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Topic

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Superficial part of masseter

The superficial part of the masseter is the larger and more prominent portion of the masseter muscle, a key muscle involved in mastication (chewing). Located on the lateral surface of the mandibular ramus, this part is thick, rectangular, and overlies the deeper (deep) part of the masseter. It originates from the zygomatic arch and inserts onto the angle and lower lateral surface of the mandible, playing a crucial role in elevating the mandible and closing the jaw.

Synonyms

  • Superficial head of masseter

  • Superficial masseter muscle

  • Pars superficialis musculi masseteris

  • Masseter pars superficialis

MRI Appearance

Proton Density (PD):

  • The superficial masseter displays intermediate to low signal intensity on PD-weighted images.

  • Muscle fibers are visualized as a striated structure.

  • Fat between muscle bundles may show slightly higher signal.

Short Tau Inversion Recovery (STIR):

  • Low signal intensity in normal, healthy muscle due to suppression of fat and fluid.

  • Pathological changes (e.g., edema, inflammation) will appear as areas of high signal intensity.

  • Distinct margin between muscle and adjacent fat, which is suppressed on STIR.

T1-Weighted Imaging:

  • Intermediate to low signal intensity typical of skeletal muscle.

  • Well-defined, rectangular appearance along the mandibular ramus.

  • Fatty tissue between muscle fibers or in the surrounding area appears hyperintense (bright), providing contrast.

  • Useful for assessing muscle atrophy or fatty infiltration.

MRI images

Superficial part of masseter muscle mri