title: False-negative hydroxyamphetamine (Paredrine) test in acute Horner's syndrome.
abstract: OBJECTIVE
  To describe a false-negative hydroxyamphetamine test.
  
  
  METHODS
  Two patients with acute unilateral Horner's syndrome whose pupils initially dilated equally to hydroxyamphetamine had pharmacologic localization to the postganglionic nerve in the second week following the onset of symptoms.
  
  
  RESULTS
  Neuroimaging confirmed the postganglionic location in both cases.
  
  
  CONCLUSIONS
  Falsely negative localization with hydroxyamphetamine can occur during the first week after injury, during which time the function of the boutons at the presynaptic terminal is lost.
authors.affiliation: Department of Neurology, Vanderbilt University School of Medicine, Nashville, TN, USA, sean.donahue@mcmail.vanderbilt.edu
authors.forename: S P
authors.initials: SP
authors.lastname: Donahue
authors.forename: P J
authors.initials: PJ
authors.lastname: Lavin
authors.forename: K
authors.initials: K
authors.lastname: Digre
mesh_terms: D000208:Acute Disease; D000328:Adult; D005188:False Negative Reactions; D006732:Horner Syndrome / Q000175:diagnosis*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009184:Mydriatics; D009883:Ophthalmic Solutions; D009885:Ophthalmology / Q000379:methods; D011237:Predictive Value of Tests; D011680:Pupil / Q000187:drug effects; D010136:p-Hydroxyamphetamine
chemical_list: D009184:Mydriatics; D009883:Ophthalmic Solutions; D010136:p-Hydroxyamphetamine