Otitis interna, or infection of the inner ear, is a relatively common disorder in the dog.
It is usually a result of extension of middle ear infection (see Chapter 14) and results in a characteristic set of clinical signs. These signs reflect the dysfunction of the inner ear organs—namely, the cochlea and vestibular apparatus.
Cochlear dysfunction manifests as decreased hearing acuity. This may be difficult to detect in the dog without electrodiagnostic testing, especially if it is unilateral. However, often the astute animal caregiver is able to detect the subtle signs of hearing loss in the animal’s natural environment. This information can be elucidated by careful questioning of the caregiver. The vestibular system is responsible for the detection of acceleration and orientation in respect to the earth’s gravitational field, and it is absolutely essential for an animal to be able to maintain normal balance and posture. It comprises components located in the bony labyrinth of the inner ear and nuclei located in the medulla oblongata.Vestibular dysfunction results in a variety of readily visible clinical signs, including head tilt, small-radius circling, nystagmus, and strabismus. The primary concern of the examining veterinarian when presented with an animal with vestibular disease is to determine whether the problem lies within the bony labyrinth (peripheral vestibular disease [PVD]) or in the brainstem vestibular system (central vestibular disease [CVD]). This determination helps when forming a diagnostic differential list and also allows for some sense of prognostication. For the most part, CVD carries a grim prognosis, whereas PVD is often treatable and carries a much better prognosis.
More on the topic Otitis interna, or infection of the inner ear, is a relatively common disorder in the dog.:
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