Frey's syndrome is a rare neurological disorder resulting from damage to or near the parotid glands responsible for making saliva, and from damage to the auriculotemporal nerve often from surgery. The symptoms of Frey's syndrome are redness and sweating on the cheek area adjacent to the ear. They can appear when the affected person eats, sees, dreams, thinks about or talks about certain kinds of food which produce strong salivation. Observing sweating in the region after eating a lemon wedge may be diagnostic.
Signs and symptoms include erythema and sweating in the cutaneous distribution of the auriculotemporal nerve, usually in response to gustatory stimuli. There is sometimes pain in the same area, often of a burning nature. Between attacks of pain there is sometimes numbness or other altered sensations. This is sometimes termed "gustatory neuralgia".
Causes
Frey's syndrome often results as a side effect of surgeries of or near the parotid gland or due to injury to the auriculotemporal nerve, which passes through the parotid gland in the early part of its course. The auriculotemporal branch of the mandibular branch of the trigeminal nerve carries parasympathetic fibers to the parotid salivary gland and sympathetic fibers to the sweat glands of the scalp. As a result of severance and inappropriate regeneration, the parasympathetic nerve fibers may switch course to a sympathetic response, resulting in "gustatory sweating" or sweating in the anticipation of eating, instead of the normal salivatory response. It is often seen with patients who have undergone endoscopic thoracic sympathectomy, a surgical procedure wherein part of the sympathetic trunk is cut or clamped to treat sweating of the hands or blushing. The subsequent regeneration or nerve sprouting leads to abnormal sweating and salivating. It can also include discharge from the nose when smelling certain food. Rarely, Frey's syndrome can result from causes other than surgery, including accidental trauma, local infections, sympathetic dysfunction and pathologic lesions within the parotid gland. An example of such rare trauma or localized infection can be seen in situations where a hair follicle has become ingrown, and is causing trauma or localized infection near or over one of the branches of the auriculotemporal nerve.
Diagnosis
Diagnosis is made based on clinical signs and symptoms and a starch iodine test, called the Minor Iodine-Starch test. The affected area of the face is painted with iodine which is allowed to dry, then dry corn starch is applied to the face. The starch turns blue on exposure to iodine in the presence of sweat.
Cochrane reviews of interventions to either prevent or treat Frey’s syndrome have found little or no evidence to support their effectiveness or safety, and conclude that further clinical trials are needed.
Epidemiology
The condition is rare, although the exact incidence is unknown.
Prevalence
The exact incidence of Frey syndrome is unknown. The disorder most often occurs as a complication of the surgical removal of a parotid gland. The percentage of individuals who develop Frey syndrome after a parotidectomy is controversial and reported estimates range from 30-50 percent. In follow-up examinations, approximately 15 percent of affected individuals rated their symptoms as severe. Frey syndrome affects males and females in equal numbers.
