Small Animal Dermatology, 3rd edition

chapter 37 Otitis Externa, Media, and Interna..........................

DEFINITION/OVERVIEW

 Otitis externa: inflammation of the external ear canal; includes anatomic structures

of the pinna, horizontal and vertical canals, and the external wall of the tympanic

membrane.

 Otitis media: inflammation of the middle ear; includes anatomic structures of the

medial wall of the tympanic membrane, bulla (tympanic cavity), auditory ossicles,

and auditory tube.

 Otitis interna: inflammation of the inner ear; includes anatomic structures of the

cochlea, semicircular canals, and associated nerves (cranial nerves VII and VIII).

 Terms are descriptions of clinical signs, not diagnoses.

 Ototoxicity: impairment or damage of the inner ear and/or eighth cranial nerve; neu-

rotoxicity (specifically during treatment of otitis externa/media) damage of the eight

cranial nerve.

ETIOLOGY/PATHOLOGY

 External ear canal:
Auricular cartilage: funnel-shaped structure that creates the pinna and the prox-

imal section of the vertical canal

Annular cartilage overlaps with the auricular cartilage and extends to the exter-

nal wall of the tympanum

Auricular projection: a fold of cartilage in the vertical canal near the junction

with the horizontal canal; must be displaced dorsally to gain access to the hori-

zontal canal

Sebaceous glands and modified apocrine glands (cerumen glands) line the canal

and produce a secretion with varying amounts of lipid (higher levels in dogs

with otitis externa); increased density of cerumen glands associated with predis-

position to otitis externa

Blackwell’s Five-Minute Veterinary Consult Clinical Companion: Small Animal Dermatology, Third Edition.
Karen Helton Rhodes and Alexander H. Werner.
©2018 John Wiley & Sons, Inc. Published 2018 by John Wiley & Sons, Inc.

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