Parkinson's disease / parkinsonism

Question 1

What is parkinson’s disease

Answer 1

Chronic disorder of the brain/substansia nigra with parkinsonism features

Question 2

How common is it and who gets it

Answer 2

0.6% at 60-64yrs and 3.5% at 85-89years

typical onset = 65yrs

Question 3

What is the cause

Answer 3

• Mitochondrial DNA dysfunction
  –> Degeneration of dopaminergic neurons in substantia nigra pars compacta (ass w. Lewy bodies)
• Reduced levels of dopamine
  = slower/abnormal nerve messages

Question 4

What is the clinical presentation of parkinson’s

Answer 4

• Bradykinesia/hypokinesia – slow voluntary + autonomic reduced arm swing
• Tremor – 4-6Hz resting tremor, induced by concentration + absent during activity.
• Postural instability +/- muscular rigidity - resistance to passive movement
• Gait – small shuffling steps w/ unsteadiness on turning + difficulty stopping (festination)
• NON-MOTOR FEAT = sense smell, constipation, visual hallucination, frequency/urgency, dribbling of saliva, depression/dementia

Question 5

What are the features of parkinsonism

Answer 5

TREMOR
- worse at rest, ‘pill-rolling’ of thumb over fingers, 4-6 cycles/sec

RIGIDITY/^ TONE
– rigidity + tremor = Cogwheel rigidity felt by examiner during rapid pronation/supination (jerky)

BRADYKINESIA/HYPOKNESIA
• slow to initiate movement
• slow, low-amplitude excursions in repetitive actions e.g. blink rate, monotonous
• hypophonic speech, micrographia

GAIT: arm swinging, festinance (shuffling steps w/ flexed trunk), freezing at obstacles/doors, expressionless face (hypomimesis)

Question 6

What are the differential diagnoses

Answer 6

• Benign essential tremor - worse on movement
• Drug/toxin induced tremor
• HUNTINGTON’S - can Px w. rigidity 1st + not chorea
• LEWY BODY DEMENTIA - parkinsonian feat
• Creutzfeldt-Jakob Disease - dementia apparent w. myoclonic jerking + ataxia

Question 7

What investigations do you perform

Answer 7

• refer to specialist
• Diagnoses = clinical –> investigations exclude other causes
• CT/MRI if pt fails to respond to L-DOPA
• PET scan can show dopamine deficiency

Question 8

How do you treat parkinson’s

Answer 8

• Specialist review every 6-12 months
  LEVODOPA
• most effective
• given w. peripheral dopa-decarboxylase inhibitor - prevents peripheral conversion

DOPAMINE AGONISTS - ropinirole, pramipexole
- Delay starting L-DOPA
- SE: drowsiness, nausea, hallucinations, compulsive behaviour
AMANTADINE (weak DA) - used for drug-induced dyskinesia in late PD

ANTICHOLINGERICS - Benzhexol, orphenadrine

• Help tremor but cause confusion in elderly
• SE: dry mouth, confusion, anxiety, dizziness, urinary retention, decrease vision + memory, hallucinations

MAOB INHIBITORS - rasagiline, selegiline

• Alt to DA-agonist given in early PD
• SE: postural hypotension + AF

COMP INHIBITORS - entacapone + tolcapone
- Lessen ‘off’ time in those w. end-of-dose wearing off

Question 9

What is on and off time

Answer 9

Off = bradykinesia + tremor +/- rigidity 
On = (more) normal movements