Horner syndrome following a selective cervical nerve root block.

A 31-year-old man with cervical degenerative disc disease was seen at an outside institution for a right selective nerve root block at C7. Following the procedure, he had right ptosis and miosis. Pharmacologic testing confirmed a right Horner syndrome. MRI and MRA showed no arterial dissection. This report documents the unusual occurrence of permanent Horner syndrome following a selective cervical nerve root block.