1 chapter 13: brainstem and basal ganglia chris rorden university of south carolina norman j. arnold...
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Chapter 13: Brainstem and Basal Ganglia
Chris RordenUniversity of South CarolinaNorman J. Arnold School of Public HealthDepartment of Communication Sciences and DisordersUniversity of South Carolina
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Muscle
Efferent Fibers
Afferent Fibers
Spinal Ganglia
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Dermatomes
Opthalmic
Mandibular
Maxillary
Branches of Cranial Nerve V (Trigeminal)
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Chickenpox
Shingles
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Brainstem Motor Mechanism
Motor – Pyramidal
Corticospinal tract and corticobulbar tract– Extrapyramidal
Facilitatory, inhibitory, and/or regulatory– Red Nucleus
Part of midbrain– Cranial Nerve Nuclei– Reticular Formation
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Brainstem Anatomy
Red Nucleus– Rubrocerebellar Tract– Important for gait in animals
without significant corticospinal tract
– Humans: upper arm and shoulder Cranial Nerve Nuclei
– Will Be Discussed With Cranial Nerves
Reticular Formation– Focus in This Chapter
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Reticular Formation
Located between caudal diencephalon & spinal cord
Network of Overlapping Dendrites and Axons
Input From– Motor Cortex– Basal Ganglia– Cerebellum– Cranial Motor Neurons
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Reticular Formation Function
Arousal Tonal Modulation Pain Processing Regulation of
– Vomiting– Coughing– Cardiovascular Functions– Respiration– Speech Functions
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Reticular Nuclei
Reticularis Gigantocellular Pontis Oralis and Cudalis Lateral Reticular Nucleus Ventral Reticular Nucleus Paramedial Reticular
Nucleus Interstitial Raphe Ceruleus
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Reticular Motor Functions (1)
Examined in anencephalic children who have no cortex or cerebellum
- Expel food
- Eat - Suck - Cry - Yawn
- Breathe -Swallow - Vomit - Sleep - Awaken
Muscle Tone Regulation - Maintains Balance of Stimulation
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Reticular Motor Functions (2)
Facilitatory Reticular Areas– Upper and Lateral Brainstem– Increases Muscle Tone in Extremities– Sleep wake cycle, alertness
Inhibitory Reticular Areas– Lower and Medial Region of Medulla– Decreases Muscle Tone in Extremities– Posture, equilibrium, motor control
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Clinical considerations
Disconnection of cortex and basal ganglia from reticular formation– Decerebrate Rigidity
Extensor posturing of all LimbsExcessive facilitatory impulses
Transection Below Vestibular Nucleus– Flaccid Paralysis – Similar to degeneration of the lower neuron
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Basal Ganglia
Modify cortically initiated motor movements (speech)– Caudate Nucleus– Putamen– Globus Pallidus– Related Brainstem Structures– Substantia Nigra– Subthalamic Nucleus
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Results of Basal Ganglia Impairment
Involuntary Motor Movements Bradykinesia (slow) or Hypokinesia (slow or
diminished) Altered Posture Changes in Muscle Tone Implicate Neurotransmitters All Result in Dysarthria and Dysphagia Parkinson’s Disease Huntington’s Disease
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Basal Ganglia
rostral– striatum
putamencaudate nucleusnucleus accumbens
– globus palliduscaudal
– subthalamic nucleus (STN)– substantia nigra (SN)
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Aliases
Lenticular Nucleus– Putamen and Globus Pallidus
Neostriatum or Striatum– Caudate Nucleus and Putamen
Pallidum– Globus Pallidus
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Structures
1. Caudate Nucleus Elongated C Shaped Mass With Head and Tail Bordered by Ventricles, Internal Capsule and
Temporal Lobe
2. Globus Pallidus Next to Putamen
3. Putamen Connected to Head of Caudate Nucleus
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The Basal Ganglia
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Neurotransmitters
Dopamine– Inhibitory Neurotransmitter– Produced in the substantia nigra and secreted in
the striatumAcetylcholine
– Facilitatory/Inhibitory Neurotransmitter Gamma-Aminobutyric Acid
– GABA Regulates Adjacent Structures– e.g. thalamus
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Clinical Considerations
Athetosis– Involuntary slow writhing (twisting) movement– Continuous stream of slow, sinuous, writhing movements, typically of
the hands and feet. – Varying degrees of hypertonia– Usually seen in lesions of the globus pallidus
Ballism (Subthalamic Nuclei – Diencephalon, chapter 6)– Violent Forceful Flinging of Arms and Legs– Most violent form of dyskinesia (movement disorder)– Usually associated with lesions in the sub-thalamic nucleus (which
regulates the globus pallidus)– Hemiballism: unilateral ballism (e.g. unilateral stroke)– Can be treated with dopamine blockade or resection of GP.
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Clinical Considerations
Chorea– Series of rhythmic involuntary movements– Predominantly in the distal extremities and muscles of the
face, tongue, and pharynx– Chorea is characterized by brief, irregular contractions that
are not repetitive or rhythmic, but appear to flow from one muscle to the next.
– These 'dance-like' movements of chorea (from the same root word as "choreography")
– often occur with athetosis and more severe cases present with ballism
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Forms of Chorea
Sydenham’s Chorea (rheumatic fever 5-15 years old)– Secondary to streptococcal infection– Most recover completely (with problems for a few months)
Huntington’s Chorea (aka Huntington’s Disease)– 1872, George Huntington– Treated families with same characteristics– Heredity, Adult Onset, Chorea, Cognitive Loss– Autosomal Dominant– 5 in 100,000 prevalence– Equal in Men and Women– Loss of Cholinergic and GABAnergic neurons in Caudate
Nucleus
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Autosomal Dominant Traits
the trait, half the children will have the trait.Example: being a boy. Your father has one copy of
the Y chromosome, and one X. Each child has a 50% chance of being a boy.
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Clinical Considerations
Dyskinesia– Generalized Disorder of Involuntary and Voluntary
Movement– Masked Face, Infrequent Blinking, Slow
Movement, Disturbed Equilibrium, Stooped Posture, Impaired Speech, Impaired Swallowing
Tremors– Alternating Movement of Opposing Muscles– Resting Tremor
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Basal Ganglia Diseases
Parkinson’s Disease (1817, James Parkinson)– Tremor at Rest– Cogwheel Muscular Rigidity– Bradykinesia (Slow execution of body movements)– Akinesia (Slow beginning or inability to initiate a movement) – Shuffling Gate– Expressionless Face– Flexed Posture– Dysarthria– 30% have Cognitive impairment
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Parkinson’s Disease Treatment
Lack of Dopamine (Inhibitor)
Tx: L-Dopa or Other Dopamine Enhancers
Prolonged L-Dopa Tx can result in tardive dyskinesia (increased facial and lingual movements)
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Basal Ganglia Disease
Parkinson's disease: loss of dopamine in the neostriatum– Treatment: increase dopamine
Schizophrenia: Too much dopamine– Treatment: Block some (D2) dopamine receptors.– Problem: Prolonged treatment using Chlorpromazine and
Haloperidol leads to Parkinson's disease-like tremors (tardive dyskinesia)
Not enough DAParkinsons
Too much DASchizophrenia
‘Normal’