Auriculotemporal nerve syndrome / Frey syndrome/Gustatory sweating

Are You Confident of the Diagnosis?

Frey syndrome is characterized by unilateral flushing and sweating of the facial skin innervated by the auriculotemporal nerve (neck, parotid region, and frontotemporal scalp), which occurs in response to gustatory or olfactory stimuli. Bilateral involvement has been reported. It is more common in adults.

What to be alert for in the history

In children, it is typically noted around 6 months of age at the time of introduction of solid foods (fruit snacks) to the diet. The erythema and flushing begin within minutes of eating the first bite of a favorite food and last for about 20 to 60 minutes. This may occur consistently with every solid food feeding. In contrast with adults, sweating usually does not occur in children.

Diagnosis confirmation

In children, the diagnosis is clinical. Elicitation of the characteristic linear erythema in the (segmental) areas innervated by the auriculotemporal nerve on solid feeding confirms the diagnosis (Figure 1). In adults, a sweat test ( Starch iodine) is performed to assess the severity of sweating.

Figure 1.

Frey syndrome has to be differentiated from food allergy, in which case the involvement is nonsegmental and bilateral. There may be associated symptoms of itching, urticaria, angioedema, or anaphylaxis.

Who is at Risk for Developing this Disease?

In children, Frey syndrome occurs in those infants delivered with forceps assistance in 50% of cases. In adults, it is common following parotid surgery.

What is the Cause of the Disease?

Etiology

In infants, trauma to the auriculotemporal nerve during forceps-assisted delivery has been implicated in 50% of cases. In the remaining 50% of cases, a congenital aberration of the auriculotemporal nerve fibers, between the parasympathetic and sympathetic pathways is hypothesized. In adults, Frey syndrome occurs mostly after parotid surgery, especially after excision of the superficial lobe or drainage of a parotid abscess.

The other possible etiologic factors include parotitis, mandibular condylar fracture, blunt trauma, herpes zoster, associated central nervous system disorders such as syringomyelia, epilepsy, and meningioma of the cerebellopontine angle tumor.

Pathophysiology

Frey syndrome is due to the misdirected regenerative process of the auriculotemporal nerve. This nerve is a sensory branch of the posterior division of the mandibular division of the trigeminal nerve. The sensory fibers innervate the auricle, external auditory meatus, tympanic membrane, temporomandibular joint, and the temporal scalp. It receives the postganglionic parasympathetic secretomotor fibers from the otic ganglion, which is destined for parotid glands.

Frey syndrome is due to damage to these autonomic fibers. During the process of healing the regenerating parasympathetic fibers intended for parotid may be misdirected and join the sympathetic fibers in the great auricular nerve, which supplies sweat glands and blood vessels. Because of this, any gustatory stimulus produces erythema and sweating instead of salivation.

Systemic Implications and Complications

Frey syndrome may occur in association with several neurologic disorders, such as syringomyelia, central nervous system tumors, and epilepsy.

Treatment Options

MEDICAL

Topical

Aluminium Chloride 20%

Botulinum toxin A (intra cutaneous injection)

Scopolamine 3% cream/Methenamine

Glycopyrrolate 0.5%-2% cream

Lidocaine/prilocaine mixture

Systemic

Clonidine 0.1-0.3mg orally three times a day or 0.1-0.3mg/day transdermal patch

Oxybutynin chloride 5mg orally twice or three times a day

Propantheline bromide15mg orally once to three times a day

PHYSICAL

Iontophoresis

Radiotherapy

SURGICAL

Transmeatal tympanic neurectomy

PROPHYLACTIC MEASURES DURING PAROTIDECTOMY

Interposition of barrier to prevent the neural anastomosis between the parasympathetic and sympathetic nerves.

– Temperoparietal fascia flap

– Superficial musculoaponeurotic system (SMAS) plication

– Hybrid SMAS

– Rotation of platysma muscle cervical fascia-sternomastoid muscle onto the parotid bed

Optimal Therapeutic Approach for this Disease

CHILDREN

Frey syndrome in children has a benign and nonprogressive course. Sweating usually does not occur. Spontaneous resolution has also been reported in children . Hence children with Frey syndrome do not require treatment. The parents need simple reassurance and counselling.

Many times children are misdiagnosed as having food allergy and subjected to unnecessary skin prick tests or blood tests for allergy. Hence recognition of Frey syndrome in pediatric population is very important to avoid misdiagnosis as food allergy.

ADULTS

Treatment is required only for adults with significant hyperhidrosis.

Step 1 approach: Conservative with topical 20% aluminium chloride for a period of 1-2 months. If the response is not satisfactory, then consider Step 2 therapy.

Step 2 approach: Intradermal injection of Botulinum Toxin A . The response may last for a period of 6 months and the treatment can be repeated. If the treatment is unsuccessful, then consider surgery.

Step 3 approach: Surgical approach. Interposition of different barriers (overlying the parotid) to prevent aberrant reinnervation between parasympathetic and sympathetic fibers, has been found to be useful.

The barriers include 1. SMAS interposition, 2. Temperoparietal fascia flap, 3. Sternocleidomastoid muscle flap, and 4. implants. These surgical techniques can also be done as a prophylactic measure at the time of initial parotidectomy

Patient Management

The condition is benign and may persist for life. There is no definitive /curative treatment. Explain the different treatment options. The treatment is only supportive. All the treatment options have been used with variable success rates.

Unusual Clinical Scenarios to Consider in Patient Management

Frey syndrome is a masquerader of food allergy, especially in children. This is because the Frey syndrome starts manifesting at the time of introduction of the solid foods around 6 months of age. But Frey syndrome can be identified by its distinctive clinical features.

In contrast to food allergy, Frey syndrome is usually unilateral, with a segmental distribution in the areas innervated by the auriculotemporal nerve. Food allergy is bilateral and presents with itching, urticaria, angioedema, or systemic symptoms or anaphylaxis.

What is the Evidence?

Sethuraman, G, Mancini, AJ. “Familial Auriculotemporal nerve ( Frey) syndrome”. Pediatr Dermatol. vol. 26. 2009. pp. 302-5. (The authors have described the unusual constellation of bilateral Frey syndrome occurring in two sisters without any known preceding parotid region trauma.)

Hussain, N, Dhanarass, M, Whitehouse, W. “Frey's syndrome: a masquerader of food allergy”. Postgrad Med J. vol. 86. 2010. pp. 1011(The authors have reported a classical case of bilateral Frey syndrome in a 6-year-old child. Frey syndrome in children may mimic food allergy, leading to unnecessary skin/blood testing and exclusion diets. The localized segmental distribution in the areas innervated by the auriculotemporal nerve following ingestion of certain foods, in the absence of itching or other hypersensitivity symptoms, will exclude food allergy.)

de Bree, R, van der Waal, I, Leemans, CR. “Management of Frey syndrome”. Nead Neck. vol. 29. 2007. pp. 773-8. (In this review, the authors highlight the various surgical options for patients who undergo parotidectomy. Interposition of various barrier systems, such as superficial musculoaponeurotic system, temperoparietal fascia flap, sternocleidomastoid muscle flap, and implants have been described to minimize the risk of developing symptomatic Frey syndrome.)

Clayman, MA, Clayman, SM, Seagle, MB. “A review of the surgical and medical treatment of Frey syndrome”. Ann Plast Surg. vol. 57. 2006. pp. 581-4. (The treatment of Frey syndrome includes both medical and surgical options. Patients with mild symptoms need only reassurance and counselling. For patients with severe sweating, various medical and surgical measures have been used with varied success. The initial conservative treatment is with topical aluminium salts (20%) . If it is unsuccessful, then several doses of intradermal injection of Botulinum Toxin A is considered. Surgical treatment should be offered to patients who fail the medical treatment.)

Kaddu, S, Smolle, J, Komericki, P, Kerl, H. “Auriculotemporal (Frey) syndrome in late childhood: An unusual variant presenting as gustatory flushing mimicking food allergy”. Pediatr Dermatol. vol. 17. 2000. pp. 126-8. (Surgical approach. Interposition of different barriers (overlying the parotid) to prevent aberrant reinnervation between parasympathetic and sympathetic fibers, has been found to be useful.
The barriers include 1. Superficial musculoaponeurotic system (SMAS) interposition, 2. Temperoparietal fascia flap, 3. Sternocleidomastoid muscle flap and 4. implants. These surgical techniques can also be done as a prophylactic measure at the time of initial parotidectomy.
The authors have described a rare case of late-onset auriculotemporal syndrome following mandibular condyle fracture in a 13-year-old Austrian girl.)

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