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Mandibular fossa

The mandibular fossa is a concave depression located on the inferior surface of the temporal bone, forming part of the temporomandibular joint (TMJ). It accommodates the condylar process of the mandible, allowing for smooth articulation and jaw movement. This anatomical structure plays a crucial role in mastication, speech, and facial expression. The integrity of the mandibular fossa is essential for normal TMJ function and is frequently evaluated in cases of joint pain, dysfunction, or trauma.

Synonyms:

  • Glenoid fossa

  • Articular fossa

  • Temporal fossa (contextual, though less precise)

MRI Appearance of the Mandibular Fossa:

• Proton Density (PD):

  • The mandibular fossa appears as a hypointense (dark) bony structure.

  • Margins are well-defined against the hyperintense (bright) joint space and articular disc.

  • PD images provide good anatomical detail of the TMJ without high fluid sensitivity.

• Short Tau Inversion Recovery (STIR):

  • The mandibular fossa remains hypointense due to its bony composition.

  • STIR sequences highlight soft tissue edema and joint effusions as hyperintense (bright).

  • The fossa borders serve as anatomical landmarks for identifying joint pathology or fluid accumulation.

• T1-Weighted Imaging:

  • The cortical bone of the mandibular fossa is hypointense (very dark), while the marrow space (if visible) is relatively hyperintense (bright).

  • Provides excellent contrast between bone, marrow, articular disc, and adjacent soft tissues.

  • Useful for detecting bone marrow pathology, erosions, or cystic changes within the mandibular fossa.

MRI images

Mandibular fossa