Cerebellum Flashcards
What are the names of the three bilateral pairs of deep cerebellar nuclei?
fastigial (most medial)
interposed
dentate (most lateral)
How is the cerebellum divided into lobes?
How is the cerebellum divided through the midline?
Anterior lobe, posterior lobe, flocculo-nodular lobe
Vermin, paravermis and lateral hemispheres
Three cerebellar peduncles connect the cerebellum to the brainstem. Which peduncles carry inputs to the cerebellum and which peduncles carry outputs from the cerebellum? Which nerve bypasses the peduncles and communicates directly with the cerebellum?
Inferior cerebellar peduncle - inputs from spinal cord and medulla
Middle cerebellar peduncle - inputs from cerebral cortex (relayed through the pons)
Superior cerebellar peduncle - outputs except vestibular output AND the afferent ventral spinocerebellar tract
The floccular-nodular lobe receives direct input from the vestibular portion of CN VIII and vestibular nuclei
What are the four tracts that carry somatosensory information to the cerebellum? What types of information does each tract carry? From what part of the body does each tract originate?
There are four spinocerebellar tracts:
dorsal spinocerebellar tract - carries pure somasthesis from lower body. Muscle spindle afferents carrying proprioception from the lower body ascend in the gracile fasciculus to terminate in Clarke’s nucleus in the thoracic spinal cord (T1-L1). Axons of these secondary neurons form the dorsal spinocerebellar tract, which projects through the inferior cerebellar peduncle on the paravermis
Cuneocerebellar tract - carries pure somasthesis from the upper body. muscle spindle afferent carry proprioception from the upper body ascend in the cuneate fasciculus and terminate on the lateral cuneate nucleus. Axons of these secondary neurons form the cuneocerebellar tract, which projects through the inferior cerebellar peduncle on the paravermis
Ventral spinocerebellar tract - carries the error signal from lower body. Golgi tendon organ afferents synapse on interneurons in the spinal cord which integrate sensory info with motor commands and generate an error signal conveying the discrepancy between the motor plan and the executed movement. Axons project through superior cerebellar peduncle to the paravermis
Rostral spinocerebellar tract - carries the error signal from the upper body. GTO afferents synapse on interneurons. Axons project through the inferior cerebellar peduncle to the paravermis
What is the pathway from the cerebral cortex to the cerebellum?
Cerebral cortex -> internal capsule -> terminate on ipsilateral pontine nuclei -> project contralaterally as the crossing fibers of the pons -> middle cerebellar peduncle -> lateral hemispheres of the cerebellum
What are the main input tracts to the cerebellum?
4 Spinocerebellar tracts
Vestibular nerve and nuclei
pontine nuclei (relaying info from the cerebral cortex)
inferior olivary complex
reticular formation
What are the main output destinations of the cerebellum cortex? What nerves make up these output tracts? What neurotransmitter do these nerves release?
Deep cerebellar nuclei (fastigial nucleus, interposed nucleus and dentate nucleus)
Axons of purkinje cells make up the output tracts of the cerebellar cortex and are all GABAergic
What are the three layers of the cerebellar cortex? What cells are in each layer?
granular layer - Golgi cells (inhibitory interneurons) and granule cells
purkinje layer - cell bodies of Purkinje cells
molecular layer - dendrites of Purkinje cells, cell bodies of stellate and basket cells (both inhibitory interneurons)

What is the difference between climbing fibers and mossy fibers?
climbing fibers - synapse directly on Purkinje cells; excited only a few Purkinje cells but synapses thousands of times on those cells; arise from the inferior olivary complex
mossy fibers - synapses indirectly on Purkinje cells (mossy fibers synapse on granule cells which synapse on Purkinje cells); excits many Purkinje cells; arise from non-olivary cerebellar inputs
What are the main output destinations of the cerebellum deep cerebellar nuclei?
output destinations: thalamus, red nucleus, vestibular nuclei
What is the cerebellar output pathway that maintains posture?
floccular-nodular lobe and vermis -> fastigial nucleus -> bilateral vestibular nuclei in brainstem -> reticulospinal and vestibulospinal tracts -> axial and neck muscles
This pathway is also very important in the control of eye movement (vestibulo-ocular reflex)
What is the cerebellar output pathway that facilitate motor control?
paravermis -> interposed nuclei -> superior cerebellar peduncle -> red nucleus -> rubrospinal tract -> distal muscles (facilitates flexor muscles and inhibits extensor muscles)
What is the cerebellar output pathway that facilitates motor planning?
lateral hemispheres -> dentate nucleus -> superior cerebellar peduncle -> ventrolateral posterior (VLp) thalamus -> cerebral cortex -> corticospinal tract
Why are cerebellar deficits always ipsilateral to the lesion?
All outputs form the cerebellum (except vestibular) go through the superior cerebellar peduncle, which decussates in the midbrain. The target structures of the cerebellar outputs give rise to descending motor tracts (rubrospinal and corticospinal) that decussate again.
What are the cardinal signs of cerebellar dysfunction?
ataxia, hypotonia, dysarthria (difficulty saying words because of problems with the muscles that help you talk), tremor (intention or postural tremor, NOT resting tremor) and oculomotor dysfunction
What are the characteristic symptoms of a vermis/midline cerebellum syndrome? What is the most common cause of vermis syndrome?
wide-based stance due to difficulty in maintaining balance in all directions
imbalance causes patient to fall in all directions
wide gait
gait abnormalities not improved by visual orientation
eye-movement disturbances and nystagmus
distal arm and leg movments are not impaired
large masses can compress the 4th ventricle and lead to hydrocephalus
Most commonly caused by chronic alcohol abuse
What are the characteristic symptoms of hemispheric cerebellum syndrome?
What are the most common etiologies of hemispheric cerebellum syndrome?
Mostly affect the limbs
impaired rapidly alternating movements
loss of coordination in ipsilateral limb
intention tremor
dysmetria (inability to stop a movement at the proper place; undershoot or overshoot eye movements, seen in finger-to-nose and heel-knee-shin tests)
scanning speech (dysarthria)
imbalance causes patient to fall towards the side of the lesion
Main causes of this syndrome is metastasis, infarcts or abscesses
What are the five types of tremors?
resting tremor
intention tremor
postural tremor
essential tremor
physiologic tremor
What is asterixis? What disease is asterixis a sign of?
NOT a tremor. Muscle tone lapses when wrist extension is attempted, resulting in wrist flexion. Usually bilateral.
A sign of hepatic encephalopathy due to build up of urea because of liver failure
What is myoclonus?
A quick movement of muscle that is NOT a tremor. Cannot be suppressed.
What portion of the cerebellum does alcohol primarily damage?
The vermis. Leads to a midline/vermis cerebellum syndrome (wide-based stance, eye movement abnormalities, truncal ataxia)
Any time a patient presents with parkinsonism symptoms, what must you keep on the differential?
manganese toxicity
What are the neurological characteristics of Friedreich ataxia? What other diseases do these patient often get? What is the age of onset?
Chronic, slowly progressive, genetic cerebellar ataxia caused by degeneration of sensory neurons that direct muscle movement through connections in the cerebellum.
Also associated with cardiomyopathy and diabetes mellitus
Usual age of onset is 2-25 years
Besides ataxia and telangiectasias, what other diseases/clinical findings are found in ataxia-telangiectasia?
Malignancies are frequent because AT is caused by a genetic mutation in the ATM gene that is involved in repairing double-strand breaks in DNA
What are the characteristics of a resting tremor? What is its etiology?
resting tremor - maximal at rest and decreases with activity but comes back after awhile;
etiology = basal ganglia disorder, parkinson’s disease, supranuclear palsy, drug-induced parkinsonism
What are the characteristics of an intention tremor? What are its etiologies?
intention tremor - maximal during movement towards a target and the closer you get to a target, the larger the tremor;
Test with finger-nose-finger
etiology = cerebellar lesions (hemispheric), multiple sclerosis, chronic alcohol abuse and Wilson’s disease
What are the characteristics of a postural tremor? How can you test for it? What are the etiologies if acute onset? If slow onset?
postural tremor - maximal when patient holds affected limb out against gravity
ask patient to hold their arms out
etiology = if acute onset, then toxic or metabolic disorder. If slow onset, then physiologic or essential tremor
What are the characteristics of an essential tremor?
Usually affects the hands, head, and voice. Postural or kinetic. Is minimal at rest. Usually bilateral. It tends to increase with aging and in 50% of patients, inheritance is autosomal dominant.