Isolated Harlequin Syndrome Following Brachial Plexus Nerve Block via Interscalene Approach: A Case Report.

Interscalene brachial plexus blockade is regularly used for postoperative pain management following shoulder surgery. A known but generally benign side effect of this technique is Horner syndrome. Another syndrome known as harlequin syndrome exists but does not appear to be as common. This syndrome consists of contralateral facial flushing and sweating secondary to ipsilateral sympathetic chain inhibition. Despite the alarming presentation in the perioperative setting, this syndrome appears to be benign and self-limiting when precipitated by regional anesthetic technique. This article describes an occurrence of harlequin syndrome without observed ptosis or miosis following a postoperative interscalene nerve block.