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Facial Nerve Paralysis, Idiopathic 321

• Only trigeminal nerve abnormalities, MM, • To maintain daily nutritional requirements, SUGGESTED READING
and anomalies of the TMJs are strictly dogs with trismus often lick liquid gruel, but Taylor SM: Disorders of muscle. In Nelson RW, et
VetBooks.ir Technician Tips Client Education AUTHOR: Paolo Pazzi, BVSc, MMedVet, DECVIM-CA Diseases and Disorders
confined to facial muscle atrophy.
additional feeding strategies (e.g., esophagos-
al, editors: Small animal internal medicine, ed 5,
tomy tube [p. 1106]) may be required.
St. Louis, 2013, Mosby, pp 1090-1102.
• Masseter muscle atrophy may lead to trismus;
a jaw should never be forced open, even Early evaluation provides the best chance of EDITOR: Leah A. Cohn, DVM, PhD, DACVIM
under anesthesia. response.

Facial Nerve Paralysis, Idiopathic Bonus Material
Online

BASIC INFORMATION Etiology and Pathophysiology neurologic function at 6 months when
• Pathogenesis unknown three or four sections of the nerve showed
Definition • Resembles Bell’s palsy in humans, which has enhancement; complete recovery was seen
Acute lower motor neuron paresis or paralysis been linked to a viral infection at 4 weeks when no enhancement was
of unknown cause affecting one or both facial • Histopathologic studies reveal demyelination observed.
nerves and axonal loss. • Electromyogram can show evidence of
denervation (spontaneous activity) when
Epidemiology musculature innervated by the facial nerve
SPECIES, AGE, SEX DIAGNOSIS is examined.
Affects adult dogs (>5 years of age) Diagnosis Overview
The diagnosis is based on clinical history and TREATMENT
GENETICS, BREED PREDISPOSITION findings from complete neurologic exam. This
No genetic link known; cocker spaniels is a diagnosis of exclusion; other causes of facial Treatment Overview
overrepresented nerve dysfunction must be ruled out. There is no specific treatment to improve the
function of the facial nerve, although there
ASSOCIATED DISORDERS Differential Diagnosis is some evidence that acupuncture can speed
Keratoconjunctivitis sicca (KCS) +/− secondary • Metabolic disease: hypothyroidism recovery and even lead to complete resolution
corneal ulceration, oral ulcerations, idiopathic • Infectious/inflammatory disease: noninfec- of clinical signs. KCS should be treated to avoid
vestibular disease tious neuritis versus infectious neuritis, otitis exposure keratitis.
media/interna or primary secretory otitis
Clinical Presentation media Acute General Treatment
HISTORY, CHIEF COMPLAINT • Trauma: causes hemorrhage into the tym- Treatment for KCS includes frequent
Acute-onset paresis to paralysis of one or both panic bulla and secondary inflammation of corneal lubrication. Topical antibiotics can
facial nerves manifesting as the facial nerve be used to treat corneal ulceration (pp. 209
• Inability to blink • Toxin: otic toxins and 568).
• Inability to hold food or water in the • Neoplasia: affecting the nerve itself (periph-
mouth eral nerve sheath tumor versus lymphoma) or Possible Complications
• Excessive drooling from one or both sides the tympanic bulla (adenocarcinoma versus Recurrent corneal ulceration if paresis/paralysis
of the mouth polyp) does not resolve
PHYSICAL EXAM FINDINGS Initial Database PROGNOSIS & OUTCOME
• Decreased to absent palpebral reflex(es) • Neurologic exam (p. 1136)
• Decreased to absent menace response(s) • Otic exam: to rule out otitis media/interna Complete or partial resolution takes weeks to
• Decreased movement of the facial muscles (p. 1144) months. Some evidence that degree of contrast
unilaterally or bilaterally when stimulated • CBC, biochemistry panel: unremarkable enhancement on MRI determines likelihood
(trigeminofacial reflex) • Thyroid testing: normal of full recovery and expected timeline of
• KCS and possible secondary corneal • Schirmer tear test: reduced tear production recovery (see Advanced or Confirmatory
ulceration associated with facial nerve deficits (p. 1137) Testing above).
• Drooping lip(s) and/or ears
• Decreased to absent contraction of the Advanced or Confirmatory Testing PEARLS & CONSIDERATIONS
lateral commissure(s) of the mouth is most • MRI (p. 1132): contrast enhancement of
evident when panting. In chronically affected affected facial nerve(s) can be observed. Comments
patients, contraction of the commissure(s) Normal facial nerves do not enhance. Daily cleaning of the oral commissures after
is/are observed. ○ Speed and completeness of recovery is meals is recommended. Food caught in weak
• Increased drooling secondary to lip weakness proportional to the percentage of the nerve lip muscles can lead to oral ulceration. Ocular
• Ulceration of the mucosa at the lateral that enhances on MRI. Dogs recovered assessment is important to ensure signs of
commissure of the mouth associated with complete function at 8 weeks when one corneal ulceration (blepharospasm, aver-
collection of food in this area, secondary section of the nerve showed enhance- sion to head palpation, discomfort) are not
to lip weakness ment; dogs showed partial resolution of present.

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