The cerebellum, derived from the Latin words for little brain, is a structure of the central nervous system. It has an important role in motor control, and cerebellar dysfunction often presents itself as motor signs. It is primarily involved in the coordination, precision and timing of movements, as well as in motor learning.
During embryonic development, the anterior portion of the neural tube gives rise to the brain and its associated structures- the Forebrain (prosencephalon), the Midbrain (mesencephalon), and the Hindbrain (rhombencephalon). The hindbrain subsequently divides into the metencephalon (superior) and the myelencephalon (inferior), from which the cerebellum develops. It is located at the posterior of the brain, immediately inferior to the occipital and temporal lobes, and within the posterior cranial fossa. It is separated from these lobes by the tentorium cerebelli, a tough layer of dura mater, while it is separated from the pons by the fourth ventricle.
The cerebellum consists of two hemispheres which are connected by the vermis, a narrow midline area. Like other structures in the central nervous system, the cerebellum has both grey and white matter - the grey matter is located on the surface of the cerebellum and is tightly folded into the cerebellar cortex, while the white matter is located underneath the cerebellar cortex and contains the four cerebellar nuclei (the dentate, emboliform, globose, and fastigi nuclei).
The cerebellum can be subdivided in three ways - anatomical lobes, zones, and functional divisions. The three anatomical lobes are the anterior lobe, the posterior lobe and the flocculonodular lobe, and these are divided by two fissures - the primary fissure and the posterolateral fissure. The three cerebellar zones are the vermis in the midline, the intermediate zone on either side of the vermis, and the lateral hemispheres lateral to the intermediate zone.
The cerebellum can also be divided by function. There are three functional divisions - the cerebrocerebellum, the spinocerebellum and the vestibulocerebellum. The cerebrocerebellum is the largest division, formed by the lateral hemispheres. It is involved in planning movements, motor learning, and regulating coordination of muscle activation. It receives inputs from the cerebral cortex and pontine nuclei, and sends outputs to the thalamus and red nucleus. The spinocerebellum is made up of the vermis and intermediate zone of the cerebellar hemispheres, and it is involved in regulating body movements by allowing for error correction, as well as receiving proprioceptive information. Finally, the vestibulocerebellum is located within the flocculonodular lobe and is involved in controlling balance and ocular reflexes.
The cerebellum, which stands for little brain, is a structure of the central nervous system which is important for motor control. It is active in the coordination, precision and timing of movements, as well as in motor learning. During embryonic development, the cerebellum develops from the metencephalon division. It is located at the back of the brain, immediately inferior to the occipital and temporal lobes, and within the posterior cranial fossa. Anatomically, the cerebellum consists of two hemispheres connected by the vermis, with grey matter located on the surface and white matter located underneath. It can be subdivided into anatomical lobes, zones and functional divisions - the cerebrocerebellum, the spinocerebellum and the vestibulocerebellum.
The vestibulocerebellum, which is the functional equivalent to the flocculonodular lobe, is involved in controlling balance and ocular reflexes, specifically the fixation of a target. It receives both sensory and motor impulses from the vestibular system, which are then sent back to the vestibular nuclei.
The cerebellum is fed by three paired arteries that provide it with its blood supply. These arteries are: the superior cerebellar artery (SCA), the anterior inferior cerebellar artery (AICA) and the posterior inferior cerebellar artery (PICA). The SCA and the AICA are branches of the basilar artery, which wraps around the anterior aspect of the pons before the cerebellum is reached. The PICA, on the other hand, is a branch of the vertebral artery. Venous drainage of the cerebellum is facilitated by the superior and inferior cerebellar veins, which ultimately drain into the superior petrosal, transverse and straight dural venous sinuses.
The dysfunction of the cerebellum can produce a wide variety of signs and symptoms, making it a diverse problem in terms of aetiology. Causes of cerebellar dysfunction can range from stroke, physical trauma, tumors and even chronic alcohol excess. The clinical picture is largely dependent on the area of the cerebellum that is affected.
Damage to the cerebrocerebellum and the spinocerebellum can lead to difficulty carrying out skilled and planned movements, as well as difficulties in motor learning. The range of manifestations that can occur from this type of damage can be remembered with the acronym ‘DANISH’, which stands for: Dysdiadochokinesia (difficulty with rapid, alternating movements); Ataxia; Nystagmus (coarse); Intention tremor; Scanning speech; and Hypotonia.
On the other hand, damage to the vestibulocerebellum can manifest itself as a loss of balance and abnormal gait, with a wide stance.
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