Lecture 23: Cerebellar Pathways, Function and Dysfunction

Question 1

Overarching principle of cerebellar organization

Answer 1

each functional lobe has its own region, its own input, its own deep nuclei, and its own output

Question 2

What is function of corticopontocerebellum/cerebrocerebellum?

Answer 2

Initiation

-planning and learning of complex movement

Question 3

What nucleus is associated with cerebrocerebellum?

Answer 3

dentate nucleus

Question 4

What are the inputs and outpus of the cerebrocerebellum?

Answer 4

Two inputs
frontal lobe  anterior lateral internal capsule  crus cerebri –< pons  pontocerebellar pathway  MCP  cerebellar cortex + dentate
Parietal-occipital-temporal lobe  internal capsule  crus cerebri  pons  crossing pontocerebellar pathway  MCP  cerebellar cortex + cortex

Output pathway:
Purkinje Cells  dentate nucleus  crossed dentate-rebro-thalamic tract  VL  motor cortex

Question 5

What is the function of spinocerebellum?

Answer 5

Senses stretch
-controls medial and lateral descending systems (so limb and axial musculature)
Muscle execution

Question 6

What are the input and outputs of spinocerebellum?

Answer 6

Input: somatosensory receptors  nucleus dorsalis of Clark  fasciculus gracilis  nuceleus dorsalis of clark  dorsal spinocerebellar pathway  ICP  cerebellar cortex  fastigial nucleus

Output: Purkinje neurons of fastigial nucleus  vestibular nucleus  vestibulospinal tract  alpha/gamma motor neurons

Question 7

Clarke’s nucleus

Answer 7

group of interneurons that is important for proprioception

-secondary neuron in proprioception pathway…relays shit to the dorsal spinocerebellar tract

Question 8

What nucleus is associated with spinocerebellum?

Answer 8

Fastigial (medial) and interposed (lateral

Question 9

What is the function of Vestibulocerebellum?

Answer 9

coordinates head and eye movements

Posture

Question 10

What nucleus is involved in vestibulocerebellum?

Answer 10

Vestibular nucleus

Question 11

What inputs/outputs for vestibulocerebellum?

Answer 11

Input: vestibular (hearing) apparatus  CN VIII can go to either vestibular nerve or ICP to flocculonodular lobe cortex

Output: purkinje cell  vestibular nerve to medial longitudinal fasciculus (MLF) and lateral vestibule spinal pathway to alpha and gamma motor neurons

Question 12

What is the hallmark sign of cerebellar disease?

Answer 12

Ataxia

Question 13

What is cerebellar ataxia?

Answer 13

Incoordination and decomposition of movement that is NOT due to weakness (paresis), alteration in tone, sensory loss

Question 14

What are other signs of cerebellar dysfunction?

Answer 14

Gait ataxia, titubation, tremor, dysmetria, dysdiadochokinesis, nystagmus, rebound/losss of check, scanning speech

Question 15

What is Titubation (truncal ataxia)?

Answer 15

-nodding movement of the head or body while you are trying to sit still
Example: lady who couldn’t sit still on a bed

Question 16

What is Dysmetria (intention tremor)?

Answer 16

inability to touch your nose

Question 17

What is Dysdiadochokinesis?

Answer 17

an inability to perform rapidly alternating movements, such as rhythmically tapping the fingers on the knee

Question 18

What is Rebound/loss of check?

Answer 18

(when the triceps does not tense up so that your arm keeps moving downward after a weight is removed)

Question 19

What is nystagmus?

Answer 19

fast uncontrollable movements of the eyes that may be side to side or up and down

Question 20

Scanning Speech

Answer 20

disruption of the metrical structure

Example saying La La La, Ka Ka Ka

Question 21

Are cerebellar syndromes common? And if not, what do they usually go with?

Answer 21

Isolated cerebellar syndromes are rare

-they are usually paired with brainstem dysfunction

Question 22

What is the recovery process of cerebellar disease like?

Answer 22

-recovery can be rapid, or with slowly progressive damage, a large volume of cerebellum could be gone by the time signs are apparent

Question 23

What is progression of cerebellar disease with transient hypotonia? Normal tone?

Answer 23

Acute = hypotonia
Chronic = normal tone

Question 24

What happens with midline cerebellar lesions?

Answer 24

Truncal and proximal limb dysfunction

Question 25

What happens with hemispheric (lateral) cerebellar lesions?

Answer 25

Lateralized/distal dysfunction

-Appendicular ataxia is maximal at the extreme endpoint of a motor act (like right before finger touches nose)

Question 26

Are cerebellar lesions cause dysfunction on the contralateral or ipsilateral side of the body?

Answer 26

Ipsilateral

Question 27

Whats the difference between cerebellum and sensory ataxia?

Answer 27

Sensory ataxia will present with a Romberg sign
Example: Tabes dorsalis (degeneration of dorsal columns)
-ataxia is greatly exacerbated without sight because patient depends on sight
-loss of sensory input to cerebellum

Cerebellar ataxia

• titubation, dysarthria
• position and vibration sense are spared
• not as greatly exacerbated by eye closure

Question 28

Aside from sensory ataxia, what else can be confused with cerebellar disease?

Answer 28

i. vestibular dysfunction
Vertigo: a sensation of spinning
	-used as a key distinguishing feature
ii. corticospinal tract disease
	Distinguished by UMN signs
iii. Proximal limb weakness
	-Distinguishing feature: weakness

Question 29

What are 7 common causes of cerebellar disease?

Answer 29

i. vascular disease (occlusion of SCA, PiCA, AiCA)
ii. Neoplasia
iii. Inflammatory cerebellar disease (multiple sclerosis, and can be due to viral infection)
iv. Cerebellar degeneration Panneoplastic cerebellar degeneration
-tumor associated degeneration associated with anti-neuronal antibodies…which are associated with cancer
v. Toxic/nutritional:
Acute toxicity = alcohol
Chronic toxicity = alcohol
vi. Metabolic: Wilson disease
vii. Congenital Cerebellar defects: chiari malformation (herniation of cerebellar tonsil)

Question 30

What should you do if you see a 2year odl that is groggy, ataxic and has nystagmus?

Answer 30

Suspect toxicity or nutritional problem
Ask if they have taken anything with carbamazepine or tegretol
Remember, lady is peds neurologist so probably cares about this type of case

Question 31

Carbamazepine/Tegretol

Answer 31

Medicine that could cause baby to be ataxic and present with cerebellar disease

Question 32

Varicella (chicken pox)

Answer 32

Can cause acute cerebellar dysfunction