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.     

Surgical management of acute ear canal separation in a cat

A 5-year-old cat presented with haemorrhagic left aural discharge, 2 days following a road traffic accident. Otoscopic examination identified disruption of the external ear canal at the auricular/annular cartilage junction. This was managed by total ear canal ablation and lateral bulla osteotomy. Left sided facial nerve deficits were present following surgery. Eighteen months postoperatively there were no auricular problems, however facial nerve deficits persisted. There are no previous reports describing management of acute separation at the auricular/annular cartilage junction of the external ear in the cat or dog. This case report describes the presentation, diagnosis and surgical management of an acute ear canal separation at the auricular/annular junction of the external ear canal in a cat.     

COMPUTED TOMOGRAPHIC APPEARANCE OF INFLAMMATORY POLYPS IN THREE CATS

This report describes the use of computed tomography (CT) to evaluate the inner ear, tympanic bullae, nasopharyngeal area, and external ear canals of three cats. All cats presented for evaluation of upper respiratory signs or chronic ear infection. Nasopharyngeal masses were present in two cats, and a mass in the external ear canal was present in the third cat. In all three cats, CT was able to define the extent of osseous bulla involvement, which was confirmed at surgery. Computed tomography also defined the extent of the polyp in the nasopharyngeal area in two cats, and in the external ear canal in one cat. Surgical removal of the polyps was accomplished with a combined oral approach and ventral bulla osteotomy in cats 1 and 2. The polyp was removed from cat 3 using a combination of ventral bulla osteotomy and excision of the mass through the external ear canal. Microscopic examination confirmed all masses as nasopharyngeal (inflammatory) polyps.     

Surgical management of chronic otitis secondary to craniomandibular osteopathy in three West Highland white terriers

Three West Highland white terriers were presented for investigation of left‐sided para‐aural abscessation. CT revealed chronic otitis media with extensive osseous proliferation surrounding the horizontal and vertical ear canals contiguous with the expanded temporal bone, consistent with a unilateral variant of craniomandibular osteopathy. A left total ear canal ablation with lateral bulla osteotomy was performed in all dogs. An ultrasonic bone curette (Sonopet; Stryker) proved useful when removing the osseous proliferation in two dogs. Histopathological examination of the ear canals was consistent with craniomandibular osteopathy and the treatment led to resolution of the presenting clinical signs in all dogs. To our knowledge, this is the first report of craniomandibular osteopathy engulfing the external ear canal, presumably leading to chronic otitis media and para‐aural abscess formation. This is also the first reported use of an ultrasonic bone curette in canine otic surgery.     

Otitis media in a llama

A 7-month-old female llama was examined because of chronic otitis media and externa of 7 months' duration. Radiographically, the tympanic bullae appeared thicker than normal, and the ventral borders were poorly defined; the left external acoustic meatus (ear canal) appeared to be narrower than the right. The llama was treated with penicillin, and the ear canals were lavaged daily. Contrast radiography was performed on day 15 to determine the shape and size of the ear canals and evaluate the integrity of the tympanic membranes. Contrast medium was visible radiographically in the left tympanic bulla, indicating that the left tympanic membrane was ruptured, but the right tympanic membrane appeared to be intact. The left ear canal was narrower than the right, and the bony ear canals had a well-defined sigmoid shape. The right ear improved with medial treatment alone, but the left ear did not. Therefore, lateral ear canal resection was performed. After surgery, however, exudate was still evident in the left ear canal, and the llama became more lethargic and more reluctant to eat. Lateral bulla osteotomy was attempted, but no purulent material was obtained, and curettage of the bulla resulted in hemorrhage. Because of this and because of the llama's poor physical condition, a decision was made to euthanatize the llama. The sigmoid shape of the bony ear canal and the multicompartmental nature of the tympanic bulla make surgical treatment of otitis media and externa in llamas difficult. Further study of surgical treatments for otitis media in llamas is needed.     

A Technique for Examining the External Ear Canal in Standing Sedated Horses

In this study ultrasonography, local anesthesia, and endoscopy were performed in both ears of 23 horses. The aim was to find a reliable technique for examination of the external ear canal in standing sedated horses and to create a grading of debris and the occurrence of abnormalities in clinically healthy horses. Local blockage of the great and internal auricular nerves was performed after caudal palpation at the base of the ear and ultrasonographic assessment of the styloid process of the auricle as a reference point for the needle placement. The otoscopic examination was accomplished with two flexible video endoscopes with 2- and 7-mm tip diameters. The depth of the styloid process varied ultrasonographically from 2.08 to 2.73 cm on the left side and from 2.04 to 2.76 cm on the right side. Local anesthesia was successful in all sedated horses, without any long-term complications. The grading of endoscopic appearance of the skin, epithelium, and ceruminous and cell debris in the cartilaginous and osseous part including tympanic membrane of the equine external ear canal ranged from I to III. Abnormalities like osteoma, granuloma, hemorrhagic or erythematous areas, and narrowing of the osseous part of the external ear canal due to stenosis (exostosis) were seen in 10 of 23 horses. The tympanic membrane was visualized in 20 of 23 horses. Local blockage of the great and internal auricular nerves was found to be a reliable method for equine ear anesthesia.     

Surgical management of 2 different presentations of ear canal atresia in dogs

A 6-year-old French spaniel and a 14-month-old German shepherd dog were diagnosed with ear canal atresia. Based on presentation, computed tomography, and auditory function evaluation, the first dog underwent excision of the horizontal ear canal and bulla curettage, and the second underwent re-anastomosis of the vertical canal to the external meatus. Both dogs had successful outcomes.     

Cholesterol granuloma as long-term complication of total ear canal ablation in a dog

A 13-year-old cocker spaniel presented with pain on opening the mouth. History of a previous left total ear canal ablation with lateral bulla osteotomy, left intermittent facial palsy and left intermittent head tilt suggested progression of a total ear canal ablation with lateral bulla osteotomy complication. Magnetic resonance imaging revealed a large mass arising from the tympanic bulla. Cytology of aspirates revealed a chronic suppurative inflammatory reaction and numerous cholesterol crystals. The mass was removed by surgical excision and an active drainage system was placed for a few days. The head tilt, facial palsy and apparent pain were resolved by the surgery. Physical examination was unremarkable nine months postoperatively. Bacterial cultures of the collected fluid were negative and histological examination confirmed the diagnosis of a cholesterol granuloma.     

Treatment of Traumatic Separation of the Auricular and Annular Cartilages Without Ablation: Results in Five Dogs

Five dogs were diagnosed as having unilateral separation of the otic cartilages (auricular and annular). Four dogs had sustained prior trauma (hit by a car). Clinical signs were typical of ear canal stenosis and included swelling at the base of the ear (n = 2), periotic fistulation (n = 2), head tilt toward the affected side (n = 2), and pain when opening the mouth (n = 1). Palpation revealed separation of the horizontal and vertical ear canals. Otoscopic findings included a shallow ear canal and a pseudotympanic membrane across the proximal end of the auricular cartilage. Findings at surgery confirmed the diagnosis of cartilage separation and included an exudate-filled horizontal ear canal and a blind-ending vertical ear canal. Surgical treatment involved isolating the distal end of the annular cartilage (horizontal ear canal), opening and evacuating the horizontal ear canal, and suturing the open end of the annular cartilage to the skin. The length of annular cartilage was variable among the dogs, although each dog had sufficient horizontal canal to appose skin to otic epithelium. The vertical ear canal was not surgically dissected or manipulated. The mean follow-up period was 46 ± 14 months (range, 31 to 68 months). All five dogs had patent horizontal ear canals when examined at the follow-up examination.     

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, cntegorised 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.     

Finite element modelling of the canine and feline outer ear canal: benefits for local drug delivery?

Current therapeutic regimes of outer ear infections in dogs and cats aim at the application of efficient local therapeutics after cleaning of the acoustic meatus. One so far insufficiently answered question is if the local application of these substances results in an individually suitable drug concentration in the external ear canal. Thus, the purpose of the present study was to develop a finite element model to calculate the values of the different areas of the external acoustic meatus in dogs and cats in order to provide a tool for the benefit of an appropriate local drug dosage determination. A 3D finite element model (FEM), based on computer tomographic (CT) data sets of four dogs and two cats, was generated to determine areas and volumes of the outer ear canal. Furthermore, various ear therapeutics and cleansers were tested concerning their optimal distribution on 5 cm2 dog and cat skin. The data shows major variations of the area values of the external auditory canal in case of the different dogs but not in the examined cats. These results suggest that manufacturer's recommendations of the pharmaceuticals might be insufficient in terms of achieving an optimal drug concentration in the outer ear canal especially in larger dogs. In conclusion, the developed finite element model has shown to be suitable to calculate areas of the outer ear canal in cats and dogs and could be of help in context with the definition of optimal drug concentrations for a local drug delivery.     

Otoscopic, cytological, and microbiological examination of the equine external ear canal

Otoscopic examination and cytology of the equine ear would be beneficial in diseases such as head trauma, headshaking, otitis externa secondary to otitis media, vestibular disease, aural neoplasia and aural pruritus secondary to parasites. In practice, otic examinations of horses are rarely done due to the perceived difficulty in visualizing the equine external ear canal and tympanic membrane, as well as the need for chemical restraint. In this study, the proximal external ear canal was examined in live horses using a handheld otoscope and in cadaver heads using video otoscopy. Visualization of the proximal ear canal of the sedated horse could be done with a handheld otoscope, but more sedation or general anaesthesia and a video otoscope would be required to adequately visualize the tympanic membrane in the live horse. The proximal ear canals of 18 horses were examined cytologically and cultured aerobically. In three horses, both ears were sampled. No cells or organisms were seen on cytological examination of 11/21 ears. Nine of the 21 ears were sterile when cultured. Ten of the 21 ears had mixed growth with low numbers of organisms (Corynebacterium sp. being most common). Two of the 21 ears had heavy growth of a single organism (Corynebacterium sp. and Staphylococcus intermedius, respectively). Equine cadaver heads were examined in cross-section by computed tomography (CT) imaging and histopathology in order to further understand the anatomy of the equine external ear canal. Equine practitioners should be aware that otic examination is possible and may provide important diagnostic information.     

Tympanographic volume measurements of the canine ear

External ear canal volumes of 50 dogs were measured by tympanography. Comparison between each dog's weight and ear volume revealed a linear increase in volume with increasing weight up to 10 kg. At weights greater than 11 kg, ear volumes did not increase. After ear canal measurement, the tympanic membranes of 30 of the dogs were punctured, permitting determination of the combined volumes of the external ear canal and middle ear. This combined volume increased with increasing weight.     

PREVALENCE OF EAR DISEASE IN DOGS UNDERGOING MULTIDETECTOR THIN‐SLICE COMPUTED TOMOGRAPHY OF THE HEAD

Previous reports describing the prevalence of ear diseases in dogs have primarily been based on dogs presenting with clinical signs of disease. The prevalence of subclinical ear disease remains unknown. The purpose of this cross‐sectional retrospective study was to describe the prevalence of lesions consistent with middle and external ear disease in dogs presented for multidetector computed tomography (CT) of the head and/or cranial cervical spine at our hospital during the period of July 2011 and August 2013. For each included dog, data recorded were signalment, CT findings, diagnosis, and treatment. A total of 199 dogs met inclusion criteria. Nineteen dogs (9.5%) were referred for evaluation of suspected ear disease and 27 dogs (13.5%) had histories or physical examination findings consistent with otitis externa. A total of 163 dogs (81.9%) had CT lesions consistent with external ear disease (i.e. ear canal mineralization, external canal thickening, and/or narrowing of the external canal). Thirty‐nine dogs (19.5%) had CT lesions consistent with middle ear disease (i.e. soft tissue attenuating/fluid material in the tympanic bullae, bulla wall thickening or lysis, and/or periosteal proliferation of the temporal bone). Findings from this study indicated that the prevalence of external and middle ear disease in dogs could be higher than that previously reported.     

Primary anastomosis of segmental external auditory canal atresia in one dog

This report describes a case of canine segmental external auditory canal atresia (EACA). The dog was managed medically with non-steroidal anti-inflammatory drugs until clinical deterioration, at which time a novel and successful end-to-end anastomosis surgical repair was performed. At the 30 day postoperative re-examination, the dog was clinically well and otoscopy confirmed that there was no evidence of auditory canal stenosis. The patient remained free of ongoing issues 20 months after the surgery. End-to-end anastomosis should be considered for treatment of developmental segmental EACA in the canine.     

Eradication of elephant ear mites (Loxoanoetus bassoni) in two African elephants (Loxodonta africana)

Elephant ear mites, not previously described in North America, were eradicated in two African elephants (Loxodonta africana) after six otic instillations of ivermectin at 2-wk intervals. The microscopic examination of a clear, mucoid discharge collected from the external ear canals of two wild-born African elephants housed in a New York State zoo for 25 yr revealed live mites (Loxoaneotus bassoni). The cytologic examination demonstrated no evidence of inflammation or infection. Both elephants were asymptomatic with normal hemograms and serum chemistry panels. A diagnosis of otoacariasis was made. Each elephant was treated six times with 5 ml of 1% ivermectin syrup instilled in each ear canal once every 2 wk. Microscopic examinations of clear mucus collected from each elephant's ear canals 9 days after the first instillation of ivermectin were negative for any life stages of ear mites. Microscopic examinations of mucus collected from both elephants' ear canals at 6, 11, and 16 wk, as well as annually post-treatment for 7 yr, confirmed eradication of the ear mites. The L. bassoni ear mite was first identified in the external ear canals of wild, asymptomatic, lesion-free, African elephants culled in Kruger National Park in South Africa. However, a new species in the same genus of mites (Loxoanoetus lenae) was identified at the necropsy of an 86-yr-old Asian elephant (Elephas maximus) living in a circus in Australia. The autopsy revealed a marked, ballooning distension of bone around the left external acoustic meatus, suggestive of mite-induced otitis externa, as seen in cattle infested with ear mites (Raillieta auris). Elephant health care providers should identify the prevalence of, and consider treatment of, elephants in their care infested with ear mites, given the possible risk for adverse health effects.     

Morphologic measurements of the external horizontal ear canal of dogs

Microscopic anatomy of the horizontal part of the external ear canal was evaluated in 24 dogs. Sixteen dogs were from breeds known to have a predisposition to otitis externa. The remaining 8 dogs were from breeds that do not have a predisposition to otitis externa. Dogs were separated into groups according to predisposition to otitis externa: group 1-predisposed dogs without otic inflammation, group 2-predisposed dogs with otic inflammation, and group 3-nonpredisposed dogs without otic inflammation. Qualitative microscopic evaluation of distribution of hair follicles revealed hair within proximal, middle, and distal regions of the horizontal ear canal in all breeds. The degree of keratinization was directly proportional to the presence of otic inflammation and was excessive in group-2 dogs. Quality of sebaceous glands within the horizontal ear canal was similar among dogs with and without otitis externa, whereas the quantity of apocrine tubular glands was significantly increased (P less than 0.05) in dogs with otitis. Quantity of apocrine tubular glands was also greater in group-1 dogs than in group-3 dogs. Thickness of the soft tissue in the external ear canal increased in direct proportion to the progression of disease and was greatest in the proximal region of the affected ear canal. Soft tissue located caudally between nonopposing ends of the annular cartilage, within the proximal region of the horizontal ear canal, contained few glands and hair follicles in dogs without otitis externa. In dogs with otitis externa, this region was infiltrated by distended apocrine tubular glands.     

Chronic otitis externa/media with total ear canal ablation and bulla curettage in a North American bison (Bison bison).

An adult female North American bison (Bison bison) with a chronic otitis externa/media of the right ear was examined because of a 4-mo history of intermittent anorexia, apparent painful behavior, and auricular discharge from the right ear. Computerized tomography (CT) demonstrated osteolysis of the tympanic, petrous, and squamous aspects of the temporal bone with soft tissue replacement and sclerosis of the right bulla. A total ear canal ablation with bulla curettage was performed, and cefazolin-impregnated polymethacrylate beads were left within the right bulla and the remnant temporal bone. Six months after the surgery, the bison had no clinical signs of otitis media.     

The aerobic bacterial flora of the middle and external ears in normal dogs

The aerobic bacterial flora of the middle and external ears was elucidated in 30 normal dogs (60 ears). Bacterial swab samples were obtained by rubbing the surface of the tympanic cavity and external ear canal. In the middle ear, bacteria were cultured from 48 per cent of the total ears and mainly included Escherichia coli (8 per cent), yeasts (8 per cent), staphylococci (7 per cent) and branhamella (7 per cent). In the external ear, bacteria were found in 46 per cent of the total ears and staphylococci (19 per cent) and yeasts (7 per cent) were the main isolates. Mycoplasma was found in one external ear sample, but in no middle ear samples in an examination of 20 ears. The same type of bacterium was hardly ever found in both the middle and external parts of each ear.