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Horner’s Syndrome 481.e3

Localizing Lesions in Horner’s Syndrome
VetBooks.ir Location Common Causes Neuron Commonly Associated Signs Diseases and Disorders
Affected
Brainstem
Altered consciousness, thermoregulation, endocrine function,
Neoplasia,* trauma, infection
UMN
Tetraparesis/plegia, hemiparesis/plegia, UMN signs in all four
Cervical spinal cord Trauma, neoplasia, FCE UMN appetite, drinking; cranial nerve deficits, motor deficits, dyspnea
limbs if cranial cervical lesion, LMN signs in thoracic limbs with
UMN signs in pelvic limbs if caudal cervical lesion
T1-T3 spinal cord Trauma,* neoplasia,* FCE UMN Thoracic limb paresis or paralysis with LMN thoracic limb signs,
pelvic limb paresis or paralysis with UMN thoracic limb signs
T1-T3 ventral nerve roots Brachial plexus avulsion,* peripheral nerve Preganglionic Brachial plexus paresis or paralysis of ipsilateral limb
sheath tumor
Cranial thoracic sympathetic trunk Lymphoma, peripheral nerve sheath tumor, Preganglionic Respiratory distress; no other signs if confined to trunk
thoracic disease
Cervical sympathetic trunk Trauma, iatrogenic, neoplasia Preganglionic May be none if unilateral; may interfere with laryngeal or
esophageal function from vagal involvement
Middle ear Otitis media,* neoplasia Postganglionic Head tilt, nystagmus, and/or facial paralysis
Cavernous sinus Neoplasia, vascular disease Postganglionic Internal, external, or complete ophthalmoplegia (may produce
mydriasis rather than miosis)
Orbital disease Abscess, neoplasia, contusion, pseudotumor Postganglionic Exophthalmos, discomfort, optic nerve or oculomotor deficits
*Most common.
FCE, Fibrocartilaginous emboli; LMN, lower motor neuron; UMN, upper motor neuron.
Modified from Collins BK, O’Brien D: Autonomic dysfunction of the eye. Semin Vet Med Surg Small Anim 5:24–36, 1990. Reprinted with permission.

syndrome generally resolves without treat- SUGGESTED READING RELATED CLIENT EDUCATION
ment in < 6 months. Dewey CW, et al: A practical guide to canine & feline SHEET
• In cats, a cause is virtually always found; neurology, ed 3, Ames, IA, 2015, Wiley-Blackwell.
idiopathic Horner’s syndrome is rare. How to Administer Eye Medications
• Strictly speaking, Horner’s syndrome also ADDITIONAL SUGGESTED
affects the surface of the face and neck READINGS AUTHOR: David M. Brewer, DVM, DACVIM
(causing erythema/flushing of the skin) and EDITOR: Karen R. Muñana, DVM, MS, DACVIM
the nasal mucosa (causing congestion), but Boydell P: Idiopathic Horner’s syndrome in the golden
retriever. J Small Anim Pract 36:382-384, 1995.
these manifestations usually have no clinical de Lahunta A, et al: Veterinary neuroanatomy and
significance. clinical neurology, ed 4, St. Louis, 2014, Elsevier.
• Pharmacologic testing to determine the site of Simpson KM, et al: Neuropharmacological lesion
the lesion has produced inconsistent results. localization in idiopathic Horner’s syndrome in
golden retrievers and dogs of other breeds. Vet
Technician Tips Ophthalmol 18;1-5, 2015.
• Horner’s syndrome is not an emergent
problem.
• Vision is typically not affected.

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