Lecture 23: Cerebellar Pathways, Function and Dysfunction Flashcards
Overarching principle of cerebellar organization
each functional lobe has its own region, its own input, its own deep nuclei, and its own output
What is function of corticopontocerebellum/cerebrocerebellum?
Initiation
-planning and learning of complex movement
What nucleus is associated with cerebrocerebellum?
dentate nucleus
What are the inputs and outpus of the cerebrocerebellum?
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
What is the function of spinocerebellum?
Senses stretch
-controls medial and lateral descending systems (so limb and axial musculature)
Muscle execution
What are the input and outputs of spinocerebellum?
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
Clarke’s nucleus
group of interneurons that is important for proprioception
-secondary neuron in proprioception pathway…relays shit to the dorsal spinocerebellar tract
What nucleus is associated with spinocerebellum?
Fastigial (medial) and interposed (lateral
What is the function of Vestibulocerebellum?
coordinates head and eye movements
Posture
What nucleus is involved in vestibulocerebellum?
Vestibular nucleus
What inputs/outputs for vestibulocerebellum?
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
What is the hallmark sign of cerebellar disease?
Ataxia
What is cerebellar ataxia?
Incoordination and decomposition of movement that is NOT due to weakness (paresis), alteration in tone, sensory loss
What are other signs of cerebellar dysfunction?
Gait ataxia, titubation, tremor, dysmetria, dysdiadochokinesis, nystagmus, rebound/losss of check, scanning speech
What is Titubation (truncal ataxia)?
-nodding movement of the head or body while you are trying to sit still
Example: lady who couldn’t sit still on a bed
What is Dysmetria (intention tremor)?
inability to touch your nose
What is Dysdiadochokinesis?
an inability to perform rapidly alternating movements, such as rhythmically tapping the fingers on the knee
What is Rebound/loss of check?
(when the triceps does not tense up so that your arm keeps moving downward after a weight is removed)
What is nystagmus?
fast uncontrollable movements of the eyes that may be side to side or up and down
Scanning Speech
disruption of the metrical structure
Example saying La La La, Ka Ka Ka
Are cerebellar syndromes common? And if not, what do they usually go with?
Isolated cerebellar syndromes are rare
-they are usually paired with brainstem dysfunction
What is the recovery process of cerebellar disease like?
-recovery can be rapid, or with slowly progressive damage, a large volume of cerebellum could be gone by the time signs are apparent
What is progression of cerebellar disease with transient hypotonia? Normal tone?
Acute = hypotonia Chronic = normal tone
What happens with midline cerebellar lesions?
Truncal and proximal limb dysfunction
What happens with hemispheric (lateral) cerebellar lesions?
Lateralized/distal dysfunction
-Appendicular ataxia is maximal at the extreme endpoint of a motor act (like right before finger touches nose)
Are cerebellar lesions cause dysfunction on the contralateral or ipsilateral side of the body?
Ipsilateral
Whats the difference between cerebellum and sensory ataxia?
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
Aside from sensory ataxia, what else can be confused with cerebellar disease?
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
What are 7 common causes of cerebellar disease?
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)
What should you do if you see a 2year odl that is groggy, ataxic and has nystagmus?
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
Carbamazepine/Tegretol
Medicine that could cause baby to be ataxic and present with cerebellar disease
Varicella (chicken pox)
Can cause acute cerebellar dysfunction
