Frey's Syndrome (Auriculotemporal Syndrome)

Introduction:

Lucie Frey first described this condition in 1923, and it 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 (it is a procedure of removing part or all of the parotid gland). 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 Is Frey’s Syndrome?

A rare neurological disorder called Frey's syndrome makes people perspire often when they eat or think about food, like sweating on the cheek, temple, or behind the ears. People may also experience flushing, redness, or discoloration in some regions. The most common way that Frey's syndrome arises is as a consequence of surgery, usually parotid gland-related. The largest salivary (spit) glands in the body are these. On each side of the face, they are situated just in front of and beneath the ears. The parotid glands produce spit to lubricate the mouth and facilitate chewing and digesting.

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 remain to be one of the following,

• Trauma to the auriculotemporal nerve branch.

• Pathologic entities or lesions of the parotid gland, such 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.

What Are the Surgeries that Can Result in Frey's Syndrome?

• Accidental nerve injury during a parotidectomy is the most common cause of Frey's syndrome. However, the subsequent medical procedures or traumas may also be the source:

• Operation on the submandibular gland.

• Surgery on the submandibular gland.

• Trauma to the temporomandibular joint.

• Surgery for the dissection of neck lymph nodes.

• Injuries sustained in the parotid area.

How Common Is Frey’s Syndrome?

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

Is Frey’s Syndrome Serious?

Even though it can be bothersome, Frey's condition poses no physical risks. Thus, in that regard, it is not a serious illness. Yet, uncontrollably high perspiration can be uncomfortable and impact one's mental well-being. If the syndrome is causing distress, one must get care. One way to manage perspiration is using Botox injections. If mental health is being affected, it could be wise to see a psychologist or therapist as well.

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, 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, salivating is a natural impulse if a person eats or thinks about food, but 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 reportedly has 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 due to “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, trauma impacts the auriculotemporal branch of the Mandibular branch (V3) of the trigeminal nerve within the parotid gland. The trigeminal nerve not only supplies the sweat glands of the 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 “starch-iodine” test, which is primarily used to evaluate sudomotor functions in patients suffering from Horner’s syndrome and Frey’s syndrome. Underactive and overactive sweat glands (hyperhidrosis or hypohidrosis) can be tested through this method. The affected face area is first painted with a tincture of iodine and then allowed to dry. The patient is given an increase in room temperature or salivary stimulating or pressure-inducing medications like Pilocarpine after dusting the dried part with cornstarch. This diagnostic method aims 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 for 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 on 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, another highly preventive strategy.

The key to effective prevention is to incorporate a barrier between the postganglionic parasympathetic nerve fibers and cutaneous tissues. 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 flaps, the temporoparietal fascia flap (TPPF) are two common surgical flap methods for increasing the accessibility, decreasing the surface area of the skin, and their increased predictability in vasculature. Hence, increased flap thickness and 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 have 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. However, BTA injection is also associated with a symptomatic recurrence rate in the patient between one and three years after the injection.

1. Intravenous Botulinum Toxin: Botox injections are the most popular treatment for gustatory sweating among medical professionals. It causes short-term harm to the sweat glands close to the injection site. Most patients who receive the injections say their overall quality of life, flushing, and gustatory sweating have improved. One will probably want further injections because the impact wears off over time, usually after nine to twelve months.

2. Anticholinergic Topical: These drugs function by reducing sweat gland activity. They need to apply them to the skin frequently, but they are successful.

3. Topical Sweat Absorbers: Though they have minimal effects, topical antiperspirants, like certain deodorants, may help reduce sweating. Like topical anticholinergics, they must be used often.

Surgical management for Frey’s syndrome is not typically advocated by surgeons owing to the risk of facial nerve injuries. However, a few documented cases of surgical transection of the 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 due to surgery in the region near the parotid glands; sweating while eating can occur for various reasons. It can be due to an underlying condition or can occur as an isolated incident. One can consult a physician to learn about the remedies or can try at-home measures to deal with Frey's Syndrome. People need not change their usual activities due to the fear of sweating while eating.