Chapter 13: Brainstem and Basal Ganglia

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Chapter 13 Brainstem and Basal Ganglia

• Chris Rorden
• University of South Carolina
• Norman J. Arnold School of Public Health
• Department of Communication Sciences and
  Disorders
• University of South Carolina

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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

• 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
• Inhibitory Reticular Areas
• Lower and Medial Region of Medulla
• Decreases Muscle Tone in Extremities

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Clinical considerations

• Disconnection of cortex and basal ganglia from
  reticular formation
• Decerebrate Rigidity
• Extensor posturing of all Limbs
• Excessive 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
• Parkinsons Disease
• Huntingtons Disease

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Basal Ganglia

• rostral
• striatum
• putamen
• caudate nucleus
• nucleus accumbens
• globus pallidus
• caudal
• 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

• Caudate Nucleus
• Elongated C Shaped Mass With Head and Tail
• Bordered by Ventricles, Internal Capsule and
  Temporal Lobe
• Globus Pallidus Next to Putamen
• 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 striatum
• Acetylcholine
• 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
• 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

• Sydenhams Chorea (5 13 years of age)
• Secondary to streptococcal infection
• Huntingtons Chorea (aka Huntingtons 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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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

• Parkinsons 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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Parkinsons 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 DA Parkinsons
Normal
Too much DA Schizophrenia