7 - Motor disorders Flashcards
Name some causes of chorea:
- Huntington’s
- Sydenham’s
- Wilson’s disease
- SLE
- Thyrotoxicosis
- Levodopa
What is the role of the cerebellum?
Role in: - coordination - precision - timing of purposeful movements
What structure separates the cerebellum from the occipital and parietal lobes?
Tentorium cerebelli
What structure separates the cerebellum from the pons?
4th ventricle
Which part of the cerebellum regulates trunk musculature?
Vermis (midline)
Which part of the cerebellum regulates limb musculature?
Lateral hemispheres
Are tracts to and from the cerebellum ipsi- or contralateral?
Ipsilateral
Name the 3 lobes of the cerebellum:
1) Anterior lobe
2) Posterior lobe
3) Flocconodular lobe
What are the symptoms of cerebellar pathology?
Dysdiadochokinesia Ataxia Nystagmus Intention tremor Slurred speech Hypotonia
Name some causes of cerebellar pathology:
Posterior fossa tumour Alcohol Sclerosis (MS) Trauma Rare causes Inherited ie Friedreich's ataxia Epilepsy med ie Carbamazepine/Phenytoin Stroke
How do midline lesions of the cerebellum often present?
- Truncal ataxia
- Abnormal gait
What is the name given to the collection of nuclei found of both sides of the thalamus, outside and above the limbic system?
Basal ganglia
Name the important structures in the basal gsanglia:
- Caudate nucleus
- Lentiform nucleus (putamen + globus pallidus)
- Substantia nigra
- Subthalamic nucleus
Name the 2 structures which form the lentiform nucleus:
- Putamen
- Globus pallidus
At rest, which pathway in the basal ganglia dominates, and what is the outcome?
Indirect pathway dominates
= Thalamus is suppressed from sending excitatory impulses to the motor cortex
= Inhibits motor cortex
What is the main excitatory neurotransmitter in the basal ganglia?
Glutamate
What is the main inhibitory neurotransmitter in the basal ganglia?
GABA
Which pathway in the basal ganglia has an overall stimulatory effect on the motor cortex?
Direct pathway
Which pathway in the basal ganglia has an overall inhibitory effect on the motor cortex?
Indirect pathway
Which structure of the basal ganglia produces dopamine?
Substantia nigra pars compacta
Dopamine is released from the substantial nigra pars compacta, on what structure in the basal ganglia does it act?
Putamen
Which dopamine receptors in the basal ganglia pathways activate the direct pathway?
D1 receptors
Which dopamine receptors in the basal ganglia pathways activate the indirect pathway?
D2 receptors
What is the role of the basal ganglia?
- Facilitates appropriate movements
- Inhibits inappropriate movements
Via which structure does the basal ganglia communicate with the cortex?
Thalamus
What are the 2 parts of the substantial nigra? Describe their position in relation to each other:
- Substantia nigra pars compacta
- Substantia nigra pars reticularis
Both in midbrain, pars reticular is a ventral stri, pars compacta lies dorsally
What happens in Parkinson’s disease to cause bradykinesia?
- Death of dopaminergic neurones in substantiatia nigra pars compacta
- Loss of inhibition on putamen in indirect pathway
+ - Loss of excitation of putamen in direct pathway
= Less excitation of motor cortex = Bradykinesia
Basal ganglia disorders typically result in what motor signs?
- Abnormal motor control
- Altered posture
- Altered muscle tone
- Dyskinesia
Name the cardinal signs of Parkinson’s disease:
- Resting tremor
- Rigidity
- Bradykinesia
Resting tremor, rigidity and bradykinesia are the cardinal sign’s of Parkinson’s disease. Name some other features:
- Hypophonia
- Pill-rolling tremor
- Cog-wheel rigidity
- Lead-pipe rigidity
- Micrographia
- Reduced facial expression
- Dementia
- Depression
- Anxiety
- Mild cognitive impairment
- Visual hallucinations
- Insomnia
- Falls
- Shuffling gait
- Urinary incontinence
- Constipation
- Erectile dysfunction
- Orthostatic hypotension
What is the main treatment of Parkinson’s disease?
Carbidopa/Levodopa (also known as Levocarb, or Co-careldopa)
= Dopamine precursor + peripheral DOPA decarboxylase inhibitor
What enzyme inhibitor is given with a dopamine precursor to treat Parkinson’s disease? Why?
Peripheral DOPA decarboxylase inhibitor
= Reduces the conversion of precursor to Dopamine in peripheral tissues
= ^^ concentration of dopamine precursor crosses BBB and available to brain
What drugs may be given as an adjunct to Carbidopa/Levodopa for Parkinson’s disease?
- Dopamine agonist ie Bromocriptine
- MAO-B inhibitor ie Selegiline
- COMT inhibitor ie Entacapone
- Amantadine
What type of drug is Bromocriptine?
Dopamine agonist
What type of drug is Selegiline?
MAO-B inhibitor
What type of drug is Entacapone?
COMT inhibitor
What type of drug is Amantadine?
NMDA antagonist = Glutamate receptor antagonist
What is the hereditary pattern of Huntington’s disease?
Autosomal dominant
Huntington’s disease is progressive cell loss in which areas of the brain?
- Basal ganglia
- Cortex
What is the average age of onset of Huntington’s disease?
30-50 yrs
What are the typical signs and symptoms of Huntington’s disease?
- Chorea
- Dystonia
- Incoordination
- Cognitive decline
- Behavioural difficulties
- Abnormal gait
What are the treatments available for Huntington’s disease?
- Antidepresssants
- Mood stabilisers
- Antipsychotics
- Speech and language therapy
What role do antipsychotics have in the treatment of Huntington’s disease?
- Antipsychotics antagonise D2/3 dopamine receptors, reducing dopamine transmission
- Loss of inhibition on putamen in indirect pathway
+ - Loss of excitation of putamen in direct pathway
= Less excitation of motor cortex = Bradykinesia - So can help suppress involuntary movements (and violent outbursts)
What is ballismus?
Rare movement disorder causes repetitive but constantly varying large amplitude involuntary movements of proximal parts of limbs
What causes ballismus?
Decreased activity of subthalamic nucleus
= Removed inhibition on thalamus
What can cause ballismus?
- Stroke
- Trauma
- Neoplasm