Tremor refers to an involuntary muscle contraction that results in a shaking movement. It is a common movement disorder that can be a symptom of conditions such as Parkinson’s disease. Parkinsonian tremors can affect the hands while at rest and may only appear in one limb or on just one side of the body.
Tremors are a common symptom that often results from altered activity in the areas of the brain that control movement. They are often associated with neurological conditions such as multiple sclerosis, stroke, and Parkinson’s disease.
Medical experts classify body tremors into two categories, which are resting tremors and action tremors. The first are tremors that occur when the muscle is at rest, and the second occurs during voluntary muscle movements. Experts then further categorize tremors into different types, of which there are more than 20. Common forms of tremor include essential, dystonic, and Parkinsonian.
In this article, we will discuss Parkinsonian tremor, how it differs from other tremors, and the treatment options available.
Parkinsonian tremor definition
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Parkinsonian tremor is an involuntary rhythmic shaking or slight movement in the body. It is often the first symptom people notice. The tremor tends to occur in the hands, though it may affect the chin, lips, face, or legs. It may start out asymmetrically, meaning it only occurs in one limb or on one side of the body but may progress to include the other side of the body.
A typical Parkinsonian tremor occurs mostly at rest, such as when the hands are resting on the lap. People may refer to this as a resting tremor. People may also present the characteristic pill-rolling tremor. This is when a person performs a circular finger and hand movement that resembles rolling a small object, such as a pill, in the hand.
A person may also experience a tremor when a body part is held against gravity, such as when holding a tray. People may refer to this as a postural tremor.
While a resting tremor is the more characteristic sign of a Parkinsonian tremor, a person may also experience an action tremor. This refers to a tremor that occurs while moving, such as when moving the hand to the face.
Other tremors and how it differs
A Parkinsonian tremor has a few distinct characteristics, though it may be easy to confuse with other types of tremors depending on the other symptoms a person shows. Doctors will look for and rule out other types of tremors to confirm their diagnosis.
The National Institute of Neurological Disorders and Stroke notes that some common tremors include:
- Essential tremor or benign familial tremor: This is a more common tremor than Parkinsonian tremor. It typically occurs in both sides of the body and occurs more often during the action, but can also occur at rest. More than half the people with this diagnosis have a family history of the condition. Essential tremor shakes are usually faster than Parkinsonian tremors.
- Dystonic tremor: A tremor due to forceful muscle spasms or cramps, caused by a condition called dystonia. It may cause abnormal body postures and an arrhythmic, jerky tremor.
- Cerebellar tremor: An easily visible tremor in the arm or leg caused by damage to the cerebellum. It usually occurs at the end of a motion, such as picking up a phone or pressing a button.
- Psychogenic tremor: A psychogenic tremor can start abruptly and affect all body parts. Symptoms get worse in times of stress and may disappear when distracted.
- Physiologic tremor: A physiologic tremor involves a very fine shaking of the hands and fingers, such as when lifting something heavy or maintaining an uncomfortable position for a long time. This is rarely visible to the eye and experts do not consider it to be a medical problem.
- Orthostatic tremor: An orthostatic tremor is a rare disorder that causes rapid muscle contractions in the legs while standing. It may not be visible to the naked eye. It can occur as part of other types of tremor disorders.
Causes
Tremors are a common symptom of Parkinson’s disease. A chemical messenger called dopamine plays a role in the condition and contributes to tremors.
Dopamine is an important neurotransmitter that plays a critical role in a number of bodily functions, such as movement and coordination. People with Parkinson’s disease produce less dopamine, which may cause them to experience movement-related problems, such as rigidity, slowness of movement, poor balance, and tremors.
Low levels of dopamine may disrupt the way the brain processes movement, which can result in movement problems. Evidence suggests that many people with Parkinson’s disease lose 60–80% of dopamine-producing cells in the brain by the time they present symptoms.
Other causes of tremors unrelated to Parkinson’s disease can include:
- certain medications
- alcohol use disorder or withdrawal
- mercury poisoning
- an overactive thyroid
- liver or kidney failure
- anxiety or panic disorder
- brain diseases or brain damage
Diagnosis
Diagnosing a Parkinsonian tremor will usually involve observing the person and their symptoms and attempting to rule out other possible causes.
Typically, to diagnose Parkinson’s disease, a neurologist will perform a physical examination to check for signs such as tremors. The doctor will also ask about symptoms, such as if the tremors occur more while at rest, and may order neurological scans and blood tests to help rule out other possible conditions.
As part of the physical exam, a doctor may ask a person to rest their hands while giving their medical history and look for signs of resting tremor. They may also ask the person to perform tests, such as holding their arms out in front of them or touching their nose with their finger, to look for signs of postural or active tremors.
Where it occurs
Tremor may occur in many places in the body, but commonly affected areas include the:
- hands and fingers
- jaw
- feet and legs
- mouth or tongue
Some people may experience an internal tremor. This occurs when the person feels as if there is a tremor inside their body.
Prevalence
Evidence suggests that tremors occur in roughly 70% of people with Parkinson’s disease. However, a 2021 study indicates that motor tremors can occur in 47–90% of cases while resting tremors can reach 76–100% of cases. Tremors would appear to be less common in younger people with Parkinson’s disease and have a higher incidence with increasing age.
Management
Managing Parkinson’s tremor generally involves treating Parkinson’s disease and making lifestyle changes. These may include:
Medications
Generally, a tremor from Parkinson’s disease will respond to other treatments for the disease. The main treatment for Parkinson’s disease is levodopa, which is the precursor to dopamine. A doctor may prescribe levodopa and carbidopa tablets to help boost dopamine levels in the brain, which may improve movement and reduce tremors. Other medications used for treating Parkinson’s disease can also help control tremors.
Deep brain stimulation
If people do not respond to medication, a doctor may suggest surgical options such as deep brain stimulation. This is a procedure that involves placing electrodes in the brain that painlessly stimulate it to help reduce tremors.
Reducing stress
As stress or strong emotions can make symptoms of tremor worse, it is important for people to try and lower their stress levels. Useful stress relief techniques may include exercise, sleep, relaxing baths, meditation, and breathing exercises.
Prognosis
A tremor may begin on one side of the body at first, and, for some people, may stay only on one side of the body for the course of their lives. In other cases, tremors can progress to include both sides of the body.
While a tremor may progress to a certain degree, it is unlikely to worsen beyond a certain point. People with Parkinson’s disease who have tremors as their main symptom typically experience a more stable and slower course of progression.
Summary
Parkinsonian tremor is a common symptom of Parkinson’s disease. It occurs due to lower levels of dopamine in the brain, which causes problems with movement. It differs from other types of tremors as it commonly occurs when at rest and may present with characteristic pill-rolling in the hands.
Tremors can make it difficult to perform many common tasks. People can try to manage tremors by taking medications for Parkinson’s disease, consider surgical options such as deep brain stimulation, and try to reduce their stress.
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