CEREBELLUM

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Title and Author

  • External and Internal Structures of Cerebellum

  • Dr. Samuel O Okoronkwo

  • Course: Neuroanatomy

  • Course Code: ANA

  • Date: September 2023

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Objective

  • Name and identify different parts of the cerebellum

  • Describe the structure and functions of the cerebellum

  • Applied anatomy of cerebellum

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Overview of Cerebellum

  • Location: Posterior cranial fossa

  • Positioned behind the pons and medulla

  • Separated from cerebrum by the tentorium cerebelli

  • Fourth ventricle intervenes anteriorly between cerebellum and pons/medulla

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Anatomical Structure

  • Consists of two hemispheres connected by the vermis

  • Two surfaces: superior and inferior

  • Deep depression (vallecula) separates hemispheres on the inferior aspect

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Surface Features

  • Vermis is separated from corresponding cerebellar hemisphere by paramedian sulcus

  • Anterior and posterior notches separate hemispheres

  • Falx cerebelli lies in posterior notch

  • Surface marked by fissures subdividing into folia

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Fissures

  • Divide cerebellum into lobes with smaller lobules

  • Key fissures:

    • Primary fissure (transverse across superior surface)

    • Posterolateral fissure (inferior aspect)

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Superior Surface

  • Lies beneath tentorium cerebelli

  • Features: raised superior vermis, large hemispheres, primary & horizontal fissures

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Inferior Surface

  • Rounded with a deep groove (vallecula) between hemispheres

  • Tonsil: part lying lateral to inferior vermis

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Lobes of the Cerebellum

  • Divided into three lobes by fissures:

    • Anterior lobe (anterior to primary fissure)

    • Posterior lobe (between two fissures)

    • Flocculonodular lobe (remaining part)

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Cerebellar Zones

  • Midline: vermis

  • Either side: intermediate zone

  • Lateral to intermediate: lateral hemispheres

  • No structural difference between lateral hemispheres and intermediate zones

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Functional Divisions

  • Three functional areas:

    • Cerebrocerebellum (planning movements, motor learning)

    • Spinocerebellum (error correction in body movement)

    • Vestibulocerebellum (balance and ocular reflexes)

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Spinocerebellum and Vestibulocerebellum Functions

  • Spinocerebellum: regulates body movements, receives proprioceptive information

  • Vestibulocerebellum: controls balance and ocular reflexes

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Vermis Structure

  • Resembles a worm with diverse components:

    • Lingula, central lobule, culmen, declive, folium,

    • Tuber, pyramis, uvula

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Parts of Vermis

  • Primary fissure, various lobules and fissures of the anterior and posterior lobes, and flocculus of the flocculonodular lobe

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Lateral Relations in Vermis

  • Subdivisions relate laterally to parts of the hemisphere with specifics on each lobule's lateral counterpart

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Grey Matter

  • Located on surface forming cerebellar cortex

  • Central core features cerebellar nuclei, including dentate nucleus

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Nuclei in Grey Matter

  • Emboliform, globose, and fastigial nuclei with distinct positions relative to the dentate nucleus

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White Matter Structure

  • Central core consists of white matter, continuous with cerebellar peduncles

  • Fibers interconnect with the fourth ventricle

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Components of White Matter

  • Afferent fibers, projection fibers to nuclei, association fibers, commissural fibers

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Cerebellar Peduncles

  • Three bundles:

    • Superior

    • Middle

    • Inferior

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Superior Cerebellar Peduncle

  • Composed of fibers mainly from dentate nucleus, crucial for output to midbrain, thalamus, and red nucleus

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Middle Cerebellar Peduncle

  • Originates from lateral part of pons and connects cerebellum with pontine nuclei, handling input from cerebral cortex

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Inferior Cerebellar Peduncle

  • Also known as restiform body, connects medulla and cerebellum, receiving proprioceptive information from various body parts

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Vasculature

  • Blood supply: SCA, AICA, PICA

  • Venous drainage into various dural sinuses

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Applied Anatomy

  • Cerebellar dysfunction leads to various symptoms triggered by causes like stroke, trauma, or tumors

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Symptoms of Dysfunction

  • Remember acronym ‘DANISH’:

    • Dysdiadochokinesia

    • Ataxia

    • Nystagmus

    • Intention tremor

    • Scanning speech

    • Hypotonia

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Particular Symptoms

  • Ataxia affects muscle coordination, causing jerky movements and impairing fine tasks

  • Dysdiadochokinesia leads to irregular rapid movements, impact on reflexes and ocular movements

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More Symptoms

  • Hypotonia leads to reduced muscle tone

  • Postural changes and gait disturbances commonly observed, along with speech disturbances and potential vermis syndrome in children.