Topics

Topic

design image
Crus I of ansiform lobule of cerebellum

Crus I is the superior and anterior segment of the ansiform (posterolateral) lobule of the cerebellum, located within the posterolateral cerebellar hemisphere. It lies superior to Crus II, extending from the primary fissure toward the horizontal fissure. Crus I is composed of cerebellar cortex with densely packed Purkinje cell layers, granular layers, and molecular layers, and white matter tracts connecting to the dentate nucleus and cerebellar peduncles.

Crus I plays a critical role in cognitive and sensorimotor integration, particularly in planning, timing of voluntary movements, and fine coordination of the upper limbs. Its cortical surface is folded into folia, increasing surface area for neural processing. Understanding Crus I anatomy is essential for neuroimaging interpretation, neurosurgical planning, and assessment of degenerative or developmental cerebellar disorders.

Function

  • Participates in fine motor coordination and precision of movements

  • Integrates sensorimotor and cognitive functions

  • Connects to dentate nucleus and cerebral cortex via cerebellar peduncles

  • Contributes to learning of motor sequences and movement timing

Synonyms

  • Crus I lobule

  • Superior ansiform lobule

  • Posterolateral cerebellar lobule

MRI Appearance

T1-weighted images:

  • Crus I appears as intermediate signal gray matter on the cerebellar cortex

  • White matter tracts appear slightly hyperintense relative to gray matter

  • Cortical folia are visible as thin hypointense lines separating cortical gray matter

T2-weighted images:

  • Cerebellar cortex shows intermediate to slightly hyperintense signal

  • White matter tracts appear hypointense, providing contrast for cortical-subcortical differentiation

  • Pathological changes (atrophy, demyelination, or infarction) appear as hyperintense lesions within the cortex or white matter

STIR (Short Tau Inversion Recovery):

  • Gray matter signal remains intermediate

  • Edema, inflammation, or infarcts appear hyperintense, useful for detecting cerebellar stroke, demyelination, or tumor infiltration

T1 Post-Contrast (Gadolinium-enhanced):

  • Normal Crus I shows no enhancement

  • Pathological conditions (tumor, infection, inflammation) demonstrate focal or diffuse enhancement, highlighting abnormal tissue or vascularized lesions

CT Appearance:

  • Crus I is difficult to delineate as gray matter on standard CT, blending with surrounding cerebellar cortex

  • White matter tracts appear slightly hypodense relative to cortical gray matter

  • CT is useful for detecting hemorrhage, mass effect, or calcifications but limited for fine cortical anatomy

MRI images

Crus I of ansiform lobule mri sag image -img-00000-00000