Horner Syndrome

Basics

A unilateral lesion along the sympathetic pathway that supplies the head, eye, and neck produces Horner syndrome:

Ptosis (drooping of the eyelid):
- Relaxation of retracting muscles in upper and lower lids
Miosis (unopposed pupillary constriction):
- Loss of pupillary dilator innervation
Anhidrosis (unilateral lack of sweating):
- Loss of sympathetic stimulation of sweat glands (may be absent)

Can be categorized based upon location of the sympathetic fiber lesion.
Central (13%):
- Stroke/infarction (Wallenberg syndrome)
- Tumor/compression
- Trauma
- Demyelinating lesions
Preganglionic (44%):
- Tension pneumothorax
- Pulmonary apical lesions:
  - Apical lung/mediastinal tumor (primary or metastasis)
  - Subclavian artery aneurysm
  - Cervical rib
  - Iatrogenic
- Infection of cervical nodes
- Thyroid malignancies
Postganglionic (43%):
- Superior cervical ganglion lesion (trauma, jugular venous ectasia, iatrogenic)
- Internal carotid artery lesion (dissection, aneurysm, trauma, arteritis, thrombosis)
- Skull base lesion (nasopharyngeal carcinoma, lymphoma)
- Cavernous sinus lesion (tumor, thrombosis, aneurysm)
- Miscellaneous (cluster headache)
Unknown (40%)

Congenital causes:
- Birth trauma (may cause damage to sympathetic chain)
- Hereditary (irregular coloration on affected side may also be present)
Acquired causes:
- Tumor (new onset in a child should prompt work up for tumor/mass such as neuroblastoma)
- Demyelination
- Thrombosis
- Idiopathic

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