Neuroscience 1A LC10 Cerebellum PDF

UNIVERSITY OF NORTHERN NEUROSCIENCE 1A LC10 Cerebellum PHILIPPINES COLLEGE OF MEDICINE, BATCH 2026...

UNIVERSITY OF NORTHERN NEUROSCIENCE 1A LC10 Cerebellum PHILIPPINES COLLEGE OF MEDICINE, BATCH 2026 Dr. Allan Viado | Nov. 2022 Transcribers: Octaviano, Paringit, Patao, Quiambao LOCATION dorsal to the brainstem; connected to the brainstem by 3 pairs of OUTLINE cerebellar peduncles. I. INTRODUCTION in the posterior cranial fossa and covered by the tentorium A. Dural Partition cerebelli B. Dorsal View of Cerebellum lies posterior to the 4th ventricle, pons and medulla and is the C. Function of Cerebellum largest part of the hindbrain. D. Gross Anatomy of Cerebellum E. Gross Anatomical Organization II. INTERNAL ANATOMY A. Contents of Cerebellum B. Cortex Matter (Outer Area) 1. Molecular Layer 2. Purkinje Cell Layer 3. Granular Layer C. The 5 Cell Types 1. Purkinje Cells 2. Granular Cells 3. Golgi Cells 4. Basket Cells 5. Stellate Cells 6. Summary of Cell Types III. AFFERENT CEREBELLAR PATHWAYS A. Cerebellar Afferent fibers from the Cerebral Cortex B. Cerebellar Afferent fibers from the Spinal Cord C. Cerebellar Afferent fibers from the Vestibular Nerve D. Major Cerebellar Inputs IV. EFFERENT CEREBELLAR PATHWAYS A. Globose-Emboliform-Rubral pathway. B. Dentatothalamic pathway Figure 3: Posterior cranial fossa C. Fastigial vestibular pathway D. Fastigial reticular pathway V. CLINICAL IMPLICATIONS A. Presentation of Cerebellar Damage B. Functional Areas of the Cerebellum C. Types of Ataxia VI. RECALLS I. INTRODUCTION CEREBELLUM: - Literally means “little brain”. - Plays an important role in the control of posture and voluntary movements - Connected to the posterior aspect of brainstem by three symmetrical bundles of nerve fibers called superior, middle, and inferior cerebellar peduncles. - It is divided into three main lobes: Anterior, Middle and Floccunodular lobe. Figure 4: Sagittal view of cerebellum A. DURAL PARTITIONS Tentorium cerebelli - separates the cerebellum from the cerebrum Falx cerebelli - separates the two cerebellar hemispheres (right and left) Figure 1 & 2: Cerebellum 1 [NEUROSCIENCE1A]-01.04 Cerebellum – Dr. Allan Viado Figure 5: Midsagittal view of Dural partitions Figure 8: MRI showing Cerebellum Falx cerebelli C. FUNCTIONS OF CEREBELLUM Coordination of movement Figure 6: Posterior view of Dural partitions controls the timing and pattern of muscle activation during movement Maintenance of Equilibrium/balance B. DORSAL VIEW OF THE CEREBELLUM - Ovoid in shape in conjunction with the vestibular system - Middle: vermis Regulation of muscle tone - Lateral: 2 hemispheres - modulates spinal cord and brain stem mechanisms - Brainstem and 4th ventricle: anterior to the cerebellum involved in postural control. ❖ NOTE: - Tone - maintenance of partial contraction of muscle - Controlled by muscle spindles - receptors measuring muscle stretch/length (muscle spindles: received by the spinal cord (dorsal column and the spinocerebellar tract). Speech/Eye movement modulation - involuntarily controlled; only modulates or fine tune those movements. Some role in cognition Figure 7: Dorsal view of cerebellum - cerebellar damage may cause loss of some cognitive functions. D. GROSS ANATOMY OF CEREBELLUM DIVISIONS - can be seen from superior view 2 lateral hemispheres 1 vermis (middle) 2 [NEUROSCIENCE1A]-01.04 Cerebellum – Dr. Allan Viado 2 MAJOR FISSURES PRIMARY FISSURE - separates anterior lobe from the posterior (middle) lobe on the superior surface. DORSO/POSTEROLATERAL FISSURE - Separates the posterior (middle) - lobe from the flocculonodular - lobe on the inferior surface Figure 9. Superior view of cerebellum. TWO SURFACES a. Dorsal or Superior Surface - no distinction between the cerebellar vermis from the lateral hemispheres. Figure 12. Inferior/Ventral View of Cerebellum E. GROSS ANATOMICAL ORGANIZATION Figure 10. Superior view of cerebellum. b. Inferior or Ventral Surface vermis lies in depth of vallecula - vallecula is a groove or column in the vermis STRUCTURES FOUND: Flocculonodular lobe Figure 13. Cortex, sulci, & white matter of cerebellum - consist of flocculos and nodules INTERNAL ORGANIZATION Cerebellar tonsils - Similar to cerebral hemisphere - involved in brain herniation (tonsillar herniation) o Cerebellar cortex: - tonsillar herniation might compress against the - gray matter (surface) medulla oblongata that could lead to sudden death. - sulci - folia (rather than gyri- cerebellum): tree-like structure, deeply folded together o White matter (internal) - Similar to cerebral hemisphere - Deep cerebellar nuclei (4 pairs) ▪ embedded within the white matter ▪ analog with the thalamus which serves as a relay station. Figure 11. Inferior/Ventral View of Cerebellum 3 [NEUROSCIENCE1A]-01.04 Cerebellum – Dr. Allan Viado a. CORTEX OF VERMIS - most medial portion of cerebellum - associated with the fastigial nucleus (of the deep cerebellar nucleus) - concerned with the regulation of muscle tone for posture and locomotion - movement of the long axis of the body (trunk) namely neck, shoulders, thorax, abdomen & hips b. PARAVERMIS or INTERMEDIATE ZONE - Part of the cerebellum associated with the interposes nucleus (of the Deep cerebellar nuclei) Figure 14. Coronal section, posterior view of cerebellum. - Participates in the control of an evolving movement by utilizing proprioceptive sensory information generated by the movement itself to correct errors in the movement. 1. INTERNAL STRUCTURES OF CEREBELLUM - Control the muscle of the distal part of the limbs especially the Cerebellar cortex: hands & feet. - folded into transverse folds known as folia - Separated by fissures c. LATERAL ZONE OF THECEREBELLAR HEMISPHERE (CEREBROCEREBELLUM) - each fold of folia contains a core of white matter and - The largest and most lateral part of the cerebellum covered superficially by gray matter. - Associated with the dentate nucleus (of the deep cerebellar nuclei) o Arbor vitae: (tree of life) - Receives input from the cerebral cortex and Pontine nuclei - resembles the tree-like outline of the white - Sends outputs to the Thalamus and the Red nucleus matter - Influences the output to the motor cortex & permits fine delicate adjustments in muscle tone—skilled movement - Concerned with the planning of sequential movements of the entire body & is involved with the conscious assessment of the movement errors - Cognitive functions Figure 15. Arbor Vitae of Cerebellum 2. LONGITUDINAL “FUNCTIONAL” ZONES Figure 17. Longitudinal zones in transverse section 3. CEREBELLAR LOBES Figure 16. Superior view of an “unrolled cerebellum, placing the vermis in place. Figure 18. Fissures & Lobes of Cerebellum 4 [NEUROSCIENCE1A]-01.04 Cerebellum – Dr. Allan Viado a. ANTERIOR LOBE: SPINOCEREBELLUM (paleocerebellum) RELATED PATHOLOGY: - Related to spinal cord, postural tone - Cerebellar Tonsillar Ectopia - Connections are spinocerebellar tracts. Controls tone, - Tonsillar Herniation posture, &crude movement of limbs (e.g.: Swinging of arms - Chiari type I Malformation while walking). - Damage results in forelimb hyperextension hindlimb hip flexion - Separated from the middle love by a wide V-shaped fissure called primary fissure. b. POSTERIOR LOBE: CEREBROCEREBELLUM (neocerebellum) MIDDLE LOBE - Corticocerebellar in connection (Cerebral cortex). - Concerned with regulation of fine movement of limbs - damage results in hypotonia, hypermetria (inability to assess distance) & intention tremor - Largest part of the cerebellum - Situated between primary and uvulonodular fissures. c. FLOCCULONODULAR LOBE= VESTIBULOCEREBELLUM - Oldest part - Chiefly vestibular in connection (CN VIII vestibular nuclei). - Controls the axial musculature and bilateral movement used Figure 20. Traumatic Subdural Hematoma. for locomotion & maintenance of equilibrium - Associated with the vestibular system (Equilibrium, eye Traumatic Subdural Hematoma movement) - in the figure pushes the brain downward, that compression of the - Damage results in disequilibrium -problem with balance: e.g. brain may also push the cerebellar tonsils down towards the Damage to the right Flocculonodular Lobe has the tendency foramen magnum – Tonsillar Herniation, this downward to lose balance and fall towards the right side) herniation of tonsils towards the foramen magnum may - Wide based gait and nystagmus- flickering of the eye compress the medulla oblongata that may lead to sudden death. - Situated posterior to uvulonodular fissure o Deep horizontal fissure separates superior from the inferior surfaces. 4. OTHER IMPORTANT STRUCTURES Figure 21. Normal cerebellum (A) vs. Chiari Type I Malformation (B). Chiari type I malformation - the Cerebellar Tonsils are well below the foramen magnum; more than 5mm downward herniation of cerebellar tonsils in the foramen magnum. Figure 19. Inferior View of Cerebellum Showing the Cerebellar Tonsil 2. CEREBELLAR PEDUNCLES 1. CEREBELLAR TONSILS “Bridges’’ Relations: - acts as bridge to connect the cerebellum to other - Medial: uvula of the vermis structures like the brainstem - Superior: flocculonodular lobe - Anterior: posterior surface of the medulla and the 3 SYMMETRICAL BUNDLES OF FIBERS/AXONS cerebellomedullary fissure o SUPERIOR CEREBELLAR PEDUNCLES - Posterior: cisterna magna - Connects cerebellum with the midbrain - it is predominantly Efferent axons (Axons Goes away from cerebellum) 5 [NEUROSCIENCE1A]-01.04 Cerebellum – Dr. Allan Viado - contains mostly efferent tracts from the deep cerebellar nuclei - some tracts cross in the decussation of the superior peduncle, then divide into a descending limb (to the pons) and the ascending limb (to the midbrain and thalamus). o MIDDLE CEREBELLAR PEDUNCLES - connects the cerebellum with the pons - contains only Afferent axons from Pontine nuclei - contains only afferent tracts (Towards the cerebellum) Figure 24 (A) and 25 (B). Cerebellum layers and cell types. (A) Cell types and o INFERIOR CEREBELLAR PEDUNCLES their location across the cerebellar cortical layers. (B) Cerebellum ISH image - connects the cerebellum with the medulla. of Calb1. The different layers can be easily discriminated. P - the Purkinje - contains both Afferent and Efferent axons. layer; G - the granular layer; M - the molecular layer; W - the white matter. B. GREY/CORTEX MATTER: OUTER AREA 1. Molecular Layer: - Superficial - 2 types of neurons: o Outer Stellate Cell o Inner Basket Cells - Neuroglial Cells present. - Consists of predominantly of unmyelinated nerve fibers from the axons of granule cells, axon of stellate and basket cells, sensory climbing fibers, dendrites of purkinje and Golgi cells. Figure 22: Sagittal section through the Vermis of the Cerebellum showing - Largely a synaptic layer the location of the Three Cerebellar Peduncle - These neurons are scattered among dendritic arborizations and numerous thin axons that run parallel to the long axis of the folia. Neuroglial cells are found II. INTERNAL ANATOMY between these structures. A. THE CONTENTS OF CEREBELLUM 1. Cortex/Gray matter: Outer Area a. Molecular Layer – external layer b. Purkinje cell layer – middle layer c. Granular layer – internal layer 2. White matter: Medullary core/Inner volume a. Axons b. Four pairs of deep cerebellar nuclei embedded in the medullary core Figure 26. Molecular Layer and its cell Figure 23. Contents of the cerebellum. 6 [NEUROSCIENCE1A]-01.04 Cerebellum – Dr. Allan Viado 2. Purkinje Layer - Intermediate layer - Consists of a single row of Purkinje cell bodies (30 million cells) o Functional unit of cerebellum o Multipolar (Structural type) or Golgi type 1 neurons (large) o Classic type of neuron - Dendrites of Purkinje neurons extend into the molecular layer and axons synapses with the deep cerebellar nuclei. - They are flask shaped and are arranged in a single layer. In a plane transverse to the folium, the dendrites of these cells are seen to pass into the molecular layer, where they undergo profuse branching. The primary and secondary branches are smooth, and subsequent branches are covered by short, thick dendritic spines. It has been shown that the spines form synaptic contacts with the parallel fibers derived from the granule cell axons. - At the base of the Purkinje cell, the axon arises and Figure 28. The cell types of Cerebellum passes through the granular layer to enter the white 1. Purkinje Cells matter. On entering the white matter, the axon - Functional unit of the cerebellum (Multipolar or Golgi type 1 acquires a myelin sheath, and it terminates by neuron) synapsing with cells of one of the intracerebellar nuclei. - Largest cells compared to other cells in the CNS (cell body = - Collateral branches of the Purkinje axon make synaptic 60- 90 um in diameter), even larger than the pyramidal cells contacts with the dendrites of basket and stellate cells in the cerebral cortex. of the granular layer in the same area or in distant folia. - Cell body: In Purkinje cell layer. A few of the Purkinje cell axons pass directly to end in - Dendrite: In molecular cell layer - where they undergo the vestibular nuclei of the brainstem. profuse branching. 3. Granular Layer: - Axon: The only projections that exit the cerebellar cortex - Consists of densely packed neurons that send axonal (Only axon that will exit the cerebellar cortex). projections into the molecular layer. - Purkinje axon make synaptic contacts with the dendrites of - Composed of Granular cells (30 to 50 billion cells). basket and stellate cells of the granular layer in the same - Each cells gives rise to four or five dendrites, which area or in distant folia. make clawlike endings - Receives inhibitory synapse (GABA) from basket cells. - Receives inhibitory synapse (GABA & taurine) from stellate cells (occurs in the molecular layer) - Receives Excitatory synapse (aspartate) from a single climbing fiber granular. Figure 27. The granular layer C. THE 5 TYPES OF CEREBELLUM CELLS 1. Purkinje cells – Inhibitory neuron 2. Granule cells – Excitatory neuron 3. Golgi cells – Inhibitory neuron 4. Basket cells – Inhibitory neuron 5. Stellate cells – Inhibitory neuron Figure 29. The Purkinje Cell ❖ Unipolar Brush cells: - Excitatory synapses (glutamate) from granular cells/parallel - Floculonodular lobe/Vermis fibers. Over 200,000 mossy fibers indirectly through Golgi - Excitatory neuron cell, then granule cell excites each Purkinje cell. 7 [NEUROSCIENCE1A]-01.04 Cerebellum – Dr. Allan Viado - Mostly project to deep cerebellar nuclei (to all four); some throughout its length, and usually branches, if at fibers project to vestibular nuclei in brainstem Often also all, only a few times near its termination. releases a peptide co-transmitter. - Virtually all of the input to Golgi Type I neurons is - The primary and secondary branches are smooth, and onto the dendrites or cell bodies and output subsequent branches are covered by short, thick dendritic occurs at the axon terminals (one way information spines. transfer). Dendrites transmit information to the - They are flask shaped and are arranged in a single layer cell body, and axons transmit messages away from where they undergo profuse branching. the cell body. 2. Granular Cells b. Golgi Type II - 1x1011 granule cells (more neurons than entire cerebral - Characterized by having short, or sometimes no, cortex) axons. - Cell body: Located in granule cell layer. - Have smaller cell bodies than do Type I neurons. - Axon: Projects from granule cell layer, through Purkinje cell - Do not send processes from one part of the layer, up to molecular layer where it forms parallel fibers nervous system to another. Rather, their (which are oriented in a horizontal plane, parallel to the processes are usually confined toa single nucleus cerebellar folia. or layer. Golgi Type Il neurons are involved in local - Receives Inhibitory synapse (GABA) from Golgi cells. interactions between nerve cells and are often - Forms excitatory synapses (glutamate) on Golgi basket and called association neurons. stellate cell projecting to the molecular cell layer. - Dendrites and axons of Type II neurons are often - Most numerous neurons found in CNS, even more numerous both pre-and post-synaptic. That is, the dendrites than entire cerebral cortex. are not exclusively receiving input, nor are the - Their dendrites ramify in the molecular layer, and their axons axons exclusively providing output, as in Golgi terminate by splitting up into branches that synapse with the Type I neurons. Rather, both dendrites and axons dendrites of the granular cells. can both receive and make synaptic contacts. - Most of the parallel fibers make synaptic contacts with the spinous processes of the dendrites of the Purkinje cells. 4. Basket Cells - Interneuron. 3. Golgi Cells - Cell body located in molecular layer. - Interneuron - Name derives from the fact that its axons form “basketlike” - Acts as interneurons that are found between your sensory terminal arbors around soma/body of Purkinje cells. and motor cortex. - Dendrites: Oriented in rostrocaudal plane (perpendicular to - Cell body located in granule cell layer. folia). - Dendrites in all three layers, receiving excitatory stimuli - Receive excitatory stimuli (glutamate from granule cells’ (from molecular to purkinje cells to granular cell layer). parallel fibers. - Granule cells’ parallel fibers from excitatory synapses - Axons: Oriented in rostrocaudal plane (perpendicular to (glutamate) in molecular layer. folia). - Climbing fibers (from inferior olivary nucleus) form - Projects from the molecular layer to Purkinje cell layer. excitatory synapses (aspartate) in molecular layer. - Forms inhibitory synapses (GABA) with Purkinje cell body. - They serve as inhibitory interneurons - They are interconnecting with each other either inhibitory or excitatory. 2 TYPES of GOLGI NEURONS 5. Stellate Cells a. Golgi Type I - Interneuron - Long-axon neurons that carry information from - Cell body located in molecular layer. one part of the bran to another (that is, from one - Dendrites: Oriented in rostrocaudal plane (perpendicular to nucleus or nuclear layer to another) from the brain folia). or spinal cord to effector organs such as muscles. - Cells have multiple branching dendrites and a relatively short See multipolar neuron picture. axon, which terminates on a nearby neuron. - They are larger than Golgi Type II neurons - Receive excitatory stimuli (glutamate) from granule cell’s - Primary, secondary and tertiary dendrites can be parallel fibers). distinguished and the finest dendrites often have - Axons: project within the molecular layer. small lollipop-shaped spines on them. On the - Forms inhibitory synapses (GABA and taurine) on Purkinje spines can be found much of the synaptic input to cell dendrites. many Golgi Type II cells. - Both basket cells and stellate cells form inhibitory synapses - Each neuron has just one axon, which, as it comes with purkinje cells in the molecular cell layer. off the cell body, is thinner than the primary - Sometimes called granule cells because of their small size dendrites. It remains roughly the same size and are polygonal in shape. - Cell bodies measure about 8m in diameter. 8 [NEUROSCIENCE1A]-01.04 Cerebellum – Dr. Allan Viado SUMMARY OF CEREBELLAR CELL TYPES o Efferent fibers Cell function - Axons from the purkinje cells Stellate cells Inhibitory neuron Inhibit Purkinje cells - Axons leave the cerebellum thru the cerebellar peduncles - Fibers that goes away from the cerebellum Basket cells Inhibitory neuron Inhibit Purkinje cells Golgi cells Inhibitory neuron Inhibit granule cells Excited by mossy fibers Granule cells Excitatory neurons Excites Purkinje cells Excited by mossy fibers Purkinje cells Inhibitory neurons Excited by climbing fiber and multiple granular cells Inhibited by stellate and basket cells Table 1. Summary of the Cerebellar Cells Figure 31. Cerebellar Pathways AFFERENT CEREBELLAR PATHWAYS - Axonal fibers going towards the cerebellum Afferent fibers o Mossy fibers and climbing fibers - terminal fibers in the afferent tracts of the white Figure 30. Cerebellar Cortex. matter of the cerebellum, afferent tracts in the white matter of the cerebellum, synapse with the neurons within the cortex of cerebellum III. AFFERENT CEREBELLAR PATHWAYS - Cerebellar afferent fibers from the cerebral cortex- conscious information being related White matter of the cerebellum - Made up of axons towards the cerebellum - Arranged into tree like pattern known as arbor vitae - Embedded within the medullary core are 4 pairs of cerebellar A. CEREBELLAR AFFERENT FIBERS FROM THE CEREBRAL CORTEX nuclei 1. Corticopontocerebellar Function: Conveys control from cerebral cortex 3 types of fibers Origin: Frontal, parietal, temporal and occipital lobes o Intrinsic (commissural) fibers - Connects neurons on the same side Destination: via pontine nuclei and mossy fibers to - Connects right and left cerebellar hemispheres cerebellar cortex o Afferent fibers 2. Cerebro-olivocerebellar - E.g. Spinocerebellar/ Cuneocerebellar Function: Conveys control from cerebral cortex (comes from the nucleus cuneatus of the Origin: Frontal, parietal, temporal, occipital lobes dorsal column of the spinal cord, carries Destination: via inferior olivary nuclei and climbing proprioceptive information from fibers to cerebellar cortex extremities) 3. Cerebroreticulocerebellar - Towards the cerebellar cortex thru the cerebellar Function: Conveys control from the cerebral cortex peduncles Origin: Sensorimotor areas - Fibers that enter cerebellum Destination: via reticular formation 9 [NEUROSCIENCE1A]-01.04 Cerebellum – Dr. Allan Viado Figure 32. Afferent Cerebellar Pathway from the Cerebral Cortex Figure 33. Afferent Cerebellar Pathway from the Spinal Cord and Internal Ear B. CEREBELLAR AFFERENT FIBERS FROM THE SPINAL CORD C. CEREBELLAR AFFERENT FIBERS FROM THE VESTIBULAR - Unconscious information NERVE 1. Anterior spinocerebellar Vestibular Nerve Function: Conveys information from muscles and joints Function: conveys information of head position Origin: muscle spindles, tendon organs and joint and movement receptors Origin: utricle, saccule ad semicircular canals Destination: via mossy fibers to cerebellar cortex Destination: via mossy fibers to cortex of flocculonodular lobe 2. Posterior spinocerebellar Function: conveys information from muscles and joints D. MAJOR CEREBELLAR INPUTS Origin: muscle spindles, tendon organ and joint - Axons entering the cerebellum receptors Destination: cerebellar cortex 1. Climbing fiber inputs 3. Cuneocerebellar Cortico-olivocerebellar fibers Function: conveys information from muscles - Arise exclusively from the inferior olivary nucleus and joints of upper limb of the caudal medulla Origin: muscle spindles, tendon organs and joint - Have a powerful excitatory effect on purkinje cells receptors upon which they synapse Destination: cerebellar cortex - Known to coordinate signals to the cerebellum to Part of the pathway that conveys information regulate motor coordination and learning thru dorsal column 10 [NEUROSCIENCE1A]-01.04 Cerebellum – Dr. Allan Viado - Mainly from posterior spinocerebellar tract: ipsilateral (Anterior spinocerebellar tract: majority of the fibers will go to the other side as it enters the spinal cord.) c. Cerebropontocerebellar fibers - Arise from pyramidal/ Betz cells (motor cells) in the cerebral cortex, synapse on pontine nuclei which send their axons to the contralateral cerebellar cortex via pontocerebellar fibers (thru middle cerebellar peduncle) - Alerts cerebellum regarding anticipated movements (skilled, conscious movements). Figure 34. Climbing Fiber Inputs The inferior olivary nucleus goes toward the other side in IV. EFFERENT CEREBELLAR PATHWAYS the olivocerebellar pathway and connects with cerebellum via cerebral peduncles. - Axonal fibers going out of the Cerebellum Major Cerebellar Efferent Outputs - Arise from Purkinje cells projecting to neurons in Deep cerebellar nuclei - Purkinje cells are the functional units of the Cerebellum Deep Cerebellar Nuclei - Pairs of nuclei (nerve cell bodies) embedded in the cerebellar white matter - Embedded within the medullary core - Only receives from one type of axon, from the Purkinje cells Figure 35. Diagram of Climbing Fiber Input 2. Mossy fiber inputs a. Vestibulocerebellar fibers - Arise mainly from the vestibular nerve and vestibular nuclei; project to flocculonodular lobe via fastigial nucleus of the deep cerebellar nuclei (coordinate head and eye movement Figure 36. Cellular organization of the cerebellar cortex. - Balance and equilibrium Pathway: dendrites of the Purkinje cells in the molecular layer --- - Enters the cerebellum via inferior cerebellar > axons in the white matter ---> deep cerebellar nuclei ---> outside b. Spinocerebellar fibers of the cerebellum. - Arise from the spinal cord via spinocerebellar tracts on the same side, go to rostral lobe; makes cerebellum aware of ongoing movements via proprioceptive input from the muscle spindles and joint receptors 11 [NEUROSCIENCE1A]-01.04 Cerebellum – Dr. Allan Viado Cerebellar Nucleus Synonyms Region of the Cerebellar cortex that sends axons to the nucleus Dentate Nucleus Lateral Cerebellar Lateral portion of the nucleus cerebellar hemisphere Emboliform Anterior interpositus Intermediate part Nucleus nucleus Globose Nuclei Posterior Intermediate part interpositus nucleus Fastigial Nucleus Medial cerebellar Medial part / Vermis nucleus Table 2: Cerebellar nucleus and regions of the cortex from which they receive projections. Figure 36: Parts of the cerebellum Cerebellar Efferent Fibers Location - Entire output is through the axons of the Purkinje cells (inhibitory Fastigial: found in the medial part input) passing thru the deep cerebellar nuclei Interposed (Interpositus) nuclei (2 nuclei): Connect with the: Interpositus – means embedded between the fastigial and - Red nucleus (Globose-Emboliform-Rubral pathway) dentate nucleus - Thalamus (Dentatothalamic pathway) o Globus: Between the Fastigial and Dentate nucleus - Vestibular complex (Fastigial Vestibular pathway) o Emboliform: Between the Fastigial and Dentate nucleus - Reticular formation (Fastigial Reticular pathway) Dentate: Most lateral nucleus. EFFERENT CEREBELLAR PATHWAYS Pathway of signals from the deep cerebellar nuclei A. GLOBOSE-EMBOLIFORM-RUBRAL PATHWAY From lateral to medial - Axons of neurons in the globose and emboliform nuclei travel - Axons leave thru the superior cerebellar peduncle through the superior cerebellar peduncle and cross the o Dentate midline to the opposite side in the decussation of the superior o Emboliform cerebellar peduncles. o Globose - The fibers end by synapsing with the cells of the contralateral - Axons leave thru the inferior cerebellar peduncle (to the red nucleus, which give rise to axons of the rubrospinal tract. Brainstem) - Thus, this pathway crosses twice, once in the decussation of o Fastigial the superior cerebellar peduncle and again in the rubrospinal tract close to its origin. By this means, the globose and Note: No nuclei exits thru the middle cerebellar peduncle, it is emboliform nuclei influence motor activity on the same side of only for entry. the body. The input to the cerebellar nuclei is derived from two sources B. DENTATOTHALAMIC PATHWAY - Axons of neurons in the dentate nucleus travel through EXCITATORY INPUT the superior cerebellar peduncle and cross the midline - derived from the fibers that originate in cells that lie to the opposite side in the decussation of the outside the cerebellum (Afferent fibers eg: cerebellar peduncle. - The fibers end by synapsing with the cells in the Vestibulocerebellar fibers towards the Fastigial contralateral ventrolateral nucleus of the thalamus. nucleus) The axons of the thalamic neurons ascend through the INHIBITORY INPUT internal capsule and corona radiate and terminate in the primary motor area of the cerebral cortex. - derived from fibers that arise from the Purkinje cells - By this pathway, the dentate nucleus can influence of the cortex. motor activity by acting on the motor neurons of the opposite cerebral cortex; impulses from the motor cortex are transmitted to the spinal segmental levels through the corticospinal tract. - Remember that most of the fibers to the corticospinal tract cross to the opposite side in the decussation of 12 [NEUROSCIENCE1A]-01.04 Cerebellum – Dr. Allan Viado the pyramids or later at the spinal segmental levels. Thus, the dentate nucleus can be able to coordinate muscle activity on the same side of the body. C. FASTIGIAL VESTIBULAR PATHWAY - The axons of neurons in the fastigial nucleus travel through the inferior cerebellar peduncle and end by projecting on the neurons of the lateral vestibular nucleus on both sides. - Remember that some Purkinje cell axons project directly to the lateral vestibular nucleus. The neurons of the lateral vestibular nucleus form the vestibulospinal tract. The fastigial nucleus exerts a faciliatory influence mainly on the ipsilateral extensor muscle tone. D. FASTIGIAL RETICULAR PATHWAY Figure 37. Cerebellar Effector Fibers - The axons of neurons in the fastigial nucleus travels through the inferior cerebellar peduncle and end by V. CLINICAL IMPLICATIONS synapsing with neurons of the reticular formation. Axons of these neurons influence spinal segmental Each cerebellar hemisphere is connected by nervous pathways motor activity through the reticulospinal tract. principally on the same side of the body. Thus, a lesion of the cerebellar hemisphere will be limited to the ipsilateral side. Pathway Function Origin Destination Globose- Influences Globose To contralateral red emboliform- ipsilateral and nucleus, then via For example, if there's a lesion on the right cerebellum, the rubral motor emboliform crossed rubrospinal presentation would be on the right side. When the lesion is on the activity nuclei tract to ipsilateral left, the presentation will also be in the left side. motor neurons in the spinal cord A. PRESENTATION OF CEREBELLAR DAMAGE Dentatothalamic Influences Dentate To contralateral ipsilateral nucleus ventrolateral nucleus 1. ATAXIA: Cerebellar Ataxia - Trunkal (Axial - head, neck, motor of the thalamus, then thorax, abdomen, hips) vs Appendicular (arms, limbs or the activity to contralateral motor cerebral cortex; extremities) corticospinal tract 2. WIDE BASED GAIT- the patient may stand with feet farther crosses midline and controls ipsilateral apart than usual to maintain balance. motor neurons in the 3. INCOORDINATION (Dysdiadochokinesia) spinal cord Fastigial Influences Fastigial Mainly to ipsilateral 4. DYSMETRIA (Distance Overshooting) - you cannot calculate vestibular ipsilateral nucleus and to contralateral the distance; “sumosobra”; instead of touching the nose, extensor lateral vestibular muscle nuclei; vestibulospinal you might be touching your eyes. tone tract to ipsilateral 5. PROPRIOCEPTION PROBLEMS motor neurons in the spinal cord 6. INTENTION TREMORS - continuous moving of fingers or Fastigial Influences Fastigial To neurons of reticular trembling. reticular ipsilateral nucleus formation; muscle reticulospinal tract to 7. PENDULAR NYSTAGMUS - eyes swinging back and forth. tone ipsilateral motor 8. HYPOTONIA - loss of influence of the stretch reflex. neurons to the spinal cord 9. DYSARTHRIC SPEECH (Slurred) - due to ataxia of the muscle Table 3. Efferent Cerebellar Pathways of the larynx Note: No Weakness 13 [NEUROSCIENCE1A]-01.04 Cerebellum – Dr. Allan Viado B. IMPORTANT PARTS TO REMEMBER: FUNCTIONAL AREAS OF THE C. APPLICATION: CEREBELLUM Unilateral cerebellar hemisphere syndrome - Unilateral limb incoordination; ipsilateral cerebellar Vermis syndrome (Side of the lesion) - influences the movement of the long axis (Trunk) of the body - Loss of limb motor coordination of the same side - Neck, shoulders, thorax, abdomen, hips (Dysdiadochokinesia) Bilateral Cerebellar Hemisphere syndrome - Bilateral limb incoordination Vermis syndrome (midline cerebellar vermis lesion) - Vermis is unpaired - Trunkal ataxia or gait ataxia without limb incoordination - Affects the head and trunk (neck, shoulders, thorax, abdomen and hips) - Does not affect the limbs/extremities Flocculonodular lobe - related to vestibular functions - Vestibular signs & symptoms: Dysequilibrium (Balance problem)/ Nystagmus (eye problem). Figure 38. Cerebellar Vermis Intermediate zone/Paravermis - Immediately lateral to vermis - Control coordination of the distal parts of the limbs, hands and feet. Lateral zone of the hemisphere (Cerebrocerebellar) Figure 40. Flocculonodular lobe near the Posterolateral fissure. - Largest - Regulates coordination of muscle activation and is TYPES OF ATAXIA important in visually guided movements (vision is involved not muscle activation) a. CEREBELLAR – involves only the cerebellum - Conscious assessment of movement errors (In Trunkal/Gait Ataxia – Vermis syndrome coordination with the Cerebral cortex) – Limb/ - feet separation, wide based, low stooping Extremities. - The patient has difficulty narrowing the station and maintaining balance. Typically, they have a wide stand to maintain balance and oftentimes there will be unsteadiness in the trunk. Appendicular Ataxia – Hemispheric syndrome - Dysdiadochokinesia, Dysmetria (Finger to nose test), Intention tremor, Abnormal heel to shin test ▪ Dysdiadochokinesia: Appendicular Ataxia - Abnormal repeated/alternating movements (Hemisphere syndrome) - Cannot perform rapid alternating movements of fingers. - Test is done by touching the thumb by the index finger and turning closed palm medially and Figure 39. Parts of the Cerebellum showing Intermediate Zone and Lateral zone of the Hemisphere. laterally. 14 [NEUROSCIENCE1A]-01.04 Cerebellum – Dr. Allan Viado ▪ Intention Tremors (trembling of fingers in Dysequilibrium / Balance-ipsilateral side only: if you have a pointing) / Dysmetria (overshooting) - cannot problem with your RIGHT ear, you will have a problem balancing touch the nose instead the eyes. yourself towards your right. ▪ Heel-to-shin test or heel-to-knee-to-toe test – in - The patient will fall on the side of the lesion a recumbent position the patient will find it difficult to place the heel on the opposite knee Pendular Nystagmus – will occur in both eyes - Ataxia of the ocular muscles and slide it down the shin to the toe. In the - Rhythmic oscillation of the eyes of the same rate in both compromised patient, the heel will oscillate to the directions right and left off the shin as the movement is - If you have a middle ear lesion, your eye will not be affected. But if the problem involves the flocculonodular lobe, and made. Variations on this test may also be seen in because it innervates both R and L vestibular nuclei, it will patients with lesions of the posterior column– occur in both eyes. medial lemniscus system. Signs of Vestibular disease - Ataxia & Gait Disturbance ▪ Abnormal reflexes: Pendular Reflex - Ataxia with base-wide stance and swaying of trunk - Occurs following tapping of the patellar tendon. - Fall, roll, or lean-to side of lesion Normally, the movement occurs and is self- - May circle to side of disorder - No weakness if peripheral limited by the stretch reflexes of the agonists - No conscious proprioception deficits if peripheral. and antagonists. In cerebellar disease, because of loss of Influence on the stretch reflexes, the SUPPLEMENTARY NOTES movement continues as a series of flexion and extension movements at the knee joint; that is, Ataxia is the word to describe the loss of control of body movements. It may affect the trunk, one side of the body, the leg moves like a pendulum. both legs or one limb. - Depending on the side of the lesion (Right, left We need to consider problems that affect the vestibular or both) system, the cerebellum and proprioceptive pathways. Problems with the vestibular system cause disequilibrium b. PROPRIOCEPTIVE ATAXIA – unrelated to the cerebellum; abnormal joint position sense and unsteadiness. Sensory ataxia – lesions in proprioceptive pathways If the problem is unilateral, the patient develops Abnormal Rombergs Test (Loss of balance in the dark or when you profound vertigo with associated nausea, and vomiting. close your eyes) and Pseudoatethosis (Abnormal writing Drugs and alcohol are the most common causes of this movements, usually the fingers) - Causes: Peripheral Neuropathies, Dorsal column disorders of type of ataxia. If it is unilateral. Meniere's disease is the spinal cord that carries proprioceptive information important to consider. (infection, autoimmune, metabolic, vascular etc.) Like the cerebrum, the cerebellum is organized in ▪ Rombergs Test: assesses patient's joint position sense and somatotopic distribution with the trunk control centrally proprioception without aid from visual input. Position the and the limbs more laterally. The midline structure is the patients with their feet together and hands outstretched vermis. Lesions affecting the area, just lateral to and in front of them. Then ask to shut their eyes for a few including the vermis result in truncal or gait ataxia. seconds. In a positive Rombergs test, when the patient Patients have a wide base gait and appear drunk. shuts their eyes they become very unsteady on their feet Lesions affecting the cerebellar hemispheres result in or they fall. It signifies poor joint position sense. problems with voluntary limb movements. This is c. VESTIBULAR ATAXIA - Vestibular nerve / or lesions in flocculonodular referred to as appendicular ataxia. lobes 15 [NEUROSCIENCE1A]-01.04 Cerebellum – Dr. Allan Viado Finger nose testing and rapid alternating movements 6. It arises from pyramidal/Betz cells in the cerebral cortex, allow observation of these difficulties. They have synapse on the pontine nuclei which send their axons to the contralateral cerebellar cortex via pontocerebellar fibers. problems judging distances known as dysmetria and are A. Spinocerebellar Fiber C. Vestibulocerebellar Fiber unable to maintain the rhythm or amplitude of the B. Cerebropontocerebellar Fiber D. None movements known as dysdiadochokinesia. 7. Which of the following Pathway synapses with the Red Speech can also be affected with variations in intensity nucleus? and slurring of words. The last part of the cerebellum is A. Fastigial reticular pathway the flocculonodular lobe. Also known as the vestibular B. Fastigial vestibular pathway C. Dentatothalamic pathway cerebellum. Problems in this region result in postural D. Globose-Emboliform-Rubral pathway instability and impaired eye movement control. Cerebellar Ataxia can result from vascular lesions, such as 8. Which of the following nuclei(s) exits the Middle cerebellar peduncles? stroke or Hemorrhage, inflammation, demyelination, A. Dentate Nucleus C. Globose Nucleus tumors, infections, hereditary disorders, drugs or alcohol. B. Emboliform Nucleus D. None For example, sensory Ataxia refers to a problem with 9. Ataxia is defined as: proprioception. A. Inability to perform rapidly alternating movements. Lesions affecting this pathway results in an inability to B. Error in the range of movement stand with your eyes closed. This is a Romberg sign. The C. Lack of continuity in the execution of movements patient may walk heavily as they cannot judge how to D. Error in the rate, force, and direction of movement E. Muscle weakness place their feet. They will often stumble or try to walk in the dark as they 10. Loss of influence of the stretch reflex. no longer have visual input to assist them with their gait. A. Hypotonia C. Dysarthric Speech B. Pendular Nystagmus D. None This type of ataxia may be caused by. For example, inflammation, demyelination, vitamin deficiencies, infections and inherited disorders. VI. RECALLS 1. Separates cerebellum into 2 hemispheres? ANSWERS A. Tentorium Cerebelli C. Commissural Fissure B. Falx Cerebelli D. Sulci 1. B. Falx Cerebelli 2. A. Flocculonodular Lobe 2. Which lobe is the oldest in cerebellum? 3. C. Molecular Layer A. Flocculonodular Lobe C. Anterior Lobe B. Temporal Lobe D. Posterior Lobe 4. A. Purkinje Cell 5. A. Climbing Fibers 3. Which is the external layer of Cerebellum? 6. B. Cerebropontocerebellar Fiber A. Granular Layer C. Molecular Layer 7. D. Globose-Emboliform-Rubral pathway B. Purkinje Layer D. None 8. D. None (There is no nuclei that exits the Middle Cerebellar 4. Which cells is the Functional unit of Cerebellum? Peduncles) A. Purkinje Cell C. Golgi Cell 9. D. Error in the rate, force, and direction of movement. B. Granular cell D. Basket Cell 10. A. Hypotonia 5. The terminal fibers of the olivocerebellar tracts. A. Climbing Fibers C. Both A and B B. Mossy Fibers D. None 16