Horner's syndrome: an unusual iatrogenic complication of pneumothorax.

A patient is reported with spontaneous pneumothorax in whom a Horner's syndrome occurred as a complication of drainage tube thoracostomy. Ascending sympathetic fibres lie in close contact with the parietal pleura at the apex of the hemithorax and may be damaged by an inappropriately positioned thoracostomy tube. It is suggested that drainage tubes found to be sited medially at the apex of the hemithorax should be immediately repositioned to avoid this complication.