Cerebellum
The cerebellum, meaning "the little brain", sits at the base of the brain in the posterior cranial fossa below the tentorium and behind the brainstem.
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Gross anatomy
The cerebellum has the following features:
- three surfaces: anterior (petrosal), superior (tentorial), inferior (suboccipital)
- three fissures: primary (tentorial), horizontal (petrosal), prebiventral/prepyramidal (suboccipital)
- two hemispheres
- single median vermis
Vermis
The vermis is divided into nine lobules: (in a clockwise rotation, looking at the patient sagittally from his left), and separated into groups by fissures:
- lingula
- central lobule
- culmen: primary (tentorial) fissure
- declive
- folium: horizontal (petrosal) fissure
- tuber: prebiventral/prepyramidal (suboccipital) fissure
- pyramid
- uvula
- nodulus
The subdivisions of the cerebellar vermis can be remembered by this mnemonic.
Cerebellar hemisphere
The cerebellar folia run parallel to the calvaria in an onion-like configuration.
Each of the nine vermis lobules is associated in both sides with two cerebellar hemisphere lobules and therefore the cerebellum has 18 cerebellar hemisphere lobules:
- wing of lingula (lingula)
- wing of central lobule (central lobule)
- quadrangular lobule (culmen): primary (tentorial) fissure
- simple lobule (declive)
- superior semilunar lobule (folium): horizontal (petrosal) fissure
- inferior semilunar lobule (tuber): prebiventral/prepyramidal (suboccipital) fissure
- biventral lobule (pyramid)
- tonsil (uvula)
- flocculus (nodulus)
Connections to brainstem
- to the midbrain via the superior cerebellar peduncles (brachia conjunctiva)
- to the pons via the middle cerebellar peduncles (brachia pontis)
- to the medulla via the inferior cerebellar peduncles (restiform bodies)
CSF cisterns
Blood supply
The cerebellum is essentially supplied by three bilateral vessels from the vertebrobasilar system:
- superior cerebellar artery (SCA): branch of the distal basilar
- anterior inferior cerebellar (AICA): branch of the proximal basilar
- posterior inferior cerebellar (PICA): branch of the distal vertebrals
Superior cerebellar (SCA)
The SCA supplies:
- whole superior surface of the cerebellar hemispheres down to the great horizontal fissure
- the superior vermis
- dentate nucleus
- most of the cerebellar white matter
- superior cerebellar peduncle
- middle cerebellar peduncle
Anterior inferior cerebellar (AICA)
The amount of tissue supplied by the AICA is variable (PICA-AICA dominance) but usually includes:
- middle cerebellar peduncle
- inferolateral portion of the pons
- flocculus
- anteroinferior surface of the cerebellum
Posterior inferior cerebellar (PICA)
The PICA has a variable territory depending on the size of the AICA, but usually supplies:
- posteroinferior cerebellar hemispheres (up to the great horizontal fissure)
- inferior portion of the vermis
- inferior cerebellar peduncle
There are some variations in the PICA:
- 18% arise extracranially, inferior to the foramen magnum
- 10% arise from the basilar rather than vertebral artery
- 2% bilaterally absent
- occasionally loops around the cerebellar tonsil
- occasionally a small vertebral artery will terminate into a common PICA/AICA trunk
It divides into lateral and medial branches that supply the inferior portion of the vermis and cerebellar hemispheres respectively.
Variant anatomy
- cerebellar agenesis
- tonsillar ectopia: asymptomatic protrusion of the tonsils through the foramen magnum by no more than 3-5 mm
Related articles
Anatomy: Brain
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brain
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cerebrum
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cerebral hemisphere (telencephalon)
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brainstem
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cerebellum (part of metencephalon)
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cranial nerves (mnemonic)
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