Medial Pterygoid
The medial pterygoid is a deep facial muscle often seen on CT or MRI scans of the head and neck. It plays an important role in chewing and jaw movement. When mentioned in radiology reports, it may indicate an abnormality such as swelling, injury, or mass in the region. Understanding this muscle’s function and its imaging features can help patients better interpret their scan results.
Where Is the Medial Pterygoid?
The medial pterygoid muscle is located deep in the face. It runs from the base of the skull (specifically the pterygoid fossa of the sphenoid bone) to the inner side of the lower jaw (mandibular angle). It works in conjunction with other muscles like the masseter and lateral pterygoid to help with chewing, especially when moving the jaw side to side or closing the mouth.
Function of the Medial Pterygoid Muscle
The main job of the medial pterygoid is to elevate the lower jaw (mandible), allowing you to close your mouth. It also assists in grinding movements by pulling the jaw from side to side, working with the opposite-side lateral pterygoid muscle. This muscle is essential for chewing and speaking.
Medial Pterygoid on MRI
MRI is often used when soft tissue evaluation is necessary. On MRI, the medial pterygoid muscle appears as a symmetric soft tissue structure on both sides of the face. It typically has intermediate signal intensity on T1-weighted images and varies on T2-weighted images depending on the presence of inflammation or injury.
MRI is especially useful for evaluating:
- Muscle tears or strains
- Infection such as abscess or cellulitis
- Tumors or masses in the masticator space
- Spread of cancer from nearby structures like the parotid gland or oropharynx
Asymmetry, abnormal enhancement after contrast, or enlargement may suggest pathology.
Medial Pterygoid on CT Scans
CT scans give excellent detail of bone and adjacent soft tissues, making them useful for assessing trauma or dental issues. The medial pterygoid can be seen as a soft tissue structure medial to the mandible. In the setting of trauma, CT is ideal for identifying:
- Fractures of the mandible involving the pterygoid region
- Swelling or hematoma
- Calcifications in chronic inflammation
- Tumor invasion into surrounding bone or soft tissue
CT is also the preferred imaging when evaluating dental infections that might spread into the masticator space, which contains the medial pterygoid.
Common Conditions Involving the Medial Pterygoid
Masticator Space Infection
Dental infections can spread into the space containing the medial pterygoid. This may appear as swelling and increased signal or enhancement on MRI or low-density areas on CT suggesting abscess formation. Patients often present with pain, jaw stiffness, and fever.
Trismus (Lockjaw)
Inflammation or spasm of the medial pterygoid can cause trismus, or difficulty opening the mouth. This may occur after dental surgery, infection, or trauma. Radiology can help rule out deeper causes like abscess or tumors.
Tumors
Tumors of the head and neck may involve or displace the medial pterygoid. Imaging helps determine if a mass is affecting this muscle directly, or if it is being invaded from adjacent spaces such as the parapharyngeal or parotid region. Malignancies like squamous cell carcinoma or sarcomas may show irregular enhancement or muscle infiltration.
Muscle Atrophy
In cases of nerve injury or long-standing disuse, the medial pterygoid may shrink, or atrophy. This is sometimes seen after trauma or surgery. On MRI, the muscle appears smaller with increased fat signal, and on CT, it looks less dense.
When to Be Concerned
If a radiology report mentions asymmetry, mass effect, or abnormal enhancement of the medial pterygoid, it may warrant further investigation. However, small variations in size or shape between the left and right sides are often normal. In many cases, findings are incidental and not related to any disease.
If symptoms like jaw pain, swelling, or trismus are present, these findings become more relevant and may guide treatment.
How Radiologists Evaluate the Medial Pterygoid
Radiologists assess:
- Symmetry: Comparing both sides of the face
- Signal intensity or density: Looking for inflammation, hemorrhage, or tumors
- Enhancement after contrast: Suggesting infection or neoplasm
- Relationship to nearby structures: Such as the parotid gland, and mandibular nerve
They integrate these findings with the clinical history to provide a meaningful impression.
What to Ask Your Doctor
If your imaging report mentions the medial pterygoid, consider asking:
- Is there a reason it was mentioned, or is it just an observation?
- Are there signs of inflammation or infection?
- Could this relate to my jaw pain or other symptoms?
- Do I need any follow-up imaging or treatment?
Summary
The medial pterygoid muscle is a key structure in chewing and jaw movement. When it appears in radiology reports, it is usually part of an evaluation for trauma, infection, tumor, or dental problems. MRI and CT scans help radiologists assess this muscle and detect any abnormalities. While many mentions are incidental, changes in this muscle can signal a treatable issue when linked to symptoms.
References
- https://pubmed.ncbi.nlm.nih.gov/2082140/
- https://www.ncbi.nlm.nih.gov/books/NBK546588/
- https://doi.org/10.3390/diagnostics15121535