LAUSR

Aparotid fistula occurs as a result of injury to the parotid duct (Stensen duct) and/or parotid gland. It is a well-known complication of parotidectomy but may also occur in the setting of penetrating or blunt trauma, head/neck malignancy, severe parotiditis, or other surgical procedures performed in the territory of the parotid gland. The development of a parotid fistula as a complication of Mohs micrographic surgery seems to be relatively rare, with only a few case reports in the literature. However, it is important for Mohs surgeons to have an awareness of this potential complication and its treatment options because Mohs surgery is commonly performed on cutaneous tumors of the lateral cheek. The management of parotid fistulas has been controversial, and numerous conservative and surgical treatment methods have been described with varying degrees of success. If a parotid duct injury is identified intraoperatively, surgical treatment is recommended and will likely require the assistance of an otolaryngologist or maxillofacial surgeon. However, if the parotid fistula has a delayed presentation, nonsurgical measures should be considered. Common nonsurgical treatment options include pressure dressings, anticholinergic drugs, botulinum toxin injections, and low-dose radiation therapy. An 81-year-old white man with a history of numerous nonmelanoma skin cancers underwent Mohs surgery for a squamous cell carcinoma (moderately differentiated; AJCC8 tumor Stage 2, BWH Stage 2a) on the left cheek. The tumor was cleared in 2 Mohs layers, and parotid glandular tissue was noted in sections on the final layer (Figure 1). No squamous cell carcinoma was identified in the parotid glandular tissue, and parotid duct was not present in the sections examined. Two weeks after the procedure, the patient reported clear drainage from the incision line thatwas most significant when eating and drinking. The drainage was cultured by the patient’s primary care provider and was negative for bacterial growth. On initial examination in the dermatology clinic, the surgical site was intact with a 2.0-mm opening at the central aspect of the incision line with actively draining clear fluid (Figure 2). There was moderate maceration inferior to the skin opening, but no significant erythema or tenderness around the surgical site. Because of high clinical suspicion for a parotid fistula, the patient was treated with 70 units of onabotulinumtoxinA (Botox, Allergan Inc., Madison, NJ) injected subcutaneously around the fistula and deeper into the parotid gland underlying the fistula (Figure 3). A pressure dressing was then applied. Adjunctive treatment with an anticholingeric agent was discussed, but ultimately deferred, given patient’s age and comorbidities. Ten days after the onabotulinumtoxinA injections, the patient-reported persistent drainage and onabotulinumtoxinA injections were repeated, with 60 units injected into the left parotid gland using a 27-G3 3.8cm needle. One week after the second round of injections, the patient continued to have drainage. An additional 66 units of onabotulinumtoxinA were injected directly into the left parotid gland using a 27-G 3 3.8-cm needle. One week after the third round of injections, the patient continued to have significant drainage from the fistula. Transdermal scopolamine patches (1.5 mg) 1 mg/3 days were initiated with no improvement. Otolaryngology was then consulted for surgical correction of the fistula.