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Anterior median fissure of medulla oblongata

The anterior median fissure of the medulla oblongata is a prominent, deep groove located along the midline of the ventral (anterior) surface of the medulla oblongata in the brainstem. This fissure separates the right and left pyramids of the medulla, extending from the lower border of the pons to the decussation of the pyramids, where it becomes less distinct. The fissure serves as an important anatomical landmark and allows for the passage of small perforating blood vessels. Its appearance and clinical significance can be evaluated through various imaging modalities including MRI (T1, T2, FLAIR) and CT scans.

Synonyms

  • Ventral median fissure of medulla

  • Median anterior fissure of medulla

Function

  • Serves as an anatomical landmark for the separation of the right and left medullary pyramids.

  • Allows passage of small perforating arteries supplying the anterior aspect of the medulla.

  • Guides neurosurgeons and radiologists in orientation during anatomical and imaging studies.

Arterial Supply

  • Primarily supplied by branches of the anterior spinal artery, which descends in the floor of the fissure.

  • Supplemented by perforating branches from the vertebral arteries.

  • Small medullary branches enter through the fissure to vascularize the medial medulla.

Venous Drainage

  • Venous blood drains via small anterior median medullary veins.

  • These veins empty into the anterior spinal vein and medullary veins, which ultimately drain into the larger vertebral venous plexus.

MRI Appearance

  • T1-weighted imaging: The anterior median fissure appears as a thin, linear hypointense (dark) groove at the midline anterior medulla.

  • T2-weighted imaging: The fissure may appear as a hyperintense (bright) or fluid-filled linear space at the ventral midline, separating the two pyramids.

  • FLAIR imaging: The fissure remains hypointense or fluid-like (dark), standing out against the relatively hyperintense medullary tissue, but is less conspicuous compared to T2.

CT Appearance

  • The anterior median fissure is typically not well visualized on routine non-contrast CT scans due to limited soft tissue contrast.

  • May be seen as a faint midline linear lucency at the anterior surface of the medulla, especially in high-resolution or thin-slice images.

MRI images

Anterior median fissure of medulla oblongata MRI 3T axial image