Frey's Syndrome

Frey's syndrome is secondary to sympathetic denervation of sweat glands – reinnervation through the auriculotemporal nerve is a secondary event. The aberrant regeneration theory explains the physiopathology of Frey's syndrome. Frey's syndrome incidence after parotidectomy, without prevention techniques, is 40-80% by clinical questioning and 80–100% by objective testing. It occurs months to years after surgery. A topographic and quantitative testing for Frey's is required prior to its treatment – the iodine-sublimated paper histogram (ISPH) test has the majority of desired features. Intradermic botulinum toxin injection is a well-tolerated and efficient treatment. The recommended dilution is 50 IU/1 ml, inter-injection distance is 1 cm, and injection volume is 0.1 ml. Complications to avoid include (1) facial muscle paralysis (rare and reversible complication; inject only intradermally and avoid injecting toward the midline) and (2) pain during injection (if bothersome could be decreased by the prior application of topical anesthetic cream).