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The parotid gland is wrapped around the mandibular ramus and extends to a position anterior and inferior to the ear. It has superficial and deep lobes, separated by the facial nerve.
The facial nerve and its branches pass through the parotid gland, as does the external carotid artery and retromandibular vein. The external carotid artery forms its two terminal branches within the parotid gland: maxillary and superficial temporal artery.
A fibrous capsule surrounds the gland, formed by the superficial (investing) layer of the deep cervical fascia, creating the parotid space. Posteriorly, this fascia condenses to form the stylomandibular ligament.
The inferior projection of the parotid is often referred to as the "tail", which overlies the angle of the mandible. The tail is not distinct from the rest of the gland, but it has been defined as the inferior 2 cm of the gland 11.
Anteriorly, there is often an accessory parotid gland, which may be separate from the main gland.
There is fatty infiltration or fatty replacement of the parotid glands with age 6.
- superior pole: external acoustic meatus, temporomandibular joint
- lower pole: behind the angle of the mandible, anterior to the sternocleidomastoid and posterior belly of the digastric
- lateral surface: subcutaneous tissue
- anterior surface: clasps the ramus of the mandible with the masseter on its outer surface and medial pterygoid on its inner surface inferiorly (separated by the stylomandibular ligament)
- anterior border: formed by the lateral edge of the anterior surface where it meets the masseter
- deep surface: indented by the mastoid process and its attached muscles (sternocleidomastoid and posterior belly of the digastric), styloid process and its attached muscles (stylohyoid, styloglossus, stylopharyngeus) and two ligaments (stylomandibular, stylohyoid)
- arterial: external carotid artery and a specific branch of the artery, the transverse facial artery
- venous drainage: plexus of veins into the internal jugular vein
Intraparotid nodes drain into the deep cervical chain.
- sensory: auriculotemporal nerve, greater auricular nerve
- parasympathetic: via auriculotemporal nerve
- sympathetic: via plexus surrounding external carotid artery from superior cervical ganglion.
- accessory parotid gland
- facial process: anterior extension of glandular tissue along the parotid duct continuous with the main gland
- ectopic parotid tissue
- parotid duct duplication 7
- congenital agenesis: either unilateral and bilateral 10
Ultrasound is often the first diagnostic procedure to evaluate morphological and structural changes of the parotid gland; for small (<3 cm) and superficial lesions, ultrasound and cytology are often sufficient for a definitive diagnosis 2.
- appears homogeneous with increased echogenicity compared to nearby muscle 1
- intraparotid lymph nodes are normally seen (unlike the submandibular gland)
- retromandibular vein and external carotid artery are also easily seen and by inference the facial nerve, which lies lateral to these vessels 1
- limitations of ultrasound are:
- difficulty visualizing deep lesions: the deep lobe is not able to be assessed as it is protected by the mandibular ramus
- difficulty visualizing deep extension 3
- CT and MRI provide useful additional diagnostic imaging if malignancy is suspected 4, with the sensitivity approaching 100% for detecting parotid neoplasms 5
- the parotid duct and retromandibular vein are usually seen and approximate the plane separating the superficial and deep lobes 12
- 1. Howlett DC. High resolution ultrasound assessment of the parotid gland. Br J Radiol. 2003;76 (904): 271-7. Pubmed citation
- 2. Grazioli L, Olivetti L, Matricardi L et-al. Comparison of ultrasonography, computerized tomography, and magnetic resonance in the study of parotid masses. Radiol Med. 1993;86 (3): 268-80. Pubmed citation
- 3. Izzo L, Casullo A, Caputo M et-al. Space occupying lesions of parotid gland. Comparative diagnostic imaging and pathological analysis of echo color/power Doppler and of magnetic resonance imaging. Acta Otorhinolaryngol Ital. 2006;26 (3): 147-53. Free text at pubmed - Pubmed citation
- 4. Howlett DC, Kesse KW, Hughes DV et-al. The role of imaging in the evaluation of parotid disease. Clin Radiol. 2002;57 (8): 692-701. Pubmed citation
- 5. Cheung RL, Russell AC, Freeman J. Does routine preoperative imaging of parotid tumours affect surgical management decision making?. J Otolaryngol Head Neck Surg. 2009;37 (3): 430-4. Pubmed citation
- 6. Lowe LH, Stokes LS, Johnson JE et-al. Swelling at the angle of the mandible: imaging of the pediatric parotid gland and periparotid region. Radiographics. 2001;21 (5): 1211-27. doi:10.1148/radiographics.21.5.g01se171211 - Pubmed citation
- 7. Aktan ZA, Bilge O, Pinar YA, Ikiz AO. Duplication of the parotid duct: a previously unreported anomaly. (2001) Surgical and radiologic anatomy : SRA. 23 (5): 353-4. Pubmed
- 8. Mcminn. Last's Anatomy. Elsevier Australia. (2003) ISBN:0729537528. Read it at Google Books - Find it at Amazon
- 9. Dongbin Ahn, Chang Ki Yeo, Soon Yong Han, Jeong Kyu Kim. The accessory parotid gland and facial process of the parotid gland on computed tomography. (2017) PLOS ONE. 12 (9): e0184633. doi:10.1371/journal.pone.0184633 - Pubmed
- 10. Teymoortash A, Hoch S. Congenital Unilateral Agenesis of the Parotid Gland: A Case Report and Review of the Literature. (2016) Case reports in dentistry. 2016: 2672496. doi:10.1155/2016/2672496 - Pubmed
- 11. Hamilton BE, Salzman KL, Wiggins RH, Harnsberger HR. Earring lesions of the parotid tail. (2003) AJNR. American journal of neuroradiology. 24 (9): 1757-64. Pubmed
- 12. Imaizumi A, Kuribayashi A, Okochi K, Ishii J, Sumi Y, Yoshino N, Kurabayashi T. Differentiation between superficial and deep lobe parotid tumors by magnetic resonance imaging: usefulness of the parotid duct criterion. (2009) Acta Radiologica. 50 (7): 806-11. doi:10.1080/02841850903049358 - Pubmed