INTRODUCTION

Frey’s syndrome, also known as auriculotemporal syndrome, represents aberrant reinnervation after an injury to the auriculotemporal nerve.¹ It presents with facial warmth, redness, and sweating in the territory of the auriculotemporal nerve that overlies the parotid gland. It may include the preauricular and temporal skin, the scalp, and the temporomandibular joint region during meals, especially with spicy and sour foods.² The incidence of Frey’s syndrome ranges between 12% and 25% among patients undergoing parotidectomy.² The objective of this study is to demonstrate the usefulness of botulinum toxin in the management of Frey’s syndrome.

CASE PRESENTATION

A 53-year-old female with a history of arterial hypertension, type II diabetes mellitus, tonsillectomy, rhinoplasty, and right superficial parotidectomy. Clinical manifestations began after superficial parotidectomy for papillary cystadenoma lymphomatosum, presenting with local temperature increase, erythema, and hyperhidrosis related to the ingestion of citrus and spicy foods (Figure 1).

On physical examination, facial mimic movements were preserved, with no evidence of infection, presence of paresthesia in the right preauricular surgical site and right cervical region, a mature scar without pathological findings, and volume deficit in the right parotid region. For botulinum toxin application, the affected area was delimited as shown in Figure 2, and intradermal injections of botulinum toxin A (Botox®) were administered at a rate of 0.1 ml of the preparation (2.5 ml of 0.9% saline per 100 units) at the center of each cm².

During follow-up, significant improvement was observed at 12 days post-application, with no symptoms at 1, 2, and 3 months (Figure 3). No adverse effects related to the toxin or the procedure were reported.

DISCUSSION

Frey’s syndrome is a low-prevalence entity that can develop after parotidectomy, submandibular surgery, facelift, thyroidectomy, mandibular fractures, penetrating injuries, and facial trauma. It commonly appears 6 months after surgery and may be disabling due to its impact on social and occupational activities.³

Preventive intraoperative measures include the creation of muscle flaps or transposition of fascia lata to form a barrier between the postganglionic parasympathetic nerves of the parotid gland and the sweat glands of the overlying fascia.⁴ Topical treatments such as atropine and scopolamine creams have been reported as initial therapy.⁵ The use of topical antiperspirants, anticholinergics, and intracutaneous injection of botulinum toxin type A (BoNT-A) has also been described. BoNT-A blocks presynaptic acetylcholine release at the neuromuscular junction, producing chemodenervation, a reproducible and protocolizable technique with low morbidity.⁶

The only statistically significant clinical predictor of developing Frey’s syndrome after parotidectomy is tumor size, with risk doubling for tumors ≥4 cm.⁷ Currently, botulinum toxin injection is considered the treatment of choice, as it is simple, effective, rapid, reproducible, and minimally invasive. Proper use requires delimiting the affected area per cm², maintaining a 1–2 cm distance between injections, and using concentrations from 1.0 to 5.0 U/cm².⁸ Repeated injections reduce symptom severity and affected area size, increasing the interval between applications.⁹ The mechanism of action may involve eccrine gland atrophy due to prolonged inhibition.

In this case, approximately 50 units of botulinum toxin were administered subdermally in the right preauricular and cervical region diluted with NaCl solution. Reevaluation at 12 days post-injection revealed significant improvement in hyperhidrosis and local erythema.¹⁰

Based on literature, the duration of effect is dose-dependent, ranging from 10 to 16 months.¹¹ Although surgical interposition with flaps may resolve many cases, it increases morbidity and costs without demonstrating superiority over botulinum toxin. In addition to symptom improvement or resolution, botulinum toxin offers the advantage of better cosmetic outcomes.¹²

CONCLUSION

Frey’s syndrome is a rare condition, most frequently secondary to parotidectomy, and should be considered as a differential diagnosis following this surgical procedure. Botulinum toxin application is a safe and effective treatment in these patients, providing better quality of life without local or systemic adverse effects.

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