You have asked...
How should I conduct thorough ear examinations in my patients?
The expert says...
A thorough physical examination of the ear should include 3 independent parts:
- Pinnal and preauricular skin examination
- Otoscopic examination
- Tympanic membrane assessment
1 Pinnal & Preauricular Skin Examination
Examination of the pinnae to assess for primary and secondary lesions can help formulate a list of differential diagnoses and diagnostic tests. Lesions found on the pinnae may also suggest conditions such as allergy, inflammatory/autoimmune conditions, infections, and infestations.
Causes of Pinnal Disease
- Immune-mediated disease
- Keratinization defects
- Malassezia spp and dermatophytes
- Atopic and contact dermatitis
- Endocrine disorders
Figure 1 Pinnal erythema on the concave surface in an English bulldog with atopy. Note the presence of pustules and papules.
Pustules on the pinnae (Figure 1) can suggest either infectious (eg, pyoderma) or sterile disease (eg, pemphigus foliaceus). Cytologic examination of the pustules may show acantholytic cells and neutrophils indicative of pemphigus. Neutrophils and bacteria can be seen in some infectious causes of pustules. Papular eruptions may also be seen with parasitic diseases.
Thick scale and erythema of the pinnal margins, particularly the apices, may indicate sarcoptic mange, especially when a “pinnal-pedal” scratch reflex occurs in response to rubbing of the pinnae. In addition, erythema, crusts, and scale may be present with demodicosis or dermatophytosis. Low-power examination of skin scrapings placed in mineral oil on a microscope slide may help identify the presence of parasites. Fungal culture may be indicated.
If vasculitis is suspected as a result of ulceration, necrosis, notching, and/or scarring of the pinnal margin, a biopsy may be necessary to examine for capillary thrombosis. Ear margin seborrhea, a nonpruritic primary cornification defect often found in dachshunds and Yorkshire terriers, may result in keratinaceous debris or alopecia along the ear margins.1 Cytologic examination of secretions may disclose colonization by Malassezia spp.
A pinna that is no longer erect may indicate ear pain. Palpation of the pinnal cartilage, especially at the ear base, may indicate bony changes suggestive of chronicity. Aural hematoma typically indicates pain or pruritus in the ear and can result from violent head shaking, trauma, or autoimmune diseases.2 An aural hematoma on one side may result from otitis externa in the opposite ear.
Excoriation of the pinnal surface indicates self-trauma from pruritus that is often caused by otitis externa. Pinnal dermatitis and crusting with accumulation of purulent material on the base of the concave pinna may result from severe suppuration with otitis externa. Hemorrhagic crusting of the ear tips of erect-eared breeds and of the pinnal folding in pendulous-eared dogs may indicate fly strike or mosquito bite hypersensitivity in cats. Traumatic injury to the pinna may mimic other conditions.
Lichenification, erythema, hyperpigmentation, and glandular hyperplasia of the concave pinnae may indicate chronic allergic dermatitis, often with concurrent otitis externa. When found in cocker spaniels, this may be a manifestation of primary idiopathic seborrhea associated with ceruminous otitis.3 Topical drug reactions—particularly to neomycin-containing otic medications—may also result in pinnal erythema and/or erosions or ulcerations.
Many pinnal tumors exist, including ceruminous gland adenomas in dogs and squamous cell carcinomas in white-eared cats.
2 Otoscopic Examination
In nonanesthetized patients, an otoscope cone of the proper diameter is gently inserted into the vertical ear canal. Once the ear canal lumen is centered in the eyepiece, the otoscope cone is advanced deeper into the ear canal. This technique avoids painful scraping of the sides of the ear canal.
As the canal narrows and bends, the pinna is grasped gently and moved outward and downward to straighten out the ear canal. After making the bend into the horizontal ear canal and advancing the speculum, the eardrum should be visualized (Figure 2).
In nonclinical dogs without any apparent signs of otitis externa, only a quick otoscopic examination is necessary. After a veterinarian becomes familiar with the normal canine and feline ear, pathologic changes should be easy to identify.
Some patients—healthy or otherwise—will require sedation or anesthesia. Sedation is also recommended for any patient that is markedly painful and/or fails to respond to empiric therapy. This is especially important for patients with unilateral ear disease as a source of discomfort (eg, foreign body lodged in the ear canal).
Figure 3 Normal canine vertical canal. Blood vessels are visible in the dermis through the thin epithelium. A glistening coating of cerumen is present on the epithelial surface.
The Ear Canal
The ear canal is lined by a modified epidermis. The wide vertical ear canal contains hairs surrounded by sebaceous glands, as well as aprocrine glands unassociated with hair follicles. The normal vertical ear canal glistens because of the cerumen coating (Figure 3). On examination of the ear canal with the otoscope, the skin of the vertical and horizontal ear canals should be nonerythematous. The epithelium of the ear canal is smooth. A network of blood vessels in the dermis is present.
In most dog breeds, the narrower horizontal ear canal has significantly fewer hair follicles with minimal glands. The exceptions are the American cocker spaniel, which has more glandular tissue density along the ear canal than do many other breeds,4 and the standard poodle, which anecdotally seems to have a higher density of hair follicles along the ear canal.
Visual Examination of the Ear Canal
- The canine ear canal consists of overlapping cartilage plates in a bent, funnel-shaped, tapered, cylindrical structure that provides the “L” shape to the vertical and horizontal ear canals. Cats have more of an arc shape to their ear canal than do dogs. Before inserting the otoscope, palpation of the vertical ear canal should be performed to assess cartilage plasticity. Any pain or bony changes to the cartilage should be noted.
- Bacterial and yeast otitis externa are typically confined to the ear canal and/or pinnae. However, bacterial exudates from chronic otitis externa pooling in the horizontal canal can cause erosion of the eardrum leading to secondary otitis media or interna. With neoplasia, trauma, or severe otitis externa, extension of infection to surrounding tissues (cellulitis, abscess) is possible.
Cerumen is composed of apocrine (watery) and sebaceous (lipid) secretions as well as desquamated keratinocytes. Normal cerumen coats the epithelium, protects against pathogens, and aids in prevention of water loss from the ear canal epithelium. Its stickiness helps trap particles and other debris.
In human cerumen, antimicrobial lipids (eg, sapienic and lauric acids) and antimicrobial peptides can be beneficial against many fungi and bacteria. These substances have yet to be identified in canine or feline cerumen.5 Cerumen changes its composition in the presence of disease; it becomes less waxy and more hydrated. Normal cats have scant, thin cerumen but may produce excessive cerumen in response to diseases such as atopy or endocrine disease.
Removal of mild cerumen accumulations in normal ears using ear cleaners is not recommended. The normal process of epithelial migration removes accumulated ceruminous secretions as the surface epithelial cells move toward the outside of the ear canal to maintain ear health. In many ear diseases, this physiologic cleaning mechanism is disrupted and copious cerumen accumulates in the ear canal.
Clinical signs of otitis with exudate in the ear canals may result in a depilatory effect from caustic enzymes dissolving the keratin that comprises the hairs—similar to the hair loss seen on the body in the form of an acute, moist dermatitis or hot spot. Clinically, this is identified as an absence of hair found in the ear canal during the acute phase of otitis externa. With resolution of ear disease, hairs will regrow as the epithelium returns to normal, and new hair growth can be seen on otoscopic examination at recheck.
Live ear mites may be seen via otoscope crawling along the epithelial surface when a patient’s head is held as still as possible. Cats tend to have larger numbers of mites; the white-colored mites in the ear canal are seen crawling along the dark brown otic secretions. Other parasites (eg, ticks, flies) or foreign material (eg, grass awns, seeds) may be seen in the canal.
Stenosis & Swelling
Any change in the epidermis, such as with ceruminous gland hyperplasia or ulceration, is significant and should be noted (Figure 4). In a patient with inflammatory ear disease, thickening of the epithelium may obscure visualization of blood vessels. The clinician should assess for presence of stenosis. Some dog breeds (eg, shar-peis, pugs) have small-diameter ear canals as part of their standard conformation. Differentiation between swelling and stenosis is necessary. Stenosis results from permanent pathologic changes within the epidermis of the ear canal (Figure 5).
For swelling of the ear canal caused by inflammation, it may be necessary to delay a complete examination of the ear canal until anti-inflammatory therapy (eg, systemic or topical corticosteroids) decreases the swelling.
If changes do not reverse, the prognosis for medical management is poor, and total ear canal ablation and/or bulla osteotomy is recommended. If the ear canal epithelium is smooth and pink in color but the ear canal diameter is narrowed, hyperplasia of the sebaceous glands may be present.
Ulceration of the ear canal epithelium is most often associated with a severe, chronic bacterial otitis externa (often Pseudomonas spp). The bacteria releases cytopathic enzymes resulting in ulceration (Figure 6). Tumors within the ear canal may be present and should be noted (Figure 7).
Note the character and volume of exudates. In general, a presumptive diagnosis of the infection type can be made based on texture and color. Dark brown waxy or dry exudates suggest yeast otitis in dogs or ear mite infestation in cats (Figure 8). In dogs, creamy, tan-colored moist exudates tend to suggest gram-positive (eg, Staphylococcus spp) bacterial infections (Figure 9).
Purulent liquid or mucoid exudates with a white, yellow, greenish, or black color may indicate a gram-negative (eg, Pseudomonas spp) bacterial infection (Figure 10). Hemorrhagic exudates can indicate ulceration of the ear canal or ulceration of a tumor mass. An ear canal epithelial examination may not be possible until the exudates are flushed out of the ear canal and the epithelial surface is exposed.
Mucus should never be found in the external ear canal; there are no goblet cells in the epithelium. Goblet cells abound in the lining of the middle ear, which is a mucous membrane. Excessive amounts of mucus can be found in the middle ear when it is inflamed and may move from the middle ear to the external ear canal through a hole in the eardrum.
All otic exudates should be sampled for cytologic examination to characterize the type of organisms present (ie, cocci, rods, yeast). An erythemic and exudative ear canal may often result in pruritus and pain without infection. This would support inflammatory disease of a primary nature (eg, allergy).
Bacterial culture and antibiotic susceptibility testing may be helpful to determine appropriate treatment, especially in refractory cases. Bacterial culture rarely reports growth of Malassezia spp yeasts; therefore, sending a culture off without cytology may result in information that has no bearing on the otitis case being treated. Some bacteria cultured from the ear may not be the pathogen(s) perpetuating the ear disease.
There is significant variability in antibiotic susceptibility testing among reference laboratories.6 Susceptibility testing may be used as a guideline in selecting topical ear therapy. The author’s preferred tools for determining whether an antibiotic is helping include follow-up ear examinations to assess clinical improvement and comparative cytologies to determine the presence, reduction, or absence of microorganisms from previous examinations. Resistance to an antibiotic on susceptibility testing may be misleading when treating otitis externa, as these susceptibilities are reported for blood levels. Topical antimicrobial levels may be hundreds of times more concentrated in the ear canal and may be effective in the face of reported in vitro resistance.
Ceruminoliths, concretions of dried medications, and foreign bodies are more often seen in the horizontal canal. Occasionally, epilated hairs will fall into the horizontal canal and become embedded in the thick wax accumulation along the floor of the horizontal canal. These hairs can be seen occluding the view of the eardrum (Figure 11).
A feline inflammatory polyp originating from the middle ear may also be seen as a fleshy mass protruding into the horizontal canal (Figure 12).
- Scott DW, Miller WH, Griffin CE. Keratinization defects. In: Scott DW, Miller WH, Griffin CE. Muller and Kirk’s Small Animal Dermatology. 6th ed. Philadephia, PA: Saunders Elsevier; 2001:1043-1045.
- MacPhail C. Current treatment options for auricular hematomas. Vet Clin North Am Small Anim Pract. 2016;46(4):635-641.
- Harvey RG, Haar G. Ear, Nose and Throat Diseases of the Dog and Cat. Boca Raton, FL: CRC Press; 2016:30.
- Harvey RG, Harari J, Delauche AJ. Ear Disease of the Dog and Cat. Boca Raton, FL: CRC Press; 2005:83.
- Little SE. August’s Consultations in Feline Internal Medicine. Vol 7. St Louis: Elsevier; 2016:323.
- Schick AE, Angus JC, Coyner KS. Variability of laboratory identification and antibiotic susceptibility reporting of Pseudomonas spp isolates from dogs with chronic otitis externa. Vet Dermatol. 2007;18(2):120-126.
- Eriksson PO, Hellström S. Degranulation of mast cells provokes a massive inflammatory reaction in the tympanic membrane. Laryngoscope. 111(7):1264-1270.
- Cole LK, Weisbrode SE, Smeak DD. Variation in gross and histological appearance of the canine pars flaccida. Vet Dermatol. 2007;18(6):464-468.
Atopy & the Pinna
Miller WH Jr, Griffin CE, Campbell KL. Muller and Kirk’s Small Animal Dermatology. 7th ed. Elsevier Mosby; 2013:372.
Zachary JF, McGavin MD. Pathologic Basis of Veterinary Disease. 5th ed. St Louis, MO: Elsevier Mosby; 2012:1171.
Cocker Ear Glands
Harvey RG. Ear Diseases of the Dog and Cat. Boca Raton, FL: CRC Press; 2005:83.
Harvey RG, Paterson S. Otitis Externa: An Essential Guide to Diagnosis and Treatment. Boca Raton, FL: CRC Press; 2014:1-6.
Gotthelf LN. Small Animal Ear Diseases: An Illustrated Guide. 2nd ed. St Louis, MO: Elsevier Saunders; 2004.
Ear Margin Seborrhea
Ear margin seborrhea. Merck Manuals. http://www.merckvetmanual.com/mvm/eye_and_ear/diseases_of_the_pinna/ear_margin_seborrhea.html. Published October 2013. Accessed October 21, 2016.
Flies and mosquitoes of dogs. Merck Manuals. http://www.merckvetmanual.com/pethealth/dog_disorders_and_diseases/skin_disorders_of_dogs/flies_and_mosquitoes_of_dogs.html. Published July 2011. Accessed October 21, 2016.
Mosquito Bite Hypersensitivity
Allergy. Merck Manuals. http://www.merckvetmanual.com/mvm/eye_and_ear/diseases_of_the_pinna/allergy.html. Published October 2013. Accessed October 21, 2016.
Gotthelf LN. Diagnosis and treatment of otitis media in dogs and cats. Vet Clin North Am Small Anim Pract. 2004;34(2):469-487.
Pemphigus on the Pinna
Gross TL, Ihrke PJ, Walder EJ. Pemphigus vulgaris. In: Gross TL, Ihrke PJ, Walder EJ, Affolter VK. Skin Diseases of the Dog and Cat: Clinical and Histological Diagnosis. Oxford, UK: Blackwell Science Ltd; 2005:32-35.
Pinnal Pedal Reflex
Mueller RS, Bettenay SV, Shipstone M. Value of the pinnal-pedal reflex in the diagnosis of canine scabies. Vet Rec. 2001;148(20):621-623.
Material from Clinician’s Brief may not be reproduced, distributed, or used in whole or in part without prior permission of Educational Concepts, LLC. For questions or inquiries please contact us.