCD affects both incoming and emitting sounds from the ear, probably due to its effect on cochlear impedance and stiffness of the middle and inner ear. The presence of DPOAEs and ABGs indicated a "third window" disease, i.e., SSCD. Due to similar PA patterns after bullotomy and SCCD, PA alone has limited diagnostic yield for patients with SCCD.

Third Window Syndrome: Surgical Management of Cochlea-Facial Nerve Dehiscence.

Objective: This communication is the first assessment of outcomes after surgical repair of cochlea-facial nerve dehiscence (CFD) in a series of patients. Pre- and post-operative quantitative measurement of validated survey instruments, symptoms, diagnostic findings and anonymous video descriptions of symptoms in a cohort of 16 patients with CFD and third window syndrome (TWS) symptoms were systematically studied.Study design: Observational analytic case-control study.Setting: Quaternary referral center.Patients: Group 1 had 8 patients (5 children and 3 adults) with CFD and TWS who underwent surgical management using a previously described round window reinforcement technique. Group 2 had 8 patients (2 children and 6 adults) with CFD who did not have surgical intervention.Interventions: The Dizziness Handicap Inventory (DHI) and Headache Impact Test (HIT-6) were administered pre-operatively and post-operatively. In addition, diagnostic findings of comprehensive audiometry, cervical vestibular evoked myogenic potential (cVEMP) thresholds and electrocochleography (ECoG) were studied. Symptoms before and after surgical intervention were compared.Main outcome measures: Pre- vs. post-operative DHI, HIT-6, and audiometric data were compared statistically. The thresholds and amplitudes for cVEMP in symptomatic ears, ears with cochlea-facial nerve dehiscence and ears without CFD were compared statistically.Results: There was a highly significant improvement in DHI and HIT-6 at pre- vs. post-operative (p < 0.0001 and p < 0.001, respectively). The age range was 12.8–52.9 years at the time of surgery (mean = 24.7 years). There were 6 females and 2 males. All 8 had a history of trauma before the onset of their symptoms. The mean cVEMP threshold was 75 dB nHL (SD 3.8) for the operated ear and 85.7 dB (SD 10.6) for the unoperated ear. In contrast to superior semicircular canal dehiscence, where most ears have abnormal ECoG findings suggestive of endolymphatic hydrops, only 1 of 8 operated CFD ears (1 of 16 ears) had an abnormal ECoG study.Conclusions: Overall there was a marked improvement in DHI, HIT-6 and symptoms post-operatively. Statistically significant reduction in cVEMP thresholds was observed in patients with radiographic evidence of CFD. Surgical management with round window reinforcement in patients with CFD was associated with improved symptoms and outcomes measures.

Cochlear Patency After Transmastoid Labyrinthectomy for Ménière's Syndrome.

Labyrinthectomy is considered the "gold standard" in the treatment of intractable vertigo attacks because of Ménière's Disease (MD) but sacrifices all residual hearing. Interest in auditory rehabilitation has lead to cochlear implantation in some patients. Concern remains that the cochlear lumen may fill with tissue or bone after surgery. This study sought to determine the incidence of obliteration of the cochlea after transmastoid labyrinthectomy. Retrospective observational study. Tertiary referral center. Eighteen patients with intractable vertigo from MD who underwent surgery. Transmastoid labyrinthectomy between 2008 and 2013. Cochleas were imaged with unenhanced, heavily T2-weighted magnetic resonance imaging (MRI). Presence of symmetrical cochlear fluid signals on MRI. There was no loss of fluid signal in the cochleas of operated ear compared with the contralateral, unoperated ear in any subject an average of 3 years (standard deviation [SD]: 1.2) after surgery. Five of 18 patients had the vestibule blocked with bone wax at the time of surgery. Blocking the vestibule with bone wax did not change the cochlear fluid signal. The risk of cochlear obstruction after labyrinthectomy for MD is very low. The significance of this finding is that patients with MD who undergo labyrinthectomy will likely remain candidates for cochlear implantation in the labyrinthectomized ear long after surgery if this becomes needed. Immediate cochlear implantation or placement of a cochlear lumen keeper during labyrinthectomy for MD is probably not necessary.

Late Sudden Deafness in Unoperated Ear of Patients with Otospongiosis: Case Studies

Background: It is not known whether there is etiological relationship between otospongiosis and sudden deafness. The most common etiologies that explain sudden deafness are viral infections, vascular and autoimmune process. Methods: Two cases of patients with otospongiosis that have developed sudden deafness are presented. Results-Case report: We report two cases of late sudden deafness in the unoperated ear of patients with otospongiosis. Both patients underwent previous surgical treatment in the contralateral ear with a a short period of hearing improvement and poor hearing outcome some days after. In both reported cases the patients with bilateral otospongiosis had sudden deafness affecting both ears. The first episodes had the onsets postoperatively at the operated ears. The second episodes were at the contralateral ears in the late follow-up, especially considering that in both cases the patients showed satisfactory results regarding hearing improvement postoperatively although temporarily we therefore question the existence of the association between otospongiosis and sudden deafness. Case Study Guimaraes et al.; BJMMR, 9(7): 1-6, 2015; Article no.BJMMR.17420 2 Discussion: Sudden deafness in patients with otospongiosis is a rare occurrence and because of the few cases reported, it is not possible to establish any relationship. Maybe there is a possible immunological cause for the association of otosclerosis and sudden deafness. Conclusion: The association between sudden deafness and otosclerosis can be considered.

A model to refine the selection of children with otitis media with effusion for adenoidectomy.

The selection of children with otitis media with effusion for adenoidectomy has been criticized on a number of grounds. In spite of the widespread popularity of the procedure there are few objective guidelines to help the otolaryngologist make a decision which is therefore usually subjective. We present a scientifically derived model using a Generalized Linear Interactive Modelling (GLIM) technique from a population of 122 children who underwent either adenoidectomy or no pharyngeal surgery. The outcome parameter studied was otoscopic clearance in an unoperated ear 1 year after treatment. This was related principally to the operation type (P < 0.001) and to the age at which the operation was performed (P < 0.005). Using a probability of clearance threshold of 50% the model was tested on a prospective population of 166 children and outcome was correctly predicted in over 72%. This model enables the surgeon to determine the probability of clearance of effusion following adenoidectomy in an individual child. At a probability threshold of 50% adenoidectomy would be offered to children with bilateral otitis media with effusion aged between 4.33 and 8.00 years. Over the age of 8 years the probability of clearance occurring spontaneously increases beyond 50%. By careful selection of the probability of clearance thresholds it was possible to produce otoscopic resolution in over 80% of those selected to undergo adenoidectomy. The model also enables the otolaryngologist to determine the proportion of children with established disease that require adenoidectomy at his own chosen probability thresholds which will ensure that a more effective resource allocation is achieved.

Effects of nitrous oxide on middle ear pressure

Recent literature data suggest that permanent or reversible hearing loss may occur after general anesthesia. The etiology varies, while hearing loss following middle ear surgery is attributed to exposure to nitrous oxide (N,0). The objective of our study was to measure, using tympanometry, the middle air pressure change caused by nitrous oxide during general anesthesia and to establish its emetogenic effects during the postoperative period. This academic (non-commercial) prospective study included two groups of patients (a total of 58), with ASA status I, II and III. The study group (n 30) consisted of patients undergoing unilateral ear surgery. In this group, the intratympanic pressure was measured in the unoperated (healthy) ear before and during the surgery. The control group (n 28) patients underwent nose, throat or neck surgical interventions. This group underwent measurement of bilateral intratympanic pressure in healthy ears, before and during the surgery. Both groups were operated under general balanced anesthesia. Pain, nausea and antiemetics were monitored during the first 24 postoperative hours. Statistical analysis was performed using the Mann-Whitney-Wilcoxon test. This perioperative study confirmed the following: highly significant (p < 0.001) increase in intratympanic pressure in nonoperated ears in the study group and significant (p < 0.05) in controls. However, there was no statistical significance (p > 0.05) between groups. Pain was more freguent in controls, and nausea in the study group, but without significant difference (p > 0.05). Postoperative audiometry findings showed no conductive or sensorineural hearing loss after interventions. Nitrous oxide can be used in general balanced anesthesia with discontinuation 15 to 45 minutes before insertion of the tvmpanic membrane and completion of middle ear surgery.

Hearing changes after diagnosis in neurofibromatosis type 2.

Describe the changes in hearing ability and progression of disease over time in subjects with neurofibromatosis Type 2 enrolled in a multicenter natural history study of vestibular schwannomas in neurofibromatosis Type 2. Retrospective clinical study. International neurofibromatosis Type 2 tertiary care centers. Study participants had a clinical diagnosis of neurofibromatosis Type 2, at least one untreated vestibular schwannoma, and were at least 5 years old. Sixty-three subjects (108 ears) with audiology data at either short-term follow-up (7 mo-2 yr) or long-term follow-up (3-5 yr) after diagnosis were examined in this study. Changes in four-frequency pure-tone average and speech discrimination score before any treatment intervention for both follow-up intervals. Within 2 years of the diagnosis of neurofibromatosis Type 2, 27% of the ears experienced a significant loss in pure-tone average relative to diagnosis, and 73% of the ears experienced no significant change in hearing. Newly diagnosed neurofibromatosis Type 2 patients who do not require immediate treatment of both vestibular schwannomas are likely to have stable hearing in the unoperated ear(s) for approximately 1 to 2 years.

Long-term hearing preservation after middle fossa removal of vestibular schwannoma

Objective We sought to determine long-term hearing preservation in vestibular schwannoma patients after undergoing middle fossa resection. Study design, setting, and outcome measures We conducted a retrospective chart review of patients undergoing middle fossa resection from 1990 to 1995 at a tertiary care center. Pure-tone thresholds, before resection and at least 5 years after resection, and speech discrimination scores are reported. Results Seventy percent of patients with immediate postoperative hearing maintained serviceable hearing at more than 5 years after surgery. Pure-tone average in the operative ear changed at the same rate as hearing in the unoperated ear during this follow-up period. Conclusions More than two thirds of patients who underwent middle fossa resection of a vestibular schwannoma with some hearing postoperatively maintain that hearing at greater than 5 years of follow-up. Surgery alone does not have a negative impact on long-term hearing preservation.

Acoustic neuroma surgery: the results of long-term hearing preservation.

To report the long-term outcome hearing results following acoustic neuroma surgery. To determine whether changes, if any, in the thresholds of the operated ear are mirrored in the contralateral unoperated side. In addition, to identify predictive factors, if any, that may predispose individuals to hearing loss in the operated ear in the late post-operative period. Retrospective patient chart review. University Tertiary Referral Centre. From 1978 to 1997, one hundred and twenty six patients with small acoustic neuromas (less than 2 cm as measured within in the cerebellopontine angle) underwent excision via the suboccipital (retrosigmoid) approach with the patient in the prone position. Hearing preservation was successful in 43 patients (34.1%). The audiometric data of thirty patients with a minimum follow-up interval of 36 months was analyzed. The mean follow-up period was 113.4 months (range 36-264, SD=57.8) and the mean age at surgery was 47.3 years (range 32 to 64, SD = 7.3). Speech Reception Thresholds (SRT), Speech Discrimination Scores (SDS) and Pure-tone Audiometry (PTA, 0.5, 1 & 2 kHz) were noted on the operated and unoperated ears. The AAO Classification according to the Committee on Hearing and Equilibrium guidelines for the evaluation of hearing preservation in acoustic neuroma was used to assess hearing serviceability. Subsequent to including corresponding changes in the unoperated ear, the means of the SRT and PTA in the operated ear between the early and late post-operative periods were statistically significantly different (p=0.0012 & 0.034 respectively). Twelve (40%) patients demonstrated significant deterioration in hearing thresholds over time. Pre-operatively, 96.7% of patients had serviceable hearing (Class A & B). This falls to 76.6% in the early post-operative period and to 56.7% in the late post-operative period. Our study highlights the finding that over time a significant number of individuals realize a greater ongoing hearing loss in the post tumour excision ear than the contralateral ear.

Evaluating otolith function with subjective visual vertical discrimination

This report summarizes our experiences with the subjective visual vertical (SVV) as a clinical neuro-otological tool. In the SVV test, patients have to orient a dim light bar in an otherwise dark surrounding earth-vertical, using a remote-control. Normal subjects in an upright position did not deviate more than 2 degrees from true vertical. After vestibular neurectomy, the SVV was consistently tilted by some 12 degrees toward the affected ear. Smaller tilts (approximately 7 degrees) of the SVV occurred in patients with spontaneous peripheral vestibular diseases. This shift in SVV disappeared within weeks to months, similar to the spontaneous nystagmus. After stapes surgery slight deviations of the SVV towards the unoperated ear were seen in about 20% of the patients, indicating a slight irritation of the otolith organs. Assessed in an upright position, the SVV thus may be regarded as reflecting tonic otolithic input differences between the two ears. Asymmetries in the shifts of the SVV induced by roll tilts of the gravito-inertial vector by eccentric rotations of the subject have been proposed as a test for otolithic sensitivity. In our studies such asymmetries in the shifts of the SVV could not be induced by 26 degrees or 90 degrees roll tilts of subjects towards the affected or healthy ears. A simple clinical test to reveal unilateral otolithic sensitivity (comparable to an otolithic "caloric test") thus still has to be found.

Drilling in Ear Surgery: A Comparison of Pre- and Postoperative Bone-conduction Thresholds in both the Conventional and Extended High-frequency Ranges

The pre- and postoperative bone-conduction thresholds for the frequencies 0.25 through 16 kHz were compared in 46 ears in which a high-speed ear drill was used. In 15 of these, thresholds were also obtained in the contralateral ear. There was no statistically significant postoperative threshold change at any single frequency in either the operated or the contralateral ear. The mean threshold elevation of 1.4 dB for the ipsilateral extended high-frequency octave of 8-16 kHz was marginally significant (p = 0.02), while this was not the case in the contralateral, unoperated ear. These findings are considered to be due to difficulties in placement of the cumbersome Präcitronic KH70 vibrator following bone removal ipsilaterally, with resultant defective transmission to the skull.

Aural polyps and cholesteatoma.

A retrospective review of 200 cases of aural polypectomy performed in Glasgow and London was assessed in previously unoperated ears and in those with mastoid cavities. In those with mastoid cavities 72% of the ears became dry whilst only 33% were dry in the previously unoperated group. Cholesteatoma was found in 33% of previously unoperated ears and in 71% with an attic or posterior marginal defect. It can be concluded from these results that aural polypectomy in the presence of a mastoid cavity is a satisfactory procedure but in a previously unoperated ear a more radical procedure should be considered because of its frequent association with underlying cholesteatoma.

Recovery from unilateral labyrinthectomy in rhesus monkey.

1. We recorded eye movements in six rhesus monkeys before and after unilateral labyrinthectomy and quantified the compensation for both the static and the dynamic disturbances of the vestibuloocular reflex (VOR). 2. When first recorded after labyrinthectomy (18-20 h postlesion), all animals had a spontaneous nystagmus with mean slow-phase velocities ranging from 24 to 54 degrees/s measured in darkness and 0-4 degrees/s measured in the light. The level of nystagmus diminished quickly, and by postoperative day 25 mean values ranged from 4 to 22 degrees/s, measured in darkness. The waveform of individual slow phases was variable, but in the first postoperative week its trajectory usually showed an increasing, or an increasing then decreasing, velocity. This finding indicates that peripheral vestibular lesions can alter the function of the ocular motor eye-position integrator. 3. The VOR gain (eye velocity/head velocity, corrected for spontaneous nystagmus) during rotations (30-300 degrees/s) in the dark was diminished from nearly 1.0 preoperatively to approximately 0.5 when first measured after labyrinthectomy, except for rotations toward the lesioned side at high speeds for which the gain was even lower. Within the first few postoperative days, for rotations toward the intact side, the VOR gain increased rapidly, to approximately 0.8. For rotations toward the lesioned side similar behavior was noted for stimuli of 30-60 degrees/s, but at higher velocities compensation proceeded more slowly. By 3 mo postoperatively gains had reached values ranging from 0.77 to 1.03 for rotations toward the intact side and from 0.61 to 0.98 for rotations toward the lesioned side. Values were higher for lower-velocity stimuli. 4. Caloric testing with ice water in the unoperated ear elicited nystagmus with a mean value of maximum slow-phase velocity of 129 degrees/s preoperatively and 195 degrees/s 3 mo postoperatively. There was no caloric response on the lesioned side. From the increase in caloric responses from the intact ear we infer considerable restoration of spontaneous activity of vestibular neurons on the deafferented side. 5. The time constant of the VOR was a function of stimulus speed preoperatively with a maximum mean value of 35 s for a 60 degrees/s stimulus. After labyrinthectomy the VOR time constant was low (6.0-9.1 s) at all speeds. Subsequently, in three animals only, there was a small increase (2-3 s) in VOR time constant during the 3-mo period following labyrinthectomy. These results indicate that labyrinthectomy profoundly and persistently impairs the action of the vestibular velocity-storage mechanism.(ABSTRACT TRUNCATED AT 400 WORDS)

Binaural interactions in cortical area AI of cats reared with unilateral atresia of the external ear canal.

Binaural interactions were recorded in auditory cortical (AI) neurons of anesthetized adult cats that had unilateral atresias created shortly after birth by surgically ligating and cutting one external ear canal. At the time of the recording experiment, the atresia and associated debris were removed and tones were delivered to both tympanic membranes via a sealed and calibrated acoustic system. The majority of neurons recorded were in the cortex ipsilateral to the previously occluded ear. Thresholds for monaural stimulation of either the operated or unoperated ear were within normal range although thresholds to stimulation of the previously operated ear tended to occupy the upper end of the normal distribution. Monotonic and nonmonotonic spike count-vs-intensity functions derived from responses to monaural stimulation of the atretic ear were indistinguishable in their shape from those recorded in normal cats. All binaural classes were represented in our sample in proportions similar to those reported in cats with two normal ears. The forms of the functions relating spike count to interaural intensity differences and interaural phase differences were essentially the same as those seen in normal animals. The main binaural deficit observed under these conditions was a shift in the interaural intensity difference to which an AI neuron was most sensitive. The intensity needed for a stimulus to the atretic ear to participate in the binaural response was as much as 50 dB higher than that at the opposite normal ear in contrast to the nearly equal SPLs required for binaural interactions in cats with two ears intact. It was suggested that elevated thresholds at the previously operated ear could account for much of the shift observed.

Some physiological consequences of neonatal cochlear destruction in the inferior colliculus of the gerbil, Meriones unguiculatus

Physiological consequences of neonatal cochlear ablation were assessed in the inferior colliculus of adult gerbils subjected at 2 days of age to ablation of one cochlea. Responses to tonal stimulation of the unoperated ear were evaluated at 100 μm intervals in the ipsilateral inferior colliculus. Compared with excitatory responses to ipsilateral stimulation in the inferior colliculus of unoperated animals, responses recorded in experimental animals are more widespread, stronger and occur at lower thresholds. The ubiquity of excitatory responses to ipsilateral stimulation in neonatally ablated animals indicates that responses to ipsilateral stimulation in normal gerbils are partly dependent upon interactions during development between pathways conveying information from each ear.

The summating potential in ultrasonic labyrinthectomy for Menière's disorder.

This paper reports SP changes pre- and post-operatively in a series of 12 patients who have undergone ultrasonic labyrinthectomy for Menière's disorder. The unoperated ear in 7 of these patients also had pre- and post- operative ECochG. The SP in the operated ear was reduced in amplitude and duration in 50 per cent and 66 per cent of ears respectively. However, the SP was also reduced in the unoperated ears by similar proportions. Statistical analysis showed no significant difference in SP change between the two sets of ears. It is concluded that the value of the SP in prediction or assessment of results of treatment in Menière's disorder is not at present proven, and that future investigations require the use of controls.

Eighteen Years Experience in Stapedectomy

The postoperative findings in almost 800 stapedectomized ears were analyzed to evaluate the proposition that complication rates in stapedectomy were affected by the size of footplate fenestration. It was concluded that small fenestra stapedectomy (diameter 0.4 mm) provided similar hearing gains to those achieved with standard techniques, that articulation problems occurred to a similar extent as with wire loop prostheses, and that there was a significantly lower incidence of a) fistual and b) immediate and delayed severe sensorineural hearing loss than with any other technique. There was also significantly less deterioration in bone conduction thresholds at 4 kHz after three years postoperatively. The incidence of severe immediate sensorineural loss in large fenestra stapedectomy (half or more of footplate removed) was significantly influenced by factors such as age, preoperative bone conduction thresholds and oval window pathology. A retrospective analysis provided no information which might predict oval window pathology. Additional information gained from the analysis indicated that with all types of stapedectomy, bone conduction did not deteriorate significantly more rapidly in the operated as compared to the unoperated ear, whereas in unoperated ears, deterioration in bone conduction was significantly greater in ears with mixed hearing losses than when the loss was purely sensorineural. It was concluded that small fenestra stapedectomy was currently the operation of choice because with it, the threat of cochlear dysfunction both immediately, and in the long term, was significantly less.

Experimental Stapedectomy

This animal experimental study (144 cats) was designed to allow observation of the healing processes at the oval window following stapedectomy during the first two postoperative weeks. The first 61 animals (Series I) had no oval window cover except for a blood clot which might form spontaneously. The second 64 animals (Series II) had Gelfoam® as a cover to the oval window following stapedectomy. A third series of 19 animals had temporalis fascia used as the oval window cover, and these ears were studied histologically for up to nine weeks. The unoperated ear acted as a control for the operated ear in all animals and after the animals were killed, both temporal bones were decalcified, imbedded in celloidin, serially sectioned at 20μ, and every tenth section stained and mounted for histologic study. It was observed that oval window closure was effected by endosteal, periosteal, and fibrous tissue proliferation from the traumatized tissues about the oval window fenestra, and that this process was facilitated by the presence of some type of scaffolding material such as a blood clot or Gelfoam®. Temporalis fascia placed in the oval window was observed to be rapidly incorporated into a much thicker oval window neomembrane and to seal the fenestra promptly. Partial removal of the footplate also facilitated more rapid closure of the smaller oval window fenestra, but fibrous tissue and new bone formation was noted to form about bony fragments still attached at the oval window level. Free bony fragments within the vestibule were not observed to stimulate new bone formation. Suppuration was observed most frequently in Series I (no oval window cover), with 67.8% of these animals having some degree of otitis media. In Series II (Gelfoam® cover) 20.6% had otitis media, and in Series III (temporalis fascia) 21% had middle ear infection. Suppuration markedly impaired but did not completely prevent the oval window reparative processes. Animals having some type of oval window cover were noted to have a lesser incidence of suppurative labyrinthine involvement when otitis media was present. Other labyrinthine complications were observed, including endolymphatic hydrops, Wittmaack's hypotonic atrophy, as well as RBC, fibrin, and albuminous precipitates in the labyrinth. Hypotonic atrophy was observed in a high incidence of animals having rupture of one or more endolymphatic structures, suggesting a mechanical mechanism as one possible explanation for this condition. Hypotonic atrophy may represent the end-stage (collapse) in the fluctuant endolymphatic ballooning of hydrops which is seen when saccular or Reissner's membrane ruptures have occurred.