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Parkinson's Disease (PK)

(Parkinson's Disease)


Hector A. Gonzalez-Usigli

, MD, HE UMAE Centro Médico Nacional de Occidente

Last full review / revision Sep 2020 | Content last changed Sep 2020
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Parkinson's disease is a slowly progressive degenerative disease affecting specific areas of the brain. It is characterized by tremor when the muscles are at rest (resting tremor), increased muscle tone (stiffness or rigidity), a slowdown in voluntary movements, and difficulty in maintaining balance (postural instability). Many patients develop mental deficits or dementia.
  • Parkinson's disease is caused by a breakdown in the area of ​​the brain that helps coordinate movement.

  • The most noticeable symptom is usually tremor, which occurs when the muscles are relaxed.

  • The muscles become stiff and the movements become slow and uncoordinated. The person easily loses balance.

  • Doctors base their diagnosis on symptoms.

  • General measures (such as easing routine tasks), medicines (such as levodopa plus carbidopa), and sometimes surgery can help, but the disease progresses and ultimately leads to severe disability and immobility.

Parkinson's disease is the second most common degenerative disease of the central nervous system after Alzheimer's disease. She concerns

  • about 1 in 250 people over 40 years of age

  • about 1 in 100 people aged 65 and over

  • about 1 in 10 people aged 80 and over

Parkinson's disease usually begins between the ages of 50 and 79. It rarely occurs in children and adolescents.

Changes in the brain

In Parkinson's disease, the nerve cells in part of the basal ganglia (known as the substantia nigra) atrophy.

The basal ganglia are a collection of nerve cells located deep in the brain. They have the following functions:

  • Triggering and smooth design of intentional (voluntary) muscle movements

  • Suppression of involuntary movements

  • Coordination of changes in posture

When the brain initiates an impulse to move a muscle (such as raising an arm), the impulse goes through the basal ganglia. Like all nerve cells, the cells in the basal ganglia release chemical messengers (neurotransmitters) that cause the next nerve cell along the nerve path to transmit an impulse. The most important messenger substance in the basal ganglia is dopamine. Its overall effect is that it increases the nerve impulses to the muscles.

When the nerve cells in the basal ganglia wither, they produce less dopamine and the connections between the nerve cells in the basal ganglia decrease. As a result, the basal ganglia cannot control muscle movements as they normally do. This leads to tremors, slow movements (bradykinesia), a tendency to move less (hypokinesia), poor posture and difficulty walking, and some loss of coordination.

Localization of the basal ganglia

The basal ganglia are a collection of nerve cells located deep in the brain. This includes the following:

  • Caudate nucleus (a C-shaped structure that tapers into a thin tail)

  • Globus pallidus (located next to the putamen)

  • Black substance (substantia nigra)

The basal ganglia help trigger voluntary muscle movements and make them supple, suppress involuntary movements and coordinate changes in posture.