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Lateral pterygoid muscle

The lateral pterygoid muscle is a key muscle of mastication located in the infratemporal fossa, playing a crucial role in jaw movements such as opening and protrusion. It is distinct among the muscles of mastication due to its horizontal orientation and dual heads, making it especially relevant in both functional assessment and pathological evaluation in maxillofacial imaging.

Synonyms

  • External pterygoid muscle

  • Musculus pterygoideus lateralis (Latin)

  • Lateral external pterygoid

Anatomy & Function

  • Composed of two heads: superior (upper) and inferior (lower)

  • Origin:

    • Superior head: infratemporal surface and crest of the greater wing of the sphenoid bone

    • Inferior head: lateral surface of the lateral pterygoid plate

  • Insertion: pterygoid fovea of the mandibular condyle, articular disc, and capsule of the temporomandibular joint (TMJ)

  • Action: protrusion and depression of the mandible, lateral movement (side-to-side), and stabilization of the TMJ

  • Innervation: Mandibular nerve (V3 branch of trigeminal nerve)

MRI Appearance

  • Proton Density (PD) Sequence:

    • Appears as a well-defined, homogenous muscle with intermediate signal intensity

    • Slightly hyperintense compared to cortical bone, isointense to adjacent masticatory muscles

    • Clear visualization of the two heads is sometimes possible, especially on oblique coronal and axial images

  • Short Tau Inversion Recovery (STIR) Sequence:

    • Muscle tissue shows  uniform low-to-intermediate signal

    • Enhanced sensitivity to edema, inflammation, or acute injury (will appear hyperintense)

    • Useful for detecting subtle muscle pathology (e.g., myositis, trauma, denervation changes)

  • T1-Weighted Sequence:

    • Lateral pterygoid muscle demonstrates uniform low-to-intermediate signal intensity

    • Excellent delineation from surrounding fat (which is hyperintense)

    • Muscle margins are sharp; separation from the medial pterygoid and temporalis muscles can be appreciated

MRI images

Lateral pterygoid muscle mri image

CT image

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