Parkinson’s Disease (PD)

Parkinson’s disease (PD) is a neurodegenerative movement disorder. Because many regions of the brain are affected, there are a variety of symptoms that can occur such as slowing of movement, tremor, muscle stiffness, and problems with balance/coordination. Symptoms usually begin gradually and worsen over time.

55-60 million people are affected with PD worldwide, and this number will continue to climb as life expectancy increases and the world population ages. The median age of onset is 60 years and the mean time between diagnosis and death is 15 years. The disease is more common in men. The cause of PD is unknown in the majority of cases, but genetic risk factors can be identified in about 5%-10% of patients.

What are common symptoms of Parkinson’s Disease (PD)?

“Parkinsonism” is the term used to describe the four (4) cardinal motor symptoms of PD. The four motor symptoms are bradykinesia, rigidity, rest tremor, and postural instability.

(1) Bradykinesia or hypokinesia (i.e., slowed movements): Patients with PD are slow in their movements, have difficulty with fine motor control, and experience problems writing and using their hands to play instruments or type on a computer keyboard. Reduced arm swing and “shuffling” of feet when walking are common findings. There is also a delay or hesitancy in initiating movements.

(2) Rigidity: Muscle rigidity occurs when opposing muscle groups are contracting at the same time or are always in a contracted state. Often there is a resistance to passive movement.

(3) Rest tremor (pill rolling tremor): Tremor is the presenting motor symptom of PD in up to 70% of patients and affects up to 90% of patients at some point during the disease process. The tremor is clasically described as a “pill-rolling” tremor that occurs at a frequency of 4-6 muscle contraction cycles per second (Hz). The tremor occurs at rest, usually starts on one side in the hands and fingers, and diminishes during voluntary movement and sleep. As the disease progresses, the tremor becomes more prominent and affects both sides.

(4) Postural instability: Patient’s with PD have difficulty maintaining appropriate posture and are seen stooped or hunched over. 

In addition to the motor symptoms above, there are many nonmotor symptoms that occur in patients with PD.

Cognitive deficits such as inattention and memory problems occur in about 30% of patients with PD. Memory problems are thought to be a result of damage to acetylcholine neurons and a build up of insoluble alpha-synuclein proteins (lewy bodies) within various brain structures.

Constipation and olfactory (i.e., sense of smell) problems develop in many cases.

Autonomic dysfunction is common and includes bradycardia (slowed heart rate), hypotension (low blood pressure), urinary retention, postural hypotension (rapid drop in blood pressure when standing from a sitting position), sweating, and drooling. 

Rapid Eye Movement Sleep Behavior Disorder (RBD) and other sleep disturbances are common in patients with PD. REM sleep is normally characterized by muscle paralysis and lack of motor movement. RBD occurs when paralysis of muscles does not occur, and patients move around while dreaming (they “act out” their dreams). Insomnia and other sleep disturbances are also common.

Mood and personality changes may include depression, apathy, anxiety, irritability, agitation, hallucinations, and paranoia.

What goes wrong in the brain of patients with PD?

Motor symptoms are believed to occur due to problems in a group of brain structures that are important in the initiation and coordination of movement. These structures are collectively called the basal ganglia. Many of the symptoms of PD occur due to a progressive loss of dopamine neurons, norepinephrine neurons, and serotonin neurons in specific brain areas.

How is Parkinson’s Disease treated?

The mainstay treatment for Parkinson’s disease is “dopamine replacement” with levodopa (L-Dopa), which is converted to dopamine in the brain. L-Dopa is given because dopamine is unable to get into the brain efficiently. 

Side effects of L-Dopa are thought to occur from the conversion of L-Dopa to dopamine, norepinephrine, and epinephrine outside of the brain. Gastrointestinal side effects such as nausea and diarrhea are the most common. Other common side effects include rapid heart rate (i.e., tachycardia), sweating, depression, anxiety, agitation, aggression, impulsivity problems (gambling, spending), hallucinations, and paranoia.

Although there is no cure for PD, the severity of symptoms can be reduced with L-dopa and other medications such as monoamine oxidase inhibitors (Selegiline and Rasagiline), Pramipexole, and Amantadine. Deep Brain Stimulation (DBS) has also proven effective in medication-resistant patients.

For more information about Parkinson’s Disease visit Parkinson’s Disease: Causes, Symptoms, and Treatments | National Institute on Aging

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