Unilateral ptosis, miosis, and sometimes facial anhydrosis
Interruption of sympathetic nervous system pathway anywhere between hypothalamus and eye
May be isolated manifestation
Main causes of acute isolated Horner syndrome: spontaneous or traumatic dissection of cervical carotid artery, neck/upper chest trauma from insertion of venous catheter
Refer patient emergently to ophthalmologist or emergency room if you find upper lid ptosis and miosis, especially if acute and accompanied by new neck pain