L3. Parkinson's disease Flashcards
what does the incidence of PD increase with
age
3 main features of PD
resting tremor
muscle ridigity
bradykinesia
what is the most common 1st sxs of PD
bradykinesia
4 other clinical feautures of PD
- postural instability
- depression
- autonomic NS dysfunction
- decreased cognitive impairment
give a few examples of autonomic dysfunction
impaired GI motility, bladder dysfunction, sialorrhoea, excessive head and neck sweating, orthostatic hypertension
give a few examples of decreased cognitive impairment
impaired visual-spatial perception and attendtion, slowness in motor tasks, impaired concentration, dementation
which part of the brain is involved in PD
substantia nigra
normal function of substantia nigra
allows smooth movements - regulation of posture and muscle tone
what is present in the substantia nigra in PD
lewy bodies and lewy neurites
what neurones are located in the substantia nigra?
dopamine
what is degraded in PD
substantia nigra
3 pathophysiological causes of PD
- loss of >80% dopamine
- loss of dopamine receptors in nigrostriatal pathway
- increase in acetylcholine in striatum
describe 4 steps in dopamine stimulation in a healthy individual
- DA stimulates basal ganglia
- basal ganglia has dampening effect on reticular formation - reducing unneccesary movements.Ach reduced
- rReticular formation sends motor info to spinal cord
- controlled smooth movement
describe 4 steps in dopamine stimulation in a person with PD
- lack of DA - basal ganglia not stimulated
- increase in ACh - inhibits smooth movement and dampening effect of RF
- info not sent to RG and therefore not sent to spinal cord
- increased muscle tension and tremor
what is parkinsonism
umbrella term used to describe conditions which have similar sxs to PD
what is the cause of PD
idiopathic
what 3 drugs can cause PD like sxs?
anti-psychotic drugs block DA receptors
MPTP
rotenone (pesticide)
what 5 things can cause secondary parkinsonism?
- drugs
- toxins
- neoplasms/strokes
- other neuronal system degenerations
- genetics
which 4 drugs can cause secondary parkinsonism?
- antipsychotics
- anti-emetics
- methyl-dopa (Anti-hypertensive)
- reserpine
what 2 toxins can cause secondary parkinsonism?
MPTP
carbon monoxide poisoning
strokes in what region of the brain can cause secondary parkinsonism?
nigrostriatal pathway
other neuronal system degenerations which can cause secondary parkinsonism?
- wilson’s disease - copper in brain
- progressive supranuclear palsy
- multiple-system atrophy
what is the only technique to differentiate PD and parkinsonism?
DAT scan (DA transporter scan)
what does the DAT scan image?
presynaptic DA transporter
2 approaches to treatment of PD
dopamine and ACh
physiology of DA approach to treatment
increase DA conc in nigrostriatal system
physiology of Ach approach to treatment
decrease influence of ACh in striatum
4 drugs used in DA approach
- MAO inhibitors
- L-dopa
- dopamine agonists
- COMPT inhibitors
2 drugs used in Ach approach
- anti-muscarinics
2. amantadine
how does levo-dopa work?
it is a precursor for DA
why are peripheral decarboxylase inhibitors used with L-dopa?
can use lower L-dopa dose - decrease side effects; nausea and vomiting
3 acute side effects of L-dopa
- hallucinations
- confusion
- dyskinesias
chronic side effect of L-dopa
benefits of the drug decline after 5 years - PD sxs reoccur
L-dopa can lead to the on-off effect. what is this?
as the drug has a short half-life, sxs reappear before taking the next dose
treatment for on-off effect
using modified release preparations (gel)
name for L-dopa + benserazide
Co-beneldopa
name for L-dopa + carbidopa
Co-careldopa
what are Co-beneldopa and Co-careldopa examples of ? which is this used in combo with?
PDI.
L-dopa
how does DA agonist work to treat PD?
stimulates D1 and D2 receptors
name 5 sxs of dopamine agonists
- nausea
- vomiting
- hallucinations
- narcolepsy
- confusion
- paranoia
- postural hypotension
- peripheral swelling
name 1 example of dopamine agonist
brocriptine pergolide pramipexol ropinirole cabergoline apomorphine
physiology of MAO inhibitors
inhibit MAO - which normally would break down DA. causing increase of DA in the synapse
1 example of MAO inhibitors
Selegiline
Rasagiline
what does COMPT inhibitors stand for?
catechol-o-methyl transferase inhibitors
physiology of COMPT inhibitors
prevent breakdown of L-dopa and DA
when are COMPT inhibitors used?
only in combo with L-dopa - used in advanced stages of the disease
1 example of COMPT inhibitor
entacopone
tolcapone
how do anti-muscarinic drugs work
block muscarinic receptors in striatum
what are anti-muscarinics useful in treating?
tremor
drug interactions of anti-muscarinincs
increase side effects of tricyclics
1 example of anti-muscarinincc
benzhexol
benztropine
procyclidine
orphenadrine
physiology of amantadine
increases release of DA
2 side effects of amantadine
- confusion
2. tolerance may develop
describe 3 steps in syntheiss of DA
- tyrosine
- DOPA
- DA
in the substantia nigra - why is DA not converted into NA?
the enzyme required is not present
2 moleucles which DA can be metabolised into
DOPAC and HVA
why may mild PD be left untreated/delayed treatment?
delay the use of L-dopa; to delay onset of its side effects
what 2 other neurological disorders are seen in PD?
depression and dementia
treatment for depression + PD
tricyclics or SSRIs
treatment for dementia + PD
reduce PD treatment dose -use clozapine
why can a vaccine which attacks alpha-synuclein be useful in treating PD?
alpha-synuclein is present in lewy bodies
what can glial cell line-derived neurotrophic factor possibly do?
stimulate growth of cells which are lost during PD