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Primary fissure

The primary fissure of the cerebellum is a prominent, deep groove located on the superior surface of the cerebellum. It serves as a major anatomical landmark, dividing the anterior lobe from the posterior lobe of the cerebellar hemispheres. The primary fissure is crucial in understanding cerebellar anatomy and is often used as a reference point in both neuroanatomical studies and clinical imaging. Its recognition is important in the evaluation of cerebellar disorders and for surgical orientation.

Synonyms:

  • Fissura prima cerebelli (Latin)

  • Fissure prima

  • Anterior-posterior fissure

Arterial Supply:

  • Mainly supplied by branches of the Superior Cerebellar Artery (SCA).

  • The Anterior Inferior Cerebellar Artery (AICA) and Posterior Inferior Cerebellar Artery (PICA) may contribute minor supply, especially at the fissure’s margins.

Venous Drainage:

  • Drained primarily by the superior cerebellar veins.

  • Additional drainage via the inferior cerebellar veins into the straight sinus, transverse sinus, and great cerebral vein (vein of Galen).

Function:

  • Acts as a landmark separating the anterior lobe (involved in spinal cord input and motor control of the trunk and limbs) from the posterior lobe (involved in coordination of fine voluntary movement).

  • Indirectly associated with motor coordination by helping to anatomically define lobes with distinct functional roles.

MRI Appearance:

  • Appears as a deep, linear hypointense (dark) groove on T1- and T2-weighted images separating the anterior and posterior cerebellar lobes.

  • Best visualized on sagittal MRI sections; the fissure runs obliquely, dividing the vermis and hemispheres.

  • Adjacent folia (cerebellar folds) are clearly delineated, aiding identification.

CT Appearance:

  • Less conspicuous than on MRI due to lower soft tissue contrast.

  • May be inferred as a subtle linear cleft between cerebellar lobes on midline sagittal or coronal reconstructions.

  • Sometimes visible in cases of cerebellar atrophy, where the fissures appear more prominent due to volume loss of cerebellar tissue.

MRI images

Primary fissure MRI 3T axial image

MRI images

Primary fissure MRI 3T coronal image

MRI images

Primary fissure MRI 3T sagittal image

CT image

Primary fissure of cerebellum CT sag anatomy image -img-00001-00001