Topics

Topic

design image
Flocculus

The flocculus is a small, rounded lobe of the cerebellum located in the posterolateral region of the cerebellar hemisphere, adjacent to the middle cerebellar peduncle and the vestibular nuclei. It is part of the vestibulocerebellum, which also includes the nodulus, and plays a critical role in balance, eye movement coordination, and vestibulo-ocular reflexes.

The flocculus receives afferent input from the vestibular system via the vestibular nuclei and the inferior cerebellar peduncle and sends efferent projections back to the vestibular nuclei, modulating eye movements and posture. Its small size and intimate association with cerebrospinal fluid spaces make it challenging to visualize, but high-resolution imaging can clearly delineate it in both axial and sagittal planes.

Function

  • Coordinates vestibular input and eye movements

  • Maintains balance and posture

  • Regulates vestibulo-ocular reflex (VOR)

  • Participates in motor learning related to gaze stabilization

  • Integrates cerebellar and brainstem signals for smooth coordinated movement

Synonyms

  • Cerebellar flocculus

  • Floccular lobe

  • Vestibulocerebellar lobe

MRI Appearance

T1-weighted images:

  • The flocculus appears as a small, isointense to slightly hypointense structure relative to the cerebellar cortex

  • Well-demarcated against surrounding CSF, which appears hyperintense on T1 FLAIR sequences

  • Pathology such as tumor, infarct, or demyelination may appear as focal hypo- or hyperintense lesions

T2-weighted images:

  • Flocculus is slightly hypointense to isointense relative to cerebellar cortex

  • Surrounded by hyperintense CSF, which highlights its boundaries

  • Edema or demyelinating lesions appear hyperintense, easily distinguishing abnormal tissue

STIR (Short Tau Inversion Recovery):

  • Normal flocculus remains low signal relative to CSF

  • Edema, inflammation, or post-infarct changes appear hyperintense, making STIR useful for acute injury or demyelination

T1 Post-Contrast (Gadolinium-enhanced):

  • Normal flocculus shows minimal or no enhancement

  • Pathological conditions such as tumors, hemangioblastomas, or metastases demonstrate focal or heterogeneous enhancement

CT Appearance:

  • The flocculus is difficult to directly visualize on standard CT due to its small size and surrounding CSF

  • Appears as a soft tissue density nodule within the cerebellar hemisphere

  • Pathology such as hemorrhage, tumor, or calcification can be detected as hyperdense or hypodense foci

  • High-resolution CT with thin sections improves delineation of floccular lesions and posterior fossa structures

MRI images

flocculus of cerebellum mri sag image -img-00000-00000

MRI images

flocculus of cerebellum

CT image

CT Flocculus sag anatomy image -img-00000-00000