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Temporalis muscle

The temporalis muscle is a broad, fan-shaped muscle located on the lateral aspect of the skull, forming part of the muscles of mastication. It originates from the temporal fossa and the temporal fascia, converging inferiorly to insert onto the coronoid process of the mandible. The muscle plays a crucial role in elevating and retracting the mandible during chewing. On MRI, the temporalis muscle demonstrates typical skeletal muscle signal characteristics, but recognizing its normal appearance is essential for distinguishing pathology from normal anatomical variations.

Synonyms

  • Musculus temporalis

  • Temporal muscle

  • Muscle of the temporal region

MRI Appearance of Temporalis Muscle

1. Proton Density (PD) Sequence

  • The temporalis muscle appears as a homogenous structure with intermediate signal intensity, slightly higher than cortical bone but lower than subcutaneous fat.

  • Muscle fascicles and surrounding fascia can sometimes be seen as fine linear hypointense lines.

2. Short Tau Inversion Recovery (STIR) Sequence

  • The muscle demonstrates intermediate to low signal intensity.

  • Increased signal may be observed only in the presence of edema, inflammation, or acute pathology.

  • The fascia appears as a low-signal-intensity rim outlining the muscle.

3. T1-Weighted Sequence

  • The temporalis muscle exhibits low to intermediate signal intensity, darker than surrounding fat.

  • Clear contrast between the temporalis muscle and the adjacent temporalis fat pad, which appears hyperintense (bright) on T1.

  • Well-defined margins without focal abnormalities in normal cases.

MRI images

Temporalis muscle mri image

CT image

Temporalis muscle CT axial image-img-00000-00000