Ear Anatomy and Cytology Clinical Pathology

Normal anatomy The ear canal is a cartilaginous structure lined with skin (epithelium). Hair follicles, sebaceous glands, and apocrine glands line the entire canal to the eardrum. In the normal ear, glandular secretions and epithelial cell migration, move dirt and debris away from the ear drum. A normal ear exam should reveal a smooth, non- inflamed epithelial lining and an intact tympanic membrane.

Anatomy continued….. The tympanic membrane is a thin, semi- transparent membrane that separates the external canal from the tympanic cavity. Transmits sounds to the hearing apparatus.

Otitis Definition: Inflammation of the ear canal and/or pinnae.

Otitis externa Inflammation of the ear canal to the tympanic membrane.

Otitis Media Inflammation of the tympanum and the tympanic bullae.

Otitis Interna Inflammation of the hearing apparatus. Neurologic signs and deafness are usually present.

Causes of ear disease Abnormal conformation Ectoparasites Systemic diseases, allergies, endocrine disease. Tumors Foreign bodies Trauma

Diagnosis of ear problems Clinical signs: Inflamed ear canal Color of discharge Neurological signs Otoscopic exam Ear swab cytology Culture/sensitivity

Ear Cytology Technique Using a cotton tip applicator, gently swab ear canal. Gently roll the swab along a clean glass slide. Heat fix Stain Diff-quick Gram stain

Cytological exam Bacteria Yeast WBC’s Epithelial cells Rods or cocci Pseudomonas, Proteus, Staphlococcus, Streptococcus Yeast Malassezia pacydermatitis WBC’s neutrophils Epithelial cells Neoplastic cells Earmites

Bacterial Otitis May see large numbers of bacteria, often phagocytized bacteria in neutrophils. May see large numbers of neutrophils. May have mixed infections (rods and cocci) Discharge color Creamy, dark, yellow-light brown usually is Staph/Strep Thick, odorous, pale yellow discharge usually is Pseufomonas, Proteus Do culture/sensitivity especially if rods are found

Malassezia Otitis Yeast are normal inhabitants >10 yeast/HPF is abnormal. Discharge: dark brownish exudate, yeasty odor. May be present with bacteria (mixed infection).

Treatment of Otitis Depends on organism causing problems. Topicals Antifungals antibacterials Systemic drugs Antibiotics Treat underlying disease