Parkinson's Disease Symptoms & Disease Progression

Parkinson's disease is a degenerative, age-related disease of the brain that affects speech, movement, thinking, memory and other functions. Except for a few patients who have genetic mutations, it is thought that Parkinson's disease is most likely caused by: direct trauma to the head; some drugs; the neurotoxin MTPT; and/or other medical disorders. In most cases, the exact cause is unknown. The incidence of Parkinson’s is slightly lower in blacks as compared to other ethnicities. It is estimated that there are between 500,000 and 1,500,000 people with Parkinson's disease in the U.S.

Physical & Cognitive Changes Caused by Parkinson's Disease

On a chemical level, the most common Parkinson's disease symptom is a decrease in dopamine, which is essentially a chemical transmitter of information, due to the death of cells in the center of the brain where dopamine is produced. The lack of dopamine stops clear transmission of information to other motor control and other areas of the brain that control movement and muscle control.

Parkinson's disease affects not only fine and gross motor function, but also mental functioning (cognitive decline), and subtle language problems. The loss of dopamine causes confusion between the facilitators and the inhibitors of movement. In other words, Parkinson's disease affects the voluntary and the involuntary aspects of the nervous system. The result of increased inhibition to the central portion of the brain called the thalamus leads to slow and impaired movement. The disease also causes abnormal signaling to the higher centers of movement in the cortex of the brain, resulting in involuntary nervous system malfunctioning. As Parkinson's disease symptoms progress, the muscles become rigid and a tremor develops (either can happen first) and then the patient begins having a slowing and coarseness of movement, before finally experiencing a loss of normal mobility.

Symptoms & Conditions Associated with Parkinson's Disease

Speech disturbances such as speaking in a monotone and an inability to get the words out may occur. Some people have rapid and poorly intelligible speech, and experience drooling and trouble swallowing. Others experience fatigue, trouble getting into or out of bed, and/or trouble sitting still.

Mood disturbances and depression occur in a majority of Parkinson's cases. Depression may even precede the diagnosis of Parkinson's disease, which may progress to anxiety. If anxiety precedes the disease, it may develop into depression. Dementia may set in as many as 30 to 50% of cases and be noticed through such symptoms as slowed reaction time, decreased attention span, losing the ability to interpret social cues, and poor impulse control. Other findings in Parkinson's disease dementia may be interference with short-term memory, disturbance with abstract memory and thought and behavior. Patients may also experience delusions, paranoia and abstract thinking. Sleep disorders and daytime sleeping may also precede the onset of Parkinson’s disease.

The Progression of Parkinson's

Although the exact order of progression can be quite variable, for 70% of cases a dominant tremor is the first of a person's Parkinson's disease symptoms. The tremor increases with voluntary movement and is usually unilateral. Next, rigidity sets in, with stiffness and increased muscle tone. As Parkinson's disease progresses, there is absence of movement, and slowness. Next, there is disorder of movement produced each time there is a rapid, repetitive movement. About this time, problems begin to occur with postural instability, leading to impaired balance and increased numbers of falls. Associated findings include gait and postural disturbances with shuffling gait, tripping, decreased arm swing and the need to turn the whole body instead of just the neck or torso. Many people with the disease are stooped forward and experience freezing of the gait from time to time as well as painful foot and toe contractions. Dizziness and fainting can also occur in patients with Parkinson's disease, along with a decreased ability to understand one’s relationships to time and space.

Author's Note: Sources: Compiled from information found at;;;,, and the; plus the Discovery edition of Brain magazine 2009.