Subtotal or Total Parotidectomy with Preservation of the Facial Nerve
The initial part of the operation is the same as in a superficial lobectomy, then the parotid tissue medial to the facial nerve is additionally removed. A subtotal parotidectomy is appropriate for benign lesions. Malignant tumors that have not invaded the facial nerve are managed by a total parotidectomy that removes all of the deep parotid tissue while preserving the facial nerve divisions.
Malignant mixed tumors located entirely within a pleomorphic adenoma and not invading the parotid tissue outside the adenoma (total parotidectomy). Some tumors may require a neck dissection and radical parotidectomy.
Separation. Glandular components are separated from the mandible and masseter muscle with dissecting scissors and also by blunt dissection along the cleavage plane. Branches of the external carotid artery will be encountered, most notably the maxillary artery and superficial temporal artery. To prevent heavy bleeding, the external carotid artery is exposed and ligated above the facial artery but still caudal to the posterior belly of the digastric, behind which the vessel continues its medial course. The medial boundary of the dissection is formed by the digastric muscle, stylohyoid muscle, and styloid process, behind which the internal carotid artery and hypoglossal, glossopharyngeal and vagus nerves are located (Fig. 13.14).
Extirpation. After the deep portion of the parotid gland has been freed from all surrounding structures including the cartilaginous and bony lateral skull base and the upper portion of the sternocleidomastoid muscle, it is mobilized from beneath the facial nerve branches and extirpated.
Iceberg tumors with predominant pharyngeal extension cannot be removed through a transparotid approach without violating the tumor capsule. In these cases the parapharyngeal space can be accessed by extending the external neck incision and exposing the vascular compartment and relevant neural structures, then mobilizing the medial portion of the tumor from below by blunt dissection with the index finger or mounted sponge. If access is still insufficient, it can be increased by temporary resection of the posterior portion of the mandible behind the trigeminal alveolar nerve.