parkinson's disease Flashcards
what is parkinsonism
symptoms similar to PD but have secondary causes
- drug/toxin - induced
- vascular (stroke)
possible causes of PD
1) age related loss of neurons
2) environmental toxins/insults
- MPTP-MPP+
- pesticides, herbicides
3) genetics
- predispositions to toxins/insults
- genetic abnormalities
pathophysiology of PD
- failure to clear abnormal/damaged proteins by ubiquitin/proteasome system -> accumulation of misfolded alpha-synuclein -> formation and accumulation of Lewy body (Aggresomes) inside neurons
- lewy body mediate functional mitochondria failure -> neuron damage and apoptosis - loss of dopaminergic neurons in substantia nigra
- long term overexpression of alpha-syn (and neuron apoptosis) -> decrease DA neurotransmission -> motor symptoms
- neuroinflammation -> activation of microglia -> further neuroinflammation and neurodegeneration -> disease progression
clinical presentation of PD - 4 characteristics features
TRAP
- tremor: resting tremor that increases w stress, not caused by events
- rigidity: muscular rigidity, cogwheel rigidity
- akinesia: slowness of movement, sense of weakness, loss of dexterity, loss of facial expression, reduced blinking
- postural instability
PD clinical presentation - initial presentation
asymmetric, +ve response to levodopa/apomorphine, sometimes impaired sense of smell
PD clinical presentation as disease progress
- unable to perform basic ADL
- choking, pneumonia, falls
PD clinical presentation - non motor symptoms
- dementia, depression, psychosis, sleep disorder
- constipation, GI motility
- orthostatic hypotension, sialorrhea (drool cuz X swallow)
PD disease progression timeline
20 year prodrome
- 20 yr: constipation, bladder problem
- -10 yr: sleep disorder, obesity, depression
20 year disease stage
- I: unilateral TRA
- II: bilateral
- III: poor balance
- IV: falls, dependency, cognitive decline
- V: chair/bed bound, dementia
classifications of PD
1) juvenile - onet PD < 20 yo
- higher freq of genetically inherited PD
2) early/young onset PD < 40 yo
- slower disease progression
- lesser cognitive decline
- earlier motor complication
- initial presentation: dystonia
- use dopamine agonist instead of levodopa
diagnosis of PD
1) 2/3 of cardinal signs present (TRAP)
2) neuroimaging
- MRI for differential diagnosis of other parkinsonism symptoms
- DAT: differentiate essential tremor and other non-dopamine deficiency aetiologies
measuring of PD disease progression
UPDRS
1) non-motor experience of daily living
- intellectual impairment, depression
2) motor experiences of daily living
- speech, salivation, swallowing, dressing, hygiene, walking
3) motor examination
- facial expression, tremor at rest, gait
4) motor complication
- dyskinesia, clinical fluctuations
general approach to PD treatment
1) increase central dopamine and dopaminergic transmission
- inhibit peripheral conversion of levodopa to dopamine by DOPA-decarboxylase, MAO-B and COM-T then inhibit central conversion of dopamine to homovanillic acid by MAO-B and COM-T
2) correct imbalance in other pathways
- anticholinergics, NMDA antagonist
non pharmaco for PD
1) med review
- correct levodopa preparations (IR vs CR, sinemet 1:10 vs 1:4)
- DDI, comorb, timing of administration
2) physiotherapy
3) occupational therapy
4) speech therapy
5) deep brain stimulation (DBS) for advanced PD
types of pharmacological treatment
1) levodopa
2) dopamine agonist
3) MAO-B inhibitors
4) catechol-O-methyl transferase inhibitors
5) anticholinergics
6) NMDA antagonist
indication of levodopa
1) try to give others first to minimise motor complications unless cannot be controlled or + other agents so can lower dose of levodopa
2) most effective for treating bradykinesia and rigidity, not so for speech, postural reflex and gait disturbances
levodopa MOA
- increase dopamine synthesis
- synthetic L-dopa that is converted into dopamine by DOPA decarboxylase, MAO-B, COM-T
DCI (benserazide) for levodopa
- peripheral DOPA-decarboxylase inhibitor to prevent systemic SE from excess DA
- only L-dopa can cross BBB, dopamine can’t
- if levodopa converted into dopamine in periphery then can’t cross BBB to take effect
- so give DCI to ensure levodopa cross BBB then can converted into dopamine to take effect
levodopa formulations
1) CR
- useful for reducing stiffness on waking
- X rush tablets (sinemet) or open capsule (madopar)
2) dose adjustment required for switching between IR and CR
- IR -> CR: increase dose by 25 - 50%
- CR -> IR: reduce dose
levodopa PK
- absorbed in proximal part of small intestines
- low F but increased w DCI
- decreased absorption with high fat/protein meal so need to space apart administration from heavy meals
levodopa AE - tldr
1) peripheral effects
2) central effects
3) motor effects
levodopa - peripheral effects
N/V, orthostatic hypotension