Cerebellum and Ataxia

Question 1

The basal ganglia are involved in the initiation and patterning of movements, and the cerebellum is involved in ___.

Answer 1

The basal ganglia are involved in the initiation and patterning of movements, and the cerebellum is involved in the coordination of movements.

Question 2

Lesions of the cerebellum can lead to . . .

Answer 2

Lesions of the cerebellum can lead to incoordination of movements (ataxia), imprecision of movements (dysmetria), difficulty with rapid alternating movements (dysdiadochokinesia), truncal and gait instability, and difficulty with articulation of speech (dysarthria)

Due to cerebellar involvement in oculomotor and vestibular function, cerebellar lesions can also cause nystagmus, vertigo, nausea, and vomiting.​

Question 3

At the midline, a cerebellar structure called ___ lies between the hemispheres of the cerebellum

Answer 3

At the midline, a cerebellar structure called the vermis lies between the hemispheres of the cerebellum

Question 4

The midline vermis controls . . .

Answer 4

The midline vermis controls coordination of the middle of the body, so pathology of the vermis leads to truncal and gait instability

Question 5

The laterally placed cerebellar hemispheres control . . .

Answer 5

The laterally placed cerebellar hemispheres control the lateral parts of the body: the limbs. Therefore, lesions of the cerebellar hemisphere can cause limb ataxia.

Question 6

Lesions in the cerebellar hemispheres cause deficits in the ___

Answer 6

Lesions in the cerebellar hemispheres cause deficits in the arm and/or leg ipsilateral to the affected hemisphere (unlike contralaterally in the cortex)

Question 7

Cerebellum anatomy cartoon

Answer 7

Question 8

Interposed nuclei of the cerebellum

Answer 8

Question 9

Cerebellar structures involved in vestibular function and eye movements

Answer 9

The left and right flocculi and the midline nodulus (together referred to as the flocculonodular lobe)

At the anterior part of the cerebellum

Question 10

Flow of information through the cerebellar peduncles

Answer 10

Question 11

Inputs and outputs of the cerebellar peduncles

Answer 11

• Inputs:
  
  • What the body wants to do
  • Where the body is in space
• Output:
  
  • How to guide movements to get there from here

Question 12

Cerebral peduncles vs cerebellar peduncles

Answer 12

• Cerebral peduncles: the name given to the corticospinal tracts at the level of the midbrain
• Cerebellar peduncles: Conduits of information into and out of the cerebellum (three paired peduncles, superior, middle, and inferior cerebellar peduncles on each side)

Question 13

The inferior cerebellar peduncles

Answer 13

• Carry inputs into the cerebellum inferiorly
  
  • The one exception being an output tract to the vestibular system that exits via the inferior peduncles
• The vestibulocerebellar tracts (vestibular information about where the head is in space), spinocerebellar tracts (proprioceptive information about where the body is in space), and olivocerebellar tracts (involved in motor learning) all travel through the inferior cerebellar peduncles to the cerebellum
• The inferior cerebellar peduncles enter the cerebellum at the most inferior level of the brainstem: the medulla.
• All inferior peduncle pathways project to the ipsilateral cerebellar hemisphere except the olivocerebellar tracts, which cross contralaterally.

Question 14

Middle Cerebellar Peduncles

Answer 14

• Carry input from the cerebral hemispheres to the cerebellum about what the brain wants the body to do
• Corticopontocebellar fibers arise from motor regions, descend with the corticospinal tracts, and cross in the anterior pons to enter the contralateral cerebellum via the middle cerebellar peduncles
  
  • The majority of fibers in the “bulge” of the anterior pons are these crossing corticopontocerebellar fibers en route to the middle cerebellar peduncles

Question 15

Superior Cerebellar Peduncles

Answer 15

• Predominantly send information superiorly, communicating the cerebellum’s plan back to the brain
  
  • There is one minor exception: One component of the spinocerebellar tracts (the ventral spinocerebellar tracts) enters the cerebellum through the superior cerebellar peduncles.
• The superior cerebellar peduncles exit the cerebellum by way of the upper pons, and cross at the junction of the upper pons/lower midbrain.
• Some crossed fibers synapse with the red nucleus (contralateral to the cerebellar hemisphere of origin), while others continue to the ventral lateral (VL) nucleus of the thalamus (contralateral to the cerebellar hemisphere of origin), which projects to cortical motor regions

Question 16

Cerebellar Peduncle Pathways cartoon

Answer 16

Question 17

Cerebellum vascular supply

Answer 17

The vascular supply of the cerebellum comes from three pairs of circumferential arteries that arise from the vertebrobasilar system: the superior cerebellar arteries (SCAs), the anterior inferior cerebellar arteries (AICAs), and the posterior inferior cerebellar arteries (PICAs).

The SCAs and AICAs arise from the basilar artery, and the PICAs usually arise from the vertebral arteries. These vessels also supply the brainstem.

Question 18

Tests of cerebellar ataxia on physical exam

Answer 18

• Rapid alternating movement - test for dysdiadokinesia
• Finger-nose test
• Heel-shin test
• Gait (gait instability may be present if there is vermis pathology)

Question 19

Lesions which may cause ataxia

Answer 19

• Lesion in the cerebellum proper
• Lesion in the cerebellar peduncles
• Disruption of the corticopontocerebellar fibers in their descent in the internal capsule or anterior pons (seen in ataxia-hemiparesis and dysarthria-clumsy hand lacunar syndromes)
• Anywhere in the dorsal column pathway (proprioception input necessary for cerebellar function, ultimate communicated via inferior pednucles – causes sensory ataxia)

Question 20

Ataxia due to cerebellar causes (as opposed to sensory ataxia) may be accompanied by additional cerebellar signs such as . . .

Answer 20

nystagmus, titubation (oscillation of the head and/or trunk at rest), and/or dysarthria

Question 21

Sensory ataxia can be distinguished from cerebellar ataxia on exam by the presence of. . .

Answer 21

. . . other sensory signs such as diminished proprioception and vibration sense and Romberg’s sign.

If sensory dysfunction is due to peripheral nervous system pathology (i.e., nerves, dorsal root ganglia, or dorsal roots), diminished or absent reflexes may be present.

Question 22

Clarification on Romberg’s sign

Answer 22

Romberg’s sign is commonly mistakenly attributed to cerebellar pathology, but it is actually a sign of impaired proprioception

Patients with severe cerebellar dysfunction are often unable to stand with their feet together even with their eyes open, let alone closed. Patients with a deficit in proprioception can stand with their feet together when using vision to compensate, but closing the eyes removes this cue and requires the patient to rely exclusively on proprioception, so the patient may lose her/his balance (Romberg’s sign)

Question 23

Cerebellar ataxia vs sensory ataxia on finger-nose test

Answer 23

• Cerebellar ataxia appears as an oscillatory movement perpendicular to the plane of movement (i.e., side-to-side when the patient approaches the target in the finger-nose task) and worsens as the patient approaches the target.
• Sensory ataxia causes what resembles a “searching” movement in which the affected limb looks as if it is approaching the target with meandering, circular movements.

Question 24

Pseudoathetosis

Answer 24

• Subtle sign of impaired proprioception
• Athetosis is a movement disorder characterized by writhing movements
• In a patient with diminished proprioception, when the patient’s arms and hands are stretched out in front of her/him with the eyes closed (as in testing pronator drift), subtle writhing piano playing–like movements of the fingers may be noted. Similar movements of the toes may be noted when testing for Romberg’s sign

Question 25

Differential for hyperacute-onset (over seconds to hours) of cerebellar pathology

Answer 25

• Vascular causes: ischemic stroke, cerebellar hemorrhage
• Acute toxicity: alcohol, cytarabine

Question 26

Diifferntial for acute- to subacute-onset (over hours to days) of cerebellar pathology

Answer 26

• Inflammatory causes
  
  • Postinfectious cerebellitis (most commonly seen in children after a viral illness, most commonly varicella infection)
  • Flare of multiple sclerosis

Question 27

Differential for subacute to chronic-onset (over weeks to months) of cerebellar pathology

Answer 27

• Infection: progressive multifocal leukoencephalopathy (aka, JCV)
• Paraneoplastic cerebellar degeneration, which can be associated with anti-Yo (ovarian and breast cancer), anti-Hu (small cell lung cancer), anti-Tr (Hodgkin’s lymphoma), anti-Ma2 (testicular cancer), and anti-GAD (often not associated with a malignancy) antibodies
• Tumor: medulloblastoma (in children), metastatic tumor (in adults)
• Vitamin E deficiency

Question 28

Differential for chronic-onset (over months to years) of cerebellar pathology

Answer 28

• Chronic drug/toxin exposure: phenytoin, alcohol
• Degenerative etiologies
  
  • Acquired:
    
    • multiple systems atrophy cerebellar type (MSA-C)
  • Inherited:
    
    • Friedreich’s ataxia (autosomal recessive)
    • Spinocerebellar ataxias (autosomal dominant)
    • Fragile X–associated tremor ataxia syndrome (X-linked)

Question 29

Vascular, infectious, multiple sclerosis lesion–related, and malignant etiologies of cerebellar disease usually lead to ___ cerebellar dysfunction, whereas drug-related, metabolic, degenerative, and non-multiple sclerosis inflammatory etiologies (e.g., paraneoplastic or postinfectious) more commonly lead to ___ cerebellar dysfunction.

Answer 29

Vascular, infectious, multiple sclerosis lesion–related, and malignant etiologies of cerebellar disease usually lead to unilateral cerebellar dysfunction, whereas drug-related, metabolic, degenerative, and non-multiple sclerosis inflammatory etiologies (e.g., paraneoplastic or postinfectious) more commonly lead to bilateral cerebellar dysfunction.

Question 30

Clarke’s nuclei

Answer 30

• Primarily located in the thoracic spinal cord
• Location of second-order neurons for the lower extremity in the dorsal spinocerebellar tract
  
  • ​​​Remains ipsilateral
• Travels lateral and antiparallel to the fibers of the corticospinal tract
• This pathway carries proprioceptive information that is not destined for conscious perception, but rather is used exclusively for unconscious cerebellar activity

Question 31

Accessory cuneate nuclei

Answer 31

• Located in the medulla
• Location of second-order neurons for the upper extremity in the dorsal spinocerebellar tract
  
  • ​Remains ipsilateral
• Travels lateral and antiparallel to the fibers of the corticospinal tract
• This pathway carries proprioceptive information that is not destined for conscious perception, but rather is used exclusively for unconscious cerebellar activity

Question 32

Cerebrocerebellar tract

Answer 32

• Tract that sends motor plan information from the motor cortex to the cerebellum by way of the internal capsule and pons
• Deccusates in the pons

Question 33

Dentatorubothalamic tract

Answer 33

• Output tract from the cerebellum that sends error calculation feedback to the motor cortex after comparing unconscious proprioceptive information to motor plan information

Question 34

Midline cross-section of the cerebellum

Answer 34

Question 35

Cerebellar vascular supply diagram

Answer 35

Question 36

Vascular territories of the cerebellum

Answer 36

Question 37

Ins and Outs of the Cerebellum

Answer 37

Question 38

Tracts that travel in the inferior cerebellar peduncles

Answer 38

• Olivocerebellar fibers
• Vestibulocerebellar fibers
• Spinocerebellar tract

Question 39

Path of information as it travels up to and through the middle cerebellar peduncles

Answer 39

Question 40

Path of information as it travels out of the superior cerebellar peduncles

Answer 40

Question 41

Cerebellar peduncle summary image

Answer 41

Question 42

Having a hard time sitting upright is a test of. . .

Answer 42

. . . truncal ataxia. Might suggest that the vermis is involved.

Question 43

Alcohol-induced neurodegeneration may be ___-predominant.

Answer 43

Alcohol-induced neurodegeneration may be cerebellar-predominant.

Question 44

Truncal ataxia differential

Answer 44

• Alcohol-use-induced neurodegeneration (over years)
• Paraneoplasm (anti-Yo)
• Neoplastic effect
• Heavy metal toxicity
• Certain heritable neurodegenerative diseases
• Ischemia/hemorrhage in area of vermis

Question 45

Medulloblastoma

Answer 45

• Common pediatric intracranial tumor
• Often in tentorium cerebelli area
• Presents commonly with cerebellar signs (truncal, limb, or both) and with pontine signs due to compression of the anterior pons

Question 46

Unilateral ataxia-hemiparesis often localizes to the. . .

Answer 46

. . . pons

This is where the corticospinal tract (hemiparesis) and middle cerebellar peduncle (ataxia) are localized

Question 47

Acute childhood cerebellar ataxia

Answer 47

• Post-viral phenomenon
• Diffuse cerebellar signs with NORMAL MRI
• Self-limited and benign

Question 48

Information entering and exiting Clarke’s nucleus in thoracic spinal cord