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Nodule of vermis (X)

The nodule of the vermis is the most inferior lobule of the cerebellar vermis, corresponding to lobule X in the Larsell classification. It forms part of the flocculonodular lobe, a phylogenetically old structure (archicerebellum) primarily involved in vestibular function and balance. The nodule projects into the fourth ventricle and is continuous laterally with the flocculi. Together, the nodule and flocculi form the vestibulocerebellum, which integrates vestibular, visual, and proprioceptive input for maintaining equilibrium and coordinating eye movements.

Synonyms

  • Lobule X of the cerebellar vermis

  • Cerebellar nodule

  • Vermian nodule

  • Part of the flocculonodular lobe

Function

  • Integrates vestibular input for balance and posture control

  • Coordinates eye movements (vestibulo-ocular reflex)

  • Contributes to equilibrium and spatial orientation

  • Works with flocculi as part of the vestibulocerebellum

  • Lesions can result in truncal ataxia, nystagmus, and balance disturbance

MRI Appearance

T1-weighted images:

  • The nodule appears as isointense to slightly hypointense relative to cerebellar cortex

  • Surrounded by hypointense CSF of the fourth ventricle, giving sharp contrast

  • Pathology (e.g., medulloblastoma) often arises from this region and may appear as a hypointense mass with post-contrast enhancement

T1 Post-Contrast (Gadolinium-enhanced):

  • Normal nodule shows no enhancement

  • Pathological processes (e.g., tumors, inflammation, demyelination) show variable enhancement, highlighting abnormal tissue

T2-weighted images:

  • Nodule is isointense to slightly hyperintense compared to cerebellar cortex

  • Fourth ventricle CSF appears bright (hyperintense), clearly outlining the structure

  • Helpful for detecting edema, demyelination, or infiltrative lesions

STIR (Short Tau Inversion Recovery):

  • Normal nodule shows intermediate signal

  • Lesions, edema, or infiltrative pathology appear hyperintense

  • Useful for highlighting subtle abnormalities against suppressed background fat signal

CT Appearance:

  • On non-contrast CT, the nodule is seen as a soft tissue density structure projecting into the roof of the fourth ventricle

  • Surrounded by hypodense CSF, which provides natural contrast

  • Calcifications are rare but may be seen in some congenital or neoplastic conditions

  • CT is particularly useful for posterior fossa mass effect, hydrocephalus, or calcified lesions

MRI images

Nodule of Vermis (X) of Cerebellum mri sag image -img-00000-00000