Harlequin syndrome is a rare dysautonomic syndrome due to a cervical sympathetic deficit at the pre- or postganglionic level of the non-flushing side.
Clinical features of Harlequin syndrome:
(1) unilateral sweating of face (hemifacial), neck and chest
(2) ipsilateral flushing of the face, neck and chest
(3) triggered by heat, emotion, or exercise
Harlequin sign refers to the above changes with oculosympathetic paresis (Horner, Adie and/or Ross syndrome).
Causes of Harlequin sign:
(1) syrinx
(2) cancer (lung, neuroblastoma, ganglioneuroma, other)
(3) idiopathic
(4) status post surgery for aortic dissection
(5) autonomic neuropathy
(6) thalamic hemorrhage
(7) status post brachial plexus nerve block or epidural anesthesia
(8) trauma involving the stellate ganglion
