Removal of the inferior half of the superficial lobe is sufficient to treat pleomorphic adenoma in the tail of the parotid gland.

Abstract

In the first half of the 20th century, benign parotid neoplasms were enucleated, irradiated, or both. Complications were common, and recurrence rates for benign pleomorphic adenomas were high (20%-45%), probably because of spillage of tumor cells into the wound. A major advance occurred when Janes (1940) and Bailey (1941) described a supraneural approach to treatment of parotid neoplasms. The facial nerve runs through the parotid gland. It enters posteriorly as a main trunk, and branches within the gland. The cervical and marginal mandibular branches of the lower division are the lowest branches of the facial nerve in the neck. Although the branches share some redundancy, the nerve does not cross over itself. Dissection along one branch will not reveal a branch deeper to it. This branching pattern divides the gland into a deeper or medial portion, now often called the deep lobe, and a much larger, more superficial portion (superficial lobe). There is no true anatomic compartmental separation of the superficial and deep parotid lobes. Rather, the facial nerve constitutes the surgical division. The radiologic demarcation between deep and superficial lobes is an imaginary line from the stylomastoid foramen to the retromandibular vein or the lateral ascending ramus of the mandible. Inperformingasupraneural approach or superficial parotidectomy totreatabenignparotidneoplasm, instead of just shelling out the tumor, thesurgeonidentified the facialnerve andremovedthetumoralongwiththe rest of the parotid tissue lateral to the facial nerve. In this way, a cuff of normal tissue surrounded theneoplasm, and the capsule of the neoplasm was notviolated,minimizingspillageoftumor cells into the wound. In the ensuingyears,superficialparotidectomy wasfurtherrefined,resultinginrecurrence rates of 0% to 3%. A major morbidity of the superficial parotidectomy is postoperative facial nerve dysfunction. Intraoperative traction on the nerve and skeletonizationoften result in temporary paresis or paralysis. Functional sequelae are more common when the upper branches of the nerve are affected resulting in corneal exposure and the potential for keratitis and otherophthalmologicproblems.Since many pleomorphic adenomas occur in the tail of the parotid gland, inferior to the inferior division of the facial nerve, some surgeons began dissectingonly the trunkandinferiordivisionofthenerve,andremovingonly the parotid tissue inferior to the inferior division (subtotal superficial parotidectomy). As long as this preserved a cuff of normal tissue around the neoplasm, it was thought that no greater recurrence rate could be expected, and the upper division of the facial nerve would be protected.