The diagnosis of Horner's syndrome.

We studied the accuracy of the clinical diagnosis of Horner's syndrome in 62 patients. The final criterion was serial photography of the darkness reflex of the pupil. This technique confirmed oculosympathetic dysfunction in only 50%. The positive predictive value of the clinical diagnosis could be increased to more than 80% by measuring the degree of miosis and ptosis on single photographs, or by assuming independent confirmation of the clinical diagnosis by a second observer. However, the chance that a patient who is judged normal in this way does still have oculosympathetic dysfunction remains 25% (photographs) to 40% (second observer). Testing with cocaine is more specific and slightly more sensitive than estimating or measuring the degree of miosis and ptosis.