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Rostrum of corpus callosum

The rostrum of the corpus callosum is the thin, curved anterior-inferior portion of the corpus callosum, forming the ventral “beak” of this major commissural fiber tract in the brain. It extends from the genu and curves downward and backward beneath the frontal horns of the lateral ventricles, connecting the orbital surfaces of the frontal lobes. Despite its small size, the rostrum plays a critical role in interhemispheric communication, particularly for the basal and prefrontal areas. Understanding its anatomy, vascular supply, venous drainage, and imaging appearances is essential for accurate interpretation in neuroradiology.

Synonyms

  • Beak of the corpus callosum

  • Rostrum corporis callosi

Function

  • Facilitates interhemispheric communication, especially for the orbital and basal regions of the frontal lobes

  • Contains commissural fibers connecting analogous regions in both hemispheres

  • Plays a role in integrating cognitive and executive functions between the frontal lobes

Arterial Supply

  • Primarily supplied by the pericallosal branch of the anterior cerebral artery (ACA)

  • The subcallosal artery (a branch of the ACA) may contribute minor supply

  • Collateral contribution from small branches of the anterior communicating artery in some cases

Venous Drainage

  • Drains mainly into the anterior septal veins

  • These veins converge into the internal cerebral veins

  • Venous blood ultimately drains into the vein of Galen and then the straight sinus

MRI Appearance

T1-weighted MRI

  • Appears as a thin, curvilinear structure of intermediate signal intensity (similar to white matter)

  • Clearly separates the frontal horns of the lateral ventricles inferiorly

T2-weighted MRI

  • Intermediate to low signal intensity (reflecting white matter composition)

  • Well-delineated from the surrounding CSF (which appears hyperintense)

FLAIR MRI

  • Low signal (white matter)

  • Surrounding CSF is suppressed, improving the definition of the rostrum against ventricular fluid

Post-Contrast T1-weighted MRI

  • Normally, no enhancement is seen in the rostrum of the corpus callosum

  • Any abnormal enhancement suggests pathology (e.g., demyelination, tumor, infection)

CT Appearance

  • Appears as a thin, hypodense white matter band beneath the frontal horns

  • Less distinctly visualized compared to MRI due to lower contrast resolution

  • No intrinsic enhancement on post-contrast CT

  • May be better appreciated in thin-slice or reformatted images

MRI images

Rostrum of corpus callosum mri 3t coronal image

MRI images

Rostrum of corpus callosum mri 3t sagittal image