Cerebellum Flashcards
Which ventricle does the cerebellum overly?
IVth ventricle
How is the cerebellum connected to the brainstem?
Via the inferior, middle and superior cerebellar peduncles
What is the cerebellum involved in?
Important role in motor control - coordination of movement and balance, therefore cerebellar dysfunction often presents with motor signs
How is the cerebellum separated from the occipital and temporal lobes of the forebrain?
via tentorium cerebelli - tough layer of dura mater
The cerebellum comprises two ovoid hemispheres joined in the midline by what?
vermis - worm like median ridge of tissue
The surface of the cerebellum is highly convoluted - what are the folds called?
folia
Describe the orientation of the grey and white matter of the cerebellum
Cerebellum consists of an outer layer of grey matter (cortex) and an inner core of white matter surrounding centrally placed aggregations of nerve cells (deep nuclei)
The cerebellum can be divided into 3 lobes - what are they?
anterior lobe
posterior lobe
flocculonodular lobe
What fissures separate the lobes of the cerebellum?
primary fissure
horizontal fissure
posterolateral fissure
What does the primary fissure separate?
primary fissure is considerably deeper and more conspicuous than other fissures - separates the anterior and posterior lobes of each cerebellar hemisphere
What does the posterolateral fissure separate?
On the underside the posterolateral fissure demarcates the location of small regions of the hemisphere (the flocculus) and vermis (nodule), which together form the flocculonodular lobe
What does the horizontal fissure do?
Landmark which divides the cerebellar hemispheres into superior and inferior portions
What is the flocculonodular lobe concerned with?
vestibular information
Cerebellum can also be divided into functional divisions - what are the three functional areas?
cerebrocerebellum
spinocerebellum
vestibulocerebellum
What is the cerebrocerebellum?
Largest division formed by the lateral hemispheres - 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
What is the spinocerebellum?
comprised of the vermis and intermediate zone of the cerebellar hemispheres - involved in regulating body movements by allowing for error correction. It also receives proprioceptive information
What is the vestibulocerebellum?
functional equivalent to the flocculonodular lobe - involved in controlling balance and ocular reflexes, mainly fixating on a target. It receives input from the vestibular system, and sends outputs back to the vestibular nuclei
Where does the cerebellum receive its blood supply from?
Blood supply received from 3 paired arteries:
- superior cerebellar artery
- anterior inferior cerebellar artery
- posterior inferior cerebellar artery
The superior cerebellar artery and the anterior inferior cerebellar artery are branches of what?
basilar artery
The posterior inferior cerebellar artery is a branch of what?
vertebral artery
What is the cerebellar tonsil?
prominent round swelling of the cerebellar cortex anteriorly on either side of the vermis
Which region of the brainstem does the superior, middle and inferior cerebellar peduncles connect to?
superior - midbrain
middle - pons
inferior - medulla
What are the 4 cerebellar nuclei embedded in the white matter of the cerebellum? Think ‘Dont eat greasy food’
dentate
emboliform
globose
fastigi
What is the dentate nucleus?
Largest and most lateral of the deep cerebellar nuclei, important for the regulation of many aspects of voluntary motor activity, including its timing, planning and inception - only cerebellar nucleus that can be seen with the naked eye/represents a crinkled bag
The dentate nucleus sends impulses to two main destinations - what are they?
thalamus and red nucleus
What are the functional connections between the cerebellum and brainstem?
Connected to midbrain, pons and medulla via superior, middle and inferior cerebellar peduncles - these tracts carry information in both directions
What pathways does the superior cerebellar peduncle carry?
efferent fibres from the dentate, emboliform and globose nuclei - send feedback to the motor cortex in the frontal lobe. Afferent fibres from the ventrospinocerebellar tract take unconscious proprioceptive information from the lower body
What pathways does the middle cerebellar peduncle carry?
corticopontocerebellar information - copy of the information from the primary motor cortex which the pyramidal tract is carrying down to lower motor neurons
What pathways does the inferior cerebellar peduncle carry?
vestibulocerebellar tract (vestibular impulses from labyrinths, directly and via the vestibular nucleus). Also unconscious proprioceptive information from the dorsospinocerebellar tract
The dentate nuclei are the largest of the paired cerebellar deep nuclei. What role do they play? Where do efferent fibres from the nucleus go?
The dentate nucleus is responsible for the planning, initiation and control of voluntary movements.
Efferent fibres travel via the superior cerebellar peduncles through the red nucleus to the thalamus.
Clinical link - what happens with a midline lesion of the cerebellum? eg - tumour
Leads to a loss of postural control, as a result its impossible to stand or sit without toppling over, despite preserved coordination of the limbs themselves
Unilateral lesions of the cerebellum cause problems on what side of the body?
Ipsilateral side
What happens with a unilateral cerebellar hemispheric lesion?
causes ipsilateral incoordination of the arm (intention tremor) and leg, causing an unsteady gait, in the absence of weakness or sensory loss
What does bilateral dysfunction of the cerebellum, caused by alcoholic intoxication, hypothyroidism, inherited cerebellar degeneration/ataxia, MS or paraneoplastic disease cause?
slowness and slurring of speech (dysarthria)
incoordination of both arms and a staggering, wide-based, unsteady gait (cerebellar ataxia)
Cerebellar lesions also impair coordination of eye movements - what problems might be experienced?
characteristic, involuntary and rhythmic to-and-fro motion = nystagmus
this is a common feature of MS
The combination of nystagmus with which two other symptoms constitutes Charcot’s triad, which is highly diagnostic of MS?
intention tremor and dysarthria
What are the three main inputs to the cerebellum?
- corticopontine from primary motor cortex to middle cerebellar peduncle
- vestibular to the inferior peduncle
- spinal sensory to the superior (contralateral) and inferior (ipsilateral) cerebellar peduncles
