Lectures 39, 40: Cerebellum Flashcards
Layers of the cerebellum (broadly)
Cortex, white matter, deep cerebellar nuclei
Structural hierarchy of cerebellum (small –> large)
Folium –> lobule –> lobe
Lobes of cerebellum and associated fissures
Anterior (primary fissure) posterior (pastero-lateral fissure) floccular-nodular
One important cerebellum lobule and location. What can happen to this lobule?
Tonsil: posterior, hangs down the furthest; tonsilar herniation
Locations of 3 cerebellar nuclei
Fastigial - vermis, Interposed - intermediate, Dentate - lateral
What are the vestibular portions of the cerebellum?
Floccular-nodular (nodular in vermis)
Cerebellum receives all of its input from…(broadly, 2)
Spinal cord and brainstem
How many spinocerebellar tracts are there and what do they carry?
4, proprioception and error information
2 lower body tracts and what they carry
Dorsal (proprioception) and ventral (error signal) spinocerebellar tract
2 upper body tracts and what they carry
Cuneocerebellar (proprioception) and rostral spinocerebellar (error signal)
How does error signals work?
These tracts also carry information from higher brain regions and through interneurons compute difference between intended and actual muscular states
Dorsal spinocerebellar tract ascends in which fascicle and terminates where? Then where does it ascend? Final synapse?
Gracile fascicle –> Clarke’s nucleus in thoracic spinal cord –> dorsal spinocerebellar tract (DSCT) –> inferior cerebellar peduncle
Cuneocerebellar tract pathway
Cuneate fascile –> lateral cuneate nucleus (medulla) –> cuneocerebellar tract –> inferior cerebellar peduncle
Ventral spinocerebellar tract pathway
Afferents from Golgi Tendon Organ + corticospinal information –> Interneurons (spinal border cells) –> cross in anterior commissure –> lateral funiculus –> superior cerebellar peduncle where they CROSS AGAIN
Why is the ventral spinocerebellar tract anomalous
- All other tracts travel via inferior cerebellar peduncle and 2. Double-crossed
Do we have to find upper body error tract? Also, what’s this tract called again?
No! Hard to determine anatomically; rostral spinocerebellar tract
Cerebellar homunculi principles (2) and name for this region
At least two homunculi; trunk of the body in vermis and arms/legs on intermediate regions; spinocerebellum
Other cerebellar inputs from medulla…(3); inferior cerebellar peducle carries which two?
Reticular formation, inferior olivary complex, vestibular nuclei; reticular and inferior olivary complex
Does the cerebellum get input from the pons? Crossed or uncrossed?
Yes! Enormous projections from pontine nuclei; crossed…duh! crossing fibers of the pons, after all!
What do pontine projections to the cerebellum form?
Middle cerebellar peduncle
How does the cerebral cortex influence the cerebellum?
Synapse on pontine nuclei
How is the crux cerebri organized?
Topographically by brain lobe that’s projecting
What portion of the cerebellum recieves pontine projections?
Lateral hemispheres (cerebrocerebellum)
Describe basic cerebellar connectivity (4 steps). Which cell type projects to deep cerebellar nuclei?
Cerebellar afferents –> cerebellar cortex –> deep cerebellar nuclei –> target nuclei; Purkinje cells
3 layers of the cerebellum and associated cell types
Molecular layer (stellate, basket cells and Purkinje dendrites), Purkinje layer, Granular layer (granule cells, Golgi cells)
Two fiber systems of cerebellum and associated input structure
Mossy fiber-Parallel fiber (all the rest of the inputs, distributed inputs) and Climbing fiber (axons from inferior olivary complex, convergent inputs)
Basket and stellate cells are…synapse on, which are?
Inhibitory; Purkinje cells, inhibitory
All cerebellar inputs are…All interneurons are…
Excitatory; inhibitory
Deep cerebellar nuclei project to what three structures. Terminate where, except? Which are crossed?
Thalamus, red nucleus, vestibular nuclei; superior cerebellar peduncle (except vestibular, which goes through inferior); tracts to thalamus/red nucleus are crossed
What portions of the thalamus receive cerebellar input? What tract (a tract by any other name…)?
Ventral group (VLp); dentato-thalamic tract (thalamic fasciculus w/ BG projections)
So, where do the outputs of the cerebellum mostly travel through?
Superior cerebellar peduncle
If a cerebellar deficit is unilateral, the deficit will be? Why?
Ipsilateral; cerebellar efferents are contralateral, synapse in cortex and then projects down contralaterally in motor pathways (ending in same side)
Ataxia definition
Unsteady gait, imbalance, broad-based stance
Guillan-Mollaret (Myoclonic) Triangle pathway and symptoms
Inferior olive –> dentate nucleus –> red nucleus; palatal myoclonus that PERSISTS during sleep
Eye movements that depend on cerebellum (2)
Smooth pursuit (cortico-ponto-cerebellar network), optokinetic nystagmus
Vermal cerebellar problems broadly involve (3)
Standing roblems (wide-based gait, ataxia of gait); nystagmus, ocular dysmetria
Define titubations
Spasmodic nodding of head and neck
Hemispheric cerebellar problems broadly involve…What about pancerebellar?
Coordination of ipsilateral limb movements, rapid alternating movements; pancerebellar is combination of both hemi and vermis syndromes
Classical cerebellar tremor is (broadly)
Intentional
Anatomical cerebellar syndrome classes
Vermis, hemispheric, pancerebellar
A common eye movement problem in dysfunction of cerebellum
Nystagmus
Testing of Station (three things to look for)
- Position of feet (ataxia is less w/ broad based); 2. Eyes open/closed (cerebellar NOT improved by visual orientation); 3. Direction of falling (lateral lesion –> falling to ipsilateral side, midline lesion –> indiscriminate falling)
What can cerebellar problem do to tone? Some features.
Hypotonia; ipsilateral, often with acute lesions, more noticeable in upper limbs/proximal muscles
What are the cerebellar hemispheric function tests (3)?
Finger-to-nose, rapidly alternating movement, heel-to-sin test
Rapid alternating movements: real name and what it means
Dysdiadochokinesis; tests ability to change direction
Finger to nose tests what?
Dysmetria (lack of coordination)
Check and rebound show what if it’s pathological?
Large rebound (overshoot)
Cerebellar dysarthria is an abnormality in what parts of speech?
Articulation and prosody: long pauses between words, may be related to hypotonia of muscles
Three types of tremor and definitions
Resting (max at rest, symptom of PD), postural (max with limb in fixed position against gravity), intention
Which tremor is more related to cerebellar disorder?
Intention
Physiologic tremor is normal/abnormal and enhanced by what?
Normal, anxiety/stress/fatigue
Essential tremor is…(genesis) and increases with what? What about at rest?
Hereditary (genetic); aging; absent at rest
Palatal myoclonus definition and lesion location. What’s special about this?
Rhythmic jerks of soft palate, lesions of Guillan-Mollaret (Myoclonic) Triangle pathway; NOT suppressed by sleep
Hypothyroidism can cause…What else (nutritional)?
Cerebellar ataxia; heavy metals (MO) and Vit E deficiency
Antiepileptic drugs and the cerebellum
Long-term antiepileptic drugs may cause cerebellar atrophy
Infections and children with cerebellar ataxia
Children can present with acute cerebellar ataxia after a non-specific viral infection
What 2 viruses can be associated with cerebellar ataxia?
HIV and Creutzfeldt-Jakob disease
What is the relationship between cerebellar ataxia and cancer?
Paraneoplastic cerebellar degeneration syndrome (autoimmune process triggered by cancer)
What food item is related to cerebellar ataxia?
Gluten (Celiac’s disease)
Define Friedreich ataxia
Progressive, genetic cerebellar ataxia w/ cardiomyopathy and diabetes
Define Ataxa-telangiectasia
Progressive ataxia with onset in infancy, genetic, capillary dilations (red nose) and malingnancies
Cardinal features of cerebellar dysfunction (7)
Hypotonia, ataxia, dysarthria, tremor, ocular motor dysfunction, decompensation of movement, impared rapid alternating movements
