Analysis of auditory and neurologic effects associated with ventral bulla osteotomy for removal of inflammatory polyps or nasopharyngeal masses in cats

Brendan B. Anders Department of Surgery, Garden State Veterinary Specialists, 1 Pine St, Tinton Falls, NJ 07753.

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Michael G. Hoelzler Department of Surgery, Garden State Veterinary Specialists, 1 Pine St, Tinton Falls, NJ 07753.

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Thomas D. Scavelli Department of Surgery, Garden State Veterinary Specialists, 1 Pine St, Tinton Falls, NJ 07753.

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Ryan P. Fulcher Department of Surgery, Garden State Veterinary Specialists, 1 Pine St, Tinton Falls, NJ 07753.

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Richard P. Bastian Department of Surgery, Garden State Veterinary Specialists, 1 Pine St, Tinton Falls, NJ 07753.

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Abstract

Objective—To determine whether cats undergoing ventral bulla osteotomy (VBO) for removal of inflammatory polyps or nasopharyngeal masses have altered ability to hear and whether polyp or mass removal affects auditory function as measured via air-conducted brainstem auditory evoked response (BAER).

Design—Prospective case series.

Animals—21 cats.

Procedures—Cats were sedated and had otic-oral examinations to confirm presence of nasopharyngeal masses; BAER testing was done immediately prior to and following the completion of a VBO and polyp or mass removal. Recheck examination, including otic examination and BAER in sedated cats, was performed when possible.

Results—17 cats met final inclusion criteria, and long-term follow-up was available for 15. Six of 17 had deafness as measured via air-conducted BAER prior to surgery. Mean followup time was 161 days, and there was no change from presurgical status in auditory ability in any cat. Eleven of 17 developed ipsilateral Horner syndrome in the immediate postoperative period, and 1 of 16 had polyp regrowth.

Conclusions and Clinical Relevance—Results suggested that in cats, VBO for removal of inflammatory polyps or masses is unlikely to affect hearing as measured via air-conducted BAER. Most cats developed short-term Horner syndrome. Cats with deafness prior to surgery did not regain auditory function. Ventral bulla osteotomy to remove nasopharyngeal polyps or masses provided no functional advantage with regard to restoration of hearing, compared with other surgical techniques. Polyp recurrence and long-term adverse effects were uncommon.

Abstract

Objective—To determine whether cats undergoing ventral bulla osteotomy (VBO) for removal of inflammatory polyps or nasopharyngeal masses have altered ability to hear and whether polyp or mass removal affects auditory function as measured via air-conducted brainstem auditory evoked response (BAER).

Design—Prospective case series.

Animals—21 cats.

Procedures—Cats were sedated and had otic-oral examinations to confirm presence of nasopharyngeal masses; BAER testing was done immediately prior to and following the completion of a VBO and polyp or mass removal. Recheck examination, including otic examination and BAER in sedated cats, was performed when possible.

Results—17 cats met final inclusion criteria, and long-term follow-up was available for 15. Six of 17 had deafness as measured via air-conducted BAER prior to surgery. Mean followup time was 161 days, and there was no change from presurgical status in auditory ability in any cat. Eleven of 17 developed ipsilateral Horner syndrome in the immediate postoperative period, and 1 of 16 had polyp regrowth.

Conclusions and Clinical Relevance—Results suggested that in cats, VBO for removal of inflammatory polyps or masses is unlikely to affect hearing as measured via air-conducted BAER. Most cats developed short-term Horner syndrome. Cats with deafness prior to surgery did not regain auditory function. Ventral bulla osteotomy to remove nasopharyngeal polyps or masses provided no functional advantage with regard to restoration of hearing, compared with other surgical techniques. Polyp recurrence and long-term adverse effects were uncommon.

Inflammatory polyps are nonneoplastic masses that develop from the mucosa of the nasopharynx, auditory tube, or middle ear.1–10 Polyps are typically found within the tympanic cavity or auditory tube and can extend into the pharynx.3,11 Prior research suggests that they most commonly occur in young cats, but polyps have been found in cats ranging from a few weeks to 15 years of age. Inflammatory polyps are listed as one of many potential differential diagnoses for upper respiratory tract signs and otitis in cats.1,3,5,6,12–17 Clinical signs include those consistent with obstructive upper respiratory tract disease; nasal, ocular, or otic discharge; change in voice; swallowing difficulties; head tilt; Horner syndrome; nystagmus; ataxia; infection; sneezing; and a visible mass within the ear canal.1,3,9,18

Presently, there are 3 main treatment options for removal of inflammatory (nasopharyngeal) polyps: traction avulsion, lateral bulla osteotomy, or VBO. These treatments have been used alone or in combination.2,3,12,17–20 Treatment options are influenced by location of the polyp, clinical signs, and associated radiographic changes. Traction avulsion alone can be used and was recommended for certain conditions in the past.3,5,11,12,18,21,22 Because of high possibilities for recurrence, this technique is often limited to cases without an aural component.20,21 Presently, VBO is considered the preferred technique for managing nasopharyngeal inflammatory polyps.2,18,20,23

Proposed benefits and advantages of VBO include increased exposure of the medial bulla compartment, preservation of the ear canal, decreased rates of recurrence, gravity-assisted ventral drainage when indicated, access to both bullae if needed, improved cosmesis, and possible preservation of conductive hearing.8,9,18,23–26 Reported complications associated with VBO include Horner syndrome, vestibular disturbances, facial and hypoglossal nerve deficits, wound drainage, auditory ossicle damage, and damage to associated vascular tissues.8,17,23,25

To our knowledge, research regarding how nasopharyngeal and aural masses affect hearing in cats and whether the use of VBO for mass removal can affect feline hearing has not yet been published. This information is considered relevant because of a perception by pet owners that hearing is associated with quality of life.27 The purpose of the study reported here was to determine whether VBO for removal of inflammatory polyps and nasopharyngeal masses would alter hearing as measured via air-conducted BAER. Additionally, short- and long-term complications of the procedure were recorded and evaluated. We hypothesized that a considerable proportion of cats with nasopharyngeal masses (polyps or neoplasia) would have deafness before surgery as measured via air-conducted BAER and that removal of the mass by use of VBO would restore hearing.

Materials and Methods

A prospective study was performed that included all cats being treated for suspected inflammatory polyps at Garden State Veterinary Specialists Referral Center during the study period. Twenty-three cases of nasopharyngeal masses were evaluated and treated between April 2005 and July 2007. History, findings on physical examination, and BAER were recorded in each cat. Feline leukemia virus and FIV status, results of imaging studies, and results of hematologic examinations were recorded when available. In all cats, at least 1 suspected inflammatory polyp was removed. Initial inclusion criteria included visible or palpable mass during sedated examination and subsequent performance of VBO.

BAERs—All cats were anesthetized with propofol administered IV and titrated to effect, and anesthesia was then maintained with isoflurane. Preoperative otic examination, soft palate palpation, and responses to air-conducted stimuli were measured following intubation. The BAER unita was used to create and record all data. The BAERs were recorded by one of the authors (BBA) with each cat in lateral recumbency by use of a computerized system and following the techniques described by Sims and Horohov.28 Briefly, electrodes were placed SC at the following positions: positive electrode at top of the head (vertex), negative electrode at the point of the mandible just below the ear, and ground electrode between the scapulae at the level of T1 through T3. Prior to recording, the BAER impedance was checked to ensure that resistance was < 5 : between any 2 electrodes. Ear buds were placed in the affected ear followed by the nonaffected ear, and responses were recorded for auditory stimuli during the initial 10 milliseconds. Contralateral masking noise was not used. Each BAER was a mean of the neural activity following at least 500 stimuli at 90 dB (normal hearing level). A default setting with auditory clicks (click duration of 0.1 millisecond and stimulation rate of 20 Hz) was used. For each case, a printout representing mean neural activity as a result of externally applied acoustic stimuli consisting of numerous negative and positive peaks was obtained (Figure 1). Each wave represented composite neuronal activity in 1 or more subcortical and cortical brain structures.27,29–34 This procedure was repeated immediately after surgery in all cats.

Figure 1—
Figure 1—

Sample of BAER obtained from a cat in a study of auditory and neurologic effects associated with VBO for inflammatory polyp or nasopharyngeal mass removal in cats. Top recording is suggestive of normal response. Lower recording was interpreted as a negative response (ie, lack of hearing).

Citation: Journal of the American Veterinary Medical Association 233, 4; 10.2460/javma.233.4.580

Only air-conducted sound stimuli were measured in this study. For the purpose of simplification, the recordings were interpreted as either normal or abnormal on the basis of similarity to reported normal findings.28,30,35 Attempts to further define values associated with the amplitude, latency, or interval between waves were not pursued. Bone-conduction BAER measurements were not obtained.

Surgical procedures—Cats were surgically prepared prior to positioning in dorsal recumbency, and a VBO was performed as described by Lanz and Wood.17 Variation of final closure was determined on the basis of surgeon preference and included open drainage, closure over Penrose drain, and appositional closure. Each cat was administered buprenorphine HCl (0.01 mg/kg [0.005 mg/lb], IV) after postoperative BAER testing but prior to recovery. Biopsy specimens were placed in neutral-buffered 10% formalin and submitted to a commercial laboratoryb for histologic examination. After surgery, each cat was treated with broad-spectrum antimicrobials (cefazolin [10 mg/kg {4.5 mg/lb}], IV, q 8 h, until discharge; and amoxicillin-clauvulanic acidc [13.75 mg/kg {6.25 mg/lb}], PO, q 12 h, administered by the owner pending bacteriologic culture and susceptibility results for samples collected during surgery). Postoperative complications were recorded in all cases. All cats were discharged from the hospital by the second day following surgery.

Follow-up—Short-term evaluation was performed by a veterinarian 10 to 14 days after surgery. Long-term evaluation, at least 6 weeks following initial surgery, was conducted by use of recheck physical examination or telephone interview. When possible, the cat was reevaluated by one of the authors (BBA) for hearing by use of BAER as well as for other possible long-term complications of VBO.

Statistical analysis—Possible association between hearing and polyp removal via VBO was evaluated with commercially available software to perform exact binomial tests for the calculations of P value and power.d Values of P < 0.05 were considered significant.

Results

Animals—Twenty-one cats and 23 ears (2 cats with bilateral disease) met the initial criteria for inclusion in the study. Breeds represented were domestic shorthair (n = 18), Maine Coon (1), Ragdoll (1), and domestic longhair (1). Two cats were independently treated for both ears; both cats were domestic shorthair and female. Sexes included 12 neutered males, 8 neutered females, and 1 sexually intact male. Mean age at the time of surgery was 54.8 months (range, 5 to 155 months). Two cats had CGA and therefore were only included in short-term data collection and excluded from long-term analysis. Without the inclusion of those 2 cats, mean age at time of surgery was 46 months. Two cats did not have the masses submitted for histologic examination and therefore were excluded from all data analysis. Each of the bilateral cases was included only once (on the basis of random selection) for data analysis, leaving information on 19 cases for the perioperative period and for 15 cases of long-term follow-up.

Preoperative diagnostic findings—Preoperative assumption of inflammatory polyp was made on the basis of prior mass biopsy results, signalment, and initial complaint or results of otic examination. Radiography of the bulla (n = 2 cases), magnetic resonance imaging (1), and computed tomography (3) were performed in some cases prior to surgery to support bulla involvement. The FeLV and FIV test results were negative in 15 cats, unknown in 3 cats, and positive in 1 cat with CGA. Eight masses were removed from the left side and 11 from the right. Seven of the cats had a negative BAER in the affected ear prior to VBO, whereas 12 had a normal BAER. All unaffected contralateral ears had a normal BAER prior to surgery.

Tympanic membranes were not visible in any of the affected ears prior to surgery and deemed grossly normal in all contralateral ears. Three cats had palpable or visible oral components in addition to an auditory mass. The remaining cats had no palpable oral component, and all had visible aural components. Four cats had a head tilt toward the side of the polyp prior to surgery. Two cats had signs consistent with Horner syndrome prior to surgery.

Immediate postoperative findings—Eighteen of the 19 ears tested had no change in BAER. One cat had a change from a normal response to air-conducted clicks before surgery to a negative response in the immediate postoperative period. This did not equate to a significant change in pre- and postoperative status (P = 0.420) between groups. There were no cats in which diminished or lack of hearing prior to surgery converted to a normal response in the immediate postoperative period. Of the 18 ears that had no change, 7 that had lack of response prior to surgery had the same pattern after surgery and 11 had normal patterns before and after surgery. No tympana were present in any of the operated ears, and all tympana from the unaffected ears were unchanged. No cat that had neurologic signs before surgery (ie, head tilt [n = 4] or Horner syndrome [2]) had a resolution of those signs in the immediate postoperative period (24 hours).

Nineteen masses were submitted to a commercial laboratoryb for histologic analysis. Findings were consistent with inflammatory polyps in 17 samples. Two samples had CGA with proliferative otitis media. Within 24 hours of VBO, 1 cat had a head tilt toward the side of the surgery and 11 of 17 developed some degree of Horner syndrome.

Short-term follow-up—Eighteen of 19 cats were reexamined by a veterinarian 10 to 14 days after surgery and were assessed for Horner syndrome and head tilt. One cat was deceased at the time of recommended reexamination. The cat reportedly developed lethargy after surgery and was subsequently treated at an alternate emergency animal hospital 6 days after surgery. The cat died, and discussion with the owner and review of the cat's record supported respiratory arrest and lack of response to resuscitation. Necropsy was not performed, and definitive cause of death was unknown. No other cat had any additional complications at that time, and resolution of Horner syndrome was reported in 1 cat. Head tilt resolution was also reported in 1 cat. Otic examination and BAER were not performed at that time.

Long-term follow-up—Long-term follow-up (t 6 weeks) was only recorded for cats with confirmation of an inflammatory polyp made on the basis of histologic examination. Sixteen cats met the criterion. Fifteen cats were available for physical examination, and 1 cat was rechecked via telephone conversation because of owner refusal to travel. According to the owner the cat did not have head tilt or Horner syndrome by 6 weeks after VBO. Recheck BAER was not performed in the cat.

Fifteen cats with inflammatory polyps were rechecked by one of the authors (BBA). Mean time to follow-up was 118 days (range, 46 to 301 days). Sedated tympanic examination and BAER were performed in 14 cats. Prior to sedation, cats were assessed for head tilt and signs of Horner syndrome. Only one of the cats that had Horner signs during the study period continued to have signs by 8 weeks. Three cats had persistent head tilt to the side of the surgery. All 3 were cats that had a head tilt prior to the procedure. One cat that had developed a head tilt in the immediate postoperative period had complete resolution at the time of recheck.

Of the 14 cats rechecked with sedation, 9 had tympanic membrane regrowth. Three cats had milky or waxy exudate that precluded complete viewing of the tympanic membrane, and therefore their status was defined as unknown. One cat that had regrowth of the polyp was also assumed to have an incomplete tympana on the basis of lack of ability to see the tympana. One cat had a grossly normal canal but no tympanic regrowth.

All cats had hearing status identical to that in the immediate pre- and postoperative periods. As found in the immediate postoperative period, there was no significant (P = 0.228) change in hearing as measured via BAER at ≥ 6 weeks. Power testing was not possible because of low sample size and binomial distribution. To obtain applicable power calculations, the required sample population would have been 250.

Two cats that received VBO without histopathologic evidence of inflammatory polyps were also rechecked more than 6 weeks after surgery. One cat had normal BAERs in both ears before surgery but had a negative BAER in the immediate postoperative period. The cat was again rechecked 668 days after surgery and had a return to normal audilogic status. Reexamination findings also revealed a grossly normal tympanic membrane and resolution of Horner syndrome. The second cat had normal BAERs in the pre- and postoperative analysis and had immediate postoperative head tilt and signs of Horner syndrome toward the side of the VBO. The recheck BAER and otic examination was done 661 days after surgery and was consistent with normal auditory function. Resolution of the head tilt and signs of Horner syndrome were noted.

Two cats were treated for bilateral nasopharyngeal masses. One cat had a normal contralateral otic examination at the time of the first surgery, whereas the second had visible canal changes but no clinical signs associated with them at initial evaluation. Because of a progression of polyp size and clinical signs associated with its presence, both cats had the second VBO approximately 4 weeks after the first. Histologic confirmation of inflammatory polyps was obtained in both ears for both cats. For the purpose of statistical accuracy, each cat was included once on the basis of random selection when calculating P values. The BAER was normal in both cats for both ears in the immediate pre- and postoperative periods. One cat had a negative air-conducted BAER at the long-term recheck examination for the second ear. This cat also developed signs of Horner syndrome in the ipsilateral eye following each surgery, which were resolved by the time of the second long-term recheck.

One polyp regrowth was found in the study group. That cat was rechecked 73 days after the original surgery and had reportedly developed recurrence of clinical signs. Sedated examination confirmed regrowth of the inflammatory polyp, and VBO was repeated 3 days after the recheck. The cat had a negative response to air-conducted BAER on all evaluations. Histologic examination confirmed diagnosis of recurrence. No other recurrences were discovered.

One cat was rechecked 40 weeks after surgery without sedation because of the owners' wishes. Prior to surgery the cat had a lack of response to air-conducted BAER in the operated ear. Postoperative findings were identical. At the long-term follow-up, no neurologic signs or signs of Horner syndrome were detected. Otic examination was incomplete because of the cat's temperament and heavy waxy buildup in both external ear canals. Reliable BAER could not be performed.

Discussion

Results of the present study suggested that inflammatory polyp removal via VBO resulted in improvement or resolution of clinical signs but had no substantial impact on auditory ability as measured with air-conducted BAER. There was no decline or improvement of BAER results during follow-up. It is important to note that a substantial proportion (6/17) of the cats that were treated with VBO for inflammatory polyps had unilateral deafness as measured by air-conducted BAER prior to surgical intervention.

The etiologic agent of inflammatory polyps is still unknown. Proposed etiologies include a response to chronic upper respiratory tract infection, otitis media, ascending infection from the nasopharynx, congenital defects (ie, remnants of the brachial arches), and feline calicivirus–induced pyogranulomatous reaction.2,3,11 A sex predilection has not been reported, and the domestic shorthair is the most commonly affected breed.3 In a study by Anderson et al,21 less than half of cats treated for nasopharyngeal or aural polyps had a visible mass. In a study15 of 53 cats with nasopharyngeal disease, 28% were determined to have polyps, making it the second most common diagnosis. Hearing was not tested in either of those studies. Diagnosis can be made by palpation of masses beneath the soft palate or visual inspection of the vertical or horizontal ear canal; however, confirmation relies on histologic analysis. Radiographic, magnetic resonance imaging, and computed tomographic changes to the tympanic bulla and middle ear have also been described.1,3,18,22,36,37 Three cats in the present study had computed tomographic imaging prior to surgical intervention, and one of the cats also had radiography of the head and bulla. Findings were consistent with those previously reported.36

Histologically, inflammatory polyps have a surface made up of stratified squamous or psuedostratified ciliated columnar or nonkeratinizing epithelium. This covers a core of fibrovascular connective tissue that contains aggregates of inflammatory cells, including lymphocytes, plasma cells, and macrophages, with numerous dilated capillaries.16,22 Areas of mucosal ulceration may also have neutrophilic infiltrates.3,16,18,22 Twenty-one of the 23 masses submitted from the cats in the present study had findings identical with those mentioned. Two of the masses were neoplastic. The high number of inflammatory polyps in this group may overrepresent the actual percentage of polyps in cats with aural masses because of case selection for referral by general practitioners and choice of inclusion criteria.

Two types of deafness are recognized in cats: conductive and sensorineural.29–34 Conductive deafness results when the conduction of sound energy is impeded in the external or middle ear canals. Sensorineural deafness occurs as the result of degeneration of the stria vascularis and subsequent loss of cochlear hair cells. This creates an alteration of hydrodynamics in the inner ear. Damage to the retrocochlear portion of the auditory pathway from the acoustic nerve to the auditory cortex can also create a sensorineural deafness.27,38 Objective assessment of the presence of auditory function and implied hearing can be measured with air-conducted or bone-conducted BAER. We speculated that the presence of an external or middle ear mass may occlude the canal to an important extent and create interference with the passage of sound—that is, a form of conductive deafness. In an effort to inform owners whether their cats were deaf or had developed deafness as the result of the surgery, we performed air-conducted BAER on all cats that received VBO.

To differentiate conductive deafness from sensorineural deafness, bone-conduction readings would have been helpful. Bone-conduction readings were not performed in this study because of lack of available instrumentation and continued availability of the ear canal (with TECA this is not possible because of ear canal removal). Without conductive testing, the type of deafness is speculative, but following study completion, conductive deafness was considered unlikely as the cause of a negative BAER in the cats of the present study. The lack in change of auditory ability for cats with normal results of the BAER before and after surgery would suggest that the normal neural pathways are not affected by the VBO procedure. Similar studies26,29,39,40 in dogs and the literature regarding otitis suggest that lateral bulla osteotomy and VBO are unlikely to cause deafness, and severe otitis externa or media rarely result in complete deafness.26,29,39,40 On the basis of those reports and our results, we suspect that the cats with negative BAERs had sensorineural deafness. The fact that cats that had a negative BAER result before mass removal did not have improved results after surgery further points to a disruption of the internal elements of hearing, such as the cochlea and vestibulocochlear nerve (ie, sensorineural deafness), as opposed to a conductive issue. This information has not previously been reported in cats and could be further substantiated with bone-conduction BAERs. The assumption that removing an obstructive or occlusive mass from the ear canal could improve or restore the response to air-conducted BAER was proven incorrect in this group of cats.

Numerous clinical studies28,30–32,34,35,38,41–47 greatly influenced our choice of study design and surgical methods. The VBO was used in all cats because it is the preferred technique for managing inflammatory polyps.2,18,20,31 Horner syndrome of the ipsilateral eye, likely the result of damage to the sympathetic nerves in the middle ear, is a commonly reported complication, regardless of treatment options. Studies3,11,12,18,20,21,23 have reported frequencies from 43% to 97% of cases. Most of the cats undergoing VBO in this study had signs of Horner syndrome develop in the immediate postoperative period. Most commonly, Horner syndrome resolves within 2 to 4 weeks; however, it has been reported to persist long term in fewer than 25% of cases.12,18,23 Our study supported this claim in that all but 1 cat in the long-term follow-up group had complete resolution of signs. Other reported complications include recurrence, wound drainage, otitis media, hypoglossal nerve damage, facial nerve paralysis, vestibular disturbances, intraoperative hemorrhage, head tilt, and damage to the auditory ossicles.3,11,12,18,20,21,23 To our knowledge, induced or continued deafness has not been listed as a potential complication in any previous report. Deafness has been investigated in relation to otitis and surgical techniques used to correct it in dogs.17,26,29,30,38–41,47–49

A study26 performed in clinically normal dogs undergoing VBO revealed retention of some degree of hearing in all dogs and reduced hearing in 15%. Conclusions suggested that VBO had no deleterious effect on BAERs to air-conducted auditory stimuli and that VBO was preferred for preservation of hearing.26 Results of our study support this claim in cats. Our initial hypothesis that hearing would be improved in cats with absence of BAERs prior to surgery was however not supported. The finding of no change in hearing among cats with inflammatory polyps in the immediate postoperative period, particularly in those with normal hearing prior to surgery, supports the claim that the surgery itself had no negative effect on auditory ability in the immediate postoperative period. Small sample size precluded detection of a significant result, but we believe the findings to be of practical importance.

Limitations to this study included the small sample size, lack of a control population, and failure to include bone-conduction measurements of hearing. The BAER amplitude, latency, and interwave interval values were not calculated. These values were beyond the scope of this project; however, we believe this information may be of interest for future studies. The choice of a single setting for decibel level was used in this study, and therefore minimum threshold information cannot be addressed. It is possible that at lower sound levels more cats may have had altered or absent air-conducted BAERs. Bone-conduction testing was not performed, and previous studies29,30,32,35,38,41,46,47 reveal that boneconduction probes when used appropriately can reliably detect sensorineural hearing.

On the basis of this population of cats, it does not seem that VBO itself should be considered as a treatment to improve hearing or a cause for impaired hearing. We found that preservation of the auditory canal, a reported advantage of VBO, as compared to TECA and lateral bulla osteotomy, may be of no functional benefit if the auditory pathway is not functional before surgery. Therefore, performing air-conducted BAER testing prior to surgery may be helpful in determining whether alternate surgical approaches may be as appropriate as VBO. It is possible that the cats in our study may have responded positively to bone-conduction stimuli and were therefore not completely deaf. This information is of interest to veterinarians but unlikely to be useful to owners of pets with conductive deafness. Such cats are unlikely to respond to verbal commands on the basis of the high decibel level needed to stimulate bone conduction. Our choice of 90 dB has been reported as that level to which humans report discomfort, and therefore it is unlikely that owner attempts to communicate with a cat would reach or exceed this level.26

This research documented that a substantial percentage of cats had a negative BAER for air-conducted stimuli prior to surgery for surgical treatment of inflammatory polyps. This finding suggests that polyp presence may disrupt normal conductive or sensorineural auditory development and function. It is uncertain why some cats are functionally deaf both prior to and following polyp removal, whereas others are unaffected by the polyp. Given that VBO seems to add no functional improvement in hearing of cats that are deaf prior to surgery, an alternate procedure, such as TECA, may be considered just as appropriate for removal of polyps in these cases.

The study also confirmed that VBO was a safe and effective treatment for inflammatory polyps. Cats in this group were unlikely to have a recurrence of polyp growth, prolonged adverse effects, or any change in their ability to hear subsequent to the procedure. On the basis of these findings, restoration of hearing cannot be included as an indication for VBO. Subsequently, an alternate technique, TECA, can be considered if hearing is not present or normal auditory ability is not imperative and in instances where diagnosis is questionable and more aggressive soft tissue resection would be beneficial—that is, in instances of suspected but unconfirmed neoplasia. In cats with hearing at the time of surgery, a VBO may be recommended to those owners who are interested in preserving normal auditory function or retaining a more cosmetic appearance because most cats will retain hearing as measured via air-conducted BAER after surgery. Further studies are needed to ascertain whether preservation of the ear canal provides additional benefits when treating inflammatory polyps in cats with concurrent hearing loss.

ABBREVIATIONS

BAER

Brainstem auditory evoked response

CGA

Ceruminous gland adenocarcinoma

TECA

Total ear canal ablation

VBO

Ventral bulla osteotomy

a.

Neuropack 2 unit, model MEB7102A, Nihon Kohden Corp, Tokyo, Japan.

b.

Antech Laboratories, New York, NY.

c.

Clavamox tablets and drops, Pfizer Animal Health, New York, NY.

d.

Excel 2003, version 10, Microsoft Corp, Redmond, Wash.

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