Thursday, 7 October 2010

MRCP revision battle 26.1: Parkinson's disease

I'm back on the revision bandwagon and am ready for another 7 battles...

MRCP revision battle 26.1: Parkinson's disease
MRCP revision battle 26.2: Lewy Body Dementia
MRCP revision battle 26.3: Malignant hyperthermia
MRCP revision battle 26.4: Benign intracranial hypertension
MRCP revision battle 26.5: Coarctation of the aorta
MRCP revision battle 26.6: Heparin
MRCP revision battle 26.7: Essential tremor

MRCP revision battle 26.1: Parkinson's disease/Parkinsonism

Parkinsonism is a triad of:
  • resting tremor (3 to 5 Hz)
  • rigidity
  • bradykinesia
 There is also loss of postural reflexes.

It is Parkinson's disease if there is degeneration of the substantia nigra dopaminergic neurones with Lewy bodies.

There are a whole list of associated features that I'm sure you're familiar with, but if you fancy a brief recap read the list below...
  • expressionless, mask-like face
  • dribbling
  • festinant gait = short shuffling steps with flexed trunk)
  • micrographia

Management of Parkinsons is by a multidisciplinary team and the pharmacological management of it is notoriously tricky, with multiple drugs which often decrease in efficacy with use and may result in 'on-off' symptoms.

Even the NICE guidelines recognise the challenge in drug prescription, stating that "it is not possible to identify a universal first-line drug choice".  They single out the following as possible first line options:
  • levodopa
    • use lowest dose possible
    • give with carbidopa to prevent peripheral breakdown
    • is of no use in neuroleptic induced Parkinsons
  • dopamine agonists
    • bromocriptine*, cabergoline*, ropinole
    • if an argot-derived agonist is used (*) ESR, UEs and CXR should be done before starting and annually while on treatment
  • MAO-B inhibitors
    • selegiline
    • decreases dopamine breakdown

Second line treatment is combining the above options, or one of the above with:
  • COMT inhibitors
    • entacapone
    • inhibit dopamine breakdown

Other medications which may be useful for specific effects include:
  • amantidine
  • apomorphine
  • antimuscarinics
    • procyclidine
    • more useful for drug-induced Parkinsons

A couple of other key points from the NICE guidelines on Parkinsons are:
  • 'drug holidays' should not be undertaken due to risk of neuroleptic malignant syndrome on restarting
  • clinicians should be aware of dopamine dysregulation syndrome, which is an uncommon disorder in which misuse of dopaminergic medication is associated with behaviours such as hypersexuality, pathological gambling and sterotypic motor acts

For the really keen:

For everyone else, lets move on to Lewy body dementia.