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Deafness 237

Deafness Client Education
Sheet
VetBooks.ir Diseases and Disorders

○ Difficult to obedience train or adult loss
BASIC INFORMATION
of responsiveness to auditory commands DIAGNOSIS
Definition ○ Tendency to startle when approached Diagnostic Overview
• Deafness: the inability to hear ○ Increased tendency to sleep Bilateral complete deafness is apparent from lack
• Sensorineural deafness results from an abnormal- ○ Not aroused from sleep with auditory stimuli of response to loud noises; diagnostic evaluation
ity in the inner ear and/or vestibulocochlear • Diagnosis of unilateral deafness is not pos- should consider history, neurologic exam, and
nerve and/or the auditory pathways in the brain. sible with behavioral markers alone, and otoscopic exam. Unilateral or partial bilateral
• Conduction deafness results from a lesion in the electrodiagnostic evaluation is required. deafness may be apparent only on auditory
outer ear and/or tympanum and/or middle ear. testing and is generally of interest for prevention
PHYSICAL EXAM FINDINGS (breeding).
Epidemiology • Animals with normal hearing may not
SPECIES, AGE, SEX respond to loud sounds in the clinical setting; Differential Diagnosis
Dogs and cats, any age, either sex behavioral response to auditory stimuli alone • Primary behavioral/psychological disorder
is unreliable for evaluating deafness. • Canine cognitive dysfunction syndrome
GENETICS, BREED PREDISPOSITION • Animals with peripheral sensorineural deaf- (geriatric dogs)
• Cats with white haircoats and blue irides are ness typically have no abnormal physical
commonly affected by congenital deafness. exam findings. Initial Database
• Dogs with white, piebald, spotted, merle, or • Animals with acquired conduction deafness • Distant and proximal physical exams
dapple haircoats are predisposed to congenital may have one or all of the following clinical • Neurologic exam (p. 1136)
deafness. signs: • Thorough aural exam (p. 1144)
• Sensorineural deafness is also seen in breeds ○ Abnormal aural exam
not related to coat colors (e.g., Doberman ○ Head tilt Advanced or Confirmatory Testing
pinscher, Rhodesian ridgeback). ○ Facial droop Brainstem auditory evoked response/potential
• Juvenile/adult onset, inherited sensorineural ○ Horner’s syndrome (BAER or BAEP) testing using air- or bone-
deafness: Rhodesian ridgebacks, working lines ○ Head shaking conducting stimuli.
of border collies ○ Neurogenic keratoconjunctivitis sicca
• Breeds with presumed inherited conditions ○ Signs of pain on ear manipulation TREATMENT
involving the conduction portion of the ear • Animals with deafness resulting from diseases
(external and middle ears) are predisposed to affecting the vestibulocochlear nerve or central Treatment Overview
developing hearing loss (e.g., Cavalier King auditory pathways will typically demonstrate • Prevent hearing loss from developing or
Charles spaniels with secretory otitis media) other concurrent neurologic signs. progressing.
(p. 728). • Improve hearing ability.
Etiology and Pathophysiology
RISK FACTORS • Acquired conduction deafness resulting from Acute General Treatment
• Old age otitis externa/media • No treatment for congenital inherited
• Repeated exposure to loud noises ○ Impaired conduction of sound waves to sensorineural deafness; careful selection of
• Breeds of cats or dogs susceptible to otitis the tympanum from debris, cerumen, or breeding animals by using only nondeaf
externa and/or otitis media pus in the external ear canal animals for breeding (perform BAER tests
• Exposure to systemic or topical ototoxic ○ Impaired sound wave transduction to on untested adults and all puppies considered
drugs, such as aminoglycosides, erythro- otic ossicles due to stiffened, fibrotic, or high risk based on breed or color).
mycin, loop diuretics, cisplatin, nitrogen ruptured tympanum • No practical treatments for animals with
mustard, or topical chlorhexidine antiseptic. ○ Impaired mechanoelectrical transduction sensorineural deafness. Custom-fit hearing
Topical drugs are potentially more ototoxic due to otic ossicle sclerosis aids are offered by some specialty practices
if the tympanum is not intact. • Acquired conduction deafness from external (consult with neurologist or audiologist).
or middle ear masses • For acquired conduction deafness, treat the
ASSOCIATED DISORDERS ○ Obstruction of sound waves to the underlying cause of the disease.
• Otitis externa and/or media tympanum • Use ototoxic drugs with caution or not at all
• External or middle ear canal neoplasia ○ Destruction of middle ear structures (topically) if the tympanum is not known
• Nasopharyngeal polyps (cats) • Presbycusis (senile deafness) to be intact.
○ Degeneration of the neural components
Clinical Presentation of the inner ear Recommended Monitoring
DISEASE FORMS/SUBTYPES ○ ± Stiffening of the tympanum Repeated BAER testing to monitor response
• Congenital, juvenile, or adult-onset ○ ± Ankylosis of otic ossicles to therapy in animals with incomplete
• Inherited or noninherited • Loud noise exposure deafness
• Sensorineural, conduction, or mixed ○ Damage to inner ear hair cells and/or
ossicles and/or tympanum PROGNOSIS & OUTCOME
HISTORY, CHIEF COMPLAINT • Congenital hereditary deafness associated
• Animals with bilateral congenital or adult- with coat color • Inherited sensorineural deafness and deafness
onset deafness ○ Abnormal migration of neural crest cells resulting from degeneration of inner ear is
○ Overly aggressive with other puppies in (precursor to melanocytes) to the inner ear permanent.
a litter (congenital deafness) (thought to provide nourishment to inner • Various prognoses for animals with conduc-
○ Nonresponsive to auditory stimuli (certain ear); associated with sacculocochlear-type tion deafness (depends on chronicity and/
frequencies/magnitudes) degeneration or severity of the disease)

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