eRadiograph Volume 7: Imaging of Oral Cavity | Page 222

Parotid Space
Introduction, Anatomy and Content
The parotid space extends superiorly from the external auditory canal and mastoid tip
inferiorly to the angle of the mandible. The parotid space is a superficial space which is
posterior to the masticator space, lateral to the parapharyngeal space and carotid
space. The posterior cervical and perivertebral spaces are posterior to the parotid
space. The posterior belly of the digastric muscle separates the carotid space from the
parotid space.
The contents of the parotid space are the parotid gland, intraparotid/extra parotid
lymph nodes, retromandibular vein, external carotid artery, extracranial branches of
facial nerve. Nearly all pathologies in the parotid space arise from the parotid gland.
The parotid gland is the largest of the salivary glands. The other salivary glands are the
submandibular, sublingual and minor salivary glands which are submucosal clusters of
salivary glands located in the soft palate, oral cavity, palate and upper areodigestive
tract. The bulk of the gland lies superficial to the masseter muscle and mandibular
ramus. Though the parotid is a single contigous structure from a surgical perspective it
is divided into superficial and deep lobes by the course of the facial nerve. the facial
nerve runs lateral to the retromandibular vein. The deep portion of the parotid gland
extends through the stylomandibular tunnel to abut the parapharyngeal space. The
stylomandibular tunnel is formed by the skull base, posterior margin of mandibular
ramus and styloid process/stylomandibular ligament.
The facial nerve enters the posteromedial aspect of the gland dividing into two main
trunks before dividing into 5 main branches the temporal, zygomatic, buccal,
mandibular and cervical nerve. The auriculotemporal nerve in embedded in the parotid
capsule it curves around the mandibular ramus connecting with the mandibular
branch of trigeminal nerve – this is a potential route of perineural spread.

The parotid duct which is approximately 7 cm long arises from the anterior aspect of
the gland passing horizontally lateral to the masseter muscle and medial to the
zygomaticus major muscles, piercing the buccinator muscle opening into a papilla in
the bucal mucosa opposite the second maxillary molar.
Intraparotid lymph nodes occur – this is due to the fact that there is late encapsulation
of the parotid gland during development as well as there is close intimacy between the
parotid gland and lymphatic system. 3 – 24 lymph nodes are seen within the parotid
gland. A painless expanding lesion in the parotid may be a neoplasm, cyst or a lymph
node

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Parotid Space

In approximately 20% of the population accessory parotid tissue is seen anterior to the
parotid gland overlying the masseter muscle between the muscle and the zygomatic
arch.