Chapter 8 DeMyer

Eleanor A. Go

Examination for Cerebellar

Dysfunction

Coordinating willed muscular contractionsCoordinate means to adjust the rate,

range, force, and sequence of willed muscular contraction.

To make a movement, the brain must know where the body part starts from to orchestrate the sequence, rate, and force of muscular contractions required to get from point A to point B

Function of the Cerebellum

The three cerebellar lobes:A. Larsell (1972) divided the cerebellum

transversely into three lobes and longitudinally into three parts, one midline vermis uniting two hemispheres

Anatomy of the Cerebellum

Archicerebellum (phylogenetically oldest; vestibulocerebellum): flocculus, nodulus- concerned with equilibrium and connects with the vestibular system; primitive animals require only a small cerebellum to coordinate the axial muscles that position the eyes, head and trunk.

Vestibulocerebellar tacts

Cerebellum: Divisions and Functions

b

Paleocerebellum (spinocerebellum): the emergence of the

vertical bipedal from the quadripedal posture places particular demands on gait coordination. This position of the cerebellum evolves to receive most of the propioceptive input from limbs and trunks, the anterior lobe.

Receives major input from the spinocerebellar tract.

Cerebellum: Divisions and Functions

Neocerebellum: (cerebrocerebellum) the newest cerebellar lobe expands in equal measure with the cerebrum, motor cortex, pyramidal tracts, pontine basis and inferior olivary nuvclei.

Major inputs from corticopontocerebellar and olivocerebellar pathways

Cerebellum: Divisions and Functions

Somatotopic representation within each nucleus Each nucleus controls a different type/mode of movement

Fastigial: stance, gait– controls muscles in modes of sitting, standing, walking

Interposed: assist segmental reflexes (stability); speeds initiation of movements triggered by somatosensory cues; damp unwanted movements (delayed check/rebound, abnormal RAM’s, action tremor, impaired finger-to-nose)

Dentate: assists tasks needing fine dexterity; delays in initiating/terminating movements, intention tremor; finger movments

Cerebellum- Deep Nuclei Functions

Superior: efferents from cerebellar nuclei (and afferents from ascending ventral spinocerebellar tract) composed mainly of efferent fibers -- send impulses to thalamus + spinal cord, with relays in the red nucleus

Middle: contains afferent fibers from cerebral cortex by way of the corticopontocerebellar pathway; consists of fibers from contralateral pontine nuclei

Inferior: contains afferents from vestibular, somatosensory and olivary sources (vestibulocerebellar, dorsal spinocerebellar, cuneocerebellar and olivocerebellar fibers); fiber systems from spinal cord and vestibular nuclei ---- efferents to vestibular nuclei

Cerebellum- Peduncles

The keys to detecting cerebellar dysfunction:Cardinal cerebellar signs consist of:

1. Ataxia (taxis means “ordered”; ataxia= “not ordered”) incoordinated contractions of muscles during volutional movements or during volitionally sustained postures.

2. Tremor (intention and Postural): intention tremor (end point or kinetic tremor)- tremor as a limb approaches a target; Postural tremor- tremor of intentionally maintained head and trunk posture or of a limb suspended in front of the body

3. Hypotonia – loose floppy joints and muscles4. Nystagmus- uncoordinated, oscillations of the

eyes

Clinical signs of cerebellar dysfunction

5. uncoordinated slurred sppech is called dysarthria

6. the person becomes silly, illogical, disinhibited and socially inappropriate

Clinical signs of cerebellar dysfunction