Inflammatory middle ear disease of the dog: the pathology of otitis media

Imaging findings in otitis media and resulting secondary lesions in dogs and cats - an image essay

Over the past 2 decades, the increasing availability of computed tomography (CT) and magnetic resonance imaging (MRI) as well as the growing professional expertise have significantly improved the diagnostics of middle and inner ear diseases in dogs and cats. In answering some of the diagnostic questions, CT and MRT demonstrate equivalent performance. For most questions, however, there are differences in the diagnostic performance due to the physical imaging properties of the 2 modalities.CT is more sensitive in demonstrating involvement of the bulla wall and is more effective for detecting abnormal content within the tympanic bulla. In addition, with CT it is often easier to guide tissue samplings. On the other hand, structural changes of the soft tissues of the skull, head, meninges, brain, and nerves are not or only insufficiently detectable on CT images. MRI is clearly superior here. Therefore, MRI is essential for the characterization of materials inside the bulla cavity and for demonstrating the extent of any central spread of otitis media (OM).In this image essay, CT and MRI features of OM and resulting secondary lesions described in the literature are analyzed and summarized. Own image examples are used for illustration. Information on the etiology, pathogenesis, pathomorphology, and clinical signs important for understanding these changes are presented in concise descriptions.

Myringotomy in dogs: Contamination rate from the external ear canal - a pilot study

Myringotomy for sample collection from the middle ear cavity for cytology and bacterial culture is considered a routine method to diagnose otitis media in dogs. The objective of this study was to determine the rate of contamination of middle ear aspirates with material from the external ear canal obtained by video-otoscopic guided myringotomy. In canine cadavers (n = 17) free from otitis externa the external ear canals were flushed under video-otoscopic control and a fluorescent dye was instilled. After removal of residual fluid a myringotomy was performed. If air was aspirated, 1 mL of saline was instilled through the same myringotomy needle into the middle ear cavity and re-aspirated. Contamination from the external ear canal was demonstrated by positive fluorescence of the aspirate. Bacterial cultures and cytological examinations of the external ear canals and middle ear cavities were performed. Data from 28 ears under investigation were included. In 19 of 28 middle ear aspirates (67.9%), clear yellow fluorescent fluid was obtained, indicating a contamination from the external ear canal. Microorganisms were detected in 4 of 26 middle ear samples (15.4%) and in 15 of 26 external ear canals (57.7%). Sample collection by myringotomy in this study was associated with a high contamination rate, implying that the suitability of this method for detection of otitis media in patients with concurrent otitis externa is questionable. Furthermore, the potential for iatrogenic spread of pathogenic microorganisms into the middle ear cavity needs to be considered.

Recurrent polyp formation with Candida tropicalis infection and otitis in a dog

To describe a case of a recurrent Candida tropicalis otitis externa, media and interna in a dog with an ear polyp. A 9-year-old Irish Setter was presented with 2 episodes of otitis sinistra, left-sided vestibular syndrome and Horner syndrome 7 months apart. At the first episode a benign ear polyp was extracted and Candida tropicalis cultured from the left middle ear. The neurological signs disappeared within 7 days, the Candida infection was more difficult to treat. Seven months later, a polyp was found in the ear again and cytology was consistent with Candida tropicalis. A unilateral left total ear canal ablation with lateral bulla osteotomy was performed and a middle ear culture confirmed Candida tropicalis. Treatment led to resolution of clinical signs. Candida tropicalis, an emerging pathogen, should be considered in cases of recurrent yeast otitis and may be difficult to treat.

Occult otitis media in dogs with chronic otitis externa - magnetic resonance imaging and association with otoscopic and cytological findings

BACKGROUND

Identification of perpetuating factors, such as otitis media (OM), is important for the successful management of canine chronic otitis externa (OE).

HYPOTHESIS/OBJECTIVES

Occult OM can occur in cases of chronic OE; a focused magnetic resonance imaging (MRI) examination is a useful tool in their management.

ANIMALS

One hundred twenty one client-owned dogs presented for investigation and treatment of chronic OE between 2009 and 2018.

METHODS AND MATERIALS

Mixed retrospective (74 dogs) and prospective (47 dogs) study of chronic OE cases without neurological signs, describing the MRI, otoscopic and cytological findings; comparing cases with and without MRI evidence of OM.

RESULTS

A total of 123 MRI studies were analysed (two dogs scanned twice). A short, focused MRI scan allowed detection of inflammation of the mucosal bulla lining as well as excellent discrimination between avascular material and vascularised soft tissue in the tympanic cavity. OM was found in 41 of 197 (21%) ears with chronic otitis externa. On otoscopy, the tympanic membrane was intact in six of 41 ears (15%), ruptured in 16 of 41 (39%) and not visible in 14 of 41 (34%) [no data in five of 41 (12%)]. Analysis of cytological findings showed that the presence of rods was only associated with an increased likelihood of OM when found together with inflammatory cells.

CONCLUSIONS AND CLINICAL IMPORTANCE

Occult OM is a not uncommon finding on MRI of dogs with chronic OE. A targeted MRI study ("bulla mini-scan") may be useful as part of the clinical investigations.

Bilateral tympanokeratomas (cholesteatomas) with bilateral otitis media, unilateral otitis interna and acoustic neuritis in a dog

Background

An aural cholesteatoma, more appropriately named tympanokeratoma, is an epidermoid cyst of the middle ear described in several species, including dogs, humans and Mongolian gerbils. The cyst lining consists of stratified, keratinizing squamous epithelium with central accumulation of a keratin debris. This case report describes vestibular ganglioneuritis and perineuritis in a dog with chronic otitis, bilateral tympanokeratomas and presumed extension of otic infection to the central nervous system.

Case presentation

An 11-year-old intact male Dalmatian dog with chronic bilateral otitis externa and sudden development of symptoms of vestibular disease was examined. Due to the dog’s old age the owner opted for euthanasia without any further examination or treatment and the dog was submitted for necropsy. Transection of the ears revealed grey soft material in the external ear canals and pearly white, dry material consistent with keratin in the tympanic bullae bilaterally. The brain and meninges were grossly unremarkable. Microscopical findings included bilateral otitis externa and media, unilateral otitis interna, ganglioneuritis and perineuritis of the spiral ganglion of the vestibulocochlear nerve and multifocal to coalescing, purulent meningitis. A keratinizing squamous epithelial layer continuous with the external acoustic meatus lined the middle ear compartments, consistent with bilateral tympanokeratomas. Focal bony erosion of the petrous portion of the temporal bone and squamous epithelium and Gram-positive bacterial cocci were evident in the left cochlea. The findings suggest that meningitis developed secondary to erosion of the temporal bone and ganglioneuritis and/or perineuritis of the vestibulocochlear nerve.

Conclusions

Middle ear tympanokeratoma is an important and potentially life-threatening otic condition in the dog. Once a tympanokeratoma has developed expansion of the cyst can lead to erosion of bone and extension of otic infection to the inner ear, vestibulocochlear ganglion and nerve potentially leading to bacterial infection of the central nervous system.

Electronic supplementary material

The online version of this article (10.1186/s13028-018-0386-4) contains supplementary material, which is available to authorized users.

Canine aural cholesteatoma: a histological and immunohistochemical study

Canine aural cholesteatoma is an epidermoid cyst that forms in the middle ear cavity as a rare complication of otitis media but the aetiopathogenesis remains controversial. In the present study, 13 cases of canine aural cholesteatoma were investigated histologically and immunohistochemically and compared with cases of chronic otitis. The immunohistochemical investigation was performed using the following monoclonal antibodies: anti-cytokeratins (CK) 14, 16, 8/18, and 19, and anti-Ki67. The proliferative indexes (PIs) of cholesteatomata and otitis epithelium were calculated as the percentage of Ki67 positive nuclei/total nuclei. Histologically, the cholesteatomata were composed of a hyperplastic, hyperkeratotic epithelium (matrix) resting on a fibrous perimatrix, infiltrated by inflammatory cells and devoid of cutaneous adnexa. Immunohistochemically, the cholesteatoma epithelium was CK14- and CK16-positive, and CK8/18- and CK19-negative. A similar pattern of CK expression was found in otitis externa. In otitis media, ciliated epithelium stained CK8/18- and CK19-positive in all layers, CK14-positive in the basal layers, and CK16-negative. The mean PIs in cholesteatomata and otitides were 18.8 and 17.8, respectively. The immunohistochemical pattern of CK expression in cholesteatomata, when compared with chronic otitis, was suggestive of hyperproliferative epithelium, but its origin could not be demonstrated. Comparable PI values were obtained in cholesteatoma and in chronic otitis, which confirmed that Ki67 is a valuable indicator of a hyperproliferative state, but not a predictor of aggressiveness.

Mucoperiosteal Exostoses in the Tympanic Bulla of African Lions (Panthera leo)

Mucoperiosteal exostoses (MpEs) of the tympanic bulla (TB), also referred as middle-ear otoliths, have been occasionally described in dogs and cats in association with clinical signs of otitis media or as an incidental finding, but they have not been recorded in other species. In this report, we describe the radiographic, gross, and histopathologic features of MpEs in 8 African lions ( Panthera leo). All animals (5 males and 3 females) were adults that had been kept in captivity and had their skeletons conserved as part of an anatomic academic collection. A radiographic study revealed mineralized structures in the TB consistent with MpEs in 7 of the 16 examined TB; a computed tomography study identified MpEs in 12 of the 16 TB. Six TB from 4 lions were sectioned, and several MpEs were demineralized for histopathologic analysis. Grossly, MpEs appeared variable in number and shape. Some were globular structures that were loosely attached to the mucosal surface of the TB; others were isolated to coalescent bone spicules extending from the mucoperiosteum. Position was also variable, but MpEs frequently developed in the hypotympanum, especially on the ventromedial aspect of the TB wall. Microscopically, MpEs were composed of osteonal bone growing from the periosteum and not by dystrophic calcification of necrotic tissue debris, as is hypothesized in dogs.

Relationship between pharyngeal conformation and otitis media with effusion in Cavalier King Charles spaniels

Otitis media with effusion (OME) is a common incidental finding in otherwise normal Cavalier King Charles spaniels (CKCS). In this study, measurements made on MRI were used to determine whether there was an association between OME and brachycephalic conformation. The results confirm that association and also demonstrate that, in CKCS, greater thickness of the soft palate and reduced nasopharyngeal aperture are significantly associated with OME. These results suggest that auditory tube dysfunction and OME may represent a previously overlooked consequence of brachycephalic conformation in dogs.

Multiple follicular cysts of the ear canal in a dog

An 11-year-old, 18-kg, neutered male standard schnauzer was presented for evaluation of recurrent otitis externa with para-aural swelling and fistulation of the right external ear canal of 6 months' duration. Otoscopic examination was impossible because of the severe stenosis of the ear canal. Right para-aural ultrasound examination and ultrasound-guided fine-needle aspiration of a mass-like lesion were performed. Cytology was suggestive of a follicular cyst. Magnetic resonance imaging revealed severe ear canal stenosis with a heterogeneous mass in the horizontal portion of the ear canal and associated otitis media. Total ear canal ablation with lateral bulla osteotomy was performed. Histopathological diagnosis was chronic otitis externa associated with multiple follicular cysts confined to the ear canal. Surgical treatment proved curative. This is the first report of multiple follicular cysts originating from the ear canal in a dog.

Magnetic resonance imaging findings in a red kangaroo (Macropus rufus) with otitis

Magnetic resonance imaging (MRI) was performed on an adult, male Red kangaroo (Macropus rufus) with a history of nonspecific neurologic signs and acute discharge from the left ear. MRI revealed findings consistent with otitis and possible osteomyelitis of the temporal and mastoid bones. To the authors' knowledge, this is the first report of otitis and MRI findings in a kangaroo.

Ototoxicity and tolerance assessment of a TrisEDTA and polyhexamethylene biguanide ear flush formulation in dogs

Clinically healthy mixed breed dogs (n = 20) were used to determine if a Tris (tromethamine)-buffered test solution, Otinide (Trademark of Dermcare-Vet Pty-Ltd, Australia), containing disodium ethylenediamine tetraacetic acid (EDTA; 1.21 g/L) and polyhexamethylene biguanide (PHMB; 0.22 g/L) caused ototoxicity or vestibular dysfunction. The dogs were randomly assigned to either a control group (group A, n = 10) receiving saline, or a treatment group (group B, n = 10) receiving the test solution. Phase 1 of the study consisted of applying 5.0 mL of saline to both ears of the control group (group A) and 5 mL of test solution to both ears of the test group (group B), for 21 days. A bilateral myringotomy was then performed on each dog under deep sedation. Phase 2 of the study then consisted of applying 2.0 mL of the saline to both ears of the control group (group A) and 2.0 mL of the test solution to both ears of the test group (group B), for 14 days. Throughout the study, dogs were examined for clinical health, and underwent otoscopic, vestibular and auditory examinations. The auditory examinations included brainstem auditory evoked potential (BAEP) threshold and supra-threshold assessments using both click and 8 kHz tone burst stimuli. The absence of vestibular signs and effects on the BAEP attributable to the test solution suggested the test solution could be applied safely to dogs, including those with a damaged tympanic membrane.

Evaluation of outcome of otitis media after lavage of the tympanic bulla and long-term antimicrobial drug treatment in dogs: 44 cases (1998-2002)

OBJECTIVE

To evaluate the outcome of otitis media in dogs after video-otoscopic lavage of the tympanic bulla and long-term antimicrobial drug treatment.

DESIGN

Retrospective study.

ANIMALS

44 dogs with otitis media treated in an academic referral practice.

PROCEDURE

Medical records were reviewed for signalment, duration of ear canal disease, previous medical treatments, dermatologic diagnosis, results of cytologic examination and microbial culture of ear canal exudate, findings during video-otoscopy, medical treatment, days to resolution, and maintenance treatments prescribed. Four independent variables (age, duration of ear canal disease prior to referral, use of corticosteroids in treatment regimens, and infection with Pseudomonas aeruginosa) were evaluated statistically for potential influence on time to resolution.

RESULTS

Mean +/- SD (range) duration of ear canal disease prior to referral was 24.9 +/- 21.6 (3 to 84) months. Otitis media in 36 dogs resolved after lavage of the tympanic bulla and medical management; mean +/- SD (range) time to resolution was 117 +/- 86.7 (30 to 360) days. Time to resolution was not significantly influenced by any variable evaluated. Three dogs were lost to follow-up, and 4 dogs eventually required surgical intervention. Seven of 36 dogs in which otitis had resolved relapsed; 4 required additional lavage procedures.

CONCLUSIONS AND CLINICAL RELEVANCE

Results indicate that lavage of the tympanic bulla combined with medical management is an effective and viable option for treatment of otitis media in dogs.

Material in the middle ear of dogs having magnetic resonance imaging for investigation of neurologic signs

The aim of this study was to determine the prevalence and potential significance of finding material in the middle ear of dogs having magnetic resonance (MR) imaging. Of 466 MR studies reviewed, an increased signal was identified in the tympanic bulla in 32 (7%) dogs. Cavalier King Charles spaniels, Cocker spaniels, Bulldogs, and Boxers were over-represented compared to the population of dogs having MR imaging. Five (16%) dogs had definite otitis media and one (3%) had a meningioma invading the middle ear. Of the remaining dogs, 13 (41%) had possible otitis media and 13 (41%) had neurologic conditions apparently unrelated to otitis media. The most common appearance of material in the middle ear was isointense in T1-weighted images and hyperintense in T2-weighted images. There was no apparent correlation between the signal characteristics of the material and the diagnosis. Enhanced signal after gadolinium administration was observed affecting the lining of the bulla in dogs with otitis media and in dogs with unrelated neurologic conditions. In dogs without clinical signs of otitis media, finding an increased signal in the middle ear during MR imaging may reflect subclinical otitis media or fluid accumulation unrelated to inflammation. Brachycephalic dogs may be predisposed to this condition.

Diagnosis and treatment of otitis media in dogs and cats

Otitis externa/media is commonly found in dogs with chronic ear diseases and in cats with upper respiratory disease and polyps. Diagnosis of otitis media requires attention to history and clinical signs, but it also requires other methods of determining disease within the bulla. If the integrity of the eardrum cannot be determined, assume that there is middle ear disease and proceed accordingly. It is prudent to take necessary precautions to avoid the use of potentially ototoxic ear cleaners or topical medications in suspected otitis media cases. Therapeutic success is possible using systemic and topical treatment within the cleaned bulla. Referral to a dermatology specialist or a radiologist for a CT scan may be indicated in some refractory cases. Surgical intervention may be required to cure these difficult cases.

Comparison of ultrasonography, radiography and a single computed tomography slice for the identification of fluid within the canine tympanic bulla

Fluid accumulation within the tympanic bulla (TB) is an important diagnostic indicator in clinical cases of canine otitis media although its identification can be a challenge using currently available imaging techniques. The aim of this study was to compare ultrasound with radiography and a single computed tomography (CT) slice for the identification of fluid within the TB of canine cadavers. A random number of TB in 66 cadavers were filled with ultrasound gel. Rostrocaudal open mouth (RCdoM) radiographs and CT images were interpreted by 2 blinded radiologists and ultrasound examinations were performed by 2 blinded sonographers. The heads were then frozen and sectioned to confirm the contents of each TB. Although CT remained the most accurate method, comparable results were obtained by one of the sonographers and even the inexperienced sonographer produced results superior to radiography. Ultrasound has several advantages over the other imaging techniques and this study suggests that it may have an application in the investigation of canine otitis media although further work in live animals would be required to confirm this.

Primary secretory otitis media in the Cavalier King Charles spaniel: a review of 61 cases

Sixty-one episodes of primary secretory otitis media (PSOM) were diagnosed in 43 Cavalier King Charles spaniels over a 10-year period. The principal findings were signs of moderate to severe pain localised to the head or cervical area, and/or neurological signs. Diagnosis was made by examination of the tympanic membrane and middle ear with the aid of an operating microscope under general anaesthesia. A bulging, but intact, tympanic membrane was found in most cases. Following myringotomy, a highly viscous mucus plug was found filling the middle ear. Treatment, consisting of removal of the mucus plug, flushing of the middle ear, and local and systemic medical therapy, had to be repeated between one and five times. The prognosis was good in all cases. PSOM is an important differential diagnosis in Cavalier King Charles spaniels with signs of pain involving the head and neck, and/or neurological signs.

Ultrasonography versus radiography for detection of fluid in the canine tympanic bulla

The tympanic bullae of 20 previously healthy cadaver animals were randomly filled with sterile saline or air. The heads were positioned using tape ties and a rostrocaudal open mouth radiograph taken. The resulting radiographs were assessed by a blinded ECVDI diplomate, with each tympanic bulla being recorded as being either air or fluid filled. Ultrasound examination of the bullae was performed, by a blinded assessor, using a B-mode 5 mHz sector probe (Sonotron-VingMed Sound A/S, PO Box 141, N3191, Horten, Norway) operating at 3 mHz. Each bulla was recorded as being either air or fluid filled. Results of radiography and ultrasonography were each compared to the actual status of the bulla in a chi square analysis. Sensitivity of radiography was 80%, with specificity of 65%. Ultrasonographic sensitivity was 100% and specificity 100%. Ultrasonography may in future provide a cheap, noninvasive, rapid and widely available method for diagnosing otitis media in clinical cases.

Review of diagnostic imaging of ear diseases in the dog and cat

Diagnostic imaging techniques (conventional radiography, computed tomography and magnetic resonance imaging) are an essential tool in the diagnostic work-up of ear diseases. Conventional radiography is commonly used, but often lacks sensitivity. Computed tomography (CT) and magnetic resonance (MR) are complementary imaging studies of the middle ear, labyrinth, internal auditory canal and their contents. CT provides excellent images of bony structures and is indicated where osseous changes are of greatest diagnostic importance. MR is superior in imaging soft tissue components including intralabyrinthine fluid. Therefore, more than one of these imaging techniques may be required in order to make a diagnosis.

Otolithiasis in three dogs

Mineral opacities within the tympanic bullae, termed otoliths, were detected in three dogs by means of radiography and computed tomography. Radiographic signs of otitis externa were present in two dogs. One dog had clinical signs of vestibular disease, whereas the other two dogs had no clinical evidence of ear disease. Otolithiasis may represent mineralized necrotic material of a current or previous case of otitis media.

Vestibular dysfunction

Vestibular dysfunction can be caused by damage to the peripheral or central components of the vestibular system. Signs of vestibular disease include ataxia, head tilt, and abnormal nystagmus. This article reviews the pathophysiology, diagnosis, and management of common vestibular disorders in dogs and cats.

Magnetic resonance imaging of otitis media in a dog

Otitis media/interna was diagnosed in a 20-month-old German shepherd with the assistance of magnetic resonance (MR) imaging. The MR images were acquired primarily to exclude a brain lesion responsible for vestibular signs. No brain lesion was detected, but obvious signs of chronic changes in the left bulla and external ear canal were confirmed. Thickening of the epithelium and soft tissue surrounding the external ear canal and a laminated appearance of high and low T2 intensities in the tympanic bulla's mucosa were present. The hypointense lines were suspected to be fibrous tissue, indicating chronic changes. This report suggests that MR imaging may serve as a useful imaging tool for otitis media and that it supplies information not obtained with radiography or computed tomography.

Evaluation of the canine tympanic membrane by positive contrast ear canalography

Positive contrast ear canalography was described briefly in 1973 as a method for detecting rupture of the tympanic membrane in dogs with otitis media. The purpose of this study was to evaluate the sensitivity and usefulness of the technique. The ears of 10 normal canine cadavers and 31 dogs with clinical signs of ear disease were examined using otoscopy, radiography and contrast radiography after infusing 2 to 5 ml of positive contrast medium into the ear canals. These examinations were repeated in the cadavers after the tympanic membrane had been punctured with a Spreull needle. In the cadavers 14 of 19 (74 per cent) of the tympanic membranes were visible otoscopically; contrast medium did not enter the tympanic bulla of any of the ears before the tympanic membrane was ruptured, but was visible in the bulla in every ear after rupture. In the clinical study, 40 of 61 (66 per cent) of the tympanic membranes were visible otoscopically, and 12 appeared to be ruptured. Radiographic signs of otitis media (increased opacity and/or thickening of the tympanic bulla) were identified in seven ears. Canalography was positive for rupture of the tympanic membrane in 13 ears, including four in which it appeared to be intact otoscopically. In normal canine ears, canalography was a more accurate method for detecting iatrogenic tympanic membrane rupture than otoscopy. In dogs with ear disease, canalography may be more sensitive for otitis media than either otoscopy or survey radiography.

Effects of otitis on hearing in dogs characterised by brainstem auditory evoked response testing

Hearing function was measured in normal dogs and in dogs with otitis using brainstem auditory evoked response testing. Data were obtained from 86 normal ears and from 105 ears with otitis, categorised into four degrees of severity. The data were analysed to illustrate the differences between the hearing function in the normal and abnormal ears and to estimate the degree of impairment associated with differing degrees of pathology. While severe hearing loss seemed to be present in the dogs with more severe otitis, only two individuals were identified as being totally deaf in the affected ears and no dogs were identified in which the cleaning and examination processes had caused damage to hearing function. Cleaning the ear canal produced measurable improvements in hearing in several dogs, indicating the profound effect of physical obstruction of the external ear canal by debris. It is concluded that most dogs with chronic otitis externa are not totally deaf and that the hearing impairment that does occur has the characteristics of conductive hearing loss.

Radiographic appearance of the middle ear after ventral bulla osteotomy in five dogs with otitis media

Radiographs of the middle ear were made in five dogs 60 to 78 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 demonstrated 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 obliterating the middle ear previously reported in normal dogs after ventral bulla osteotomy was not seen in any of these patients.

Demonstration of Mycoplasma hyorhinis as a possible primary pathogen for porcine otitis media

A study of the pathology of the ear was performed on 479 pigs ranging in age from 1 day to 1 year. Histologically, 364 (76.0%) of 479 pigs were affected with otitis. Eustachitis was the most common and preceded an inflammation of other sites of the ear, and an acute eustachitis occurred from as early as 1 week of life. Immunohistochemical examination of frozen cryostat sections revealed Mycoplasma hyorhinis (Mhr) antigens on the luminal surface of the eustachian epithelia in 14 (50.0%) of 28 piglets examined. All the pigs positive for Mhr had an acute eustachitis. Ultrastructural examination on the auditory tubes with positive immunostaining disclosed many mycoplasmas among the cilia. Mhr was isolated from the auditory tubes and tympanic cavities of 19 (67.9%) and 16 (57.1%) of 28 piglets examined, respectively. Porcine otitis media may be caused primarily by Mhr infection in the auditory tube.

Aural cholesterol granuloma in a dog

A five-year-old female Irish setter was referred for surgery for a left-sided aural mass. The dog was generally well, but had signs of left-sided otalgia for one week. Biopsy identified the lesion as a cholesterol granuloma. The mass was removed three weeks later by a total canal ablation/lateral bulla osteotomy. The dog recovered from surgery without any complications. Ten months later, there was no evidence of recurrence. The purpose of this paper is to report the clinical and histopathological findings of this unusual form of granuloma which has not previously been reported in the canine ear.

Diseases of the ear canal

Otitis externa can be a complicated and difficult disease to diagnose and treat. Because of the unique physiology of the ear canal and common pathophysiology of otitis externa regardless of the underlying cause, the clinician must rely on history, dermatologic examination, and ancillary tests to determine the cause and appropriate therapy for a particular case.