FALSE-NEGATIVE HYDROXYAMPHETAMINE (PAREDRINE) TEST IN ACUTE HORNERS-SYNDROME

PURPOSE: To describe a false-negative hydroxy amphetamine test. METHOD : Two patients with acute unilateral Horner's syndrome whose pupils in itially dilated equally to hydroxyamphetamine had pharmacologic locali zation to the postganglionic nerve in the second week following the on set of symptoms. RESULTS: Neuroimaging confirmed the postganglionic lo cation in both cases. CONCLUSION: Falsely negative localization with h ydroxyamphetamine can occur during the first week after injury, during which time the function of the boutons at the presynaptic terminal is lost.