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Neuroradiology Case of the Week

Case 425

July 2009

Balasubramanya Kolar, MD, Henry Wang, MD, PhD,
and P-L Westesson, MD, PhD, DDS

Clinical Presentation: A 54-year-old female with history of lung carcinoma underwent MRI for evaluation of metastatic lesions.

Imaging Findings: MRI showed bilateral and symmetrical extension of the parotid gland much anterior than normally found. A comparative image in a control patient shows the normal extent of the gland.

Diagnosis: Accessory parotid gland

Discussion: Accessory parotid glands which may be extensions of the main parotid gland are found in approximately 21% of the population [1].They are usually located between the skin and masseter muscle about 6mm anterior to the main parotid gland [2]. Both the main and accessory parotid glands drain in to the Stensen's duct. The zygomatic and buccal rami of the facial nerve run superficial to the accessory parotid gland [1].
     The most common tumor of the accessory gland is a pleomorphic adenoma.The majority of lesions are benign tumors accounting for about 50- 74% [3].Both the glands do share histological properties however there have been some studies which showed the glands to be more similar to submandibular glands in their histological composition [4].

References:

1. Frommer J. The human accessory parotid gland: Its incidence, nature, and significance. Oral Surg Oral Med Oral Pathol. 1977 May;43(5):671-6. PMID: 266146 [PubMed]
2. Batsakis JG. Accessory parotid gland. Ann Otol Rhinol Laryngol. 1988 Jul-Aug;97(4 Pt 1):434-5. PMID: 3408119 [PubMed]
3. Perzik SL, White IL. Surgical management of the preauricular tumors of the accessory parotid apparatus. Am J Surg. 1966 Oct;112(4):498-503. PMID: 5915294 [PubMed]
4. Toh H, Kodama J, Fukuda J, Rittman B, Mackenzie I. Incidence and histology of human accessory parotid glands. Anat Rec. 1993 Jul;236(3):586-90. PMID: 8363063 [PubMed]