Minimally Invasive Video-Assisted Parotidectomy
Mu-Kuan Chen
INTRODUCTION
A wide variety of tumors occur in the parotid gland. Thus, parotidectomy requires a precise preoperative evaluation. A detailed history, clinical examination, and imaging studies are essential in defining the location and extent of these tumors, and fine needle aspiration biopsy (FNAB) may also provide important diagnostic information. Most of the lesions in the parotid space originate in the gland itself, and about 80% of parotid tumors are benign. However, other types of benign and malignant tumors may appear in this area (Table 28.1). Surgical treatment of the parotid gland is a challenging undertaking, due primarily to the intraparenchymal course of the facial nerve.
HISTORY
A mass within the parotid space poses a diagnostic problem, since it may represent inflammatory disease, glandular lesion, lymph node, primary or metastatic tumor, connective tissue tumor, vascular lesion, neural tumor, or other miscellaneous disease. The history, clinical examination, and imaging studies may suggest a specific etiology. The final diagnosis of a lesion in the parotid space may be elusive and, in these situations, relies on pathologic evaluation of the parotidectomy specimen.
PHYSICAL EXAMINATION
A lesion in the parotid space should be inspected carefully and should be evaluated by bimanual palpation; the dimensions and the location of the lesion should be measured and recorded. Detailed inspection of facial nerve function should be performed. Any sign of weakness of the facial nerve branch(es) should be recorded. Fixation of the skin, facial weakness, and pain without other infectious signs strongly suggest the presence of a malignant tumor.
INDICATIONS
Indications for endoscopic parotidectomy include chronic sialadenitis and benign neoplasms located in the tail of the parotid gland.
CONTRAINDICATIONS
Suspected cases of a malignant parotid tumor, sialadenitis during acute inflammation, tumors too large to extract through the surgical wound, and revision surgery are relative contraindications to this technique through an endoscopic approach.
TABLE 28.1 Lesions Reported in the Parotid Space | ||||||||||||||
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PREOPERATIVE PLANNING
Imaging Studies
Imaging studies provide valuable information that can help in the differential diagnosis of a mass in the parotid gland. Both computed tomography (CT) and magnetic resonance imaging (MRI) may be used in evaluating the mass in the parotid gland. While the CT scan is specific in defining the anatomic localization and extent of a mass in the parotid gland, it has limited value in differentiating benign from malignant tumors. The sensitivity, specificity, and accuracy for detecting malignant parotid tumors are approximately 87%, 94%, and 93%, respectively, for MRI scanning. The reliability and associated anatomic information of MRI in parotid gland tumor diagnosis may make MRI the radiographic test of choice although cost and feasibility vary by clinical site. High-resolution ultrasonography (US) may be useful, if available, and may also assist in FNAB.
Fine Needle Aspiration Biopsy
FNAB is a noninvasive, and quick examination which may be useful information for the assessment of parotid lesions. However, the diagnostic utility of FNAB in guiding the extent of surgery remains a matter of controversy.
In my opinion, morbidity, such as hemorrhage, facial nerve damage, and introduction of infection after FNAB, can be minimized using US guidance. Technical factors may reduce the accuracy of diagnosis if the FNAB is not under US image guidance. Misdiagnoses could also result from relatively inexperienced FNAB technique by the pathologist or even the radiologist. Nonetheless, FNAB is a precise, less invasive tool with which to diagnose a mass in the parotid.
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