Neurology Flashcards
What is used in idiopathic Parkinson’s disease to improve motor symptoms?
Levodopa
Outline the pathology of idiopathic Parkinson’s disease
- Neurodegeneration
- Lewy bodies
- Loss of pigment due to increased turnover
- Reduced dopamine
Clinical features of Parkinsonism
Tremor
Rigidity
Brradykinesia
Postural instability
Diagnosis of idiopathic Parkinson’s disease
- clinical features
- exclude other causes of Parkinsonism
- response to levodopa
- structural neuro imaging is normal
- must have bradykinesia
What is idiopathic Parkinson’s disease?
Progressive neurodegenerative disorder due to loss of substantia nigra dopamine neurones
At what point of loss of pigment in idiopathic Parkinson’s disease do symptoms present?
> 50% loss
Non motor manifestations of idiopathic Parkinson’s disease
- mood changes
- hallucinations
- sleep disorder
- fatigue
- urinary symptoms
- hypotension
Describe Parkinsonian tremor
Low frequency
Pillrolling
At rest
Stops with movement
Describe Parkinsonian rigidity
Lead pipe
Tension all the way through flexion
Describe Parkinsonian gait
- short shuffling steps
- struggle to initiate + stop
- turning on block
- asymmetric arm swing
What enzyme converts levodopa to dopamine?
Dopa decarboxylase
Outline catecholamines synthesis
L tyrosine > levodopa > dopamine > noradrenaline > adrenaline
Why is levodopa used instead of dopamine to treat idiopathic Parkinson’s disease?
Levodopa crosses the blood brain barrier but dopamine cannot
Pharmacokinetics of levodopa
- oral administration
- absorbed by active transport
- t1/2 2 hours
- 90% inactivated in intestinal wall
How is levodopa converted to dopamine?
- Cross BBB
- Taken up by axons within substantia nigra
- Converted into dopamine in the cell
- Catalysed by dopa decarboxylase
Describe the formulation of levodopa
- used in combination with peripheral dopa decarboxylase inhibiotr
- co-careldopa: levodopa + carbidopa
- co-beneldopa: levodopa + benserazide
- tablet only P.O.
Why is levodopa given in combination with peripheral dopa decarboxylase inhibitor?
- Reduces conversion in peripheral tissue
- Reduces dose required
- Reduces side effects
- Increased levodopa reaching brain
Advantages + disadvantages of levodopa
Advantages:
- high efficacy
- low side effects
.
Disadvantages:
- loss of efficacy long term due to degeneration of axons
- needs enzyme conversion
- motor complications long term