Wound Healing and Brain Stem Auditory Evoked Potentials After Experimental Ventral Tympanic Bulla Osteotomy in Dogs

Ventral tympanic bulla osteotomy was performed in 13 normal dogs to evaluate healing and retention of brain stem auditory evoked potentials (BSAEP). Healing was evaluated by gross and microscopic examination of the middle ears after 1 (n = 2), 4 (n = 8), 5 (n = 1), and 6 (n = 1) weeks. One dog was eliminated from the study. Brain stem auditory evoked potentials were measured using an air-conducted sound stimulus before and after surgery and before killing. Nine of 12 dogs re-formed the tympanic bulla by formation of fibrous connective tissue lined with cuboidal epithelium in the osteotomy site. Four of the nine dogs had a reduced tympanic bulla volume (estimated 20% to 40% volume reduction) caused by soft tissue ingrowth through the osteotomy. Nine of 12 dogs had proliferation of subperiosteal new bone from the inner surface of the tympanic bulla that varied in severity. Three of these nine dogs had nearly complete obliteration of the tympanic cavity by proliferating subperiosteal new bone. Eight dogs had nodules of granulation tissue containing new bone and mineralization diffusely distributed on the surfaces of the middle ear. The measured BSAEP sensitivity before killing was equivalent to preoperative levels in 11 dogs. The remaining dog had no change in auditory sensitivity after surgery but had a markedly reduced BSAEP detection threshold before killing. This appeared to be attributable to mechanical impingement on the ossicles and tympanic membrane by proliferating bone within the tympanic cavity. This study showed that after ventral tympanic bulla osteotomy the tympanic bulla rapidly re-forms with no deleterious effect on hearing in most dogs treated. However, the internal surfaces of the middle ear appear to be sensitive to surgical trauma, and extensive new bone proliferation is easily induced. This response may be extreme, resulting in middle ear obliteration and reduced auditory sensitivity.     

Atresia of the external acoustic meatus in a dog

Summary: A 3 year old, female great Dane with atresia of the right external ear canal had recurrent episodes of ear pain. Radiography revealed absence of air in the right external acoustic meatus, thickened bone of the right tympanic bulla and increased radiodensity of the chamber of the bulla. Total ear canal ablation and lateral bulla osteotomy were performed. The superficial portion of the external ear canal was absent and the deeper segment of the vertical ear canal began as a blunt ended cartilage tube. A patent lumen in the existent portion of the external ear canal and the tympanic bulla contained wax, hair and exfoliated squames. The tympanic membrane was not intact. No bacteria were cultured from the contents of the external and middle ear. The dog responded well to surgery and was free of pain 11 months later. Failure to surgically correct atresia of the ear canal in young dogs may allow the accumulation of cellular and sebaceous debris with subsequent involvement of the middle ear in an inflammatory response.     

BAER testing in a dog with bilateral external ear canal atresia

A 3 yr old male castrated Labrador retriever presented for evaluation and treatment of bilateral atresia of the external ear canals. The owners reported that the dog could hear only loud and high-pitched noises. Computed tomography of the head revealed intact vertical and horizontal ear canals filled with debris and a debris-filled right tympanic bulla. Air- and bone-conducted brainstem auditory evoked response (BAER) testing revealed an elevated response threshold to air-conducted stimuli and greater amplitude waveforms evoked by bone-conducted stimuli. The ear canals were surgically corrected via lateral ear canal resection. BAER testing postoperatively revealed a decrease in the air-conducted BAER threshold. This case is an example of the use of bone-conducted BAER testing to aid in the diagnosis of conductive deafness, and in determining prognosis for normal hearing after surgical treatment of external ear canal atresia.     

Inflammatory polyps of the middle ear in 5 dogs

OBJECTIVE: To describe inflammatory polyps of the middle ear in 5 dogs. STUDY DESIGN: Case series. ANIMALS: Five dogs with ear disease. METHODS: Medical records (1995-2001) were reviewed to identify dogs with inflammatory polyps of the middle ear. Signalment, clinical signs, ancillary diagnostic procedures, treatment, postoperative complications, and outcome were recorded. Owners and referring veterinarians were contacted to document outcome. RESULTS: Dogs with inflammatory polyps of the middle ear were male and aged 4 to 13 years. Two dogs had bilateral polyps, whereas 3 had unilateral polyps. The most common clinical presentation was otitis externa and media, with radiographic evidence of otitis media. Polyps were treated by ventral bulla osteotomy (VBO) in 1 dog and total ear canal ablation with lateral bulla osteotomy (TECA-LBO) in 4 dogs. Polyps consisted of a fibrovascular stroma infiltrated with neutrophils, macrophages, lymphocytes, and plasma cells. The overlying epithelium was frequently ulcerated. Immediate postoperative complications included a seroma after VBO (1 dog) and transient unilateral facial nerve paralysis after bilateral TECA-LBO (1 dog). No recurrence occurred within 9 to 69 months. CONCLUSIONS: Unilateral or bilateral, inflammatory polyps can occur in the middle ear of dogs in association with otitis externa and media. No recurrence occurred after surgical removal of the polyps. CLINICAL RELEVANCE: Inflammatory polyps of the middle ear in dogs can be a cause of otitis externa/media. Surgical removal of aural polyps has a good prognosis.     

A surgical technique for implantation of the vibrant soundbridge middle ear implant in dogs

Objective: To report a surgical implantation of the Vibrant Soundbridge (VSB) middle ear implant in dogs. Study Design: Pilot study. Animals: Dogs (n=3). Methods: A lateral approach to the tympanic bulla was used to insert the floating mass transducer of the VSB into the tympanic bulla. Using microscopic guidance the transducer was moved to and inserted into the round window niche by manipulation through the acoustic bony meatus, after reflection of the tympanic membrane. VSB position was confirmed by computed tomography (CT) imaging. Results: No intraoperative complications occurred and CT images confirmed correct placement of the VSB. Conclusions: A VSB can be safely implanted in the middle of dogs.     

COMPUTED TOMOGRAPHY FEATURES OF MIDDLE EAR CHOLESTEATOMA IN DOGS

We describe the computed tomography (CT) findings in 11 dogs with middle ear cholesteatoma. The cholesteatoma appeared as an expansile tympanic cavity mass with a mean attenuation value of 55.8±4.2 Hounsfield units. There was no appreciable contrast enhancement of the tympanic bulla contense but ring enhancement was seen in four dogs. Due to the slow progressive growth, the lesion causes severe bone changes at the contour of the tympanic bulla, including osteolysis, osteoproliferation and osteosclerosis, expansion of the tympanic cavity, and sclerosis or osteoproliferation of the ipsilateral temporomandibular joint and paracondylar process. Cholesteatoma can cause lysis of the petrosal part of the temporal bone, leading to intracranial complications. Although not definitive, CT provides useful information for distinguishing a middle ear cholesteatoma from otitis media and neoplasia. In otitis media, enlargement of the tympanic cavity is not routinely observed. In tumors that primarily affect the middle or inner ear, the predominant signs are lysis of the contour of the tympanic bulla or the petrosal part of the temporal bone, soft tissue swelling around the middle ear and marked contrast enhancement. In tumors that arise from the external ear, a soft tissue mass is visible within the external acusticus meatus, and the middle ear is only involved secondarily.     

ULTRASONOGRAPHIC EVALUATION OF THE EXTERNAL EAR CANAL AND TYMPANIC MEMBRANE IN DOGS

Ultrasonographic imaging of the canine external ear canal, tympanic membrane, and tympanic bulla was described in five healthy beagle dogs before and after infusion of saline into the ear canal. Saline served as an acoustic window. With this method, the external ear canal, and tympanic bulla were visible in the same imaging plane and the integrity of the tympanic membrane could be evaluated indirectly by confirming an intact tympanic membrane, which appeared at the end of the ear canal as a hyperechoic line with reverberation. Experimentally, perforated tympanic membrane could be evaluated by identifying anechoic saline in the tympanic bulla lumen. The air and fluid-filled tympanic bulla were also visualized. Ultrasonography with saline as an acoustic window appears to be helpful for the evaluation of the external ear canal, tympanic membrane, and tympanic bulla and it may have the potential to be a useful clinical tool in evaluation of integrity of the tympanic membrane.     

Chronic Otitis Externa and Otitis Media Treated by Total Ear Canal Ablation and Ventral Bulla Osteotomy in Thirteen Dogs

Ventral bulla osteotomy was combined with total ear canal ablation for the treatment of chronic otitis externa and otitis media in 13 dogs (14 ears) that had been refractory to medical and surgical treatments. Resolution of disease occurred in 11 dogs (12 ears). One dog with unilateral disease underwent a second operation before achieving a good result. One dog was euthanatized for persistent unilateral disease after three surgical procedures. The recurrence of disease in these two dogs (15%) was associated with remnants of ear canal integument within the osseous horizontal canal or tympanic bulla. Facial paralysis occurred in four dogs (31%) and there were no complications in eight dogs (62%). This technique shows no advantage over lateral bulla osteotomy combined with total ear canal ablation for the treatment of chronic otitis externa and otitis media.     

Passive Drainage Versus Primary Closure After Total Ear Canal Ablation-Lateral Bulla Osteotomy in Dogs: 59 Dogs (1985–1995)

Objective- Compare passive wound drainage to primary closure of total ear canal ablation-lateral bulla osteotomy (TECA-LBO) in dogs.
Study Design- Retrospective analysis of medical records.
Sample Population- Fifty-nine dogs with end-stage otitis externa or neoplasia of the external and middle ear.
Methods- Medical records of dogs with TECA-LBO were reviewed. Dogs were divided into postoperative drain and primary closure groups. Statistical analyses were performed to identify differences in data for signalment, preoperative treatment, duration of hospitalization, immediate complications, and long-term complications between groups.
Results- No significant differences were detected in signalment, diagnosis, and duration of medical management between groups ( P >.05). Duration of hospitalization was greater for dogs in the drain group ( P <.05). Immediate postoperative complications occurred in 26 of 59 dogs and included ipsilateral facial palsy, incision swelling, vestibular signs, premature drain removal, and one dog died of aspiration pneumonia. Long-term (>6 months) complications were identified in 12 of 50 dogs and included dermatitis of the medial aspect of the pinna, chronic fistula formation, and permanent facial paralysis. No association between immediate or long term complications and method of closure was identified.
Conclusions- Primary closure is an acceptable alternative in dogs undergoing TECA-LBO when surgical wound dead space can be managed with meticulous hemostasis, complete debridement of devitalized tissue, and accurate apposition of tissue planes.     

Bulla curettage for chronic otitis media and interna in dogs.

In a series of 10 clinically affected and 6 clinically normal dogs, the technique of bulla curettage via the external ear canal, after lateral ear resection, was evaluated. In 5 of the 10 dogs with chronic otitis media and interna, the head carriage became normal 2 to 8 weeks after surgery and remained so for at least 18 months; 4 other dogs improved, but the improvement was either temporary or incomplete. In the clinically normal dogs, postsurgical complications were minimal; the tympanic membrane healed completely in 4 of the 6 dogs.     

Virtual otoscopy for evaluating the inner ear with a fluid-filled tympanic cavity in dogs

The feasibility of virtual otoscopy (VO) imaging was evaluated in five dogs with experimentally induced otitis media, two control dogs, and two canine patients with otitis media. VO images of the tympanic cavity and ossicles were generated with commercially available software using raw computed tomography (CT) data. Eight out of 10 ears inoculated with pathogen exhibited obvious clinical signs associated with otitis externa. CT images revealed soft tissue density material occupying the tympanic bulla compatible with otitis media in three dogs with experimentally induced otitis media and two patients. No remarkable features were observed on the radiographs. Four different VO views (ear canal, tympanic bulla, eustachian tube, and ossicular chain) were created. Promontory, cochlea window, tympanic, and septum bulla as well as ossicles were easily and clearly distinguished except for the incus and stapes of the clinical patients. VO images were not more suitable than images created with conventional CT for accurately diagnosing otitis media in this study. However, it appears that VO could be more feasible for assessing the complex structure of the inner ear in dogs with fluid-filled tympanic cavities since fluid accumulation within the tympanic bulla did not affect the evaluation of bony tissue in the middle ear on VO images.     

PREVALENCE AND CHARACTERIZATION OF SMALL TYMPANIC BONE SPICULES AND DRUMSTICK‐LIKE HYPEROSTOTIC TYMPANIC BONE SPICULES IN THE MIDDLE EAR CAVITY OF DOGS

Rounded, sessile, hyperattenuating structures detected in computed tomography (CT) studies of canine tympanic bullae have been termed “otoliths.” These have been proposed to represent dystrophic mineralizations or heterotopic bone formations in the middle ear that are potentially related to chronic otitis media. Aims of the current study were to describe the prevalence, macroscopic, and histological features of structures consistent with “otoliths” in the canine tympanic cavity. Tympanic bullae from 50 routinely necropsied dogs and 139 retrospectively retrieved CT scans of canine clinical cases were examined. Small tympanic bone spicules with pointed or clubbed tips essentially arising from the free margin of the septum bullae were bilaterally present in the tympanic cavities of all 50 of the necropsied dogs. In 48% of the dogs, “otolith”‐like CT‐detectable bone spicules carrying drumstick‐like hyperostoses that were 1–6 mm in diameter were also present. In the retrospective survey of bulla CT scans of 139 cases, the prevalence of hyperostotic tympanic bone spicules (HTBS) was 20%. Findings from the current study indicated that the presence of small tympanic bone spicules in adult dogs is most likely due to physiological bone growth in the septum bullae and that HTBS represent osseous proliferations of small tympanic bone spicules. However, the factors inducing formation of hyperostotic spicules from small tympanic bone spicules remain unknown. The high prevalence of HTBS displaying a similar appearance in bulla CT scans in dogs suggests that these spicules should be included in a differential diagnosis list for “otoliths.”     

RADIOGRAPHIC APPEARANCE OF THE MIDDLE EAR AFTER VENTRALBULLA OSTEOTOMY IN FIVE DOGS WITH OTITIS MEDIA

Radiographs of the middle ear were made in five dogs 60 to 70 months after ventral bulla osteotomy was performed to treat otitis media. The clinical results of surgery were considered satisfactory in four dogs and unsatisfactory in one. In 4 dogs with satisfactory results, radiographs demonstratd complete reformation of the bulla in 3 operated middle ears (3 dogs), with partial bulla reformation in the three middle ears (3 dogs). Radiographs in one dog with unsatisfactory results showed complete bulla reformation with no increase in lumen opacity. The proliferative bony response obilerating the middle ear previously reported in normal dogs after ventral bulla osteotomy was not seen in any of these patients.     

CONTRAST-ENHANCED COMPUTED TOMOGRAPHIC IMAGING OF THE AUDITORY TUBE IN MESATICEPHALIC DOGS

Computed tomography after contrast medium injection was performed in three mesaticephalic canine cadavers to image the auditory tube. Cadavers were positioned in lateral recumbency for imaging. A myringotomy incision was made in the left tympanic membrane of each dog, and contrast medium was infused into the ear canal and middle ear through a balloon-tip catheter. With this method, contrast medium filled the left bulla and auditory tube in all three cadavers. Computed tomography following contrast medium injection was effective for evaluation of the canine auditory tube. Future studies are required to determine the usefulness, as well as the safety, of this procedure in the evaluation of the auditory tube in other breeds of dogs as well as dogs with otitis     

Aural Cholesteatoma in Twenty Dogs

Objective— To determine the clinical course in dogs with aural cholesteatoma. Study Design— Case series. Animals— Dogs (n=20) with aural cholesteatoma. Methods— Case review (1998–2007). Results— Twenty dogs were identified. Clinical signs other than those of chronic otitis externa included head tilt (6 dogs), unilateral facial palsy (4), pain on opening or inability to open the mouth (4), and ataxia (3). Computed tomography (CT) was performed in 19 dogs, abnormalities included osteoproliferation (13 dogs), lysis of the bulla (12), expansion of the bulla (11), bone lysis in the squamous or petrosal portion of the temporal bone (4) and enlargement of associated lymph nodes (7). Nineteen dogs had total ear canal ablation–lateral bulla osteotomy or ventral bulla osteotomy with the intent to cure; 9 dogs had no further signs of middle ear disease whereas 10 had persistent or recurrent clinical signs. Risk factors for recurrence after surgery were inability to open the mouth or neurologic signs on admission and lysis of any portion of the temporal bone on CT imaging. Dogs admitted with neurologic signs or inability to open the mouth had a median survival of 16 months. Conclusions— Early surgical treatment of aural cholesteatoma may be curative. Recurrence after surgery is associated with advanced disease, typically indicated by inability to open the jaw, neurologic disease, or bone lysis on CT imaging. Clinical Relevance— Presence of aural cholesteatoma may affect the prognosis for successful surgical treatment of middle ear disease.     

Computed tomographic features of feline nasopharyngeal polyps

The computed tomographic (CT) findings of histopathologically confirmed nasopharyngeal polyps are described in 13 cats. Most polyps were mildly hypoattenuating to adjacent muscles and isoattenuating to soft-tissue (n= 13), homogeneous (n = 12) and with ill-defined borders (n = 10) on precontrast images. After contrast medium administration, the polyps were homogeneous (n = 11), with well-defined borders (n = 13), oval (n = 13), and had rim enhancement (n = 13). Nasopharyngeal polyps were pedunculated in 11 cats with a stalk-like structure connecting the polyp through the auditory tube to an affected tympanic bulla. All cats had at least one tympanic bulla severely affected, with CT images identifying: (1) complete (n = 12) or partial (n = 1) obliteration of either the dorsal or ventral compartments with soft-tissue attenuating material; (2) pathologic expansion (n = 13) with wall thickening (n = 10) that was asymmetric in nine cats; and (3) identification of a polyp-associated stalk-like structure (n = 11). Nine cats had unilateral tympanic bulla disease ipsilateral to the polyp, and four cats had bilateral tympanic bulla disease, most severe ipsilateral to the polyp with milder contralateral pathologic changes. Two cats had minimal osteolysis of the tympanic bulla. Enlargement of the medial retropharyngeal lymph node was seen commonly (n = 8), and in all cats it was ipsilateral to the most affected tympanic bulla. One cat had bilateral lymphadenopathy. CT is an excellent imaging tool for the supportive diagnosis of nasopharyngeal polyps in cats. CT findings of a well-defined mass with strong rim enhancement, mass-associated stalk-like structure, and asymmetric tympanic bulla wall thickening with pathologic expansion of the tympanic bullae are highly indicative of an inflammatory polyp.     

Effect of tympanic cavity evacuation and flushing on microbial isolates during total ear canal ablation with lateral bulla osteotomy in dogs

OBJECTIVE: To evaluate differences in bacterial numbers, identity, and susceptibility in samples obtained from the tympanic cavity on entry (preflush) and after evacuation and lavage (postflush) and assess perioperative and empiric antimicrobial selection in dogs that underwent total ear canal ablation (TECA) with lateral bulla osteotomy (LBO) or reoperation LBO. DESIGN: Prospective clinical study. ANIMALS: 34 dogs. PROCEDURE: TECA with LBO or reoperation LBO was performed on 47 ears. Pre- and postflush aerobic and anaerobic samples were obtained from the tympanic cavity. Isolates and antimicrobial susceptibility patterns were compared. RESULTS: Different isolates (31/44 [70%] ears) and susceptibility patterns of isolate pairs (6/44 [14%] ears) were detected in pre- and postflush samples from 84% of ears. Evacuation and lavage of the tympanic cavity decreased the number of bacterial isolates by 33%. In 26% of ears, bacteria were isolated from post-flush samples but not preflush samples. Only 26% of isolates tested were susceptible to cefazolin. At least 1 isolate from 53% of dogs that received empirically chosen antimicrobials postoperatively was resistant to the selected drugs. Anaerobic bacteria were recovered from 6 ears. CONCLUSIONS AND CLINICAL RELEVANCE: Accurate microbiologic assessment of the tympanic cavity should be the basis for selection of antimicrobials in dogs undergoing TECA with LBO. Bacteria remain in the tympanic cavity after evacuation and lavage. Cefazolin was a poor choice for dogs that underwent TECA with LBO, as judged on the basis of culture and susceptibility testing results.     

Traumatic tympanic bulla fracture

A Pekingese dog was presented for evaluation of head trauma with ventral head and neck swelling, puncture wounds, palpable mandibular fractures, and loss of menace, severe miosis, and loss of palpebral reflex of the right eye. Computed tomography confirmed multiple mandibular and zygomatic fractures, a right ear canal avulsion, and a complete right tympanic bulla fracture with ventral displacement. The tympanic bulla fracture was managed conservatively. Topical lubrication and antibiotic ointment was prescribed for the right eye. A subtotal hemimandibulectomy was performed to address the mandibular fractures. A temporary oesophagostomy feeding tube was placed. No short‐term complications developed as a result of the fractured bulla and avulsed ear canal being left in situ, and no complications were reported 18 months after the injury. To the authors’ knowledge this is the first report of a traumatic tympanic bulla fracture in the dog.