Pharmacologic testing in Horner's syndrome - a new paradigm.

For more than three decades, topical cocaine has been used to confirm the diagnosis and hydroxyamphetamine to localise the causative lesion in oculosympathetic palsy or Horner's syndrome. More recently, other drugs have demonstrated the ability to point to the diagnosis or anatomical site. Apraclonidine and phenylephrine, given their similar diagnostic efficacy and increased availability, may have superseded cocaine and hydroxyamphetamine as first-line pharmacological testing agents in Horner's syndrome.