Clinical Features

• Miosis (constriction of the pupil)

  • Occurs because the sympathetically controlled iris dilator muscle fails to contract

  • Leads to anisocoria and a dilation lag on exam

• Partial ptosis (drooping of the upper eyelid)

  • Occurs because the sympathetically controlled superior tarsal muscle fails to keep the upper eyelid raised

  • It is milder than ptosis associated with oculomotor nerve or levator palpebrae muscle lesions.

• Anhidrosis (absence of sweating) or reduced sweating on the face and arm, depending on the location of the lesion

  • Occurs because the sympathetic innervation of the facial sweat glands is impaired

  • Seen in central and preganglionic lesions

• Facial flushing due to vasodilatation

• (Apparent) enophthalmos

• Associated symptoms depending on the etiology:

  • Atrophy of arm and hand muscles

  • Pain in the neck or face

Remember the symptoms of Horner syndrome by the great HORNs of the PAMpas deer: Ptosis, Anhidrosis, and Miosis.