Which first-order neuron lesions cause 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 may also be classified as involving first-order, second-order, or third-order neuron lesions. First-order neuron lesions that may give rise to the syndrome include the following:

  • Arnold-Chiari malformation

  • Basal meningitis (eg, syphilis)

  • Basal skull tumors

  • Cerebral vascular accident (CVA)/Wallenberg syndrome (lateral medullary syndrome)

  • Demyelinating disease (eg, multiple sclerosis)

  • Lesions in the hypothalamus or medulla

  • Intrapontine hemorrhage

  • Neck trauma (eg, traumatic dislocation of cervical vertebrae or traumatic dissection of the vertebral artery) - Horner syndrome occurring in association with spinal cord trauma suggests a high cervical cord lesion because it does not occur with lesions below T2 or T3

  • Pituitary tumor

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