What is Essential Tremor?
Essential tremor is a neurological disorder in which a person experiences involuntary, rhythmic shaking movements, often in their hands. The tremors may also affect other parts of the body, including the head and torso, and the person’s voice may also be affected. Unlike other movement disorders such as Parkinson’s disease, essential tremor generally has shaking movements as its only symptoms. However, some scientists believe that in some cases, the disorder might produce problems with balance, too.
Essential tremor is a common disorder, affecting an estimated 1% of people overall and 5% of people over age 60. It is most common in older adults but can affect anyone at any age.
Symptoms of Essential Tremor
Essential tremor symptoms can vary in severity from case to case. Common symptoms include:
- Uncontrollable trembling of the hands
- Tremors in the torso, face, head, or neck
- Involuntary side-to-side or up-down movements of the head
- Tremors in the voice
Difference from Parkinson’s Disease
Essential tremor symptoms may be similar to those of Parkinson’s disease, but the two disorders have fundamental differences, including:
- Essential tremor symptoms usually occur when the person uses the affected body part. Parkinson’s tremors are more likely to happen when the body part is at rest.
- Essential tremor often affects the head and neck. Parkinson’s is unlikely to affect these parts of the body.
- Essential tremor rarely affects the legs, but Parkinson’s often does.
- Tremors are usually the only symptom of essential tremor. Parkinson’s symptoms typically include problems with walking, posture, and broader movement-related functions.
What Causes Essential Tremor?
Scientists don’t yet know what causes essential tremor. The cause likely lies in the cerebellum, the part of the brain that controls movement. The problem could be in the cerebellum itself or in the communication between the cerebellum and the brain stem, the lower part of the brain that passes movement signals to the rest of the body. However, research has not yet discovered the mechanism that interferes with normal movement.
Is Essential Tremor Hereditary?
Most essential tremor cases appear to run in families. This suggests that the disorder has a genetic component and can be passed from parent to child. Most of the time, the disorder appears to be inherited in an autosomal dominant pattern, meaning that children may develop the disorder if they inherit even one copy of the mutated gene from either of their parents. If a parent carries the disorder-causing mutation, they will have a 50 percent chance of having an affected child with each pregnancy.
Although many cases of essential tremor seem to be inherited, researchers have not yet identified a gene or genes that are definitely associated with the disorder. It is also possible to develop essential tremor even if you have no family history of the condition.
How Is Essential Tremor Detected?
Possible signs of essential tremor include:
- Shaking of the hands causing difficulty with tasks such as writing
- Involuntary nodding of the head
- Trembling voice
- Tremors that get worse when you’re active
- Tremors that get worse when you’re under stress
- Tremors that get worse when you consume caffeine
- Tremors that get better when you consume a small amount of alcohol
How Is Essential Tremor Diagnosed?
To pinpoint the cause of tremors, doctors look for a pattern of symptoms, risk factors, and family history. The diagnostic process typically includes physical examinations, tests, and a review of medical and family history.
Diagnostic steps may include:
- A physical exam. This exam aims to rule out specific physical conditions that could be causing the symptoms.
- Neurological tests. These tests measure the function of the patient’s nervous system. They evaluate functions such as balance, reflexes, memory, visual perception, and language.
- Laboratory tests. Blood and urine tests may be used to look for conditions such as thyroid dysfunction that could be causing the symptoms.
- Imaging scans. These tests, such as MRIs, CTs, and PET scans, may be used to rule out other neurological causes of the symptoms. In the case of essential tremor, imaging scans are usually normal.
How Is Essential Tremor Treated?
Essential tremor has no cure. The disorder may not require treatment when essential tremor symptoms are not severe and don’t cause significant impairment. In severe cases, medications, non-drug therapies, and procedures, or a combination of treatment approaches may effectively control symptoms.
Medications commonly prescribed for essential tremor include:
- Beta-blockers such as propranolol
- Anti-convulsant drugs such as primidone, gabapentin, or topiramate
- Benzodiazepine sedatives such as clonazepam
- Botulinum toxin injections
Possible non-drug treatments include:
- Deep brain stimulation (DBS)
- Focused ultrasound
- Radiation therapy
- Physical therapy
- Occupational therapy
How Does Essential Tremor Progress?
Essential tremor is not, in itself, life-threatening, but it is a life-long condition that can cause significant impairment. The condition is usually progressive, although some people only ever experience mild symptoms. More often, tremors gradually get worse and may spread to different parts of the body as time goes on.
People with severe symptoms may have trouble with daily tasks such as dressing, grooming, cooking, and eating. In some cases, they may be unable to care for themselves or live independently.
How Is Essential Tremor Prevented?
There is no known way to prevent essential tremor.
Essential Tremor Caregiver Tips
Some people with essential tremor also suffer from other brain and mental health-related issues, a situation called co-morbidity. Here are a few of the disorders commonly associated with essential tremor
- People with essential tremor may be at increased risk of depression or anxiety disorders.
- Alcoholism and substance abuse may be more likely in people with essential tremor.
Essential Tremor Brain Science
Although scientists have long suspected that problems in the cerebellum, the brain’s movement-processing center, cause essential tremor, an understanding of precisely what is going wrong has been elusive. However, a recent study at Columbia University may have put researchers on the trail of a potential cause.
The study found that people with essential tremor have both structural changes and unusual activity in their cerebellum. The atypical activity included oscillating brain waves, with stronger oscillations associated with more severe tremors. The researchers also found that the oscillations were likely caused by an unusually high number of connections, or synapses, between two different types of nerve cells in the cerebellum. In addition, the scientists theorized that the abnormal connections could result from a deficiency of a particular type of protein in the brain cells.
The study’s authors expressed hope that their findings could lead to more effective treatments for essential tremor. For example, transcranial magnetic stimulation (TMS) might be used to reduce the abnormal signaling in the cerebellum, or new drugs could boost the production of the protein deficient in people with the disorder.
Essential Tremor Research
Title: Responsive Deep Brain Stimulator for Essential Tremor
Principal investigator: Aysegul Gunduz, PhD
University of Florida
Essential tremor is an incurable, degenerative brain disorder that results in increasingly debilitating tremors and afflicts an estimated 7 million people in the US. In one study, 25% of essential tremor patients were forced to change jobs or take early retirement because of tremors. In addition, essential tremor is directly linked to progressive functional impairment, social embarrassment, and even depression. The tremor associated with essential tremor is typically slow, involves the hands (and sometimes the head and voice), worsens with intentional movements, and is insidiously progressive over many years. Deep brain stimulation has emerged as a highly effective treatment for intractable, debilitating essential tremor. However, since the intention tremor of essential tremor is typically intermittent and commonly absent at rest, the currently available continuous deep brain stimulation may be delivering excessive current to the brain that increases undesirable side effects such as slurred speech and walking difficulty, and hastens the depletion of device batteries, necessitating more frequent surgical procedures to replace spent pulse generators. The overall objective of this early feasibility study is to provide preliminary data on the safety and efficacy of “closed-loop” deep brain stimulation for intention tremors using novel deep brain stimulation devices capable of continuously sensing brain activity and delivering therapeutic stimulation only when necessary to suppress tremors.
This study aims to investigate brain signals related to intention tremor in essential tremor to deliver deep brain stimulation only when the patient is showing symptoms. By providing stimulation only when needed, the investigators hypothesize that the treatment will be more effective, will cause fewer adverse side effects, and will increase the battery time of the device (reducing the number of battery replacement surgeries).
Participation in this study will require extensive pre-surgical screening to determine eligibility for deep brain stimulation surgery, a deep brain stimulation surgical procedure, and regular follow-ups. Subjects will be seen monthly post-surgery for 6 months. After 6 months, data will be assessed, and closed-loop deep brain stimulation may be offered as a stimulation setting. If so, the stimulator settings will be changed from chronic to responsive. If not, the subject will continue to receive chronic deep brain stimulation. Subsequent visits will be scheduled every 6 months until a total of 24 months of study participation (also at month 9).
At the end of the initial 24-month study period, subjects will have the choice of 1) continuing active stimulation at the current setting, 2) continuing stimulation but searching for a new setting, 3) discontinuing stimulation (turning the device off), and 4) having the device removed. If the subject continues to receive active stimulation, they will be followed by the investigators and seen at yearly intervals.
Title: Long-Term Transcutaneous Stimulation and Essential Tremor: A PET Study
Principal investigator: Kendall H. Lee
Essential tremor (ET) is the most common movement disorder in the United States and affects up to 5% of the population. ET patients experience involuntary shaking of the hands, head, and/or voice that can range from mildly limiting to severely disabling.
Treatment options are limited and there are currently no medications specifically designed to treat it, and medications that are prescribed to relieve tremors are often limited by either inadequate efficacy or intolerable side effects. A subset of essential tremor patients whose tremors are inadequately treated by medication choose to undergo deep brain stimulation (DBS) of the ventral intermediate thalamic nucleus. DBS has been shown to be highly effective for tremor suppression. However, DBS carries significant risks. As a result, a very small (less than 3%) percentage of essential tremor patients undergo DBS therapy.
The medical technology company Cala Health has developed a wristband device (the Cala TWO) that offers individuals with essential tremor a novel non-pharmacological, non-invasive alternative, in the form of stimulation of peripheral nerves, to aid in hand tremor relief. This innovative form of therapy can potentially have significant health, quality of life, and economic benefits for essential tremor patients.
The present pilot study (Aim 1) will assess the effectiveness of 3-month, twice-daily treatment with the Cala TWO device to aid in the relief of hand tremors in adult essential tremor subjects that have been approved to undergo deep brain stimulation surgery at Mayo Clinic – Rochester. This study is a prospective, within-subject, non-significant risk study at Mayo Clinic – Rochester, enrolling approximately 20 subjects.
A completely optional component of this study (Aim 2) is seeking to perform three standard PET/CT sessions on a subset of these subjects (n=10) at Mayo Clinic – Rochester to evaluate changes in brain metabolic activity as a result of 3 months of treatment with the device. The first session would take place upon a subject’s entry into the study (start of month 1) and before any treatment with the Cala device, a second the following day after a 40-minute treatment period with the Cala device, and a third session at the end of the third month. This study is a prospective, within-subject, greater than minimum risk study.
Title: Environmental Epidemiology of Essential Tremor (RULET)
Principal investigator: Nora C Hernandez, MD
University of Texas Southwestern Medical Center
This study’s research is devoted to studying the causes of tremor, especially essential tremor (ET), which is the most common type of tremor. Previous studies have revealed a link between harmane [HA], a dietary neurotoxin, and ET; these studies now also suggest a link between this toxin and Parkinson’s disease (PD), a related tremor disorder. Yet these links are tentative rather than conclusively established; therefore, in this new patient-based proposal, which incorporates investigations spanning two continents (North America and Europe), utilizes several complementary study designs (prospective cohort, case control), and draws on several types of tissue (blood, brain), the investigator’s goal is to nail down the links between HA and ET and to further solidify the emerging links between HA and PD.