Horner's Syndrome
Horner's Syndrome is the clinical picture resulting dysfunction of sympathetic nerve supply to the eye, which originates in the hypothalamus and emerges in the root of the neck before innervating the pupil. Damage at any joint in this pathway will result in Horner's syndrome. On examination, there is a constricted pupil (loss of sympathetic dilator tone) and a partial ptosis resulting from denervation of Müller's muscle in the upper eyelid. There may also be anhydrosis (loss of sweating) on the affected side. Diagnosis may be confirmed by administering cocaine eye drops, which will cause pupil dilatation in the unaffected pupil but no dilatation on the affected side. Causes of Horner's syndrome include demyelination, neck trauma / surgery, apical lung tumour (Pancoast tumour) and carotid artery dissection.
