Overview

Frey syndrome is a rare neurological disorder that causes an individual to secrete copious amounts of sweat from pores and glands whilst eating or even thinking about food. There is some evidence that Frey syndrome can be  hereditary disorder (being a familial pattern).. Also known as Baillarger’s syndrome, auriculotemporal syndrome, Dupuy syndrome, or gustatory hyperhidrosis, it affects 30-64% of the population.¹

In this article, the causes and development of Frey syndrome will be detailed, as well as many helpful preventative strategies that can be implemented to minimise and stop its development or worsening. Furthermore, potential treatments and cures will also be covered.

Understanding the mechanism and cause behind Frey Syndrome

Mechanism

Frey syndrome’s cause has been localised to damage coming to the auriculotemporal nerve (ATN) The ATN is a branch of the larger nerve, the Mandibular nerve, that provides sensation to the ear, jaw, scalp and side of the face.² 

Damage to the ATN causes Freys syndrome because the ATN innervates a particular gland: the parotid gland. The parotid gland is found under the jaw on either side of the face and is responsible for saliva production as well as sweat in the scalp and face.¹

Upon being damaged, the body will attempt to regenerate the ATN to heal the issue and re-innervate regions that the ATN once supplied. This is called: aberrant nerve regeneration. During the regenerative process, some of the nerve endings of the ATN are incorrectly connected and end up innervating the wrong regions. This causes neuronal miswiring and triggers unnatural symptoms seen in Frey Syndrome: excessive sweating and salivation, particularly when seeing or eating food.³

Causes

ATN damage can occur through trauma, infection, genetic or hereditary causes. However, the most common cause is from a parotidectomy surgery in the parotid region of the face. Frey syndrome is a common side effect of a parotidectomy surgery (a surgery that removes the parotid gland.)^1,4

During this surgery, the ATN branches that innervate this gland are damaged, and, without reconstructive surgery, the nerve fibres can be regenerated incorrectly and misdirected, hence resulting in the development of Frey syndrome.

Other common causes of Frey's Syndrome include:

• Head and neck tumours 
• Trauma
• Radiation therapy 
• Infection 
• Autonomic neuropathy

Pre-operative preventative measures for Frey Syndrome 

Thus far, it has been established that parotidectomy surgery without reconstructive surgery is a leading cause for ATN damage and Frey syndrome development. Therefore, in order to prevent this syndrome's development, a few methods can be implemented beforehand to minimise developing this syndrome at all.⁵ 

Patient Assessment and Counseling

• A clear line of communication between the surgeon and the patient is imperative. This includes pre-operative appointments for clarification about the operation and informing the patient about this surgery, involving risk factors and the benefits⁵
• A comprehensive evaluation of each patient undergoing a parotidectomy surgery should be completed since each individual has unique risk factors that need to be planned and accommodated for⁵

Surgical Planning

Trends have found that with the parotidectomy surgery, the more invasive the surgery, the higher the likelihood of developing Frey’s syndrome. This is due to deeper tissue and nerve damage occurring from the invasive nature of the surgery. Therefore, this is where surgical planning is imperative, as this minimises the damage that has to occur during this procedure. 

Planning strategies include:

• Pre-surgical imaging (such as ultrasound) and careful planning to minimise nerve damage⁶
• Choosing less invasive surgical approaches when possible

Intraoperative techniques to prevent Frey Syndrome

It is common for Frey syndrome to occur post parotid gland removal. However, to minimise its severity, surgeons can do the following things during the surgery:

Identifying and preserving nerves

During the parotidectomy procedure, identifying and preserving nerves surrounding the gland can minimise and prevent damage coming to them since surgeons are now aware of their location and vulnerability.⁷

• In a recent paper published in March 2024, one out of the four main objectives for a parotidectomy surgeon is to identify the parotid gland to ensure an accurate surgery with minimum invasion and damage to the surrounding anatomical structures⁷
• Furthermore, a great amount of caution should be taken when handling delicate nerve and gland tissue to prevent unnecessary nerve damage⁷

Use of interpositional materials

On top of being aware of the surrounding anatomical structures of the parotid gland, surgeons can also use particular materials such as dermal fat, tissue grafts, dermal matrices and collagen sheeting.⁴

All of these materials have been used for reconstructive surgery for a long period of time. Doctors and surgeons have used them as a ‘scaffold’ for tissues that attempt to regenerate post-surgery. The dermal matrix acts as a barrier between the area where the gland was removed and the facial skin. This prevents ATN aberrant nerve regeneration.⁴

Minimising surgical trauma

In order to minimise surgical trauma, the least invasive procedure needs to be carried out, so this strategy draws together both of the previous preventative methods. The most effective method to minimise the invasiveness of the procedure is described below:

• The first way to minimise trauma in surrounding tissue is through dissection precision. By only creating incisions where necessary, less tissue is harmed. The surgeon must have an in-depth understanding of the parotid gland location to minimise cutting around the area and only where they need to

Postoperative strategies to prevent Frey Syndrome

Postoperative care is imperative to prevent Frey syndrome. In order to pave an efficient and minimally traumatic path for surgery recovery, postoperative preventative strategies can be a key factor for success. There are two main periods of time post-operation to be aware of: immediate and long-term. Surgery recovery strategies are imperative in both time periods. More detail about each is listed below:

• Immediate postoperative care involves close monitoring post-surgery for any signs of early nerve regeneration issues as well as implementing strategies to increase healing and minimise scar tissue formation. Scar tissue is prevented because it has a stiff, fibrous structure that could compress nerves nearby and ultimately lead to altered sensation⁸
• Long-term monitoring and management involves interval follow-up appointments to observe the ATN and other surrounding nerves, as well as strategies to manage symptoms and prevent the progression of Frey syndrome if it eventually develops

Non-surgical prevention techniques

So far, only surgical interventions have been introduced that can help to prevent or slow the development of Frey syndrome. However, there are available non-surgical and less invasive prevention techniques. They may be less effective but could be safer due to the non-invasive nature of the treatments. 

Some of the non-surgical treatments have been listed below:

• A very common non-surgical and non-invasive approach is a pharmacological one. Some possible drug treatments involve botulinum toxin (Botox) injections as a preventive measure. Botox prevents nerves from stimulating the sweat gland in the cheek, thus preventing excessive sweat production, which is one of the main symptoms of Frey syndrome¹⁰
• Topical antiperspirants have also started to be used more frequently. They do not control and prevent gustatory sweating fully, but they have been found to be effective in controlling sweat for short periods of time (less than 24 hours.)¹⁰
• Injections of alcohol into branches of the facial nerve have been found to prevent sweating; however, this injection can trigger the onset of other symptoms, which could prove to be more troublesome than Frey syndrome symptoms themselves. Some symptoms the alcohol injection could induce are: vision blurring, respiratory distress, and tachycardia. These symptoms are arguably worse than Frey syndrome itself, hence alcohol injections being rather unpopular^1,11

Other treatment strategies

Surgical techniques are continuously undergoing improvement. A surgical technique that targets aberrant nerve regeneration has been found to target the cause of the main symptom of Frey syndrome: ATN regeneration causing excessive gustatory sweating. This surgery is called the Jacobson neurectomy and it has been shown to decrease gustatory sweating by 82%.⁹

Summary

Frey's syndrome is a disorder that stimulates excessive gustatory sweating when viewing or eating food. A lot of the time, the excessive sweating is triggered by trauma or surgeries, particularly, the parotidectomy surgery, which causes aberrant nerve regeneration at the auriculotemporal nerve (ATN) 

Prevention techniques range from operative and invasive surgical techniques that can be carried out separately (Jacobson neurectomy) or during the parotidectomy to noninvasive methods such as topical antiperspirants and botox injections.