12 - Cerebellar Disorders Flashcards
What are the functions of the cerebellum?
Make movements smooth by continually making small corrections; motor planning, motor learning.
Limbs, trunk, voice, eyes
Matching motor intention with sensory feedback.
What provides input to the cerebellum? What does the cerebellum provide info to?
To cerebellum: cortex, body and environment
From cerebellum: cortex (via thalamus) which is excitatory
If you were the cerebellum, what information would you want?
Vestibular
Visual
Muscle and tendon stretch
Efferents copy for motor intention - when the cortex intends to do something, it sends a copy of it to the cerebelum so it can adjust what the cortex is doing if there’s a problem
What are the general rules about rapid alternating movements when testing clincally?
Many of our daily movements such as waking, speaking, and eye movements rely on rapid alternative movements.
So all of these will demonsrate the same pattern of abnormailty in all disorders.
What aspect of rapid alternating movements (RAM) does the cerebellum mainly impact? What is seem with disorders here?
Main impact is amplitude and frequency.
Disorder in cerebellum causes an irregular pattern of RAM in aplitude and frequency.
What aspect of rapid alternating movements (RAM) does the basal ganglia mainly impact? What is seem with disorders here?
Mainly impacts amplitude.
Disorders of the basal ganglia result in RAM patterns that are small and fast. Also results in extra movements.
What aspect of rapid alternating movements (RAM) does the motor cortex mainly impact? What is seem with disorders here?
Impacts frequency of the RAMs.
Disorders of the motor cortex result in RAM patterns that are slow and large.
What is the rule of 3 for the cerebellum?
3 regions
3 peduncles
3 sensory inputs (4 total)
3 types of outputs
Besides the rule of three, what are the other two rules that pertain to the cerebellum?
Actions are IPSI to the body due to double crossing.
Excitatory-inhibitory rule:
- projections INTO the cerebellar cortex are EXCITATORY
- projections OUT of cerebellar cortex are INHIBITORY
Name the cerebellar inpus and outputs?
Inputs: mossy fibers from the pontine nuclei and climbing fibers from the inferior olivary nucleus
Outpus: from the deep cerebellar nuclei and vestibular nuclei
What are the four functional regions of the cerebellum? What is the funciton of each region and what projection is affected?
- Lateral hemisphere: fine motor planning; affects lateral corticospinal tract (LCT)
- Intermediate hemisphere: distal limb sensory-motor match and execution; affects LCT + rubrospinal tract
- Vermis and flocculonodular lobe: prox lim, trunk muscle coordination and balance;affects corticopsinal, reticulospinal, vestibulospinal, and tectospinal.
- Flocculonodular lobe: vestibuloocular reflexes; affectrs the medial longitudinal fasciculus
For cerebellar input: What is the course, tract, projection, and peduncle involved in intention?
Source: motor, visual, and sensory cortex
Tract: cerebral peduncle
Projection: pontine nuclei (brainstem)
Peduncle: middle
For cerebellar input: What is the course, tract, projection, and peduncle involved in proprioception?
Source: tendon organs
Tract: dorsal spinal cerebellar and cuneocerebellar
Projection: clarke’s column (spinal cord)
Peduncle: inferior
For cerebellar input: What is the course, tract, projection, and peduncle involved in vestibular function?
Source: middle ear
Tract: CN VIII
Projection: Vestibular nuclei (medulla)
Peduncle: inferior
For cerebellar input: What is the course, tract, projection, and peduncle involved in trophic/learning?
Source: all areas + red nucleus
Tract: parvocellular-IO tract
Projection: inferiour olive (medulla)
Peduncle: inferior
Decribe the homunculus of the cerebellum?
Anterior lobe has trunk and lower limbs.
Posterior lobe has head, upper limbs, trunk, and lower limbs.
Vermic and intermediate lobe do more with the trunk and the lobes do more of the limbs.
A lot of repetition; not as clear as cerebral humunculus.
What is the impact of a lesion in the lateral hemisphere?
Limb ataxia, dysdiadochokinesis, action or postural tremor.
What is the impact of a lesion in the intermediate hemisphere?
Inability to manage limb mass and tie to center of gravity in accordance with intended movements; ie hard to counter balance with the rest of the body when doing something.
What is the impact of a lesion in the vermis and floculonudular lobe?
Trunk mucsles, gait ataxia, postural instability; falls, head titubation (nodding movements of head).
What is the impact of a lesion in the flocculonodular lobe?
Nystagmus, inability to stay on a target – overshoot of eyes: ocular dysmetria
What is ataxia?
A lack of order in time. Uncoordinated muscle movement; disorders speed, range, force, or timing.
What eye findings occur with cerebellar lesions? What lesions commonly cause this?
Nystagmus: mediated by the cortex. Can be horizontal, vertical, or rotational. Typically a lesion of the flocculonodular lobe (this region involves movement of eyes).
Saccades: quick, voluntary eye movements; slowed with cerebellar lesions.
What impact do cerebellar lesions have on tone?
Hypotonia: decreased gamma motor neuron bias and intrafusal fibers become loose.
What impact do basal ganglia lesions have on tone? What exam can be used to see this?
Rigidity caused by extrapyramidal tract disinhibition.
Contralateral activation exam.
What impact do motor cortex lesions have on tone?
Increased spasticity caused by cerebellar gamma motor neuron bias (through the red and vestibular nucleus).
Besides cerebellar lesions, what else could cause hypotonia and weakness mistaken for ataxia?
Corticocerebellar tract dysfunciton.
Ataxic appearing movements alone may be due to impaired proprioception.
Describe the cause of a focal complaint when it’s acute, subacute, or chronic.
Focal Acute: Vascular epileptic
Focal Subacute: I’s: Infectious, immune, inflammatory, infiltrative
Focal Chronic: Mass lesion
Describe the cause of a diffuse complaint when it’s acute, subacute, or chronic.
Diffuse Acute: Cardiac Epileptic
Diffuse Subacute: Toxic-metabolic
Diffuse Chronic: Degenerative, metabolicm, genetic
What makes something focal vs diffuse?
Focal if it’s on one side only.
Diffuse if it’s on both sides.
What makes something acute, subacute, or chronic?
Acute: seconds to minutes
Subacute: hours to days
Chronic: weeks to months
What is the difference between an ischemic and hemorrhagic stroke?
Ischemic: deprivation of blood
Hemorrhagic: ruptube of blood vessel
What can chronic alchololism do to your cerebellum? What about acute intoxication?
Cause cerebellar vermian atrophy.
Acute EtOH intoxication causes dysfunciton of the vermis.
What causes an essential tremor? What parts of the body are impacted?
Most common movement disorder - bilateral postural and action tremor affecting hands/arms, head, and voice.
Autosomal dominant in 50%
Neurodegenerative - gradual loss of purkinje cells.
What is an astrocytoma?
Most common brain tumor in children, can slowly grow in the cerebellar hemisphere and thus cause cerebellar dysfunction.
What causes spinocerebellar ataxia?
>30 types
Triplet repeat expansion: CAG repeat expansion in various different genes. Aut dominant.
Causes neurodegeneratoin of purkinje cells that affects all portions of the cerebellum (pans-cerebellar presentation).
What is multiple sclerosis? What is seen on imaging?
An autoimmune disorder, more common in young white men.
Accumulate lesions (plaques) in cerebellar white matter, spinal cord, and cerebral white matter.
