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Key Features

  • Caused by an abnormality or lesion to the sympathetic chain

  • Congenital variety is most commonly the result of birth trauma

  • Acquired cases may occur in children who have had cardiothoracic surgery, trauma, neoplasm, or brainstem vascular malformation

  • Most worrisome cause is neuroblastoma of the sympathetic chain in the apical lung region

Clinical Findings

  • Ptosis is usually mild with a well-defined upper lid crease

  • Heterochromia of the two irides, with the lighter colored iris occurring on the same side as the lesion

  • Anhidrosis can occur in congenital and acquired cases

  • Of note, not all of the three signs must be present to make the diagnosis


  • Physical examination, including palpation of the neck and abdomen for masses, and MRI of structures in the head, neck, chest, and abdomen should be considered

  • An excellent screening test for neuroblastoma is the spot urine vanillylmandelic acid/creatinine ratio

  • Pharmacologic assessment of the pupils with topical cocaine and hydroxyamphetamine or epinephrine helps determine whether Horner syndrome is due to a preganglionic or postganglionic lesion of the sympathetic chain

  • Apraclonidine may be a more practical drug to use in the diagnosis


  • Management of any underlying disease is required

  • Ptosis and vision should be monitored by an ophthalmologist

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