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Inferior head of lateral pterygoid muscle

The inferior head of the lateral pterygoid muscle is an important masticatory muscle located in the infratemporal fossa. It plays a vital role in mandibular movement, especially in opening the mouth and protruding the jaw. Recognizing this muscle’s anatomy and MRI appearance is essential for accurate evaluation of temporomandibular joint (TMJ) disorders and adjacent pathologies.

Synonyms:

  • Inferior belly of lateral pterygoid

  • Lower head of lateral pterygoid muscle

  • Musculus pterygoideus lateralis caput inferius

Anatomical Description:

  • Origin: Lateral surface of the lateral pterygoid plate of the sphenoid bone.

  • Insertion: Pterygoid fovea on the neck of the mandible.

  • Function: Depresses and protrudes the mandible; assists in lateral jaw movements.

  • Relationship: Positioned inferior to the superior head of the lateral pterygoid; lies close to the TMJ capsule and maxillary artery.

MRI Appearance:

  • Proton Density (PD):

    • Appears as a well-defined, intermediate signal intensity muscle mass.

    • Muscle striations may be visualized, especially in thin slices.

    • Provides good anatomical detail, useful for differentiating muscle from adjacent fat and neurovascular structures.

  • Short Tau Inversion Recovery (STIR):

    • Shows the muscle with low to intermediate signal intensity.

    • Fat is suppressed and appears dark, enhancing the visibility of the muscle.

    • Any edema, inflammation, or pathology in the muscle will appear hyperintense (bright).

  • T1-Weighted Imaging:

    • Muscle displays low to intermediate signal intensity, darker than surrounding fat.

    • Outlines the margins of the inferior head, differentiating it from adjacent fat planes and bone.

    • Useful for assessing muscle atrophy, mass effect, and chronic changes.

MRI images

Inferior head of lateral pterygoid muscle mri