What is Parkinson's Disease?

  First described by James Parkinson, an English doctor, in 1847, Parkinson's disease is a progressive deterioration of muscular function producing muscle tremors, rigidity and akinesia. Parkinson's disease afflicts 1 out of 100 people over age of 60, men more often than women making it one of the most common crippling diseases in the US.

What causes Parkinson's disease?

  A dopamine deficiency of the extrapyramidal nuclei, especially in the basal nuclei (corpus striatum, globus pallidus and substantia nigra) brought on by degeneration of dopaminergic neurons. It is not known, though, what initiates the destruction of these neurons in this disease.

Left:Midbrain section showing loss of pigmented cells of the substantia nigra in Parkinson's disease. Right:Midbrain section showing normal substantia nigra. From: CNS Pathology.

Left:Histology of Parkinson's disease showing loss of pigmented neurons in substantia nigra. Right:Histology of normal substantia nigra showing many pigmented neurons. From: CNS Pathology.

  Acetylcholine levels are also increased in these areas and the resulting neurotransmitter imbalance is thought to bring about most of the symptoms.
 
  Parkinson's disease does not appear to run in families as only 5% of patients show a family history of the disease.

What are the symptoms of Parkinson's disease?

  The cardinal symptoms are muscle rigidity and tremors that begin in the fingers (unilateral "pill-rolling" tremor). Anxiety or stress antagonizes these symptoms. Other symptoms include:

Difficulty walking (gait lacks normal parallel motion or is retropulsive)
Mask-like facial expression and drooling
Loss of posture control (walking with body bent forward)
Dysphagia or inability to feed oneself
Cognitive function is not usually impaired, though dementia does occur in some patients

How is Parkinson's diease diagnosed?

  It is diagnosed mostly by the patient's age, history and clinical manifestations displayed. Diagnosis also involves eliminating other possible causes including CVA (stroke), cerebral arteriosclerosis, drug toxicities, brain tumors or metabolic disorders. Urinalysis for dopamine metabolites can reveal decreased dopamine levels to support the diagnosis.

What is the treatment for Parkinson's disease?

  Current treatments can only relieve the symptoms of this disease, there is no way to stop the progression of the disease or cure it. Therapies typically center on increasing the levels of dopamine and decreasing the levels of acetylcholine.
 
  Drug therapy includes administering levo-dopa (l-dopa) in the early stages to replace the lost dopamine. It is typically administered in increasing dosages until symptoms are alleviated. Side effects are common so l-dopa is often given in combination with carbidopa which blocks peripheral dopamine synthesis. Alternate drugs include anticholinergics (trihexyphenidyl), antihistamines, or amantadine. Drugs to inhibit enzymatic breakdown of dopamine such as deprenyl or seligiline(monoamine oxidase B inhibitors), enhances effectiveness of l-dopa. Careful monitoring of drug treatments and dosages are important to prevent side effects.
 
  Supportive physical therapy tailored to the patients' needs include both active and passive range-of-motion exercises, massages, and routine daily walks.
 
  In some cases (especially younger patients) surgery to destroy the ventromedial nucleus of the thalamus may prevent unilateral tremors and involuntary movements, though this is not a cure.
 
  In experimental cases, fetal brain cells (from those areas rich in dopaminergic cells) have been tranplanted into patients with severe Parkinson's disease quickly resulting in some improvement for the patient. Though still experimental (and controversial) this approach shows promise.

For more information on Parkinson's disease, see the following sources:
WebDoctor
Harvard Parkinson's Web
CNS Pathology
Parkinson's Sites