Cerebellum

Question 1

Embryologically, where is the cerebellum derived from?

Answer 1

The cephalic end of the neural tube forms three parts that give rise to the brain and associated structures:

1) Forebrain (prosencephalon)
2) Midbrain (mesencephalon)
3) Hindbrain (rhombencephalon)

The cerebellum is associated with the rhombencephalon. This is subdivided by the metencephalon and myelencephelon. The cerebellum is formed from the myelencephalon.

Question 2

Anatomical location?

Answer 2

Located immediately inferior to the temporal and occipital lobes.

Located within the posterior cranial fossa.

It is separated from the cerebrum by the tentorium cerebelli, a reflection of dura mater.

Lies at the same level of the pons and it is posterior to it, only separated by it with the fourth ventricle.

Question 3

Basic anatomical structure?

What type of tissue is it made of?

Cerebellar cortex?

Nuclei?

Answer 3

Consists of two hemispheres, connected to the vermis, a narrow midline area.

It consists of grey and white matter:

Grey matter - located on the surface of the cerebellum. Tightly folded to form the cerebellar cortex.

White matter - located beneath the cerebellar cortex. Embedded in the white matter are four nuclei: dentate, emboliform, globose, and fastigi.

Question 4

Anatomical structure - anatomical lobes?

Answer 4

There are three lobes of the cerebellum:

1) Anterior
2) Posterior
3) Flocculonodular

These are separated by fissures:

1) Primary fissure
2) Posterolateral fissure

Question 5

Anatomical structure - zones?

Answer 5

There are three zones of the cerebellum:

1) Centrally - vermis.
2) Lateral to the vermis - intermediate zone
3) Lateral to the intermediate zone - lateral zone

Question 6

Functional divisions of the cerebellum?

Answer 6

There are three functional divisions of the cerebellum:

1) Cerebrocerebellum - largest division - formed by the lateral hemispheres - involved in planning movements and motor learning. It also regulates coordination of muscle activation and is important in visually guided movements.

Receives inputs from the cerebral cortex and pontine nuclei.

Sends outputs to the thalamus and red nucleus.

2) Spinocerebellum - formed by the vermis and intermidate zones of the cerebral hemispheres. Involved in regulating body movements and error correction. It also received proprioceptive information.
3) Vestibulocerebellum - functional equivalent of the flocculonodular lobe. It is involved in controlling balance and ocular reflexes, mainly fixation on a target.

Receives input from the vestibular system.

Sends output to the vestibuli nuclei.

Question 7

Vasculature of the cerebellum?

Answer 7

Blood supply:

1) Superior cerebellar artery - branch of the basilar artery -
2) Anterior inferior cerebellar artery - a branch of the basilar artery -
3) Posterior inferior cerebellar artery - a branch of the vertebral artery

Blood drainage:

1) Superior (medial) cerebellar vein
2) Inferior (lateral cerebellar) vein

These veins drain into the petrosal, straight and transverse sinuses.

Question 8

Clinical relevance - cerebellar dysfunction?

Answer 8

Produces a widerange of symptoms and signs.

Aetiology is varied - stroke, physical trauma, tumours and chronic alcohol excess.

Problems with the cerebrocerebellum and spinocerebellum presents with problems in skillled and planned movements in motor learning.

The acronym, ‘DANISH’ can be used to learn the manifestations:

D - dysdiodochokinesia - difficulty in carrying out rapid, alternative movements.

A - ataxia - trouble with swalling, walking, speaking, balance, high degrees of control (e.g. eating and writing) and vision.

N - nystagmus - involuntary eye movements

I - intention tremor

S - scanning speech - spoken words are broken up into separate syllables.

H - hypotonia - decreased muscle tone

Damage to the vestibocerebellum can result in problems with loss of balance, abnormal gait with a wide stance.

Image: left sided cerebellar stroke