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Minimally Invasive Approaches – Extracapsular Dissection
Introduction
Extracapsular dissection (ECD) challenges the need to remove most of the parotid gland to prevent tumor recurrence. The dissection takes place within the parotid tissue, 2–3 mm peripheral to the palpable and visible tumor edge. In traditional parotidectomy, tumor removal with wide surgical margin (>5 mm) is not achieved in most cases because the facial nerve runs in close proximity to the tumor capsule. A partial ECD is undertaken in most traditional operations. There is ample evidence now to show that ECD is a safe technique with low morbidity. A second difference is that the facial nerve does not dictate the surgical approach. At the start of the traditional procedure the facial nerve trunk is identified and the nerve dissected from the parotid gland. Only then is attention turned to the tumor. In ECD, the tumor is central to the dissection. Careful technique and continuous facial nerve monitoring mean the surgeon can move through the gland with confidence.
History of Parotid Surgery
In the 1930s, McFarland became aware of the high recurrence rate (~40%) of parotid tumors. Surgical provision of care was different at that time. There was no pathologic classification of benign parotid tumors and no subspecialization. The operators were true “general surgeons” with their practice aimed at gross disease and ranging across the body. By comparison, an apparent cyst or benign developmental lump in the parotid was a modest challenge. Surgery was under local anesthesia and the common approach was an incision made directly over the lump. Poor access meant that spillage was common. By the 1940s there was a move by prominent surgeons, notably Janeway in Canada, Hamilton Baily in London, and Redon of Paris, to introduce a new anatomic approach to parotid surgery, namely separating the parotid gland into two halves by dissecting along the facial nerve. This coincided with an improvement in results and a proposed explanation by Patey and Thackray placing the blame for recurrence on the biology of the tumor (dehiscent capsule) and not the operative technique. Nicholson, who was practicing ECD through the 1930s and 1940s, held that the wide surgical exposure dictated by this new surgical approach was the true explanation for the decrease in recurrent disease. He continued with ECD, as did Gleave, and their results confirmed that careful dissection around the periphery of the tumor was safe. The results of ECD have since been confirmed in meta-analysis.
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