Basal Ganglia
Motor output from Sustantia Nigra pars reticulata
conveys information from head and neck
Motor output from Globus Pallidus
conveys infromation from the rest of the body
Oculomotor channel: sources of cortical input
posterior parietal cortex; prefrontal cortex
Huntington's progression
slow progression
Main structures of Basal Ganglia
1. Caudate Nucleus 2. Putamen 3. Globus Pallidus 4. Subthalamic Nucleus of Luys 5. Substantia Nigra
Four main sources of input to the Basal Ganglia
1. Cerebral Cortex 2. Substantia Nigra pars Compacta (SNc) 3. Thalamus 4. Raphe Nucleus
Two main pathways of intrinsic Basal Ganglia connections
1. Direct pathway 2. Indirect pathway
Two segments of Globus Pallidus
1. Internal Segment/Medial 2. External Segment/Lateral
Parallel Channels through Basal Ganglia
1. Motor channel 2. Oculomotor channel 3. Prefrontal channel 4. Limbic channel
Classic triad of Parkinson's
1. Resting tremor 2. Bradykinesia 3. Cogwheel rigidity accompanied by postural instability that causes an unsteady gait
Output from internal segment of Globus Pallidus and Substantia Nigra pars reticulata gets sent to what structures
1. Thalamic Nuclei: - Ventral Anterior Nucleus - Ventral Lateral Nucleus - CentreMedian/Parafasicular Nucleus - Dorsomedial N. (impt, re: limbic pathways) 2. Reticular Formation in Pons and Medulla
Olivopontocerebellar atrophy
Characterized by parkinsonism together with ataxia
Treatment of hemiballismus
Dopaminergic antagonists such as haloperidol
Genetic anticipation
Earlier onset of disease in each successive generation
Basal Ganglia is apart of what system
Extrapyramidal motor system
Oculomotor channel: Cortical targets of outputs
Frontal eye fields; supplementary eye fields
Workhorses of Nervous System
GABA and Glutamate
Indirect pathway in the intrinsic Basal Ganglia connections
Globus Pallidus external segment---> Subthalamic Nucleus of Luys ----> Globus Pallidus internal segment or Substantia Nigra pars reticulata
Motor channel: basal ganglia output nuclei
Globus Pallidus internal segment and Substantia Nigra pars reticulata
Oculomotor channel: Basal Ganglia output nuclei
Globus Pallidus internal segment and Substantia Nigra pars reticulata
Prefrontal channel: Basal Ganglia output nuclei
Globus Pallidus internal segment and Substantia Nigra pars reticulata
GABA is synthesized from what neurotransmitter
Glutamate
Classic cause of hemiballismus
Lacunar infarct of the subthalamic nucleus of Luys which leads to decreased pallidal inhibition of the thalamus
Most effective drug for treatment of Parkinson's
Levodopa plus carbidopa
Anteropulsion
- A continual appearance of falling and shuffling forward
Progressive Supranuclear Palsy
- Also called Steele-Richardson-Olszewski syndrome - Degeneration of Superior Colliculus, Red nucleus, dentate nucleus, subthalamic nucleus, and globus pallidus - Range of vertical eye movement is markedly limited
Pill-rolling tremor
- Assymmetrical and involves mainly the hands and upper extremities - Rolling something between their thumb and other fingers
Striatum
- Caudate Nucleus + Putamen - Receives all inputs to the basal ganglia
Atypical Parkinsonism
- Differs from idiopathic Parkinson's disease by having relatively symmetical symptoms, absence of resting tremor, early appearance of postural instability, and little response to dopaminergic agents
End result of cortical input via Direct Pathway
- Excitation of Thalamic Nuclei - Facilitates movement through its connections with motor and pre-motor cortex
Basal Ganglia Input from Cerebral Cortex
- Excitatory - Most input from cortex uses glutamate as neurotransmitter
Internal Capsule
- Fiber system - Separates the Caudate and the Putamen - Caudate and Putamen continues to exchange info via cellular bridges
Cortical basal degeneration
- Has parkinsonism - Plus limb dystonia and marked cortical features such as apraxia and wandering or alien limb syndrome
Bradykinesia and hypokinesia examples in Parkinson's
- Hypomimia/masked faces - Decrease in spontaneous blink rate - Hypophonic voice - Slow saccades - Micrographia - Stooped posture - Postural instability, the diminished ability to make reflex postural adjustments - Diminished arm swing
Huntington's Disease genetics
- Inherited autosomal dominant genetic condition that results in expanded trinucleotide repeats and progressive neurodegeneration - Gene is on Chromosome 4 - Individuals with over 40 CAG repeats either have Huntington's disease or will ultimately develop it. The higher the number of repeats, the younger the onset
End result of cortical input via Indirect Pathway
- Inhibition of Thalamic Nuclei - Inhibits movement through its connections back to the cortex
Striatonigral Degeneration
- Loss of dopaminergic neruons of the substantia nigra pars compacta, globus pallidus, and substantia nigra pars reticulata - Atypical parkinsonism is often present
Shy-Drager Syndrome
- Marked atrophy of the intermediolateral cell column of the spinal cord - Parkinsonism plus autonomic disturbances usch as marked orthostatic hypotension, impotence, and urinary incontinence
Limbic channel: Thalamic relay nuclei
Mediodorsal and ventral anterior nuclei
Psychiatric symptoms Huntington's
- May precede motor or cogntive symptoms in persons unaware that they have HD gene - Most common pyschiatric problems: depression, anxiety, impulsivity, OCD-like symptoms, psychosis
Input from Substantia Nigra pars Compacta
- Nigrostriatal Pathway uses DA as its neurotransmitter - Excitatory and inhibitory neurotransmitter to other neurons
Festinating gait
- Once walking starts - Walk with small shuffling steps
Wilson's disease
- Parkinsonian symptoms can also cause tremor, rigidity, and bradykinesia
Retropulsion
- Pulled backward slightly - Take several backward steps to regain balance or may fall
Machado-Joseph disease and dentatorubropallidoluysian atrophy
- Rare neurodegenerative disorders that often include parkinsonian features - Transmitted by autosomal dominant inheritance - Caused by expanded trinucleotide repeats
Lesions to Basal Ganglia
- Result in hyperkinetic movement disorders (e.g. Huntington's Disease) or hypokinetic movement disorders (e.g. Parkinson's Disease) - Also have cognitive function
Multisystem Atrophy Disorders
- Striatonigral degeneration - Shy-Drager syndrome - Olivopontocerebellar atrophy
Huntington's disease
- Trinucleotide repeat disorder - Presents with predominantly parkinsonian features in the unusual patient in which the onset is in childhood or early adulthood
On-off phenomenon
- With advanced Parkinson's - Fluctuation between dyskinesia and immobility with very little functional time
Dementia with Lewy Bodies
- important cause of parkinsonism and dementia - accompanied by prominent psychiatric symtoms
Pathological signs of Parkinson's
- loss of pigmented dopaminergic neurons in the substantia nigra pars compacta - Remaining dopaminergic neurons often contain characteristic cytoplasmic inclusions--- Lewy bodies
Striatum receives most of incoming info from what
The telencephalic Basal Ganglia
What percent of individuals over age 65 have parkinson's
1%
Oculomotor channel: Basal Ganglia input nuclei
Caudate, body
Prefrontal channel: Basal Ganglia input nuclei
Caudate, head
Dorsal Striatal pathway
The first three channels together
Huntington's prevalence
4.5 cases/100,00 people except in specific areas in Venezuela its 50/50
Usual age of onset of Parkinson's
40-70 years
Huntington's death
About 20 years post onset of symptoms
Basal Ganglia influences what
Activity of the descending motor systems
Limbic channel: cortical targets of output
Anterior cingulate; orbital frontal cortex
Medication causes of Parkinsonism
Antipsychotic and antiemetic dopaminergic antagonists can cause rigidity and hypokinesia Onset is usually abrupt and symptoms are symmetrical
What Basal Ganglia structure receives the most input
Caudate + Putamen Receives input from other structures and then sends to the rest of the Basal Ganglia
Huntington's pathology
Hallmark is progressive atrophy of the striatum, especially involving he caudate nucleus
Cause of Parkinson's Disease
Idiopathic
Discovery of Huntington's gene
In 1993 by Nancy Wexler using genetic material from affected persons in Maracaibo Venezuala
Myerson's sign
Inability to suppress blinking when the center of the brow ridge is tapped repeatedly
Two structures responsible for output from Basal Ganglia
Inhibitory 1. Internal segment of Globus Pallidus 2. Substantia Nigra pars reticulata Use GABA
Glycine
Inhibitory neurotransmitter, particularly in the Spinal Cord and brainstem
Ventral Striatal pathway
The fourth channel
Glutamate
Most abundant excitatory neurotransmitter in the nervous system
GABA
Most abundant inhibitory neurotransmitter in the nervous system
Input from Intralaminar Thalamic Nucleus
Most important input comes from CentreMedian/Parafasicular nucleus
Limbic channel: Basal Ganglia input nuclei
Nucelus accumbens ; ventral caudate; ventral putamen
Periods of freezing in Parkinson's
Occurs during the wearing off of medications when the person becomes unable to move
Other locations of lesions of hemiballismus
Other regions of the basal ganglia, especially the striatum
Common causes of Huntington's death
Pneumonia, heart disease, suicide
Prefrontal channel: Sources of cortical input
Posterior parietal cortex; premotor cortex
Prefrontal channel: Cortical targets of output
Prefrontal cortex
Input from Raphe Nucleus
Provides serotonin to Basal Ganglia
Motor channel: basal ganglia input nuclei
Putamen
Parkinsonism plus syndromes
Several neurodegenerative conditions are associated with parkinsonism Produce atypical parkinsonism
Motor channel: sources of cortical input
Somatosensory cortex; primary motor cortex; premotor cortex
What movements typically follow hemiballismus
Sublter choreoathetotic movements
Other output from from Substantia Nigra pars reticulata
Superior Coliculus and influences Tectospinal tract
Motor channel: Cortical target of output
Supplementary motor area; premotor cortex; primary motor cortex
Limbic channel: Sources of cortical input
Temporal cortex; hippocampus; amygdala
Direct pathway in the intrinsic Basal Ganglia
Travels from striatum directly to internal Globus Pallidus or to the Substantia Nigra pars reticulata
En bloc turning
Turns are executed without the normal twist of the torso
Hemiballismus Clinical presentation
Unilateral flinging movements of the extremities contralateral to a lesion in the basal ganglia
Additional causes of hemiballismus
Unilateral lesions of the basal ganglia such as hemorrhage, tumor, infectoin or inflammation
Lateralization of movement
Unilaterl but later becomes bilateral, although the severity often remains asymmetrical
Huntington's onset
Usually between 30-50 years of age.
Progression of Parkinson's
Usually insidious over the course of 5-15 years
Oculomotor channel: Thalamic relay nuclei
Ventral Anterior Nucleus and Mediodorsal
Prefrontal channel: Thalamic relay nuclei
Ventral Anterior Nucleus and Mediodorsal Nucleus
Motor channel: Thalamic relay nuceli
Ventral Lateral and Ventral Anterior
Limbic channel: Basal Ganglia output nuclei
Ventral pallidum; Globus Pallidus internal segment; Substantia Nigra pars reticulata
Huntington's onset
insidious
Huntington's affects
movement, cognition, emotional/psychiatric functioning
