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Cerebellum and Basal Ganglia David Roman Renner, MD Suzanne Stensaas, PhD 2009 Kenya Curriculum BG CBLM Courtesy of Stephen C. Voron, MD BG CBLM Courtesy of Stephen C. Voron, MD pyramidal cell in the motor homunculus of the frontal lobe BG CBLM Courtesy of Stephen C. Voron, MD corticospinal tract BG CBLM Courtesy of Stephen C. Voron, MD BG CBLM decusation at the pyramids (spinomedullary junction Courtesy of Stephen C. Voron, MD BG thalamus: AKA the “gate keeper” prevents unwanted movements T CBLM Courtesy of Stephen C. Voron, MD BASAL GANGLIA BG consultant on automatic movements T CBLM Courtesy of Stephen C. Voron, MD provides input into the thalamus Cerebellum: consultant on rapid movements BG CBLM Courtesy of Stephen C. Voron, MD provides input into the thalamus Basal Ganglia Cerebellum • • • • • • • • • • • • • • • • • • • • • • • resting tremor postural instability festination rigidity masked facies bradykinesia dyskinesia torticollis chorea athetosis hemiballismus akathisia intention tremor dysmetria dysdiadochokinesia hypotonia heal to shin finger to nose rebound ataxic gait titubation nystagmus dysmetric saccades Basal ganglia lesions produce contralateral signs. Cerebellar lesions produce ipsilateral signs. Most movement disorders produced by cerebellar and basal ganglia pathology disappear during sleep. Cerebellar and basal ganglia signs are usually not present if the corticospinal tract is damaged. The cerebellum is the great comparator: 1. It compares cortical willful command with muscle tension, joint position, & tone (via ipsilateral spinocerebellar tracts) 2. Advises the cortex on how much, how many, how fast 3. The motor cortex sends the revised command down the corticospinal tract The BASAL GANGLIA are the autopilot for procedural movements. The CEREBELLUM is the refiner of finely controlled movements (particularly of fingers). COMPARISON OF MOTOR SYSTEMS http://library.med.utah.edu/neurologicexam/html/home_exam.html Lowe r Motor Neuron Spina l Cord Uppe r Motor Neuron Corticospina l Tract Cerebellum Basal Ganglia Efferent part of monosynaptic reflex Volunta ry movement Muscle tone by inhibiting antagonists Maintains muscle fibers (trophic factors) Muscle tone Rapid coordinated alternating skilled movements that are learned Eye-head movements Facilitates intentional movements and inhib it extraneous movements Autopil ot for motor activities Normal Weakness or paralysis Fine control, espec. finger flexors Inhibitory to Lower motor neurons Weakness or paralysis Posture and Gait Balance, equili brium, orientation in space timi ng, duration, and ampli tude Voluntary movements in an automatic manor. Hyperreflexia Hyperactive deep tendon reflexes Babins ki- extensor plantar reflex Spasticity Trunca l ataxia, gait ataxia Shuffling or festinating gait, small steps, hard to turn Nystagmus, Dizziness, Masked facies, few bli nks Decomposition of movement Diffi culty turning or starting, hypo kinetic = bradykinesia Paucity of associated movements Abno rmal Areflexia Fasciculation Muscle Atrophy Flaccid paralysis Dysmetria- ataxia of arms Dysynergia Dysdiadocho kinesia- inabili ty to do rapid alternating movements Hypotonia- pendular reflexes Intention tremor Scanning speech Chorea, athetosis, hyperkinetic Rigidity ( lead-pipe ) (cogwheel), Resting tremor Soft speech Courtesy of Stephen C. Voron, MD
