An Overview of Parkinson's Disease

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Parkinson's is a progressive disease that develops as a result of the death of dopamine-producing nerve cells in the brain, primarily in the substantia nigra—an area of the midbrain that releases neurotransmitters for controlled movements and coordination. Dopamine is one of those vital chemical messengers that helps regulate muscle activity. When it is depleted, classic Parkinson's symptoms like shaking, stiffness, and walking difficulties occur.

While Parkinson's disease used to be considered solely a motor disorder, experts now recognize that it also causes non-motor related symptoms like sleeping problems and constipation. What's interesting is that these symptoms may actually predate the motor symptoms by many years, even decades.

Symptoms

The symptoms of Parkinson's disease can be subtle early on. In fact, they may even go unnoticed. But eventually, the symptoms slowly worsen with time.

Hallmark symptoms of Parkinson's include:

  • Tremor: In Parkinson's, this is often called a "pill-rolling" tremor because of the way it appears—as if a person is rolling a pill or other tiny object between his or her thumb and index finger. It's also described as a resting tremor because it occurs when a body part (like, but not limited to, the hand) is relaxed and resting.
  • Bradykinesia: This is a person's decreased ability to move. A person may progress from difficulty using his or her fingers (for example, opening a jar or typing) to difficulty using their legs, leading to a shuffling gait with short steps.
  • Rigidity: A person with rigidity experiences muscle stiffness and resistance to muscle relaxation. They may not swing their arms much when walking, for example. Rigidity can be painful and contribute to difficulty moving.
  • Postural instability: This symptom, defined as a sense of imbalance when standing up, usually arises later on in the course of Parkinson's disease.

Other motor-related symptoms can include decreased eye blinking, speech and swallowing issues, and reduced facial expressions.

Non-motor symptoms of Parkinson's, which are getting increased research attention, include hallucinations, mood disorders, sleep problems, skin issues, and sensory disturbances.

Not everyone experiences these additional motor and non-motor symptoms of Parkinson's to the same degree, if at all.

Non-motor symptoms are often more debilitating for a person than their motor symptoms, and they can start years earlier.

Causes

While the precise cause of a person's Parkinson's disease is usually unknown, experts believe that it results from a complex interaction between one's genes and their environment.

Examples of environmental exposures that may trigger the development of Parkinson's disease in a genetically vulnerable person are pesticides or rural living. Other risk factors for Parkinson disease are increasing age and gender (Parkinson's disease is more common in men).

Diagnosis

The diagnosis of Parkinson's disease requires a careful and thorough evaluation by a doctor, usually a neurologist. They will ask several questions about sleep, mood, memory, walking problems, and recent falls. They will also perform a physical examination to check reflexes, muscle strength, and balance.

There are specific criteria doctors follow to diagnose Parkinson's disease. For example, one that supports a diagnosis is a person with Parkinson-like symptoms demonstrating marked improvement after taking levodopa (a medication used in the treatment of Parkinson's disease).

While the diagnosis is straightforward in some people, it may be more challenging in others, especially since there are other neurological health conditions that share similar symptoms with Parkinson's disease.

There is no slam-dunk blood test or brain imaging test that can confirm Parkinson's, but testing may be done to rule out other reasons for one's symptoms.

Treatment

There is no cure for Parkinson's disease, but there are a number of treatment options to ease symptoms so you or your loved one can live well with it.

Deciding when to start a medication for motor symptoms depends on the person and how debilitating their symptoms are.

In the early stages of Parkinson's disease, medication may not be needed.

Carbidopa-levodopa, which goes by brand names Sinemet or Parcopa, is the primary and most effective Parkinson's medication. Levodopa is converted into dopamine in the brain, which helps restore muscle control. Carbidopa makes levodopa more effective by preventing it from converting into dopamine outside of the brain.

The downside of this otherwise very effective medication is that once a person has been on it for years, it may not be as good at managing motor symptoms—this is called the "wearing off" effect. In addition, movements that are out of your control like muscle spasms or jerking (called dyskinesia) may occur after prolonged use of levodopa.

Dopamine agonists like Mirapex (pramipexole) and Requip (ropinirole) stimulate dopamine receptors—docking sites—in the brain, tricking the brain into thinking it has the dopamine it needs to get the body to move. Dopamine agonists are less effective than levodopa, and they do have a number of potential side effects such as visual hallucinations, sleep attacks (acute sleepiness), and compulsive behaviors like gambling, eating, shopping, or sexual behavior.

That being said, dopamine agonists are sometimes used in the earlier stages of Parkinson's disease, postponing the need for levodopa until later on in the disease course. This can help prevent long-term complications of levodopa like the "wearing off" effect and out-of-control body movements.

Monamine oxidase inhibitors (MAO-B inhibitors) include Eldepryl, Emsam, and Zelapar (selegiline) and Azilect (rasagiline), which treat motor symptoms by inhibiting the enzyme that normally inactivates dopamine in the brain. This allows active dopamine to hang around in the brain more.

The downsides of monoamine oxidase inhibitors are that they are not as effective as levodopa for people with Parkinson's disease, and they can interact with other medications, like antidepressants.

The upside is that they can sometimes provide benefit in suppressing motor symptoms in the earlier stages of Parkinson's disease, essentially buying a person some time before having to start levodopa.

COMT inhibitors like Comtan (entacapone) and Tasmar (tolcapone) work by increasing the effect of levodopa in the brain (so they are taken with levodopa). They are used to treat people who experience the "wearing off" effect of being on levodopa long-term. Monitoring of liver blood tests is needed if a person is on Tasmar (tolcapone).

Anticholinergics like Artane (trihexyphenidyl) and Cogentin (benztropine) are prescribed to minimize the discomfort of tremor in people with Parkinson's disease. They work by increasing acetylcholine in the brain.

The downside is that anticholinergics have numerous potential adverse effects like blurry vision, dry mouth, retaining urine, constipation, and confusion (especially in older adults). Because of this, they are reserved for those individuals with Parkinson's disease under the age of 70.

Symmetrel (amantadine) is an antiviral medication that is used in early Parkinson's disease to manage mild tremor and rigidity. Potential side effects include dry mouth, constipation, skin rash, ankle swelling, visual hallucinations, and confusion.

Deep brain stimulation is reserved for those with advanced Parkinson's disease whose motor symptoms are not effectively treated anymore with medication. Deep brain stimulation is particularly effective for people with persistent, disabling tremors, and those with uncontrollable movements (called dyskinesia) or fluctuations ("waxing and waning" symptoms), which are complications of using levodopa long-term.

Deep brain stimulation entails a neurosurgeon implanting a wire deep within the brain. This wire is connected to a battery-operated device called a neurostimulator, which is placed under the skin near the collarbone. Electrical pulses delivered from the neurostimulator (controlled by the patient) is believed to alter the intricate nerve pathways in the brain that control movement (so normal movements are produced instead of abnormal ones, like tremor).

It's important to understand that this surgical treatment is not a cure and does not stop a person's Parkinson's disease from progressing. There are also serious risks involved, warranting a thoughtful discussion with a person's neurologist, surgeon, and family before undergoing it.

Treatment of Non-Motor Symptoms

Aside from the movement problems associated with Parkinson's disease are the often less visible symptoms like sleep problems, cognitive problems, and mood changes, which can negatively impact a person's quality of life.

The good news is there are excellent therapies to address non-motor symptoms of Parkinson's disease.

For example, depression is common in Parkinson's disease, but it can be treated with traditional antidepressants, like selective serotonin reuptake inhibitors. For dementia (thinking and memory problems), the skin patch Exelon (rivastigmine) may be prescribed.

Hallucinations and psychosis can be especially disturbing for a person (and their loved ones) with Parkinson's disease. To address this, a neurologist may stop or decrease the dose of their Parkinson's medication (for example, levodopa). For more serious cases of hallucinations, an antipsychotic medication may be prescribed.

Rehabilitation therapies like speech, occupational, and physical therapy are also commonly used to improve the quality of life in Parkinson's disease.

A Word from Verywell

Parkinson's disease is a complex neurodegenerative disorder that affects not only how a person moves, but also how they think, feel, sleep, and even smell. While these symptoms can be disabling, there are effective ways to reduce their impact on your or your loved one's life.

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