What is Frey Syndrome? 

Frey Syndrome is a unique condition whereby a person sweats when they eat or even think about food. Even though the mechanism behind this condition isn't fully understood, the mix-up of nerves that control sweating and salivation is the most commonly agreed-upon reason.¹

The sweating is often only on one side of the face and may also present with redness/flushing of the skin.² Moreover, the condition typically presents after a parotidectomy (removal of the parotid gland), or after traumatic injury to the face.³

Although Frey syndrome is not life-threatening, it can significantly affect the quality of life of patients.⁴ Sweating and flushing in public spaces and among social circles is often deemed embarrassing among most individuals with this condition. This makes Frey syndrome a condition most people want to treat. Before exploring the treatment of Frey syndrome, it is pertinent to understand the underlying causes and anatomy behind the condition itself.

Why is it caused?

The parotid gland is the largest of the three glands that produce saliva in the human body.⁵ Sometimes after surgery in this area (parotidectomy), the facial nerve gets severed and regenerates incorrectly, causing a mix-up between salivation and sweating. Therefore, the brain sends electrical signals to the sweat glands instead of the salivary gland when the individuals are about to eat/thinking of eating.¹

Role of the Facial nerve

The facial nerve is an important part of human anatomy. It is primarily involved in controlling facial movement and the production of saliva.⁶ Moreover, it has several branches, which are at high risk of injury during surgery or trauma near the parotid area. Once damaged, the facial nerve can regenerate.⁷ However, in cases where the nerve regenerates incorrectly, conditions such as Frey’s syndrome result.¹ Therefore, understanding the anatomical significance of the facial nerve is paramount in comprehending how surgical interventions can be employed to prevent or treat it. 

Prevention Of Frey’s Syndrome

Nerve reconstruction

One of the most widely used methods to prevent Frey’s syndrome is nerve reconstruction. After a parotidectomy, surgeons can attempt to repair or reroute the damaged nerve endings to their anatomically appropriate branches.⁸

There are two widely accepted ways of surgically preventing Frey’s syndrome post-parotidectomy: 

• Immediate nerve grafting: A nerve from a different part of the body is attached to the damaged facial nerve to achieve continuity⁹ 
• Local tissue barriers: Surrounding tissue is used to make a barrier to completely hinder the facial nerve from regrowing into sweat glands¹⁰ 

Current literature on the topic suggests that although local tissue barriers work in theory, the usage of nerve grafts is still the most preferred method of prevention.¹¹ Moreover, the lack of curative options for established Frey’s syndrome makes these preventive methods crucial in improving patient outcomes. 

Earlier methods of nerve reconstruction for Frey syndrome were limited by the lack of technology and understanding at the time. The current technological advancements have led to more precise tools and a better understanding of the underlying causes of Frey syndrome, leading to better preventative outcomes.¹⁰ 

How do we test for Frey's syndrome 

Diagnosing Frey's syndrome is crucial to dictate management options, especially after preventative methods have been exhausted. The syndrome is primarily identified through a thorough medical history, clinical examination, and a specialised test called the Minor’s iodine starch test.

• Medical History: The clinician would specifically focus on the relevant medical history of any recent trauma/surgeries to the face or its surrounding regions
• Clinical examination: thorough neurological examination of the facial nerve
• Minor’s iodine starch test: One side of the face is painted with an iodine solution and subsequently covered with starch powder. Then a sialagogue (a lemon slice/candy) is applied to stimulate gustatory sweating. If the iodine solution converts from blue to brown, a diagnosis of established Frey’s syndrome can be made¹²

Treatment of established Frey's syndrome

Non-surgical treatments

Pharmacological interventions can be beneficial in less severe cases of Frey’s syndrome.

Botox Injections, also known as botulinum toxin, are a method of treatment whereby the toxin is injected into the tissues surrounding the sweat glands to block the nerves from eliciting a sweat response.¹³ 

Another common but less effective technique is the usage of aluminium chloride, a key ingredient in topical antiperspirants. This aims to form a physical plug that blocks the sweat glands and masks the symptomatic effects of Frey’s syndrome.¹⁴

Surgical treatments 

On the other hand, surgical treatment is often reserved for advanced Frey’s syndrome. The curative methods and preventative methods are quite similar, in that they both focus on either nerve grafting or blocking the passage of the nerve to the sweat glands. 

Nerve reconstruction is often done by harvesting nerves from other areas of the body and attaching them to the severed/newly grown nerve.¹⁵ This method helps provide complete restoration of nerve function and reduce sweating. Moreover, skin grafts and tissue flaps can be implanted to form a physical barrier that restricts sweat gland activation.¹⁶

As a last resort option, some surgeons resort to the extreme option of removing all innervation (supplying nerves) to that particular area of the body directly from the spinal cord (formally called a sympathectomy).¹⁷ 

More about nerve reconstruction

Numerous studies have shown that nerve reconstruction is a reliable option to both prevent and surgical repair established Frey’s syndrome.¹¹ The procedure involves grafting a segment of a different nerve (usually from the ear) to the affected nerve. This aims to restore the appropriate anatomical innervation to the parotid gland, thereby reducing the risk of rogue nerve regeneration and Frey’s syndrome.¹⁸

However, nerve reconstruction also presents its own set of challenges. The underlying physiology of these peripheral nerves restricts them from completely healing, regardless of surgical manipulation.¹⁹ This could lead to poor outcomes and even complete loss of sensation in the target area. More large-scale studies need to be done to quantify this risk within the context of Frey Syndrome. 

Outcomes and prognosis 

Nerve reconstruction and its associated techniques have shown great promise in the prevention and management of established Frey’s syndrome. To add, current literature also reflects positively on the efficacy of nerve reconstruction in reducing gustatory sweating post-parotidectomy.

Additionally, the psychological advantages of nerve reconstruction are undeniable. Making patients feel better both cosmetically and physiologically is a key advantage of preventative nerve reconstruction.²⁰

FAQ’s

What is Frey’s Syndrome?

Frey’s syndrome is a condition characterised by gustatory sweating (sweating after eating), often caused by surgery or trauma to the face.

How do we diagnose Frey’s Syndrome?

It is diagnosed in a multitude of ways, from clinical examinations, a medical history and a special test called Minor’s iodine test. A clinician often uses information from all three of these modalities to ultimately diagnose established Frey’s Syndrome. 

Can Frey syndrome be prevented?

Yes, it is a very preventable condition. Techniques such as nerve reconstruction and tissue blockades are very effective during operations.²¹ 

What are the treatment options after developing established Frey syndrome?

Treatments range from symptomatic control with Botox injections, to curative options such as nerve grafting and tissue blocks.

Is prevention better than cure? 

Yes, especially in the case of Frey syndrome, the prevention of the condition during surgery often produces far better outcomes than the treatment of established Frey syndrome. 

Summary

All in all, Frey’s syndrome represents a condition characterised by gustatory sweating (sweating after eating). It is a preventable and treatable condition that often arises due to surgery or trauma to the face. With surgery (parotidectomy) being one of the most pertinent causes of Frey syndrome, the best prevention options are those that are done during the operation itself. Namely, nerve reconstructions and tissue-blocking methods.

Moreover, it is important to note that, although less effective, the aforementioned methodologies can also be used for those with established Frey syndrome. Whereas, less intensive options, such as botox and the usage of aluminium chloride, are excellent options for short-term symptomatic relief.

Conclusively, with new treatments being developed day by day, the future for interventional treatments for established Frey’s syndrome looks promising.