Pharyngeal Mucosal Space
This space lies deep to the middle layer of the deep cervical fascia and is anatomically divided into the nasopharynx and oropharynx. Its inferior continuation in the hyoid region is the hypopharynx, which already belongs to the visceral space.
Nasopharynx (Nasopharynx) The upper part of the pharynx, bounded by the skull base superiorly and the soft palate inferiorly. The most significant pathology here is nasopharyngeal carcinoma.
- It most commonly arises in the lateral pharyngeal recess (Rosenmüller fossa).
- The tumor tends to invade the skull base (for example, through the foramen ovale or foramen lacerum).
- There is a strong association with the Epstein-Barr virus (EBV).
- The imaging method of choice is MRI, as it better demonstrates soft-tissue extension.
- For differential diagnosis, it is important to remember benign lesions: adenoid hypertrophy (striated contrast enhancement pattern) and midline Thornwaldt cyst.
Oropharynx (Oropharynx) Includes the tongue base, valleculae, palatine tonsils, and soft palate. Inflammatory processes and malignant tumors frequently develop in this zone.
- Abscesses: Peritonsillar abscess (seen on CT as an enlarged tonsil with central necrosis and ring enhancement) can spread into the parapharyngeal or masticator space.
- Tumors: Almost all of them are squamous cell carcinoma. Today, the proportion of HPV-associated cancer (marker p16) is increasing. Such tumors are more common in younger patients and have a significantly more favorable prognosis.
Carotid and Retropharyngeal Spaces
Carotid Space (Carotid Space) Contains the carotid arteries, internal jugular vein (IJV), and cranial nerves (IX–XII in the suprahyoid part, X in the infrahyoid part).
- Carotid artery dissection: optimally detected on T1-weighted fat-suppressed MRI (hyperintense intramural hematoma is visible).
- Paragangliomas (glomus tumors): vascularized lesions with the classic MRI "salt and pepper" sign (areas of hemorrhage and signal void from blood flow). Carotid paragangliomas characteristically splay the external and internal carotid arteries.
- Schwannomas: fusiform lesions; unlike paragangliomas, they do not cause permeative bone erosion, but rather remodel foramina (e.g., the jugular foramen).
Retropharyngeal Space (Retropharyngeal Space) Most commonly affected secondarily—due to malignant lymphadenopathy in pharyngeal cancer or sinonasal tumors. The key task for the radiologist is to check whether the thin fat-density line of this space is preserved. With lymph node enlargement or the spread of infection, the retropharyngeal space displaces the prevertebral muscles posteriorly.
Masticator Space and Mandible
The masticator space (Masticator Space) includes the muscles of mastication, the posterior part and ramus of the mandible, as well as the mandibular nerve (V3 branch, giving rise to the inferior alveolar nerve).
Mandibular pathologies are extremely diverse, and CT or CBCT is best suited for their evaluation:
- Inflammation and osteonecrosis: Frequently related to teeth. Osteonecrosis can be caused by radiation therapy or bisphosphonate use (MRONJ). CT shows fragmentation, sequestration, and periosteal reaction.
- Tumors:
- Osteomas: well-defined foci (multiple may indicate Gardner syndrome).
- Squamous cell carcinoma: invades from the mucosa.
- Osteosarcoma: a rare tumor with an aggressive sunray periosteal reaction.
- Cysts: Due to remnants of odontogenic epithelium, cysts occur more frequently in the jaws than in other bones. Inflammatory radicular cysts, follicular cysts, and odontogenic keratocysts are distinguished.
Visceral Space and Hypopharynx
The infrahyoid neck contains five spaces, but only one of them is located exclusively here—this is the visceral space (Visceral Space). It includes the thyroid and parathyroid glands, larynx, trachea, and hypopharynx (Hypopharynx).
Anatomically, the hypopharynx consists of the pyriform sinuses, the posterior pharyngeal wall, and the postcricoid region.
- Almost all neoplasms of this zone are squamous cell carcinomas, which are closely associated with smoking and alcohol consumption.
- The majority of tumors are localized in the pyriform sinuses.
- Due to their concealed clinical course, patients often present at advanced stages when massive cervical lymphadenopathy is already present (in 50% of patients at initial presentation).
Briefly: answers to topical questions
What branches does the mandibular nerve give off in the masticator space?
The mandibular nerve gives off a number of branches in the interpterygoid space, predominantly motor branches to the muscles of mastication and sensory branches to adjacent areas.
- Masseteric nerve (n. massetericus) — to the masseter muscle
- Deep temporal nerves (nn. temporales profundi anterior et posterior) — curve around the lateral pterygoid muscle to the temporalis muscle
- Buccal nerve (n. buccalis) — passes between the heads of the lateral pterygoid muscle to the buccal mucosa
- Auriculotemporal nerve (n. auriculotemporalis)
- Inferior alveolar nerve (n. alveolaris inferior) with the n. mylohyoideus branch
- Lingual nerve (n. lingualis) — between the buccal and inferior alveolar nerves
What anatomical structures pass through the foramen ovale of the skull base?
The mandibular nerve—the third division of the trigeminal nerve—passes through the foramen ovale (foramen ovale), along with an accessory meningeal branch.
- Mandibular nerve (n. mandibularis) — exits the cranial cavity through this foramen
- Accessory branch of the meningeal artery
Additionally, it is noted that the meningeal branch of the mandibular nerve (r. meningeus spinosus) branches off inferior to the foramen ovale and enters the skull through the foramen spinosum rather than the foramen ovale.
Which layers of the cervical fascia form the walls of the retropharyngeal space?
The walls of the retropharyngeal space are formed by the visceral layer of the middle cervical fascia anteriorly and the prevertebral fascia posteriorly.
- Anteriorly — the posterior wall of the pharynx, covered by the visceral layer of the deep (4th) cervical fascia
- Posteriorly — the prevertebral fascia
- In the midline — the space is divided into right and left halves by a connective tissue septum
In the suprahyoid neck, the deep cervical fascia is generally represented by three layers that form the boundaries of the true anatomical spaces of the neck.
For differential diagnosis of prevertebral muscle displacement: retropharyngeal space lesions push them posteriorly (since they are located anterior to them), whereas perivertebral space pathologies push them anteriorly.
Class and exam questions
How to differentiate carotid paraganglioma from vagal schwannoma on imaging?
Carotid body paraganglioma characteristically splays the internal and external carotid arteries and demonstrates the "salt and pepper" sign on MRI. A schwannoma, conversely, displaces vessels, has a fusiform shape, and when extending into the jugular foramen, remodels the bone rather than causing aggressive erosion.
What does p16 status mean in oropharyngeal tumors?
p16 is a surrogate biomarker for the human papillomavirus (HPV). HPV-positive squamous cell carcinoma of the oropharynx has significantly better survival rates, which directly impacts staging according to the TNM classification.
What key features should be evaluated when deep neck infections are suspected?
It is critically important to rule out internal jugular vein thrombosis and carefully trace the pathways of purulent spread into adjacent spaces (e.g., parapharyngeal, masticator, or retropharyngeal spaces).
What else to study on this topic
- Pathways of intracranial spread of nasopharyngeal carcinoma (perineurally via the foramen ovale and along fascial planes).
- Differential diagnosis and classification of odontogenic and non-odontogenic cysts of the mandible.
- Criteria for carotid artery involvement in tumor processes (loss of the fat plane, encasement greater than 180 degrees).
- Anatomic landmarks for palatine tonsil borders on MRI (relationship to the faucial pillars and pharyngeal constrictors).
- Medication-related osteonecrosis of the jaw (MRONJ): radiologic patterns and differential diagnosis.
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