Coordination 1z6n47

COORDINATION

Adelina Yasmar Alfa

Bag/SMF Ilmu Panyakit Saraf FK-Unpad / RS-Hasan Sadikin Bandung 2001

Cerebellum as center of coordination -Anatomy

-Physiology -Its disorder

Anatomy • Occupies most of the posterior cranial fossa • Dorsal to the brainstem and attached to it by cerebellar peduncles : – Superior cerebellar peduncle (Brachium conjunctivum)  midbrain – Middle cerebellar peduncle (Brachium pontis)  pons – Inferior cerebellar peduncle (restiform body)  medulla oblongata

• Other relationship : – The fourth ventricle – Tentorium cerebelli

Anatomy (ctnd) • Composition – Cerebellar hemispheres

– Vermis : cortex and medulla (incl. Nuclei)

• Lobes – Anterior lobe (palaocerebellum) • C/o most of the vermis and anterior aspect of hemispheres • Associated with proprioceptive (spinecerebellar) and exteroceptive input • Significant role in regulation of muscle tone (maintain posture)

– Posterior lobe (neocerebellum) • The largest part; c/o main bulk of hemisphere and part of vermis • Receive connections of cerebrum through nuclei & brachium pontis • Role in muscular coordiantion of phasic movement

– Flocculonodular lobe (archicerebellum) • C/o paired flocculi of hemispheres and unpaired nodulus • Cerebellar portion of vestibular system (somatic afferent collumn) • Significant role in muscle tone, equilibrium, and posture (trunk muscles)

Anatomy (ctnd) Cerebellar cortex • Layers – Molecular layer : • Outer layer – synaptic integrative layer • Input from granular layer and deep cerebellar nuclei • C/o nerve fibers and some basket cell

– Purkinje cell layer • Middle cell layer –Output layer to the intrinsic cerebellar nuclei

– Granular layer • Innermost layer – receive input from outside

• Cell and Nerve types

Anatomy (ctnd) Cerebellar cortex (ctnd) • Cell and Nerve types – Granule cells, Purkinje cells, Basket cells, Golgi cells – Mossy fibers • Primary cerebellar input from pontine nuclei and spinocerebellar pathways • Function : to excite the granule cell

– Climbing fibers (Cf) – Its cell bodies located in the inferior olivary nucleus

– Synapse with primary and secondary dendritic branches of Purkinje cells at many sites  each action potential in Cf cause a giant EPSP

 a burst of repetitive Purkinje cell firing

Anatomy (ctnd) Subcortical cerebellar nuclei • Dentate nuclei • Emboliform nuclei* • Globose nuclei • Fastigial nuclei* Relationship of cerebellar cortex and subcortical nuclei • Lateral areas of cortex to dentate nuclei • Paramedian areas to emboliform and globose nuclei

• Median area (vermis) to globose and fastigial nuclei * The emboliform and globose nuclei are collectively called the nucleus interpositus

Anatomy (ctnd) Cerebellar connections All fibers carrying information to and from cerebellum do of the cerebellar peduncles

so by way

Incoming (afferent) fibers •

Superior cerebellar peduncle : anterior spinocerebellar tract (paleo-), tectocerebellar tract (midbrain tectum to neocerebellum), trigeminocerebellar tract

•

Medial cerebellar peduncle (entirely afferent!!) : corticopontocerebellar tract !! Each cerebellar hemisphere monitors the activity of the opposite cerebral hemisphere

•

Inferior cerebellar peduncle : conveys “unconscious” exteroceptive and proprioceptive fibers from the spinal cord and vestibular system : – Dosrsal spinocerebellar (to paleo-) – Vestibulocerebellar (to archi- of the same and opposte sides)

Anatomy (ctnd) Cerebellar connections Outgoing (efferent) fibers : No direct cerebellospinal pathways exist !! •

Superior cerebellar peduncle : primarily c/o the efferent fibers from dentate (-rubral, -thalamic,-reticular), emboliform and globose nuclei (the last two project to red nucleus, inferior olive, reticular formation)

•

Medial cerebellar peduncle : No efferent fibers

•

Inferior cerebellar peduncle : Through juxtarestiform body – Fastigiobulbar tract (fastigial nuclei to vestibular and reticular nuclei

Physiology Normal cerebellar function Responsible for muscle synergy (coordination) throughout the body Coordinates the action od muscles and times their contraction  movement smoothly and accurately

As a monitor of other center of the brain (not the iniator!) The modulator (regulator) of motor activities; integrated with : •

Vestibular system (maintain muscle tone and equilibrium)

•

General proprioceptive and exteroceptive receptors

•

Auditory and visual system

Basically a somatic afferent organ !!

Cerebellar Disorder • Neocerebellum – Dysmetria –inability to stop the movement at the desired point (overshoots or stops before it is reached) – Intention tremor – evident during purposeful movement, but absent/diminished with rest. Titubation : rhytmic tremor iof the head, 3-4x/minute- lesion in the midline of cerebellum – Postural disturbance – A/dysdiadochokinesis - inability to stop a movement and follow it immediately by directly opposite action – Hypotonia – ipsilateral to the lesion site; loss of cerebellar facilitation to the stretch reflex – Eye disturbance : skew deviation and nystagmus (also occurred in vestibular lesion and its connections) – Disturbance of articulation and phonation : scanning speech/stacatto – Gait disturbance : cerebellar ataxia (tend to fall to the lesion site)

Cerebellar Disorder • Paleocerebellum – Symptoms and signs of postural and muscle tone disrturbance

• Archicerebellum – Truncal ataxia (swaying while sitting) – Vertigo

Examination of coordination • Equilibratory coordination - maintanance of balance and the coordination of the body as a whole; examination of station and gait – Truncal ataxia, titubation – Romberg sign, Walk tandem

• Non-equilibratory coordination – ability to carry out discrete, relatively fine, intentional movement with extremities. – Dysmetria, Dysdiadochokinesia – Nose-to-finger test, finger-to-finger test, heel-to-knee-to-toe test – Rebound test, test pointing and past pointing – Functional test : button-unbuttoning, writing, picking coin at desk