Parkinson's Disease

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Parkinson's disease (PD)

Parkinson's disease (PD)
is an age-related deterioration of certain nerve systems, which affects your movement, balance, and muscle control.
  • Parkinson's disease is one of the most common movement disorders, affecting 1% of people older than 60 years. PD is about 1.5 times more common in men than in women, and it becomes more common as you age.
  • The average age of onset is about 60 years. Onset before age 40 years is relatively uncommon, but the recent diagnosis of actor Michael J. Fox shows that younger people are also vulnerable.
  • In PD, brain cells deteriorate (or degenerate) in an area of the brain called the substantia nigra. From the substantia nigra, specific nerve cell tracts connect to another part of the brain called the corpus striatum, where the neurotransmitter (a chemical messenger in the brain) called dopamine is released. Dopamine is an important neurotransmitter and alterations in its concentration can lead to different medical problems.
  • The loss of these specific brain cells and decline in dopamine concentration are the cornerstone of signs and symptoms of PD as well as the target for treatment. The biological mechanism responsible for the brain cell loss has not been identified.


The 3 key signs of Parkinson's disease are tremor (shaking) at rest, rigidity, and slowness in the initiation of movement (called bradykinesia). Of these features, 2 are required to make the diagnosis. Postural instability is the fourth key sign, but it happens late in the disease, usually after having PD 8 years or more.
  • Tremor at rest
    • Tremor usually begins in one arm and may start and stop.
    • As with most tremors, it worsens when under stress and improves during rest or sleep.
    • After several months to a few years, both arms may become affected, but the beginning asymmetry (lopsidedness) is often maintained.
    • PD tremor may also involve the tongue, lips, or chin.
    • The characteristic PD tremor is present and most prominent with the limb at rest.
    • The tremor may appear as a pill-rolling motion of the hand or a simple oscillation of the hand or arm.

  • Rigidity
    • Rigidity refers to an increase in resistance to someone else moving your joint.
    • The resistance can be either smooth (lead-pipe) or start and stop (cog wheeling). (Cog wheeling is thought to be a tremor rather than rigidity.)
    • Having someone else flex and extend your relaxed wrists tests for rigidity.
    • Rigidity can be made more obvious with voluntary movement in the opposite limb.

  • Bradykinesia
    • Bradykinesia refers to slowness of movement but also includes a lessening of unplanned movements and decreased size of movement.
    • Bradykinesia is also expressed as micrographia (small handwriting), hypomimia (decreased facial expression), decreased blink rate, and hypophonia (soft speech).

  • Postural instability
    • Postural instability refers to imbalance and loss of reflexes used to keep you upright.
    • This symptom is an important milestone, because it is not easy to treat and a common source of disability in late disease.

  • Other symptoms
    • You may experience freezing when starting to walk (start-hesitation), during turning, or crossing a threshold such as going through a doorway.
    • Flexed postures of neck, trunk, and limbs may occur.
    • Altered mental status generally occurs late in PD and affects 15-30% of people with PD.
    • Short-term memory and visio-spacial function may be impaired.
    • The onset of PD is typically lopsided, with the most common initial finding being an asymmetric rest tremor in one arm. About 20% of people first experience clumsiness in 1 hand.
    • Over time, you will notice symptoms related to progressive bradykinesia, rigidity, and problems with walking (called gait disturbances).

  • The initial symptoms of PD may be nonspecific and include fatigue and depression.
    • Some people experience a subtle decrease in dexterity and may notice a lack of coordination with activities such as golf, dressing, or climbing stairs.
    • Some people complain of aching or tightness in the calf or shoulder region.
    • The first affected arm may not swing fully when walking, and the foot on the same side may scrape the floor.
    • Over time, posture becomes progressively flexed and your stride becomes shorter leading to a shuffling gait.
    • Decreased swallowing may lead to excess saliva and ultimately drooling.
    • Symptoms of problems with your involuntary nervous system are common and may include constipation, sweating abnormalities, and sexual dysfunction.
    • Sleep disturbances are also common.

  • The best clinical predictors of a diagnosis of PD are asymmetry, the presence of rest tremor, and a good response to dopamine replacement therapy.

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