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Posterolateral fissure

The posterolateral fissure of the cerebellum is a deep, prominent anatomical groove located on the inferior surface of the cerebellum. It serves as a key landmark, separating the flocculonodular lobe (the oldest phylogenetic part of the cerebellum, also called the vestibulocerebellum) from the posterior lobe (neocerebellum). This fissure runs transversely and can be seen dividing the cerebellar hemispheres as well as the vermis. Its identification is crucial in neuroanatomy and neuroimaging for understanding the lobar anatomy of the cerebellum and localizing cerebellar pathologies.

Synonyms

  • Fissura posterolateralis (Latin)

  • Posterolateral cerebellar fissure

  • Fissure of Vicq d’Azyr (historical, less commonly used)

Arterial Supply

  • Posterior Inferior Cerebellar Artery (PICA): Major supply to the region around the posterolateral fissure, especially the flocculonodular lobe and inferior vermis.

  • Anterior Inferior Cerebellar Artery (AICA): Contributes minor branches, especially to the lateral parts of the cerebellar hemispheres.

  • Superior Cerebellar Artery (SCA): Supplies the superior aspects of adjacent cerebellar lobes but less directly related to the fissure itself.

Venous Supply

  • Inferior Cerebellar Veins: Drain blood from the region adjacent to the posterolateral fissure into the straight, transverse, and sigmoid sinuses.

  • Superior and Inferior Vermian Veins: Drain the medial portions of the fissure and the adjacent vermis.

Function

  • Anatomical Landmark: Separates the flocculonodular lobe (vestibulocerebellum) from the posterior lobe, thus helping define functional regions of the cerebellum.

  • Clinical Relevance: Helps localize lesions or pathologies that affect balance, vestibular function, and coordination.

  • No Direct Functional Role: The fissure itself does not perform a function, but the structures it demarcates (especially the flocculonodular lobe) are critical for equilibrium and coordination of eye movements.

MRI Appearance

  • T1-Weighted and T2-Weighted Images: Appears as a thin, dark (hypointense) linear structure separating the brighter cerebellar cortex and white matter.

  • Well-Defined in Sagittal and Coronal Planes: The fissure is best visualized on mid-sagittal and coronal images, helping in lobar identification.

  • Adjacent Structures: The flocculonodular lobe lies anterior/inferior to the fissure; the posterior lobe lies posterior/superior.

CT Appearance

  • Non-Contrast CT: The fissure may appear as a subtle hypodense (dark) line, but is often less conspicuous than on MRI.

  • Contrast-Enhanced CT: Enhancement is not seen in the fissure itself, but adjacent vascular structures (arteries and veins) may be visible.

  • Best Seen in Thin Sections: Fine cuts in the axial or coronal plane may allow identification, but MRI remains superior for detailed anatomy.

MRI images

Posterolateral fissure MRI 3T axial image

MRI images

Posterolateral fissure MRI 3T coroal image

MRI images

Posterolateral fissure MRI 3T sagittal image

CT image

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