Topics

Topic

design image
Median sulcus of the 4th ventricle

The median sulcus of the 4th ventricle is a crucial midline anatomical landmark located on the floor of the fourth ventricle within the brainstem. It runs longitudinally, dividing the floor into symmetrical right and left halves. This structure is particularly important in neuroanatomy and radiology as it helps orient clinicians to adjacent nuclei and tracts within the rhomboid fossa, which forms the ventricle’s floor. Understanding its appearance on MRI and CT, as well as its clinical significance, is vital for accurate diagnosis and assessment of posterior fossa pathologies.

Synonyms

  • Median groove of the 4th ventricle

  • Sulcus medianus ventriculi quarti

  • Median longitudinal sulcus (floor of 4th ventricle)

Function

  • Acts as a midline anatomical landmark separating the right and left halves of the rhomboid fossa (floor of the 4th ventricle).

  • Aids in identifying the position of nearby cranial nerve nuclei and other brainstem structures during radiological or surgical evaluation.

  • Has no direct physiological function but is important for anatomical orientation.

Arterial Supply

  • Supplied primarily by branches of the posterior inferior cerebellar artery (PICA), a branch of the vertebral artery.

  • Additional minor contributions from the anterior inferior cerebellar artery (AICA) and superior cerebellar artery (SCA).

Venous Drainage

  • Drained by small veins of the medulla and pons, which ultimately empty into the petrosal veins and the superior and inferior petrosal sinuses.

  • Venous drainage also connects with the internal cerebral veins and the great cerebral vein (of Galen).

MRI Appearance

  • T2-weighted MRI:

    • The median sulcus appears as a thin, linear hypointense (dark) line in the midline of the hyperintense (bright) CSF-filled 4th ventricle.

    • Helps define the floor of the ventricle and may be more prominent in thin-slice or high-resolution scans.

  • T1-weighted MRI:

    • The sulcus is typically not distinctly visualized, but the CSF in the ventricle appears hypointense (dark), and the sulcus is seen as a faint midline groove within the floor.

  • FLAIR MRI:

    • Similar to T2, but CSF is suppressed (dark), and the sulcus may appear as a subtle midline indentation in the floor of the ventricle.

CT Appearance

  • The median sulcus itself is not directly visualized on CT due to its fine structure.

  • It may be inferred as the midline division of the 4th ventricle’s floor, with the ventricle appearing as a CSF-density space.

  • Important primarily as a radiological reference for localizing midline in posterior fossa imaging.

MRI images

Median sulcus MRI 3T axial image