Frey's Syndrome (Auriculotemporal Syndrome)

Introduction:

This condition was first described by Lucie Frey in 1923 and is also commonly known as an auriculotemporal syndrome in the medical literature. Frey’s syndrome, hitherto thought to be rare, is a nerve injury-related traumatic postoperative phenomenon that may occur after a parotid gland surgery. The main characteristics that distinguish Frey’s syndrome are gustatory sweating or flushing. To put it in simpler terms, the patient starts to sweat whenever salivation tends to occur.

What Causes Frey’s Syndrome?

Frey’s syndrome occurs due to nerve aberration, which can be related to the direct or indirect injury to the auriculotemporal nerve and most often follows a surgical injury to the parotid salivary gland most commonly after parotidectomy (the surgical excision of this large salivary gland usually precedent due to infections or neoplasms that would be benign or malignant).

The causes though not exactly correlatable in all the cases, mainly remains to be one of the following,

• Trauma to the auriculotemporal nerve branch.

• Pathologic entities or lesions of the parotid gland as in neoplasms (benign or malignant tumors).

• Parotid gland infections.

• Sympathetic nerve dysfunctionalities.

• Accidental injuries to the preauricular area or the face.

• Local or systemic infections that affect salivary glands.

How Common Is Frey’s Syndrome?

Initially, in the earlier decades, this syndrome was thought of as a rare postoperative syndrome or an adverse effect of the auriculotemporal nerve, but it is not a very uncommon diagnosis by the physicians now given that the incidence of 4 to 62% of post parotidectomy patients presents with Frey’s syndrome in a period of the half to one and a half year post-surgery. This is the reason why most parotid gland surgeries are also treated with facial reconstructive surgeries post the procedure because the incidence of parotid gland surgery without facial reconstruction is thought of as another major cause of this syndrome.

What Are the Characteristic Features of Frey’s Syndrome?

The syndrome is not limited to only salivary stimulus but also reflects in the patient during a masticatory stimulus that aggravates the clinical symptoms (in response to masticatory or bite stimuli). The sweat glands and cutaneous areas are innervated by the parasympathetic postganglionic nerve fibers that may extend into the cutaneous tissues. This results in the clinical features of flushing, sweating, or even itching, burning sensations that may be a source of great discomfiture and personal anxiety to the suffering patient.

Sweating or often both sweating and flushing happens over the preauricular areas. Whenever it starts to happen, it is accompanied by flushing or reddening of the cheeks, temple region of the forehead, or over the neck whenever the person is in a natural situation to salivate. For example, if a person eats or thinks about food, salivating is a natural impulse, but in this case, when the nerve is injured, the patient starts to flush and sweat.

Apart from the clinical features of erythema or facial redness and sweating instead of salivating in response to a salivary stimulus, the patient can also reportedly have nasal discharges that can be embarrassing while smelling food. Between the painful bouts or attacks, the patient can experience a temporary form of numbness or altered sensations like burning in the affected area (paresthesia sensation often as a result of “gustatory neuralgia”).

What Is the Pathogenesis of Frey’s Syndrome?

Frey’s syndrome prevalence is almost equal in males and females. In the early part of the course, the auriculotemporal branch of the Mandibular branch (V3) of the trigeminal nerve within the parotid gland is impacted by trauma. The trigeminal nerve not only functions to supply the sweat glands of our scalp but also supplies parasympathetic nerve fibers to the parotid gland.

How Is the Diagnosis of Frey’s Syndrome Made?

The diagnosis of Frey’s syndrome is usually most commonly by the test called the “starch-iodine” test that is primarily used for the evaluation of sudomotor functions in patients suffering from Horner’s syndrome and Frey’s syndrome. Underactive as well as an overactive sweat gland (hyperhidrosis or hypohidrosis) can be tested through this method. The affected area of the face is firstly painted with a tincture of iodine and then allowed to dry. An increase in room temperature or salivary stimulating or pressure-inducing medications like Pilocarpine is given to the patient after dusting the dried part with cornstarch. The aim of this diagnostic method is to visualize sweat when it reaches the cutaneous or skin surface. In the presence of iodine solution, the starch turns blue if sweat is present. The color change is a useful indicator in detecting Frey’s syndrome.

How Can Frey’s Syndrome Be Prevented?

Minimally Invasive Surgeries and Facial Reconstruction: Though facial reconstructive surgery post a parotidectomy procedure or surgery of the parotid gland may be useful in preventing Frey’s syndrome, current modalities of surgical treatment to minimize the traumatic impact onto the preauricular area remains the most effective strategy to prevent this condition from occurring. Most surgeries of the parotid gland are more traditional in approach and do not use any barrier methods or techniques while operating. However, evidence suggests that Frey’s syndrome can be prevented by using barrier reconstruction between the salivary gland nerves and the sweat glands post a parotidectomy procedure and is another highly preventive strategy.

The incorporation of a barrier between the postganglionic parasympathetic nerve fibers and cutaneous tissues is the key to effective prevention. Similarly, research studies show that a decrease in the skin surface area reduces the overall severity of this condition as it occurs as a post-surgical effect. To prevent the reinnervation of the postganglionic fibers to the sweat glands, fascia flaps, or transposition muscle flap, the temporoparietal fascia flap (TPPF) are two common surgical flap methods for increasing the accessibility, decreasing the surface area of the skin, and also for their increased predictability in vasculature. Hence increased flap thickness, autologous and biosynthetic material grafting can be useful surgical methods during surgery. Endoscopic surgeries, transoral parotidectomy, and parotidectomy performed by mini incisions are some of the minimally invasive alternate surgical techniques to prevent this syndrome.

What Treatment Methods Are Available for Frey’s Syndrome?

Topical antiperspirant medications like Scopolamine, Glycopyrrolate, or currently the most commonly used BTA injection (Botulinum Toxin A) into the affected area intradermally, has proven effective in these patients. Studies have demonstrated that BTA injection significantly improves the patient’s life quality by reducing stress and anxiety and improving gustatory symptoms. But BTA injection is also associated with a symptomatic recurrence rate in the patient between 1 to 3 years after the injection.

Surgical management for Frey’s syndrome is not typically advocated by surgeons owing to the risk of facial nerve injuries though a few documented cases of surgical transection of auriculotemporal, tympanic, or greater auricular nerve are present.

Conclusion:

Frey's Syndrome is medically referred to as 'gustatory sweating'. It is a rare condition that usually occurs as a consequence of surgery in the region near the parotid glands. Sweating while eating can occur due to various reasons. It can be due to an underlying condition or can occur as an isolated incident. One can consult a physician to know about the remedies or can try at-home measures to deal with Frey's Syndrome. One need not change their usual activities due to the fear of sweating while eating.