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Paramedian lobule

The paramedian lobule of the cerebellum is a distinct anatomical region situated on the inferior and lateral aspect of the cerebellar hemisphere. It is primarily found in the posterior lobe, spanning both the superior and inferior surfaces, but more prominent on the ventral (inferior) side. This lobule is involved in the integration and coordination of complex motor activities, especially those associated with the limbs. It plays a vital role in the modulation of voluntary movements, motor learning, and balance.

Synonyms:

  • Paramedian lobule

  • Lobulus paramedianus

  • Paramedian cerebellar lobule

  • Intermediate cerebellar lobule (less commonly used)

Arterial Supply:

  • Supplied mainly by branches of the Posterior Inferior Cerebellar Artery (PICA).

  • The lateral portion may receive blood supply from the Anterior Inferior Cerebellar Artery (AICA).

  • Superior aspects can also have contributions from the Superior Cerebellar Artery (SCA).

Venous Drainage:

  • Venous blood from the paramedian lobule drains via the superior and inferior cerebellar veins.

  • These veins ultimately empty into the straight sinus, transverse sinus, and sometimes directly into the vein of Galen.

Function:

  • Coordination of Voluntary Movements: Integrates sensory and motor information for smooth, coordinated movements, especially of the limbs (arms and legs).

  • Motor Learning: Plays a role in adapting and refining learned motor skills.

  • Balance and Posture: Contributes to the maintenance of equilibrium and postural stability.

  • Integration of Proprioceptive Input: Processes information from the spinal cord and cerebral cortex for precise movement adjustments.

MRI Appearance:

  • T1-weighted images: The paramedian lobule appears isointense to the surrounding cerebellar cortex, with the white matter core (arbor vitae) appearing slightly hyperintense.

  • T2-weighted images: The cortical region of the lobule is hyperintense relative to white matter.

  • High-resolution 3D imaging: Reveals detailed foliation and separation from adjacent lobules.

  • Pathological findings: Lesions may appear as areas of signal abnormality, depending on the underlying condition (e.g., infarct, demyelination).

CT Appearance:

  • Non-contrast CT: The paramedian lobule is not distinctly demarcated but forms part of the cerebellar hemisphere, with density similar to the rest of the cerebellar cortex.

  • Contrast-enhanced CT: May help highlight vascular structures, but individual lobules remain difficult to distinguish without pathology.

  • Pathological changes: Infarcts or hemorrhages in this region will present as hypodense (infarct) or hyperdense (acute hemorrhage) areas in the paramedian region of the cerebellar hemisphere.

MRI images

Paramedian lobule MRI 3T axial image

MRI images

Paramedian lobule MRI 3T coronal image

MRI images

Paramedian lobule MRI 3T sagittal image

CT image

Paramedian lobule CT sag anatomy image -img-00001-00001