The three classic signs of Horner's syndrome are miosis (constricted pupils), ptosis (drooping eyelids), and anhidrosis (lack of sweating). These symptoms result from disruption of the sympathetic nervous system, and can be caused by a variety of conditions, including stroke, tumor, traumatic injury or infection. Miosis and ptosis are often the first symptoms noticed, with anhidrosis appearing later. Other symptoms that may be present include facial flushing, facial drooping, and a decreased production of tears. Diagnosis is made through a physical examination and sometimes other tests, such as a CT scan or MRI. Treatment depends on the underlying cause and may include medication, surgery, or other therapies.