Neurology - Parkinson's disease Flashcards
Epidemiology of PD
Akinetic- rigid syndrome
Affects approx 1% of population over the age of 60
No gender bias
What is the difference between Parkinsonism and PD?
Most cases of PD are idiopathic (cause is unknown)
Parkinsonian features may be present in many disorders (i.e. other akinetic rigid syndromes) that are not always treatment responsive
Shared features of bradykinesia and rigidity
Causes of akinetic-rigid syndromes
1) Inherited - Wilson’s Disease
2) Idiopathic - PD and mimics (see later)
3) Inflammatory - post encephalic
4) Drugs - Da antagonists (e.g. neuroleptics, antiemetics)
5) Toxins - MPTP
6) Vascular - multiple lacunar infarcts
7) Trauma
8) Neoplasia - very rare tumours of the basal ganglia
How does MPTP suggest that environmental factors may play a role in PD?
= Synthetic heroin byproduct
Causes selective CNS damage and acute Parkinsonism
Another environmental trigger more widely available and acting in the same way as MPTP may be responsible for PD
How does MPTP cause selective CNS damage?
MPTP crosses BBB
Converted into active metabolite MPP+ by MOA-B in glia
MPP+ is a free radical - concentrated in dopaminergic neurones
MPP+ - mitochondrial poison, inhibits complex I of respiratory chain
Pathology of PD
Dopaminergic neurones in the nigrostriatal pathway (i.e. projecting from the substantial nigra pars compacta to the striatum)
Microscopically - atrophy of the substantial nigra seen by loss of pigmentation (neuromelanin)
Macroscopically - surviving neurones show Lewy bodies (intracytoplasmic eosinophilic inclusion bodies)
How much neuronal loss is required to cause symptoms of PD?
60-80% of nigrostriatal dopaminergic neurones
Classic triad of PD
1) Rigidity
2) Tremor
3) Bradykinesia
Clinical features of PD
“TRAPPS PD”
PD usually has asymmetric onset - side of onset remains worse
- Tremor: at rest, incr by stress, decr by sleep
- Rigidity: cog wheel (if superimposed on tremor), lead pipe
- Akinesia: slow initiation, difficulty with repetitive movements, micrographia, mask-like face
- Postural instability: stooped gait with festination
- Postural hypotension + autonomic dysfunction
- Sleep disorders: insomnia
- Psychosis: esp visual hallucinations
- Depression/ Dementia
What autonomic dysfunction to patients with PD experience?
Combined effects of drugs and neurodegeneration
- Postural hypotension
- Constipation
- Hypersalivation
- Urgency, frequency and nocturia
How many patients with PD experience sleep disorders?
Approx 90%
REM behavioural sleep disorder
- Loss of muscle atonia during REM sleep
- Violent enactment of dreams
Diagnosis of PD
Based on classic clinical triad
Brain imaging is rarely helpful - DAT scan can be helpful in borderline cases
Parkinson’s plus syndrome
= Conditions with features that mimic PD but are less responsive to L-DOPA therapy Usually idiopathic They include: 1) PSP 2) Multiple system atrophy 3) Lewy body dementia 4) Cortico-basal degeneration 5) Vascular Parkinsonism
What is PSP?
Very rare degenerative condition of the upper brainstem similar to PD (i.e. mask face, rigidity, cogwheeling, falls)
(VIVID - red flags) Vertical gaze palsy and early postural instability
Pseudobulbar palsy (swallowing problems)
NB - PSP is also known as Steele-Richardson-Olszewski syndrome
Multiple system atrophy
Extrapyramidal features occur in combination with one or more of the following:
- Autonomic features (VIVID red flag) - e.g. Impotence, postural BP etc
- Cerebellar signs
- Pyramidal signs
NB - MSA is also called Shy-Drager syndrome
