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Pyramis of vermis

The pyramis of vermis is a small, wedge-shaped structure located in the inferior part of the cerebellar vermis. It forms a prominent part of the posterior cerebellar vermis and is positioned between the uvula above and the tuber vermis below. As part of the cerebellar vermis, the pyramis is involved in the coordination of motor activities, particularly those related to posture and balance. It is best appreciated on midsagittal sections of the cerebellum, both grossly and on neuroimaging.

Synonyms:

  • Pyramis vermis

  • Pyramid of the vermis

  • Cerebellar pyramid

  • Vermian pyramid

Anatomical Description:

  • Wedge-shaped midline structure on the inferior (caudal) aspect of the cerebellar vermis

  • Located between the uvula (superiorly) and the tuber vermis (inferiorly)

  • Forms part of the inferior vermis, within the posterior lobe of the cerebellum

Arterial Supply:

  • Mainly supplied by branches of the posterior inferior cerebellar artery (PICA)

  • Additional supply from branches of the superior cerebellar artery (SCA) and anterior inferior cerebellar artery (AICA) may also contribute, depending on vascular anatomy

Venous Drainage:

  • Drained by the superior and inferior cerebellar veins

  • These veins ultimately drain into the straight sinus, transverse sinus, or the great cerebral vein (vein of Galen)

Function:

  • Involved in the control and coordination of posture and gait

  • Modulates trunk and proximal limb movements

  • Plays a role in balance and muscle tone by integrating sensory and motor information from the body

MRI Appearance:

  • On T1-weighted images: Isointense to surrounding cerebellar cortex; visible as part of the vermian midline structure

  • On T2-weighted images: Iso- to mildly hyperintense compared to surrounding cerebellar cortex

  • Best visualized in midsagittal plane, where it appears as a small, triangular structure between the uvula and tuber

  • No specific imaging characteristics distinguish the pyramis alone in normal cases, but atrophy or malformations (e.g., in Dandy-Walker malformation) can make it more conspicuous

CT Appearance:

  • Difficult to delineate as a separate structure due to limited soft tissue contrast

  • Appears as part of the midline cerebellar vermis, isodense with surrounding cerebellar tissue

  • Can be better appreciated if there is vermian hypoplasia or midline malformation

MRI images

Pyramis of vermis MRI 3T axial image

MRI images

Pyramis of vermis MRI 3T coronal image

MRI images

Pyramis of vermis MRI 3T sagittal image

CT image

Pyramis of vermis of cerebellum CT sag anatomy image -img-00001-00001