Cerebellum Flashcards
Where is the cerebellum found?
Posterior cranial fossa
What is the name for the “gyri” of the cerebellum? In which direction do they run?
Folia
Mediolateral
What is the name of the midline part of the cerebellum?
Vermis
What are the names of the three lobes of the cerebellum?
What divides the anterior and posterior lobe?
Anterior, posterior and flocculonodular lobes
Primary fissure
Which part of the cerebellum forms part of the roof of the fourth ventricle?
Nodulus lobe
What is the most common site of an infarct in the posterior circulation?
PICA - posterior inferior cerebellar artery
What is the blood supply to the cerebellum? (3)
Posterior inferior cerebellar artery (PICA)
Superior cerebellar artery
Various branches of the basilar artery
How many layers does the cerebellar cortex have? Describe them.
Three
Outer molecular layer - pale with mostly axons & only a few cells
Middle layer - single row of ‘purkinje cells’
Inner layer - granule layer. Thick with a vast number of granule cells.
Inputs and outputs to cerebellum are via the…
Cerebellar peduncles
What are the three cerebellar peduncles called? What do they each do?
- Superior cerebellar peduncle - output fibres
- Middle cerebellar peduncle - input fibers from (contralateral) cerebral cortex and cranial nerves via pons
- Inferior cerebellar peduncle - input fibers from the spinal cord via dorsal and ventral spinocerebellar tracts
Is the dorsal (posterior) spinocerebellar tract ipsilateral or contralateral? Which peduncle does it enter? What type of information does it carry?
Ipsilateral
It enters the inferior cerebellar peduncle.
Proprioceptors from joints and muscle spindles
Is the ventral (anterior) spinocerebellar tract ipsilateral or contralateral in the spinal cord? What type of information does it carry?
Contralateral
It carries information about state of reflexes and inter-neurons in the spinal cord.
If a patient has a cerebellar lesion, the signs are always…
On the same side as the lesion
Describe what happens with the ventral (anterior) spinocerebellar tract in the spinal cord/brainstem.
It is contralateral in the spinal cord but then RECROSSES in the brain stem to end up on same side it enters cord. Information from the body is passed to the same side in the cerebellum.
What are the names of the deep cerebellar nuclei? Which nuclei connect to which parts of the cerebellum?
Fastigial (medial) - vermis
Globose - anterior lobe
Emboliform - anterior lobe
Dentate (lateral) - posterior lobe
What is the role of the deep cerebellar nuclei? Where are they found?
All inputs and outputs are routed through these nuclei - they receive input from afferents and send axons down the spinal cord or up to the motor thalamus (via the cerebellar cortex) in order to regulate movement.
They are found in the white matter below the cortex.
The different parts of the cerebellum link to the deep cerebellar nuclei. What does the flocculonodular lobe link to?
The lateral vestibular nuclei of the pons.
Does the cerebellum initiate movements?
What is it’s role in movement?
No.
It helps the motor cortex produce accurate and smooth movements by refining the motor cortex commands using feedback from proprioceptors & other sensory organs.
What does cerebellar damage cause? (3)
Which muscles does it particular affect?
Clumsiness
Fatigue
Instability of movement
The extra-ocular eye muscles.
What does the neuronal plasticity mean in relation to patients with damage to the cerebellar cortex?
What about patients with damage to the deep nuclei?
This means partial recovery of function is possible, as the cerebellar cortex has neuronal plasticity.
Damage to the deep nuclei causes persisting disability.
What are the three functional zones of the cerebellum? What do they compromise of?
- Vestibulocerebellum (flocculonodular lobe)
- Spinocerebellum (anterior lobe and vermis)
- Cerebrocerebellum (posterior lobe)
What does the vestibulocerebellum co-ordinate? (3)
Head and eye movements (stability of gaze)
Balance of the head on the body, via the medial vestibulospinal tract
Balance of the body on the ground via the lateral vestibulospinal tract
Where is information from vestibular apparatus, extra-ocular eye muscles, and neck muscles about head movements sent?
What do the vestibular nuclei then do?
(Part of how vestibulocerebellum coordinates movement)
Vestibular nuclei in the pons & medulla
The vestibular nuclei compute the necessary muscle actions to keep the eyes balanced in the head, the head balanced on the body, and the body balanced on the ground.
Motor commands to the neck and eye muscles are sent via…
Medial longitudinal fasciculus and the medial vestibulospinal tract
Motor commands to the legs are sent via…
Lateral vestibulospinal tract
What does the spinocerebellum control? (3)
Which tracts are motor commands sent down?
Locomotion, limb co-ordination, and posture
Lateral vestibulospinal and reticulospinal tracts
What does the cerebrocerebellum control? (3)
Movement initiated by motor cortex - speech, voluntary movements of hands and arms, and hand-eye co-ordination.
What are the three major cerebellar syndromes?
- Flocculonodular/midline cerebellar syndrome
- Anterior lobe syndrome
- Neocerebellar syndrome
Describe a patient with flocculonodular syndrome. (6)
Poor balance
Disordered eye movements - e.g. nystagmus, ocular dysmetria, poor tracking
Trunkal ataxia
Titubation
Little control of axial muscles
Cannot sit or stand without falling in severe cases (tendency to fall to side of lesion)
What is titubation?
What is trunkal ataxia?
Bobbing motion of the head or trunk.
Unable to sit on their bed without steadying themselves.
What is the Romberg test?
How does it relate to flocculonodular syndrome?
A test used to assess balance. The patient stands with feet together with eyes open, then closes them - you are assessing how much they sway.
These patients are unable to stand in Romberg test with eyes open or closed - they can’t well perform tandem gait. They have an ‘ataxic’ gait, reeling and swaying.
Flocculonodular syndrome is most common in…?
Young children with medulloblastoma in 4th ventricle.
Anterior lobe syndrome is correlated with damage to the ____ and is characterised by ____?
Spinocerebellum
In-coordination of the limbs.
Symptoms of anterior lobe damage. (4)
Ataxic gait
Hypotonia
Dysdiadochokinesis (irregular performance of rapid alternating movements)
Depressed reflexes
Anterior lobe syndrome is often seen in…?
Why?
Alcoholics
Malnutrition and vit B deficiency
Symptoms of neocerebellar syndrome. (8)
Loss of hand-eye co-ordination
Dysmetria (inaccurate reaching with intention tremor)
Dysdiadochokinesis
Slurred speech
Loss of cognitive eye movement
Deficits in selective attention and perception
Motor difficulties involving skilled movements
Intention tremors
Most common causes of neocerebellar syndrome. (4)
Stroke
Tumour
Trauma
Degenerative diseases
The following are symptoms of which medical problem?
- Sudden and severe onset of headache, vertigo, nausea, and vomiting
- Eye changes (typically involving only one eye), such as nystagmus, ptosis and constricted pupils
- Dysarthria and dysphagia (due to weakening of oesophageal muscles)
- Ataxia
- Arm weakness and in-coordination (and trembling hands/arms)
Cerebellar stroke
Define ataxia.
Loss of balance and coordination while walking.
Define dysathria.
Motor disorder of speech weakening the muscles of the mouth, face and respiratory system. Speech may be slurred, slow, monotonous and hoarse.
Why does alcohol intoxication mimic many features of cerebellar damage?
Because the cerebellum has many GABA-ergic inter-neurons which are especially sensitive to the effects of alcohol.
Medulloblastoma accounts for how many percent of paediatric brain tumours?
15 to 20 %
Where does medulloblastoma usually originate?
The wall of the fourth ventricle.
What was medulloblastoma originally considered to be? What is it known to be now?
Glioma
Cranial primitive neuroectodermal tumour
How many % of medulloblastoma patients are diagnosed before the age of…
5?
5-9?
40%
31%
Using current treatments for medulloblastoma, how many % of those without disseminated disease can be cured?
80-90%
How many % of medullablastoma patients can be expected to be free of disease 5 years later?
More than 50%
