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Topic

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Inferior frontal sulcus

The inferior frontal sulcus is a prominent groove located in the lateral aspect of the frontal lobe of the brain. It separates the middle frontal gyrus from the inferior frontal gyrus and plays a significant role as an anatomical landmark for both clinical and radiological assessments. Understanding its location, variants, and imaging features is crucial in the context of neuroimaging, especially in pre-surgical planning, functional studies, and assessment of pathology.

Synonyms

  • Sulcus frontalis inferior

  • Inferior frontal fissure

Function

  • Primarily an anatomical landmark; it does not have a direct function, but:

    • Separates middle and inferior frontal gyri

    • Serves as a guide for localization of Broca's area (important for speech production, located in the inferior frontal gyrus)

    • Used as a reference in functional MRI (fMRI) studies to delineate frontal lobe regions

Arterial Supply

  • Supplied mainly by branches of the middle cerebral artery (MCA), specifically:

    • Prefrontal branches of the MCA

    • Sometimes supplemented by branches from the anterior cerebral artery (ACA) (frontal polar branch)

Venous Drainage

  • Drained via the superior sagittal sinus and superficial middle cerebral vein

  • Smaller cortical veins may also contribute to drainage into the superior anastomotic vein (vein of Trolard)

MRI Appearance

  • T1-weighted imaging:

    • Appears as a hypointense (dark) linear structure between the gray matter of the middle and inferior frontal gyri

  • T2-weighted imaging:

    • Appears as a hyperintense (bright) CSF-filled groove between the cortical gyri

    • Better visualization due to higher CSF contrast

  • FLAIR imaging:

    • Sulcus appears as a hypointense (dark) line, as CSF is suppressed

    • Useful for detecting subtle pathologies involving adjacent cortex or abnormal sulcal effacement

CT Appearance

  • Visible as a low-density (hypodense) linear gap separating the middle and inferior frontal gyri

  • May be less well defined than on MRI, but becomes more conspicuous in the presence of mass effect, edema, or cortical atrophy

MRI images

Inferior frontal sulcus MRI 3T axial image

MRI images

Inferior frontal sulcus MRI 3T sagittal image