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Parkinson's Disease

From Mediwikis

This degenerative neurological condition was first detailed by James Parkinson, describing 6 patients with similar signs. Not to be confused with Parkinsonism, which is the umbrella term describing parkinsonian features, but not neccessarily caused by Parkinson's Disease.

Parkinsonism

This is the syndrome of parkinsonian signs.

I think my patient has Parkinsons, by AEME

Causes

  • Parkinson's Disease
  • Cerebral Infarct
  • Post-Encephalopathy
  • Trauma
  • Drugs: Prochlorperazine, Metoclopramide
  • Toxins: Copper(Wilson's Disease), MPTP

Pathophysiology

Selective loss of dopaminergic neurons in the substantia nigra of the basal ganglia. Lewy bodies(pathological protein aggregates) form in the same area, but it's not certain whether cell death causes Lewy body formation, or vice versa.

Clinical Features

Divided into motor, and non motor signs:

Motor

Unilateral onset:

  1. Bradykinesia(slowed movements)
    1. Parkinsonian gait
    2. Speech difficulties
  2. Tremor ("pill-rolling")
  3. Rigidity
  4. Postural Instability

Clinical on/off states, where symptoms are controlled by medication(on), then as the medication wears off, the symptoms return. The patterns of PD are such that some experience mainly tremor, and some mainly have rigidity. Those with the rigid clinical pattern generally have a poorer prognosis.

Non Motor

  1. Cognitive Impairment
  2. Anosmia
  3. Psychiatric disturbances
    1. Depression
    2. Hallucinations
    3. Illusions
    4. Behavioural changes
  4. Sleep disturbance
    1. Lucid Dreams
    2. REM Behaviour Disorder (RBD)- physically acting out ones dreams
    3. High risk of dementia
  5. Autonomic dysfunction
    1. Dry mouth
    2. Dribbling

Detailed Examination

As with Upper Motor Examination, but focus on the following:

  • Careful inspection for tremor while talking
  • Gait
  • Tone- Reinforce by using distraction- ask patient to "paint the wall" with the opposite arm to the one being examined.
  • Power is usually normal
  • Reflexes may be normal, however the glabellar tap test may be abnormal (see video).
    Glabellar Tap, courtesy of AllAccessMedicine.

Risk Factors

Age is the most important, but family history & environmental factors, such as the potent neurotoxin MPTP, or pesticides, are also implicated. Cigarette smoking also appears to be protective. [1]

Prognosis

Motor symptoms advance with age, over about 10 years. Life expectancy is reduced, and disability is high. The disease progression may partly be monitored using the Hoehn and Yahr criteria[2]:

Stage Hoehn and Yahr Scale Modified Hoehn and Yahr Scale
1 Unilateral involvement only usually with minimal or no functional disability Unilateral involvement only
1.5 - Unilateral and axial involvement
2 Bilateral or midline involvement without impairment of balance Bilateral involvement without impairment of balance
2.5 - Mild bilateral disease with recovery on pull test
3 Bilateral disease: mild to moderate disability with impaired postural reflexes; physically independent Mild to moderate bilateral disease; some postural instability; physically independent
4 Severely disabling disease; still able to walk or stand unassisted Severe disability; still able to walk or stand unassisted
5 Confinement to bed or wheelchair unless aided Wheelchair bound or bedridden unless aided

Differential Diagnoses

Drug-Induced Parkinsonism

  • Anti-emetics
    • Metoclopramide
    • Prochlorperazine
    • Cyclizine
  • Antipsychotics
    • Haloperidol
    • Risperidone

Vascular Parkinsonism

  • Typically bilateral, and more affecting the lower limbs
  • Acute onset

Essential Tremor

  • Tremor is worse on action than at rest
  • Familial link
  • No bradykinesia
  • Alcohol helps with the tremor (quite dramatically)

Sometimes a DaTSCAN may be needed to distinguish between Parkinson's Disease and Essential Tremor- it's not used for any other diagnostic purposes, as it's very expensive

Management

See Parkinson's Disease Management

Physiotherapy Medications aim to replenish lost dopamine

  • Levodopa- precursor to dopamine
  • Dopamine agonists- structurally similar to dopamine e.g. Ropinerole
  • Anticholinergics: Benzhexol
  • Monoamine Oxidase B inhibitors- prevent breakdown of dopamine

References

  1. http://linkinghub.elsevier.com/retrieve/pii/S1474442206704719
  2. http://www.ncbi.nlm.nih.gov/pubmed/6067254