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Pars orbitalis of inferior frontal gyrus

The pars orbitalis is a distinct anatomical subdivision of the inferior frontal gyrus (IFG) located in the frontal lobe of the human brain. It forms the anterior-inferior portion of the IFG, lying adjacent to the orbitofrontal cortex and above the lateral orbital sulcus. The pars orbitalis plays a crucial role in language, emotion, and cognitive functions. Its unique anatomical boundaries and connectivity make it a key region in both clinical neuroanatomy and neuroimaging.

Synonyms

  • Brodmann area 47

  • BA47

  • Orbital part of the inferior frontal gyrus

  • Pars orbitalis gyri frontalis inferioris

  • Orbitalis (abbreviated term in neuroimaging)

Arterial Supply

  • Primarily supplied by branches of the middle cerebral artery (MCA), especially the orbital branches of the MCA.

  • Additional minor contributions may arise from the anterior cerebral artery (ACA), particularly the orbitofrontal branches.

Venous Drainage

  • Venous blood is drained mainly via the superior sagittal sinus and superficial middle cerebral vein.

  • Additional drainage may occur through the orbital veins and small cortical veins to adjacent venous sinuses.

Function

  • Involved in semantic processing, particularly in language comprehension and word retrieval.

  • Plays a role in emotion regulation and social cognition due to its proximity to the orbitofrontal cortex.

  • Participates in executive functions such as decision-making and response inhibition.

MRI Appearance

  • T1-Weighted Imaging:

    • Appears as a well-defined cortical ribbon with intermediate signal intensity

  • T2-Weighted Imaging:

    • Gray matter of the pars orbitalis shows higher signal intensity compared to adjacent white matter.

    • Provides good contrast for cortical thickness and sulcal patterns.

  • FLAIR Imaging:

    • Similar to T2, with high signal intensity of cortical gray matter, but improved suppression of CSF signal in adjacent sulci.

    • Useful for detecting subtle cortical lesions or edema involving the pars orbitalis.

CT Appearance

  • On non-contrast CT, the pars orbitalis is not distinctly visible as a separate structure, but forms part of the anterior-inferior frontal cortex.

  • Appears as a region of uniform low attenuation corresponding to cortical gray matter.

  • Pathological changes (such as infarct, edema, or mass lesions) may cause focal hypoattenuation or loss of gray-white differentiation in this area.

MRI images

pars orbitalis of inferior frontal gyrus MRI 3T axiall image

MRI images

pars orbitalis of inferior frontal gyrus MRI 3T sagittal image

CT image

Pars orbitalis of inferior frontal gyrus CT sag anatomy image