Definition of "Parkinson's disease"

Last modified: over 2 years



Parkinson's disease (PD, aka hypokinetic rigid syndrome) is a degenerative disorder of the CNS, mainly affecting the motor system.

Patient information

What is Parkinson's disease?
It's a disease of the brain, that just gets worse. And worse. And worse.

Pathophysiology
  • Accumulation of alpha-synuclein into Lewy bodies, causing death of dopaminergic neurons in the substantia nigra, a region of the midbrain
  • The causes of this cell death are poorly understood
  • Many risks and protective factors have been investigated, the clearest evidence is for an increased risk of Parkinson’s disease in people exposed to certain pesticides and a reduced risk of tobacco smokers
  • Where the Lewy bodies are located is often related to the expression and degree of the Sx of an individual

Patient information

It doesn't sound to great... But what makes the brain just get worse?
Proteins in the nerve cells in the brain, clump up. They're called Lewy bodies. It particularly targets the nerve cells which make dopamine.

So Parkinson's disease is a disease of low dopamine?
Yeah. Basically.

Sx
  • Motor Sx, Parkinsonism (aka parkinsonian syndrome) are the main motor Sx, including:
    • Parkinsonian tremor (see page)
    • Shaking
    • Rigidity
    • Hypokinesia (slow movement)
    • Difficulty with walking and gait
  • Later, thinking and behavioral problems may arise
  • Depression is the most common psychiatric Sx
  • Other Sx include:
    • Sensory
    • Sleep
    • Emotional problems

Patient information

What happens if you have clumps in the brain causing low dopamine? What is dopamine?
Dopamine is used by the brain to send signals. It's particularly involved with preventing you from moving when you don't want to. So because it's low, you have these unwanted movements in Parkinson's. Shaking. Being rigid. Slow to move. Dopamine is also involved in the motivation system, so there can be behavioral and emotional problems too.

Classification
  • Primary, is referred to as idiopathic (having no known cause), although some atypical cases have genetic origin
  • Secondary, is due to known causes like toxins
Dx
  • Dx of typical cases is aminly based on Sx
  • Tests e.g. neuroimaging being used for confirmation
Tx
  • L-DOPA (Levodopa), which is the precursor to the catecholamines (dopamine, noradrenaline and adrenaline). The precursor is used rather than dopamine, because L-DOPA can cross the BBB, thereby increasing the doapmine concentration to Tx PD. Side effects are caused by conversion into dopamine in the peripheral PNS. This is countered by co-administering a peripheral DOPA decarboxylase inhibitor, which inhibits peripheral metabolism of L-DOPA, such that more of it will cross the BBB before conversion. Examples of inhibitors include:
    • Carbidopa, of which combinations of carbidopa+levodopa include Levocarb (Duodopa), Sinemet CR
    • Benserazide, of which combinations of carbidopa+benserazide include Madopar
  • Dopamine agonists

Patient information

What can you do about clumps in the brain causing low dopamine?
You can give dopamine. The only problem is that too much dopamine however, and you have schizophrenia. You go a bit looooopy. That's why in schizophrenia, you actually give a drug, which DECREASES dopaimne (which in turn, can cause Parkinsonian like problems!).

I heard that by giving dopamine, you can actually CAUSE a shake...?
Yeah you can. That's why we give a DOPA decarboxylase inhibitor. Basically, it helps prevent dopamine from being created throughout the body. It only creates dopamine in the brain, where you want it work. So it decreases the motor problems side effects of dopamine.

Epidemiology
  • Most commonly occurring in elderly Pt's, with most cases occurring after 50yo, when it is seen in young adults, it is called young onset Parkinson’s disease

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Amanda Gordon

Female Psychologist
Armchair Psychology - Edgecliff NSW
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Definition of Parkinson's disease | Autoprac


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