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481.e2 Horner’s Syndrome

Horner’s Syndrome Client Education
Sheet
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ventral nerve roots → thoracic sympathetic
BASIC INFORMATION
lesion is postganglionic.
trunk → vagosympathetic trunk → cranial ○ Mydriasis occurs in < 20 minutes when
Definition cervical ganglion (synapse; lesion preceding ○ Mydriasis occurs in 20-45 minutes when
Manifestations of loss of sympathetic innerva- this point is preganglionic or upper motor lesion is preganglionic.
tion to the eye. Signs are miosis (small pupil), neuron (UMN)/central, and lesion after this ○ Mydriasis occurs in > 45 minutes when
ptosis (dropped upper eyelid, causing a smaller point is postganglionic) → middle ear → lesion is central/UMN.
palpebral fissure), enophthalmos, and protrusion ophthalmic branch of the trigeminal nerve ○ Results have been inconsistent; reliability
of the third eyelid. → orbit → orbitalis muscle, ciliaris muscle, of test is controversial.
and smooth muscle of the pupil.
Epidemiology • An immune-mediated mechanism has been
SPECIES, AGE, SEX speculated as a possible cause for idiopathic TREATMENT
Dogs and cats of any age and either sex Horner’s syndrome. Treatment Overview
Horner’s syndrome is not treated; it is a sign
GENETICS, BREED PREDISPOSITION DIAGNOSIS that can indicate an underlying lesion that may
Male golden retrievers may be overrepresented require treatment.
(of 155 dogs with Horner’s syndrome in one Diagnostic Overview
study, 110 were golden retrievers; 100 of them History and physical/neurologic exam are Acute General Treatment
had idiopathic Horner’s syndrome, and 95 were generally sufficient for differentiation. Treat any underlying cause. Prevent/treat corneal
male). ulcerations secondary to exposure keratitis.
Differential Diagnosis
RISK FACTORS • Other causes of miosis (e.g., uveitis) (p. 846) PROGNOSIS & OUTCOME
Blunt trauma (e.g., hit by car), other cervical/ • Phthisis bulbi causing protrusion of the third
thoracic spinal cord damage (fibrocartilaginous eyelid and a small palpebral fissure • The prognosis depends on resolution of the
embolization, intervertebral disc disease) or • Hypothyroidism underlying cause. Patients with traumatic
infiltration (lymphoma), surgical trauma or causes have quicker resolution (days/weeks)
neoplastic infiltration of the neck (affecting the Initial Database than patients with idiopathic or iatrogenic
sympathetic trunk), intracranial neoplasia, otitis • Minimum database causes.
media or other middle ear lesions, retrobulbar • Otoscopic exam • In idiopathic Horner’s syndrome, essentially
inflammation or mass • Thoracic and cervical radiographs all patients have resolution of the signs of
Horner’s syndrome within 6 months after
ASSOCIATED DISORDERS Advanced or Confirmatory Testing diagnosis.
• Exposure keratitis: the inability to blink • Thyroid testing
normally is mostly compensated for by • MRI of brain and cervical spine PEARLS & CONSIDERATIONS
the third eyelid, but a band of desiccated • Cerebrospinal fluid (CSF) analysis
cornea can occur across the central cornea • Pharmacologic testing. Suggested protocol: Comments
(lagophthalmos). ○ Topical 10% phenylephrine solution 1 • Approximately 50% of cases of Horner’s
• Keratoconjunctivitis sicca (p. 568) and facial drop applied to affected eye syndrome in dogs are idiopathic, and the
neuropathies have also been associated with
Horner’s syndrome.
Clinical Presentation
HISTORY, CHIEF COMPLAINT
• Signs referable to the underlying cause
• Trauma (e.g., hit by car) to the head, neck,
chest, or brachial plexus is the most common
historically identifiable cause in dogs and
cats, followed by history of a recent or current
ear infection.
• Ocular signs observed by the owner
PHYSICAL EXAM FINDINGS
• Enophthalmos (retracted/sunken globe)
• Ptosis
• Miosis
• Third eyelid protrusion
• Other associated signs can be present,
depending on the location of the inciting
lesion.
Etiology and Pathophysiology
• Interference with the sympathetic innervation HORNER’S SYNDROME Right-sided Horner’s syndrome in a 9-year-old pointer-cross dog. Note right-sided
to the eye: brainstem → cervical spinal cord ptosis, miosis, and protruding third eyelid caused by enophthalmos. The hematocrit was 75%, and pathologic
→ T1-T3 spinal cord segments → T1-T3 proteinuria was present, leading to a suspicion of thromboembolic disease as the cause of the Horner’s syndrome.

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