Falx cerebelli

Last revised by Bahman Rasuli on 5 Oct 2021

The falx cerebelli is a small infolding of the dura in the sagittal plane over the floor of the posterior cranial fossa. It partially separates the two cerebellar hemispheres 1.

The falx cerebelli is attached posteriorly in the midline to the internal occipital crest of the occipital bone where it contains the occipital sinus 2. Its anterior edge exists freely between the partially separated cerebellar hemispheres in the posterior cerebellar notch. Superiorly it is attached to the tentorium cerebelli 1. Inferiorly, it extends to the posterior edge of the foramen magnum. At this point, it sometimes divides into two separate parts which extend anteriorly either side of the foramen magnum 2-3. Abnormalities of the falx cerebelli may be seen in normal individuals but are more common in the setting of brain or craniofacial abnormalities (particularly posterior fossa abnormalities) 5.

  • anteriorly: cerebellum
  • posteriorly: occipital bone
  • inferiorly: foramen magnum 
  • superiorly: tentorium cerebelli 
  • morphology can vary from linear to shapes resembling the letters “Y,” “V,” or “U”
  • duplication or triplication of the falx cerebelli
  • absence of the falx cerebelli may be seen in many instances but is present in nearly 100% of patients with Chiari II malformation 4-5

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