What are causes of Horner syndrome?

Updated: May 01, 2019
  • Author: Christopher M Bardorf, MD, MS; Chief Editor: Edsel Ing, MD, MPH, FRCSC  more...
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Causes of Horner syndrome include the following:

  • Lesion of the primary neuron

  • Brainstem stroke or tumor or syrinx of the preganglionic neuron – In one study, 33% of patients with brainstem lesions demonstrated Horner syndrome [2]

  • Trauma to the brachial plexus

  • Tumors (eg, Pancoast) or infection of the lung apex

  • Lesion of the postganglionic neuron

  • Dissecting carotid aneurysm – In one study, 44% (65/146) of patients with internal extracranial carotid artery dissections had painful Horner syndrome, which remained isolated in half the cases (32/65) [3]

  • Carotid artery ischemia

  • Middle cranial fossa neoplasm

Horner syndrome is uncommon. No age, sexual, or racial predilections are known to exist. The prognosis and the complications to be expected depend on the underlying cause of the syndrome, as does treatment.

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