Cerebellum PDF

Cerebellum Anne K. Galgon PT, PhD, NCS Eric S. Pelletier PT DPT PCS  Objectives Identify specific structures of the cerebellum and connections Identify and describe the function of the cerebellum Identify the functional divisions of the cerebellum Identif...

Cerebellum Anne K. Galgon PT, PhD, NCS Eric S. Pelletier PT DPT PCS  Objectives Identify specific structures of the cerebellum and connections Identify and describe the function of the cerebellum Identify the functional divisions of the cerebellum Identify the specific neurons of the cerebellum and their functions Describe impairments of cerebellum function.  Cerebellar Function Maintenance of balance and posture Coordination of Voluntary Movements Motor Adaptation and Learning Cognitive Functions**  Cerebellar Anatomy Cerebellum means “little brain” Accounts for 10% brain volume Contains >50% of neurons in brain Two Hemispheres that communicate with each other – degree of somatotopic organization o Hemispheres separated by the vermis Folia – small ridges that run medial to lateral on the surface (means “leaves”) Cerebellum Sagittal View Thalamus  Cerebellar Lobes Flocculonodular Lobe o Located deep to the posterior lobe o Touches the brainstem Anterior Lobe o Superior o Separated from posterior lobe by primary fissure Posterior Lobe  Cerebellar Lobes The primary fissure Separates the Anterior and Posterior Lobes Cerebellar Lobes Cerebellar Lobes and Regions This is a schematic representation of the cerebellum From Schenkman ML et al. Clincial Neuroscience for Rehabilitation. Pearson (2013), p. 148. Regions Paravermis Lateral hemispheres  Cerebellar Nuclei Fastigial Interposed Nuclei o Emboliform o Globose Dentate From Schenkman ML et al. Clincial Neuroscience for Rehabilitation. Pearson (2013), p. 149  Cerebellar Nuclei Fastigial o Most medially located o Receives input from the vermis and from cerebellar afferents that carry vestibular, proximal somatosensory, auditory, and visual information. o Projects to the vestibular nuclei and the reticular formation.  Cerebellar Nuclei Interposed Nuclei o Globose o Emboliform o Receive input from the intermediate zone and from cerebellar afferents that carry spinal, proximal somatosensory, auditory, and visual information o Project to the contralateral red nucleus (the origin of the rubrospinal tract) Function of Rubrospinal Tract?  Cerebellar Nuclei Dentate Nucleus o Largest of the nuclei o Receives afferent fibers from medulla o Projects to the contralateral red nucleus and the ventrolateral (VL) thalamic nucleus.  Vestibular Nuclei Located in the rostral Medulla/ caudal Pons Functionally like the cerebellar nuclei o Connectivity patterns the same as cerebellar nuclei Receive input from the flocculonodular lobe and from the vestibular labyrinth Project to various motor nuclei and originate the vestibulospinal tracts Cerebellar Peduncles Form walls of the fourth ventricle Inferior Cerebellar Peduncle o Restiform Body (spinocerebellar fibers) o “Ropelike Body” o Justirestiform (vestibular cerebellar fibers) Middle Cerebellar Peduncle o Brachium Pontis o Massive connections to the pons Superior Cerebellar Peduncle o Brachium Conjunctivum Anterior spinocerebellar fibers Cerebellothalamic fibers  Cerebellar Peduncles Inferior cerebellar peduncle o afferent fibers from the medulla, as well as efferents to the vestibular nuclei. (Posterior spinocerebellar and vestibulocerebellar) o Mainly carry inputs Middle cerebellar peduncle o connect with pons, contain afferent fibers o Mainly carry inputs Superior cerebellar peduncle o efferent fibers from the cerebellar nuclei, as well as some afferents from the spinocerebellar tract o connect with midbrain, contain mostly efferent fibers o Mainly carry outputs Cellular Anatomy: Histology  Microanatomy of the Cerebellum Unique circuits for temporal and spatial processing of information (coordination of movement) Excitatory output of deep cerebellar nuclei Influenced by; o Excitatory inputs of afferent collaterals o Inhibitory influences of efferent cells Temporal processing through timing variances Spatial processing through various body components pp. 442-443 Haines  Cerebellar Cellular Anatomy Three Cell Layers o Molecular Layer o Purkinje Cell Layer o Granule Cell Layer  Neuronal Cell Types Purkinje Granule Basket Stellate Golgi  Neuronal Cell Types Purkinje Granule Basket Stellate Golgi  Purkinje Cell Layer Purkinje Cells o Extensive dendritic tree Dendrites extend only to molecular layer Numerous spines o Axons synapse with the deep cerebellar nuclei Axons of this type are the only ones that leave the cerebellar cortex o Modify the output of the cerebellum o GABA is neurotransmitter – inhibitory Purkinje Cells are the ONLY output cells for the cerebellar cortex  Granule Cells Axons of Granule cells project to the folia where they bifurcate and form the parallel fibers Higher density of parallel fibers relative to one Purkinje cell Excitatory synapses with Purkinje cells  Basket Cells Found in the molecular layer Dendrites extend into superficial molecular layer and receive excitatory input from parallel fibers Axons extend across folia (perpendicular to parallel fibers) and send collateral branch to Purkinjes o Inhibitory  Stellate Cells Found in Molecular Layer Axons extend across the folia perpendicular to parallel fibers o Stellate cells receive excitatory input from parallel fibers Inhibitory synapses on Purkinje o Have discrete influence on dendrites  Golgi Cells Deep to the Purkinje cells Dendrites extend to molecular layer o Excitatory connections with parallel fibers Axons enter granule layer o Inhibitory to granule cells  Cerebellar Glomerulus Complex synaptic structure Formed by o Golgi cells axons o Granular cell dendrites (RED) o Mossy Fibers (Red below, Blue right)  Cerebellar Cellular Fibers 4 fibers Types o Mossy fibers (vast majority) o Climbing fibers (olivocerebellar) o Parallel fibers (terminals of granule cells) o fibers from : Hypothalamus Pontine raphe nuclei Locus ceruleus  Mossy Fibers Excitatory afferent fibers that determine the output of Purkinje Fibers. Formed by efferent axons from Pontine nuclei Spinal cord Vestibular nuclei Reticular formation (Brainstem) Synapse with granule cell dendrites Make excitatory connections within glomeruli 1 mossy fiber connects to 600 granule cells which in turns connect to greater than 5000 Purkinje cells Mossy Fibers  Climbing Fibers Formed by afferent axons from Inferior olivary nucleus (in medulla) Olivary nuclei act as a major staging area for motor and sensory information entering the cerebellum Enter through inferior cerebellar peduncle Synapse with purkinje cell dendrites Collateral branches make excitatory connections deep cerebellar nuclei o Slow firing rate, strong enough to initiate action potential o Open Calcium channels affecting metabolism of Purkinje cell Mechanism that is responsible for motor learning. 1 climbing fiber can connect to as many as 300 Purkinje cells Climbing Fibers  Cerebellar Circuits Mossy fibers influence cerebellar output via two pathways: o a direct pathway to the cerebellar nuclei o a less direct pathway through the cerebellar cortex. Climbing fibers are thought to convey error signals to the Purkinje cells Excitatory inputs from : o Granule cells ( Parallel fibers) o Mossy fibers o Climbing Fibers o Aminergic fibers Inhibitory inputs from : o Purkinje cells o Stellate and basket cells o Golgi cells  Afferent-Efferent Communication Inferior Olive serves as relay center for sensory information into cerebellum o Descending input via the cortex and spinal cord Error detection system, Cerebellum analyzes the afferent information Compares planned movement to sensory experiences and Output from cerebellum via Purkinje cells signals for online adjustments o Refinement of motor activities of movements Impairment to Purkinje cells and inferior olive o Causes ataxia, loss of coordination, dysphagia, dysarthria  Functional Divisions Based on connections made within CNS Vestibulocerebellum o Congruent with flocculonodular lobe and vermis Spinocerebellum Cerebrocerebellum  Vestibulocerebellum Functional name for the Flocculonodular lobe Receives afferent input from: o Vestibular Nuclei o Vestibular apparatus Projects to o Vestibular nuclei Output reaches LMNs via o Vestibulospinal tract Regulates equilibrium Example: Person reaches for a book from a high shelf, vestibulocerebellum provides anticipatory contraction of lower limb and back muscles to maintain balance. If absent, the person would fall forward  Vestibulocerebellum Green Represent EFFERENT FIBERS Magenta Represent AFFERENT FIBERS Orange-Yellow Represent Motor Tracts to Trunk and Limbs Flocculonodular Lobe  Spinocerebellum Functional name for the vermis and paravermal region Receives input from: o Spinal cord o Vestibular nuclei o Auditory and vestibular info from brainstem nuclei Projects output to: o Vestibular nuclei o Reticular nuclei (via fastigial nucleus) o Motor Cortex (via fastigial nucleus) o Red Nucleus (via globose and emboliform nuclei) Regulates gross limb movements Example: Spinocerebellum coordinates the upper limb movement as the person reaches for the book. Without this input – the movement would be jerky and inaccurate.  Spinocerebellum Magenta Represent AFFERENT FIBERS from the spinocerebellar tracts Orange-Yellow Represent Descending Tract Fibers Green Represents output to cerebellar cortex  Cerebrocerebellum (Pontocerebellum) Functional name for the lateral cerebellum Receives input from: o Cerebral cortex (via pontine nuclei) Projects output to: o Motor and premotor cortices (via dentate nucleus and motor thalamus) o Red Nucleus Extends to LMNs via o Lateral corticospinal tract o Corticobulbar tract o Rubrospinal tract Regulates distal limb voluntary movements Example: Cerebrocerebellum would coordinate the finger and thumb movements necessary to grasp the book. From Lundy-Ekman L. Neuroscience: Fundamentals for Rehabilitation, 3rd Ed. Saunders Elsevier (2007), p. 263. Cerebellar Vasculature Branches of Basilar and Vertebral Arteries SCA – Superior Cerebellar Artery AICA – Anterior Inferior Cerebellar Artery PICA – Posterior Inferior Cerebellar Artery  Superior Cerebellar A. Supplies o Middle Cerebellar Peduncle o Superior Cerebellar Peduncle o Deep Cerebellar Nuclei o Cerebellar White Matter Infarction Causes: o Limb and Gait Ataxia o Abnormal saccades o Nystagmus Anterior Inferior Cerebellar Artery Supplies o Medulla and Pons o Inferior Middle peduncle o Inferior Peduncle o Flocculus o Vermis o Inferior Cerbellar Cortex Infarctions Cause o Limb and gait ataxia Posterior Inferior Cerebellar Artery Supply o Dorsolateral Medulla o Inferior/Posterior Vermis o Inferolateral surface of cerebellum o Dentate Nucleus Infarctions cause o Rotatory dizziness o Nausea, vomiting, imbalance, nystagmus  Cerebellum Clinical Disorders Lesions of Cerebellum affect the ipsilateral side of the body Signs of Cerebellar Dysfunction o Ataxia/Ataxic Gait o Nystagmus o Dysdiadochokinesia o Dysmetria o Decomposition of Movement o “Intentional tremor”  Ataxia Area Involved: Any lesion causes ataxia Ataxia is voluntary, normal-strength, jerky, and inaccurate movements Vermal and flocculonodular lesions lead to truncal ataxia Paravermal lesions result in gait and limb ataxia Lateral cerebellar lesions cause hand ataxia Testing for speed and accuracy Finger to finger or finger to nose Demonstrating intentional tremor  Vestibulocerebellar Lesions Signs o Ataxic Gait Patient will fall toward side of the lesion Cerebellar Gait (http://www.youtube.com/watch?v=eBvzFkcvScg) o Nystagmus o Vertigo o Emesis  Spinocerebellar/Cerebrocerebellar Lesions Dysdiadochokinesia – loss of timing between agonist and antagonist o Cannot perform rapid alternating movements o Sequence of individual muscle contraction is impaired Dysmetria – performance deteriorates as the motor act progresses o Different than intention tremor Hypermetria – forceful rebound of limb Decomposition – performance of motor activity by moving only one joint at a time because of an inability to control the entire movement o Helps improve movement o Ataxia – disruption in the precision of motor acts  Videos Abnormal Coordination Exam ; o Hand Rapid Alternating Movements Dysdiadochokinesia o http://www.youtube.com/watch?v=ylcWsoBOGzk Dysmetria o http://www.youtube.com/watch?v=jnQcKAYNuyk Abnormal Coordination Exam ; Finger-to-nose o http://www.youtube.com/watch?v=-dFMisBl1aM  Comparison of basal ganglia and cerebellum. Assignment 5 Spinocerebellar Sensory input  Comparison of lesions in basal ganglia versus cerebellum. Assignment 5 Basal ganglia Cerebellum o Resting tremor o Intention tremor o Bradykinesia or hypokinesia o Normal velocity of movement (reduced amplitude of (but patients tend to slow down movement) as a strategy to be accurate) o Hyperkinesia o No hyperkinesia o Rigidity o Hypotonia o No ataxia o Ataxia o Secondary disequilibrium o Loss of equilibirum o No nystagmus o Nystagmus  Clinical Case A 47 year old woman is seeing a physical therapist for an initial examination. Her primary complaint is of increasing right sided clumsiness and shaking. She reports that the onset of these symptoms has been gradual and began approximately 4 months ago. Examination findings reveal the following: o Normal somatosensation, autonomic function, and muscle strength t/o o Coordination normal left upper and lower extremity o Right side – rapid alternating movements are slow and uncoordinated, intention tremor occurs during finger to nose and heel to shin tests. o Right dysmetria on finger-to –nose test. o Abnormal involuntary eye movements.  Question 1 What is the location of the lesion (structure and which side)?