It is Frey’s Syndrome

Frey syndrome is a postoperative phenomenon following salivary gland surgery and less commonly neck dissection, facelift procedures, and trauma that is characterized by gustatory sweating and flushing. Frey syndrome was first described by Lucie Frey in 1923 and was termed auriculotemporal syndrome. It described sweating and flushing in the preauricular area in response to mastication or a salivary stimulus. Initially thought to be rare, it was later recognized as a common occurrence after salivary gland surgery, occurring in 4% to 62% of postparotidectomy patients 6 to 18 months after surgery.

Theories for pathogenesis of Frey’s Syndrome

List & Peet (1938) postulated a hypersensitivity of the denervated sweat glands to acetylcholine liberated from either the cut surface of the parotid or from adjacent cholinergic nerve endings which were still intact. It was demonstrated that local injections of pilocarpine induced a sweating reaction. Since this theory was postulated other workers have failed to verify the above findings in the first month following denervation when one would expect denervation sensitivity to be maximal. If the theory of List & Peet was correct one would also expect heat stimulation to evoke a strong reaction through adjacent intact cholinergic nerves, whereas most workers have demonstrated a diminished or absent response.

The second theory postulated transaxonal excitation of a regenerated axon by adjacent nerves supplying a different end-organ. The possibility of this phenomenon occurring is facilitated by postoperative scarring approximating tissues, swelling of residual parotid glandular tissue or compression by nearby mobile structures such as the temporomandibular joint. Granit et al. (1944) demonstrated the fact that transaxonal excitation will occur experimentally, but to postulate this as the cause of Frey’s syndrome demands the belief that the normal sympathetic innervation of the sweat glands in the overlying skin remains intact. The lack of response to thermal stimulation in this area following parotidectomy shows that the normal sudomotor nerve supply is not present. This theory has, therefore, in the main been abandoned.

Ford & Woodhall (1938) considered the possibility of misdirected regeneration of axons supplying a different end-organ as a possible factor in the aetiology of Frey’s syndrome. These authors felt that parasympathetic fibres from the glossopharyngeal nerve, travelling with the auriculotemporal nerve, which were originally secretomotor to the parotid gland, become misdirected and eventually innervate the overlying sweat glands. This ‘abberant regeneration theory’ has gained wide acceptance. It is a well-documented fact that peripheral nerves, when sectioned, regenerate by neurofibril production. Checkout https://financejar.co.uk for financial needs. These neurofibrils will attempt to follow degenerating axon sheaths, but often become misdirected.

Symptoms

The symptoms of Frey syndrome can include flushing, sweating, burning, neuralgia, and itching. Generally, the symptoms are mild but can result in discomfort as well as social anxiety and avoidance.

Diagnosis

Diagnosis of Frey syndrome is based on clinical history, but confirmatory testing can be done with a Minor starch-iodine test. The starch-iodine test consists of painting the patient’s postsurgical affected region with iodine. Once dry, dry starch is then applied to the painted area, and a salivary stimulus is given. The starch turns blue/brown in the presence of iodine and sweat (Fig. 2. Patients who underwent parotidectomy had a positive Minor starch-iodine test in 62% of cases, whereas the self-reported incidence of symptoms was only 23% in the same group.

Surgical methods for preventions

Increased Skin Flap Thickness

Within the facial skin, the sweat glands are positioned at the same level or slightly deeper than the base of the hair follicles. Based on this, it has been presumed that increasing the thickness of the elevated skin flap, to keep the sweat glands from being exposed, affords protection from the aberrant parasympathetic nerve regeneration that results in Frey syndrome.

Transposition Muscle or Fascia Flaps

Similar to increasing the thickness of the elevated skin flap to shield the facial sweat glands from aberrant reinnervation, pedicled muscle and fascia flaps have been used to cover the resected parotid gland in an attempt to create a physical barrier between the overlying dermis and the transected nerve fibers within the parotid.

Temporoparietal fascia flap

The temporoparietal fascia flap (TPFF) is a broad, vascularized fascia flap that is based off the superficial temporal artery

Superficial musculoaponeurotic system flap

Another technique, focused on creating a physical barrier between the underlying regenerating auriculotemporal nerve fibers and the overlying dermis, is a superficial musculoaponeurotic system (SMAS) flap.

Biomaterial and Autologous Implantation

Autologous and biosynthetic material have been used to create the physical barrier between the transected parotid and the overlying cutaneous tissues. Numerous products have been reported, but the most commonly cited are acellular dermal matrix implantation and autologous fat grafting.

Acellular dermal matrix

ADM is a soft tissue matrix graft that is generated by decellularization of tissue that results an intact extracellular matrix. It is commonly used in wound healing and reconstructive surgery because it provides a scaffold for regenerating tissues. Since its development, it has been used in parotidectomy for the prevention of Frey syndrome. As with muscle or fascia flaps, the goal of this graft is to create a biologic barrier between the facial skin flap and the transected parotid gland.

Management

Medical Management

Although intraoperative techniques try to reduce severity and incidence of Frey syndrome, postoperative interventions have been focused on ameliorating symptoms once they develop. Most of the therapies used are given via injection therapy or by topical application. Previous agents have included topical antiperspirants as well as injection with alcohol, scopolamine, glycopyrrolate, or botulinum toxin A (BTA). Currently, BTA is the most widely used agent for intradermal injection.

Surgical Management

Historically, surgical treatment of Frey syndrome has not been used. Reports of surgical transection of the auriculotemporal nerve, tympanic nerve, and greater auricular nerve have been described for the management of Frey syndrome, but they are not commonly practiced.