Cerebellum

1. Cerebellum Lecture Class by Pratap Sagar Tiwari, MD, Lecturer, NGMC

2. Nervous System Development : Anatomical subdivisions Source : http :// en.wikipedia.org/wiki/File:EmbryonicBrain.svg Reference: Gray’s Anatomy

3. Nervous System Development : Anatomical subdivisions Primary division of neural tube Sec. subdivision Final segments Prosencephalon 1. Telencephalon 2. Diencephalon The cortex ,  Caudate ,  Putamen ,  Globus pallidus 2. Thalamus, hypothalamus, subthalamus , subthalamic nuclei Mesencephalon Mesencephalon Mesencephalon (Midbrain),  Substantia nigra pars compacta ( SNc ) , Substantia nigra pars reticulata ( SNr ) Rombencephalon 1. Metencephalon 2. Myelencephalon 1. Pons and cerebellum 2. Medulla

4. The cerebellum is divided into anatomically distinct lobes. The main body of cerebellum has three functional regions: the central vermis and the lateral and intermediate zones in each hemisphere. It is divided by the primary fissure into anterior and posterior lobes. The posterolateral fissure separates the flocculonodular lobe. The Cerebellum Has Three Functionally Distinct Regions

5. Cerebellum & its connections Connections with brainstem: Superior cerebellar peduncle connects to midbrain Middle cerebellar peduncle connects to pons Inferior cerebellar peduncle connects to medulla

6. Afferent connections with spinal cord and brain Afferent connections with spinal cord and brain Cortico -cerebellar projection Ventral spinocerebellar tract Dorsal spinocerebellar tract

7. Efferent connections Efferent connections Thalamus Red nucleus Reticular formation Vestibular nucleus

8. Sections of the Cerebellum Vestibulocerebellum or archicerebellum Comprises the flocculonodular lobe Extensive connections with the vestibular system Spinocerebellum or paleocerebellum Comprises the vermis (medial) & paravermal (intermediate) region Extensive connections with the spinal cord & brainstem Cerebrocerebellum or neocerebellum Comprises lateral portions of cerebellar hemispheres (excluding paravermal regions) Extensive connections with cerebral cortex through relay stations in cerebellar nuclei and dorsal thalamus

9. CEREBELLAR PEDUNCLES

10. Superior cerebellar peduncle (brachium conjunctivum ) Connects to midbrain Afferents: only ventral spinocerebellar tract Efferents : Most of the efferents from the cerebellum All of the efferents from three (out of four) pairs of nuclei: dentate, emboliform , and globose

11. Middle cerebellar peduncle ( brachium pontis ) Connects to pons Afferents: from cerebral cortex (“ corticoponto -cerebellar system”). Corticopontine projections (originating in the cerebral cortex) synapse in ipsilateral basal pons.  From there, most pontocerebellar projections decussate, pass through middle cerebellar peduncle and enter cerebellum. A small number remain ipsilateral . Efferents : none.

12. Inferior cerebellar peduncle (“corpus restiform ” or “ restiform body ”) Connects to medulla Two components: Restiform body Afferents: Ascending spinal proprioceptive fibers from three of the spinocerebellar tracts (dorsal, rostral, and cuneocerebellar ) Ascending fibers from contralateral inferior olivary nuclei to cerebellar cortex ( olivocerebellar projections) Reciprocal connections with motor reticular formation and spinocerebellum ( paleocerebellum ): reticulocerebellar and cerebelloreticular projections Juxtarestiform body Mostly contains reciprocal connections to and from vestibulocerebellum ( archicerebellum ) and vermal portion of spinocerebellum ( paleocerebellum ): vestibulocerebellar and cerebellovestibular fibers

13. Cerebellar Anatomy Cerebellar Cortex Deep Cerebellar Nuclei: Dentate Interposed Fastigial PNS Fig. 42-1

14. General View Gross features of the cerebellum, including the nuclei, cerebellar peduncles, lobes, folia, and fissures. (Adapted from Nieuwenhuys et al. 1988) A. Dorsal view. Part of the right hemisphere has been cut out to show the underlying cerebellar peduncles. B. Ventral view of the cerebellum detached from the brain stem. C. Midsagittal section through the brain stem and cerebellum, showing the branching structures of the cerebellum.

15. upper motor neuron UMN BASAL GANGLIA Pyramidal Tract and Associated Circuits lower motor neuron UMN pyramidal tract Cerebellum

16. Motor Hierarchy Exerts influence at all levels Intent Actual 1° Som sensory

17. IV th vent Vermis Intermediate hem. Spinocerebellum: Vermis Intermediate hem. Spinocerebellum (Vermis + Intermed. Hem) Control of limbs and trunk Lateral hem. Cerebrocerebellum: Lateral hem. Cerebrocerebellum (Lateral hemisphere) Planning of movement+ Floculo-nodular lobe Vestibulo-cerebellum (Floculo-nodular lobe) Control of eye & head movements Balance Cerebellar divisions NTA Fig. 13-1

18. Inputs and Outputs of Cerebellum

19. The Cerebellum Has Three Functionally Distinct Regions

20. Cerebellar Cortex Inputs Output Interneurons Climbing fibers •from Inferior olive Mossy fibers Purkinje neurons Stellate neurons Granule neurons Basket neurons Golgi neurons Molecular Purkinje Granular NTA Fig. 13-11

21. The Cerebellum Has Three Functionally Distinct Regions The three functional regions of the cerebellum have different inputs and outputs.

22. Cerebellar Ataxia Ataxic gait and position: Left cerebellar tumor a. Sways to the right in standing position b. Steady on the right leg c. Unsteady on the left leg d. ataxic gait a b c d

23. Cerebellar dysfunction Dysfunction: damage produces the following: • Ataxia - a disturbance that alters the direction and extent of voluntary movements; abnormal gait and uncoordinated movements • Dysmetria - altered range of motion (misjudge distance) • Intention Tremor -oscillating motion, especially of head,during movement • Vestibular signs - nystagmus , held tilt

24. Cerebellar dysfunction 1. Small lesions produce no signs or only transient symptoms; small deficits are compensated for by other parts of the brain 2. Lesions of the cerebellar hemispheres result in loss of muscular coordination and jerky puppet-like movements of the limbs on the ipsilateral side (same side as lesion) 3. Lesions of the vermis result in truncal tremor and gait ataxia (splayed stance and swaying of the body while walking )[

25. References