More than one million Americans currently live with Parkinson’s disease (PD), a number expected to triple over the next decades as the U.S. population ages.1 Parkinson’s is a chronic, progressive neurological disease that manifests in a variety of physical, cognitive, and psychological symptoms.
Many early symptoms of PD, which is diagnosed in stages, are so subtle and varied that the disease may go unnoticed for years. As it takes time to develop obvious motor symptoms, such as hand tremors, early detection is essential both to confirm a PD diagnosis and to begin treatment.2 While there are no definitive biomarkers for PD, physicians know to be on the lookout for early symptoms if patients have a family history of the disease.
According to Dr. Lawrence Severt, Attending Neurologist at Beth Israel Hospital in New York, physicians look for early evidence of non-motor or pre-motor symptoms, factors that may influence a PD diagnosis, long before motor symptoms appear.
“While there are many other pre-motor symptoms that researchers are currently considering, the following four symptoms have been statistically validated as early indicators of a potential PD diagnosis,” Severt says. “They are a diminished sense of smell, a long history of constipation, REM-sleep behavior disorder (body movements during REM-sleep when only the eye muscles should move), and a history of anxiety and depression.”3 Other non-motor symptoms may include:
- Speaking in a low-volume voice (hypophonia)
- Changes in speech (slurring, hesitation, or speaking monotonously)
- Difficulty finding words (dysarthria)
- Low blood pressure when standing
- Painful foot cramps
- Emotional changes in personality
- Problems with skin
- Increased sweating
- Increased urination urgency/frequency
- Erectile dysfunction
Parkinson’s disease is primarily a movement disorder. It is one of a spectrum of progressive neurological disorders that reduce the production of chemical messengers in the brain called neurotransmitters. Parkinson’s disease depletes the neurotransmitter dopamine.
Nerve cells use dopamine to send messages that control muscle movement, so a brain that is low in dopamine has less control over muscle function. That lack of control leads to a host of motor symptoms that affect movement.
As dopamine in the brain decreases, PD symptoms progressively worsen. Parkinson’s cardinal symptoms affect movement and muscle control and become more noticeable as the disease progresses. Both movement and neurological symptoms are apparent when 80 percent of the brain’s dopamine is exhausted.
There are four main motor symptoms of PD. They include tremor (trembling in the hands, arms, legs, jaw, or head); muscle rigidity (stiffness of the limbs and/or torso); bradykinesia (slow movement); and poor balance/posture that may affect gait. Not everyone with PD will have all the cardinal motor symptoms; similar symptoms are common in other neurological disorders.
Motor symptoms may begin on just one side of the body at first and progress to both sides as the disease worsens.4 Additional motor symptoms may include some or all of the following:
- Loss of automatic movements, such as smiling and blinking
- “Masked” face, or a lack of expression
- Shuffling gait
- Trouble rising from seated position
- Difficulty swallowing and/or eating
- Stooped posture/impaired balance
- Decreased arm swinging when walking
- Small handwriting (micrographia)
- Freezing, or walking in quick small steps (festination)
- Trouble moving, turning in bed
- Slowed daily activities
- Staying in the same position for long periods
There are also many motor symptoms of PD associated with vision that relate to the muscle movements of the eyeball. A person with PD might have trouble focusing, experience blurred or double vision, and/or suffer from eyestrain or chronic dry eye (due to a lack of automatic blinking). Other vision-related PD symptoms may include trouble opening the eyes (apraxia), eyelid spasms (blepharospasm), and/or excessive blinking.
In addition to vision changes, people with PD often combat significant cognitive impairments. Sometimes those changes interfere with thinking. Problems with memory and the ability to pay attention, solve problems, or make quick decisions are all common PD symptoms. Some of those changes may be less obvious because they occur gradually.
Cognitive symptoms will likely be more noticeable in the later stages of the disease. If they are discovered early, they are typically confined to specific domains of brain function. Below are examples of specific domains that are influenced by decreasing dopamine:
- Executive functions: People with PD may have trouble forming concepts, making plans, or reaching goals. It may also be more difficult for them to anticipate the consequences of their actions.
- Slowed thinking: Typical daily tasks are challenging for people with PD. Problems are more difficult to solve. Following directions, as in recipes, is more difficult. People with PD also sometimes have trouble accessing specific words.
- Impaired memory: Those with PD often have difficulty remembering, storing, and accessing information.
- Difficulty paying attention: People with PD often find it difficult to follow complex scenarios, such as fully understanding a multi-person conversation.
- Impaired ability to understand spatial relationships: PD may impair patients’ ability to determine where they are in space in relation to everything else. That impairment may affect their ability to operate a moving vehicle.
Stages of Parkinson’s Disease
Although Parkinson’s disease is categorized in five stages, the course of its progression is individualized. This is especially true as advancements in treatment effectively slow its course. It is not uncommon to skip stages, or to have a variety of non-motor, motor, cognitive, and psychological symptoms (depression, anxiety, insecurity) at the same time. The pace at which PD worsens varies greatly. Various treatments including medication, surgery, and lifestyle changes can effectively slow the progression of the disease.
In PD, Stage I, motor symptoms are confined to one side of the body. In PD, Stage 2, motor symptoms appear on both sides of the body, but balance remains intact. In PD, Stage 3, balance becomes more challenging. In PD, Stage 4, motor functions are severely disabled but walking independently is still possible. Finally, in PD, Stage 5, people are wheelchair-bound or bedridden.