Parkinson's disease

Introduction

slowly progressive degenerative disorder of the CNS mainly starting in those aged over 60yrs (when it occurs before age 50yrs it is called early-onset PD)
motor impairments (“parkinsonism”) arise from the death of cells in the substantia nigra (in the basal ganglia within the midbrain) leading to a dopamine deficit.
1st detailed description was made by English doctor James Parkinson in 1817

coffee, tea drinking and tobacco smoking appear to offer reduced risk
genetic factors
pesticide / herbicide exposure eg. paraquat seems to double risk in those who live near where paraquat is sprayed such as grain fields
PH head injuries
low serum urate levels have been correlated with increased risk

early cognitive features
- 19% have cognitive impairments at time of diagnosis (most patients present with motor symptoms first)
  - those who develop dementia before or at the same time of PD motor symptoms are usually given the diagnosis of dementia with Lewy bodies
- executive functioning impairments
  - multitasking, switching tasks, and solving problems
- trouble recalling information but their long-term memory function generally remains intact
- attention difficulties
  - trouble maintaining focus, especially as the complexity of a situation increases
- slowed thinking or processing, also known as bradyphrenia
  - problem-solving, conversations
- impaired word finding, naming objects, generating words, comprehension, and verbal concepts
- visual-spatial impairments
  - difficulties in perceiving, processing, discriminating, and acting on visual information around the person
motor impairments
- reduced arm movements when walking
- reduced eye blinking
- monotone voice
- flattened facial expression range
- Parkinsonian tremor
- difficulty initiating movements resulting in increased falls
autonomic dysfunction
- orthostatic hypotension and falls risk
- constipation
- impaired stomach emptying (gastric dysmotility)
further, later, cognitive impairments may include
- psychosis - occurs in 50% and may herald onset of dementia
- apathy
- anhedonia
- depression (esp. if early-onset PD, women, PH depression, severe motor symptoms)

toxins which can cause parkinsonism include:
- manganese
- carbon disulfide
- trichloroethylene (TCE)
reversible parkinsonism may be caused by medications such as:
- phenothiazines (chlorpromazine, promazine, etc.)
- butyrophenones (haloperidol, benperidol, etc.)
- metoclopramide
- tetrabenazine
vascular parkinsonism
- the presence of Parkinson's disease symptoms combined with findings of vascular events (such as a cerebral stroke).
multiple system atrophy (MSA)
- MSA includes disorders that historically had been referred to as Shy-Drager syndrome, olivopontocerebellar atrophy, and striatonigral degeneration
progressive supranuclear palsy
corticobasal degeneration
dementia with Lewy bodies
brain tumours
Alzheimer's disease
concussions, repetitive brain trauma
encephalitis
Wilson's disease
Huntington's disease
systemic lupus erythematosus (SLE)

initial treatment options include:
- levodopa (L-DOPA)
- MAO-B inhibitors
- dopamine agonists
over time these become less effective and these may also cause:
- involuntary movement disorder
- dopamine dysregulation syndrome including impulse-control disorders, gambling, compulsive sexual behaviours, etc
- “punding” - complicated, repetitive, aimless, stereotyped behaviors occur for many hours
surgery to place microelectrodes for deep brain stimulation has been used to reduce motor symptoms in severe cases where drugs are ineffective