Many people associate involuntary shaking of the body with Parkinson’s disease, a neurodegenerative disease that affects an individual’s movement. But while this uncontrollable trembling is a hallmark sign of Parkinson’s disease, it is often mistaken for another — more common — neurological movement disorder: essential tremor.
Essential tremor affects an estimated 10 million Americans, according to the International Essential Tremor Foundation. In contrast, Parkinson’s disease affects about 1 million people in the United States, with about 60,000 new diagnoses each year, based on statistics from the Parkinson’s Foundation.
At first blush, both Parkinson’s disease and essential tremor appear to be the same condition with the same symptoms. They both cause rhythmic trembling of the hands, head, legs and other parts of the body.
However, there are key differences.
Who Does It Affect?
Essential tremor is most commonly seen in people ages 40 and older, but it can affect people of all ages — even children and adolescents, according to the National Institute of Neurological Disorders and Stroke.
On the other hand, age is a major risk factor for developing Parkinson’s disease, with the average age of diagnosis around age 60 or older. In a small subset of the population, the disorder can also develop in younger individuals, known as early onset Parkinson’s disease. In fact, an estimated 10% to 20% of people with Parkinson’s disease are under 50 and — among that population — half of them are under age 40, based on data from the American Parkinson Disease Association.
“Because these diseases are typically associated with older individuals, they are often overlooked in younger people,” says Dr. Stewart Factor, professor of neurology and director of the Jean and Paul Amos Parkinson’s Disease and Movement Disorder Program at Emory University School of Medicine. “The disease often goes undiagnosed or misdiagnosed in younger people for longer periods of time.”
Shared Symptoms of Parkinson’s and Essential Tremor
Despite their differences, Parkinson’s disease and essential tremor share several similar symptoms and characteristics.
“It can be hard to recognize the differences between the two conditions because they can look a lot alike,” says Dr. Rachel Dolhun, senior vice president of medical communications at the Michael J. Fox Foundation for Parkinson’s Research. “That’s why it’s important to see a neurologist or movement disorder specialist who is familiar with the nuances between them.”
Dolhun adds that some people may even be diagnosed with both disorders. Various studies, including a 2016 systematic review published in Parkinsonism & Related Disorders, suggest there is a link between the two diseases and genetic mutations shared by both conditions.
While research continues to investigate both conditions together and separately, experts agree that there are certain symptoms in common between both disorders, including:
— Difficulty using hands for writing or feeding.
— Mild smell deficit.
— Speech problems, such as shaking voice and slow talking.
— Tremor that affects the hands.
— Tremor that affects the legs and feet (less likely with essential tremor).
Key Differences Between Parkinson’s and Essential Tremor
While Parkinson’s disease and essential tremor share several similar symptoms — namely tremor in the hands — the two conditions differ in several key ways:
— Type of tremor: In Parkinson’s disease, tremor is one of several prominent features affecting about 75% of those diagnosed with the disorder. People living with Parkinson’s disease experience tremors that vary from other movement disorders because it’s a “resting tremor,” meaning it is more visible when the muscle is at rest, not during movement.
— Parts of the body affected: Parkinson’s disease tremors usually start in the hands, but may affect almost any part of the body, including mouth, jaw, legs and feet. It’s common for Parkinson’s disease to initially affect one side of the body or one limb. Over time, the disease eventually impacts both sides of the body.
— Genetic factor: Most cases of Parkinson’s disease are unrelated to family history, but 15% of people with the condition have a genetic link, according to Johns Hopkins University. Researchers have identified five main genes LRRK2, PARK2, PARK7, PINK1 and SNCA associated with Parkinson’s disease.
— Type of tremor: Unlike resting tremors from Parkinson’s disease, essential tremor is characterized by shaking in the hands that becomes more noticeable with movement. This can lead to difficulty using hands to write, hold utensils or handle tools. Tremors can be triggered by increased stress, fatigue or even extreme temperatures.
— Parts of the body affected: Essential tremor primarily affects a person’s hands, head and voice box, making daily tasks — like lifting a spoon, buttoning a shirt or speaking — more difficult. In rare instances, essential tremor may affect the legs or feet. Essential tremor commonly begins on both sides of the body at the same time.
— Genetic factor: If one parent has essential tremor, there is a 50% chance the condition will be passed down to the child. For this reason, it’s known as an autosomal dominant trait. The exact genes involved are still unknown.
Diagnosing Parkinson’s Disease and Essential Tremor
An accurate diagnosis is made by a neurologist after a thorough examination and review of an individual’s medical history.
Currently, there are no blood or imaging tests that can accurately diagnose Parkinson’s disease or essential tremor. However, these tests are sometimes ordered to help rule out other related conditions.
When diagnosing Parkinson’s disease, doctors must identify at least three symptoms, including: tremor, rigidity and slowness of movement and speed, also referred to as bradykinesia.
To differentiate between Parkinson’s and essential tremor, doctors may ask individuals to drink from a glass, hold arms outstretched and write a sentence. Diagnosing essential tremor involves similar neurological and performance examinations.
“While there is no cure for either condition, available treatments can reduce signs and symptoms and help individuals maintain a better quality of life,” Factor says.
Some people with either condition may not require immediate treatment, but some may require surgery or medication to better manage symptoms once they start to interfere with routine tasks.
“If you experience shaking or tremor of any sort, it’s important to speak with your physician,” Dolhun says. “That way, you can work together to determine what’s causing it and what you can do about it.”
The main treatment options available for Parkinson’s and essential tremor include:
— Deep brain stimulation: For those with Parkinson’s disease or essential tremor who do not respond to medications, this surgical procedure involves implanting small electrodes in certain areas of the brain to deliver electrical impulses that help regulate the abnormal neural activity. The electrodes are attached to a pacemaker-like device — known as a neurostimulator — that allows doctors to modulate the strength and frequency of the electrical impulses.
— Focused ultrasound: First approved by the Food and Drug Administration for essential tremor in 2016 and Parkinson’s disease in 2018, this non-invasive surgical option delivers highly concentrated ultrasound beams to destroy a very small portion of brain tissue to interrupt abnormal electrical signaling in the brain thought to be responsible for causing tremor.
— Physical therapy: This is often used as the first-line of defense to help individuals with milder forms of Parkinson’s disease and essential tremor to help reduce tremor, increase mobility and coordination and improve muscle control.
— Prescription medications: There are several available drugs used to treat conditions and to increase certain brain chemicals to help better control certain symptoms. Well-tested, but separate treatments are available for Parkinson’s disease and essential tremor.
Medications for Parkinson’s disease
Current treatments for Parkinson’s disease are designed to re-establish the effects of dopamine and reduce the severity of major symptoms. While dopamine-targeted medications effectively address the motor problems of the disease, they come with side effects like involuntary movements, hallucinations, dizziness and confusion. Be sure to report any unexplained side effects to your doctor after beginning treatment.
— Adenosine receptor antagonist: This non-dopamine approach focuses on the adenosine that is responsible for coordinating different responses to dopamine and other neurotransmitters responsible for motor function and learning. In 2019, the FDA approved istradefylline (Nourianz) as an add-on to levodopa-carbidopa to treat “off time” when Parkinson’s symptoms return between treatment.
— Anticholinergics: Several available anticholinergics (e.g., benztropine, trihexyphenidyl) help suppress the action of acetylcholine, a neurotransmitter in the brain that affects movement. These medicines can help reduce tremor and may influence painful cramping. Potential side effects may include blurred vision, dry mouth and constipation.
— Antidyskinetics: Amantadine (Symmetrel) has long been used to treat Parkinson’s disease and more recently has been proven to help those with involuntary movements, known as dyskinesia. Extended release forms of amantadine are available. In 2017, Gocovri was approved by the FDA as the first medicine proven to treat dyskinesia in Parkinson’s disease. In 2018, the agency granted approval for Osmolex to treat Parkinson’s.
— Catechol O-methyltransferase (COMT) inhibitors: There are several COMT inhibitors available that are used to prolong the effect of levodopa-carbidopa. In 2020, the FDA approved the COMT inhibitor opicapone (Ongentys) for Parkinson’s.
— Dopamine agonists: These medicines simulate the effects of dopamine without having to be converted into dopamine. The FDA has approved several dopamine agonists, including injectable apomorphine (Apokyn, Kynmobi), pramipexole (Mirapex), ropinirole (Requip) and rotigotine (Neupro).
— Levodopa: Discovered more than 50 years ago, levodopa is the cornerstone of treatment for Parkinson’s disease. Levodopa is converted into dopamine in the brain, thus increasing dopamine levels to help control movements. Levodopa is usually combined with carbidopa to prevent some of levodopa’s side effects like nausea and vomiting.
— MAO-B inhibitors: This type of medication inhibits type-B monoamine oxidase (MAO-B) to improve motor symptoms of Parkinson’s disease. Selegiline, rasagiline and safinamide are three MAO-B inhibitors often used in combination with other Parkinson’s medications.
There are various medication-free ways to treat Parkinson’s disease — including exercise, occupational therapy and acupuncture — that can be used in conjunction with or in place of pharmacological interventions.
Medications for essential tremor
There are several FDA-approved drugs that can help improve symptoms associated with essential tremor. Individuals often see improvement with these medications, but when the condition interferes with quality of life and medications stop working, there are surgical and non-surgical options available.
— Anti-seizure medications: There are several anti-seizure medicines — including primidone, gabapentin and topiramate — that are used to suppress tremor. Primidone is thought to reduce tremor in many individuals. Topiramate is effective in treating moderate to severe essential tremor. Gabapentin is given either alone or in combination with other treatments for essential tremor.
— Beta blockers: Approved for use in treating high blood pressure, beta blockers are considered first-line treatment for essential tremor and have been shown to help suppress tremor. Propranolol is the beta blocker most often prescribed to treat essential tremor. Propranolol does not eliminate tremor, but will help reduce the frequency — especially seen in the hands and voice.
— Botulinum toxin injections: Known for its cosmetic applications, botulinum toxin — commercially known as Botox, Myobloc or Jeuveau — is helpful in treating some forms of tremor, particularly affecting the head and voice and sometimes the hands. Botulinum toxin may cause temporary weakness in the limb. The effects of botulinum toxin are not long lasting and need to be repeated every three months.
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Parkinson’s vs. Essential Tremor: What’s the Difference? originally appeared on usnews.com
Update 01/04/23: This story was previously published at an earlier date and has been updated with new information.