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Clinical Anatomy Richard Snell
INTRODUCTION
It is a structure within the central nervous system.
It has an important role in motor control, with cerebellar dysfunction often presenting with motor signs.
In particular, it is active in the coordination1, precision2 and timing of movements3, as well as in motor learning4.
By Khaleel Alyahya, PhD, MEd
LOCATION
The cerebellum is located at the back of the brain inferior to occipital and temporal lobe, and within the posterior cranial fossa.
It is separated from these lobes by the tentorium cerebelli, a tough layer of dura mater.
It lies at the same level of the pons posteriorly, from which it is separated by the fourth ventricle.
Posterior and lateral to the cerebellum are the occipital bone and its overlying layer of dura mater.
By Khaleel Alyahya, PhD, MEd
ANATOMICAL STRUCTURE
The cerebellum consists of two hemispheres which are connected by the vermis, a narrow midline area.
Like other structures in the CNS, the cerebellum consists of grey matter and white matter:
• Grey matter located on the surface of the cerebellum. It is tightly folded, forming the cerebellar cortex.
• White matter located underneath the cerebellar cortex. Embedded in the white matter are the four cerebellar nuclei.
o dentate, emboliform, globose, and fastigi nuclei.
By Khaleel Alyahya, PhD, MEd
DIVISIONS
There are three ways that the cerebellum can be subdivided.
• Anatomical lobes
ANATOMICAL LOBES
There are three anatomical lobes that can be distinguished in the cerebellum:
• The anterior lobe
• The posterior lobe
• The flocculonodular lobe
• The primary fissure
• The posterolateral fissure
CEREBRAL LOBES
The anterior lobe extends from the level of the cerebellar peduncles anteriorly and includes the anterior two-thirds of the superior vermis, along with the anterior third of each hemisphere. This lobe terminates at the primary fissure.
From this point posteriorly and laterally and continuing along the inferior surface to the posterolateral fissure is the larger posterior lobe.
The flocculonodular lobe is a flattened lobe that lies between the posterolateral fissure (inferiorly) and the inferior medullary velum and the cerebellar peduncles (superiorly).
By Khaleel Alyahya, PhD, MEd
ZONES
In the midline of the cerebellum is the vermis.
Either side of the vermis is the intermediate zone.
Lateral to the intermediate zone are the lateral hemispheres.
There is no difference in gross structure between the lateral hemispheres and intermediate zones
By Khaleel Alyahya, PhD, MEd
FUNCTIONAL DIVISIONS
• The cerebrocerebellum
• The spinocerebellum
• The vestibulocerebellum
CEREBROCEREBELLUM
It is involved in planning movements and motor learning.
It receives inputs from the cerebral cortex and pontine nuclei and sends outputs to the thalamus and red nucleus.
This area also regulates coordination of muscle activation and is important in visually guided movements.
By Khaleel Alyahya, PhD, MEd
SPINAOCEREBELLUM
Comprised of the vermis and intermediate zone of the cerebellar hemispheres.
This region is responsible for the maintaining balance.
It is involved in skilled, volitional movements.
It also receives proprioceptive information.
It consists of the lobes near the midline.
By Khaleel Alyahya, PhD, MEd
VESTIBULOCEREBELLUM
The functional equivalent to the flocculonodular lobe.
It is involved in controlling balance and ocular reflexes, mainly fixation on a target.
It receives inputs from the vestibular system and sends outputs back to the vestibular nuclei.
By Khaleel Alyahya, PhD, MEd
CEREBELLAR PEDUNCLES
There are three-foot processes that not only anchor the cerebellum to the brainstem, but also provide a pathway for neuronal tracts to travel to and from the cerebellum.
These structures are the superior, middle and inferior cerebellar peduncles.
The following are connections between the cerebellum and the respective parts of the brainstem:
• To midbrain: superior cerebellar peduncles
• To pons: middle cerebellar peduncles
• To medulla: inferior cerebellar peduncles
By Khaleel Alyahya, PhD, MEd
BLOOD SUPPLY
The cerebellum receives its blood supply from three paired arteries:
• Superior cerebellar artery (SCA)
• Anterior inferior cerebellar artery (AICA)
• Posterior inferior cerebellar artery (PICA)
The SCA and AICA are branches of the basilar artery, which wraps around the anterior aspect of the pons before reaching the cerebellum.
The PICA is a branch of the vertebral artery.
By Khaleel Alyahya, PhD, MEd
VENOUS DRAINAGE
Venous drainage of the cerebellum is by the superior and inferior cerebellar veins.
Then they drain into:
• The superior petrosal sinuses
CLINICAL NOTES
Damage to the cerebellum often causes motor-related symptoms.
It depends on the part of the cerebellum involved and how it is damaged.
Damage to the flocculonodular lobe may show loss of equilibrium by difficulty in balancing (irregular walking gait).
Damage to the cerebrocerebellum will cause problems with
planned movements.
Damage to the lateral zone typically causes problems in skilled
voluntary and planned movements which can cause errors in the
force, direction, speed and amplitude of movements.
By Khaleel Alyahya, PhD, MEd
QUESTIONS?