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Medial pterygoid muscle

The medial pterygoid muscle is one of the key muscles of mastication, located in the deep face region. It plays a crucial role in elevating the mandible and enabling side-to-side jaw movements. Positioned deep to the mandibular ramus, it mirrors the masseter muscle but lies on the inner (medial) aspect of the mandible. The muscle extends from the medial surface of the lateral pterygoid plate (of the sphenoid bone) and the maxillary tuberosity to insert onto the medial aspect of the mandibular angle. Understanding the MRI appearance of the medial pterygoid muscle is essential for evaluating pathologies such as infection, tumor, and trauma in the masticator space.

Synonyms

  • Medial pterygoid

  • Musculus pterygoideus medialis (Latin)

  • Internal pterygoid muscle

MRI Appearance

  • Proton Density (PD):

    • The medial pterygoid muscle demonstrates intermediate signal intensity, similar to other skeletal muscles.

    • The muscle fibers are homogenous, and the outline is well-demarcated from the adjacent fat and bone.

  • Short Tau Inversion Recovery (STIR):

    • On STIR sequences, the medial pterygoid appears as a structure of low signal intensity.

    • There is marked contrast with adjacent fat, which appears hyperintense, making muscle boundaries more conspicuous.

    • Edema or inflammatory changes within the muscle will appear hyperintense on STIR.

  • T1-weighted Imaging (T1):

    • The medial pterygoid muscle typically displays low signal intensity (dark) relative to surrounding fat, which is bright on T1.

    • The anatomy of the muscle and its interface with adjacent structures (mandibular ramus, medial pterygoid plate) are well depicted.

    • Pathologies such as tumor infiltration or muscle atrophy may alter the normal T1 signal pattern.

MRI images

Medial pterygoid muscle mri

CT image

Medial pterygoid muscle CT axial image-img-00000-00000