Silent Horner Syndrome

Background Horner syndrome is clinically suspected when the patient demonstrates pupillary miosis and ipsilateral upper lid ptosis. Occasionally, an isolated ptosis or isolated anisocoria is the only clinical sign of the oculosympathetic defect of Horner syndrome [ 1 ], [ 2 ]. We present two patients with transient anisocoria and ptosis to highlight the importance of maintaining clinical suspicion of the diagnosis even if the miosis and ptosis disappear, as the oculosympathetic defect may persist subclinically.