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Superior head of lateral pterygoid muscle

The superior head of the lateral pterygoid muscle is a key muscle of mastication, located in the infratemporal fossa. It originates from the infratemporal surface and infratemporal crest of the greater wing of the sphenoid bone and inserts into the articular disc and capsule of the temporomandibular joint (TMJ), as well as the pterygoid fovea of the mandibular condyle. The superior head functions primarily in stabilizing and controlling the movements of the TMJ, especially during closing of the jaw. Due to its crucial role in jaw dynamics and frequent association with TMJ disorders, it is a focus of clinical and radiological evaluation.

Synonyms

  • Upper head of lateral pterygoid muscle

  • Caput superius musculi pterygoidei lateralis (Latin)

  • Superior division of lateral pterygoid

MRI Appearance of the Superior Head of Lateral Pterygoid Muscle

• Proton Density (PD) Sequence:

  • The superior head appears as a well-defined, isointense to mildly hyperintense structure compared to adjacent muscles.

  • It is located anteromedially to the TMJ, often distinguishable from the inferior head by subtle differences in signal and orientation.

• Short Tau Inversion Recovery (STIR) Sequence:

  • On STIR images, the muscle shows low to intermediate signal intensity, similar to other skeletal muscles.

  • Any pathology, such as edema or inflammation, would appear as a bright (hyperintense) signal within the muscle fibers.

• T1-Weighted Sequence:

  • The superior head typically appears as an intermediate (isointense) structure relative to adjacent muscles.

  • Clear anatomical margins help in differentiating it from fat (which is hyperintense on T1) and from adjacent bone (which is hypointense).

MRI images

Superior head of lateral pterygoid muscle mri