Definition used here
The radiological convention calls the prestyloid compartment the parapharyngeal space and the poststyloid compartment the carotid space. This convention facilitates differential diagnosis. [4–6]
Parapharyngeal Space
The parapharyngeal space (PPS), also called the prestyloid parapharyngeal space, is a deep head and neck compartment around which most other suprahyoid fascial spaces are arranged. It consists largely of fat and neurovascular structures, with the retromandibular part of the deep lobe of the parotid gland included in some definitions.
Reference Images
Shape and extent
An inverted pyramid with its base at the skull base and its inferior apex pointing toward the greater cornu of the hyoid bone. [2]
On axial CT/MRI it appears triangular, with density or signal consistent with fat.
Localization
Displacement of PPS fat helps localize lesions in adjacent deep neck spaces.
A primary PPS lesion displaces the carotid space posteriorly and the pharynx medially.
Terminology
Two naming conventions coexist. The convention familiar to most head and neck surgeons divides the parapharyngeal space into prestyloid and poststyloid (retrostyloid) compartments. [1–3,10] This page uses the radiological convention described above.
Other names include the lateral pharyngeal space and pharyngomaxillary space; less common terms are pterygomaxillary, pterygopharyngeal, peripharyngeal and pharyngomasticatory space. [1] Although pterygomandibular space has rarely been used for this location, that term is best reserved for the subcompartment of the masticator space.
Contents
- Fat: the main component.
- Vessels: internal maxillary artery and ascending pharyngeal artery, depending on their courses; the portion of the pterygoid venous plexus surrounded by fat (the remainder lies in the masticator space).
- Nerve: a small branch of the mandibular division of the trigeminal nerve (cranial nerve V3), supplying the tensor veli palatini muscle. [15]
- Salivary tissue: minor or ectopic salivary glands/rests; the retromandibular portion of the deep lobe of the parotid gland in some definitions. [1–3]
Lymph nodes and muscle are excluded from the radiological definition. The supplied mnemonic for the contents is FATPIG; an expansion was not supplied.
Boundaries
The complex fascial margins occupy the space between the muscles of mastication and the muscles of deglutition. [1–6]
| Aspect | Boundary |
|---|---|
| Superior | Base of skull. |
| Inferior | Greater cornu of the hyoid bone; some authors describe a functional end higher, at the styloglossus muscle at the level of the angle of the mandible. [1] |
| Medial | Middle layer of the deep cervical fascia covering the superior pharyngeal constrictor and levator and tensor veli palatini muscles. |
| Lateral | Superficial layer of the deep cervical fascia extending between the styloid process and mandibular ramus, covering the parotid and lateral pterygoid muscle. Some authors describe the fascia as creating the stylomandibular tunnel through which part of the deep lobe of the parotid protrudes into the space. [1] |
| Anterior | Pterygomandibular raphe and superficial layer of the deep cervical fascia covering the medial pterygoid muscle. |
| Posterior | An extension of tensor veli palatini fascia, termed the tensor-vascular-styloid fascia [1,10–12]; alternatively, an extension of fascia of the stylopharyngeus, styloglossus and levator veli palatini muscles [13,14]. |
Relations
| Relationship | Adjacent space or structure |
|---|---|
| Posteromedial to | Masticator space, particularly the medial pterygoid muscle. |
| Anteromedial to | Parotid space. |
| Posterolateral to | Pharyngeal mucosal space. |
| Anterolateral to | Prevertebral space, retropharyngeal space and danger space. |
| Anterior to | Carotid (poststyloid parapharyngeal) space. |
| Overlaps with | Infratemporal fossa. [5] |
CT/MRI and displacement patterns
The space is triangular in the axial plane and has fat density/signal. The displacement patterns below aid localization of lesions in adjacent deep head and neck spaces.
| Lesion origin | Direction of fat displacement |
|---|---|
| Masticator space | Posteromedially |
| Parotid space | Anteromedially |
| Pharyngeal mucosal space | Posterolaterally |
| Retropharyngeal, danger or prevertebral space | Anterolaterally |
| Carotid (poststyloid parapharyngeal) space | Anteriorly |
Primary PPS involvement: the carotid space is displaced posteriorly and the pharynx medially.
Related pathology
Lesions involving the prestyloid PPS include: [7]
Tumors
- Salivary gland tumors (most common), most commonly pleomorphic adenoma.
- Neurogenic tumors, such as trigeminal schwannoma.
- Lipoma.
Tumor source markers: [8,9].
Inflammatory and developmental lesions
- Parapharyngeal abscess or phlegmon/cellulitis.
- Cystic hygroma/lymphangioma.
- Second branchial cleft cyst in an atypical location.
Additional items on the supplied PPS slide
The teaching slide also lists venous malformations, asymmetric pterygoid venous plexus, and benign and malignant salivary tumors. The third graphic compares the adjacent pharyngeal mucosal space; its pathology list applies to that space.
Source limitations
The supplied prose contains numbered citation markers, preserved here in brackets, but no bibliography or reference links. The references therefore cannot be identified from the supplied material. Alternative definitions of the inferior limit, posterior fascia and parotid inclusion are retained as supplied.
The three teaching graphics are reproduced unchanged. No separate figure captions or attribution details were supplied; captions describe their visible annotations.