What is Essential Tremor?
Tremor refers to an uncontrollable, rhythmic shaking of a part of the body. This shaking occurs with a fairly constant number of shakes per second, but the size of those shakes (the amplitude) can vary. This shaking is caused by the back-and-forth contraction of opposing muscles. Of all types of movement-related disorders, tremor is the most common, and a condition called essential tremor is the most common neurological cause of tremor that happens when someone is holding a position or performing an action.
Usually, essential tremor appears as a rapid (6 to 12 times per second) bilateral, or both-sided, shaking of the hands. This shaking often happens when someone is trying to hold a position (postural tremor) but may also happen when someone is moving (kinetic tremor) or at rest. The shaking often looks similar in both hands, but as the condition progresses, it may also involve the head, voice, and less frequently, the legs, jaw, face, and torso.
While essential tremor doesn’t reduce a person’s life span, it can be very embarrassing, and for a small number of people, it can cause serious disability. The symptoms tend to get worse over time and can be severe enough to force people to change jobs or retire early.
What Causes Essential Tremor?
Essential tremor is a condition where the cause isn’t completely understood. In about half the cases, it appears to be due to changes in our genes, although we don’t currently know the exact gene responsible. This is known as a familial tremor, a condition you can inherit from your family, which normally takes effect in both of your body parts at once, rather than just one side.
However, the onset of the tremor can vary in age and might also randomly occur in people without a family history of the condition. Even identical twins, who share the same genetic makeup, don’t always both have essential tremor. This suggests that things in our environment might also play a role in causing the condition.
The Movement Disorders Society, a group of professionals dedicated to improving the lives of patients with movement disorders, includes the following criteria for diagnosing essential tremor:
- The tremor affects both sides of the body equally and occurs when holding a position.
- The tremor involves the forearms and hand.
- The tremor is ongoing and can be seen.
- The tremor may be associated with only the head shaking.
Risk Factors and Frequency for Essential Tremor
Essential tremor, a neurological disorder that causes uncontrollable shaking while doing actions or maintaining a posture, is the most common of its kind. It is estimated that up to 5% of people worldwide have this condition. Nearly half of the people affected have other family members with the same condition, and this rises to 90% in cases involving identical twins. The likelihood of developing essential tremor increases as people age, but it can also affect the young, particularly in families where it’s already present.
Signs and Symptoms of Essential Tremor
Essential tremor is a condition that usually affects the hands and arms on both sides equally. However, it can sometimes impact one side of the body more than the other. Interestingly, in such cases, the less dominant arm often experiences the more severe tremor. While less common, the tremor can also affect the head, voice, face, legs, and trunk. The tremor severity can vary greatly from minor, high-frequency shaking when holding a posture to larger, more visible tremors during certain postures and actions.
The shaking becomes most noticeable in the arms when they are held out in front of the body. The tremor also intensifies at the end of direct movements, like reaching for an object or touching one’s nose. As a person ages, the intensity of the tremor tends to increase, while the frequency decreases. Despite the wide range in severity, essential tremor can be quite disabling for many affected individuals. Research suggests that the degree of disability tends to be related to the intensity of the kinetic tremor in the upper limbs. Anxiety and other factors can sometimes exacerbate the tremor.
Interestingly, small amounts of alcohol can often relieve essential tremor, although this is not a recommended treatment. Unlike physiological tremor, caffeine does not usually worsen essential tremor. In some cases, individuals may also exhibit signs of imbalance or unsteady movements.
A leg tremor is uncommon with essential tremor and is more frequently associated with Parkinson’s disease. A head and neck tremor may present as vertical or horizontal movements and is typically accompanied by hand or voice tremor. If a head tremor occurs on its own, it may be indicative of a different condition known as cervical dystonia. Early studies also suggest that people with essential tremor may be at a higher risk of developing cognitive issues, including memory difficulties, reduced executive function, dementia, and Parkinson’s disease.
Testing for Essential Tremor
Essential tremor is diagnosed based on the patient’s symptoms and by ruling out other possible causes. The main criteria to consider include a shakiness that occurs in response to movement (action tremor) that’s present in both hands and forearms, and the absence of other unusual signs in the nervous system. Additional supporting information could be having had the tremor for a long time (more than three years), having a family member with essential tremor, or noticing that the tremor goes away after drinking alcohol.
A thorough examination of the nervous system is important in the diagnosis to identify specific characteristics of the tremor, such as how fast or slow it is, how strong it is, its pattern, and where it occurs in the body. It’s also important to find out if there are factors that can trigger or worsen the tremor like caffeine, alcohol, medications, exercise, fatigue, or stress. A full list of the patient’s current medications will be reviewed to rule out the possibility of tremor as a side effect.
Currently, there are no specific biological signs or imaging findings that can confirm essential tremor. However, tests may be necessary to rule out other conditions that can cause tremor. These tests may include checks on thyroid function, urinary copper and a protein called ceruloplasmin to rule out a genetic disorder known as Wilson disease, or tests for heavy metal poisoning such as lead if any of these causes are suspected.
Imaging tests of the brain, like a scan or an MRI, can be helpful in patients where it is suspected that the tremor may be due to a physical change in the brain, such as Wilson disease, brain trauma, stroke, or mass lesion. However, if none of these are suspected, imaging of the brain is usually not needed. In some cases, a specialized imaging test using a radioactive substance called Ioflupane I123 may be used. This test can help distinguish patients with Parkinson’s disease and other related conditions from patients with essential tremor.
Treatment Options for Essential Tremor
For some patients with lesser symptoms of tremors, they might decide not to have any treatment. Others, though not physically hindered by tremors, seek treatment due to the discomfort of their symptoms. Treatment options vary based on the severity of the tremors and these include non-medical treatment, medicine-based treatment, or surgical treatment.
Non-medical treatments are those which don’t require any prescribed medicine or surgical procedures. For example, wrist weights can help reduce tremors for some patients. Stress relaxation techniques such as biofeedback are also helpful as stress and tension can make tremors worse. It’s also recommended to avoid certain medications known to trigger tremors or reduce their intake. Avoiding food and drinks high in caffeine could also reduce the intensity of tremors. There are also a number of tools designed to help those people suffering from tremors, like utensils with added weight or using technology that can counteract tremors.
Medicine-based treatments often involve a trial approach since what works well for one patient might not work as well for another. The drugs used to treat tremors fall into three categories. The first category, or the first-line therapy, includes the ones approved by the food and drug administration (FDA), like propranolol and primidone. If these don’t work on their own, they can sometimes be combined to have an effect. The second category, or second-line therapy, is backed up by scientific studies but has not been fully approved by the FDA. Some examples are gabapentin, pregabalin, topiramate, benzodiazepines, beta-blockers, and zonisamide. The third category, or third-line therapy, is based on smaller scale studies or cases and includes drugs like nimodipine and clozapine.
If the tremors continue to persist after medical treatments or if the side effects of the drugs are too strong, interventional or surgical therapies can be considered. These include deep brain stimulation (DBS), focused ultrasound, radio-surgical gamma knife thalamotomy, and botulinum toxin injections, based on the patient’s specific tremor symptoms.
DBS is the most common surgical treatment, which involves placing an electrode into the brain. This electrode emits electrical stimulation that can help control tremors. It’s typically done through a small hole in the skull and could be done on one or both sides of the brain. This mostly depends on which areas of the patient’s body are being affected by the tremor. If both hands are affected, starting with the dominant hand is preferred. Doing this on both side of the brain may lead to difficulties with speech and balance.
Other surgical treatments, such as thalamotomy, involve creating a lesion in a certain part of the brain. Focused ultrasound is also a new procedure, approved by the FDA in 2016, that creates lesions in the brain using high-intensity sound waves. It does this non-invasively, meaning it doesn’t require making any direct incisions in the skull or the brain. However, it’s worth noting that this is a lasting treatment with permanent effects.
Another treatment called radio-surgical gamma knife thalamotomy focuses high-energy gamma rays on a specific area of the brain to control tremors. However, this isn’t a widely-accepted treatment yet because of concerns about potential side effects from radiation, like the long-term risk of forming secondary tumors.
What else can Essential Tremor be?
When diagnosing essential tremor, doctors need to rule out several other conditions that may exhibit similar symptoms. These include:
- Physiologic tremor: This is typically an action tremor that is mostly bilateral and symmetrical. It has a high frequency (10 to 12 Hz) and there might be a known cause like medications, hyperthyroidism, or hypoglycemia.
- Parkinson Disease Tremor: Mainly present when at rest and is asymmetrical. It usually doesn’t produce head tremor and has a frequency of 4 to 6 Hz.
- Orthostatic tremor: This is a postural tremor that mainly affects the torso and lower limbs when standing; it may also occur in the upper limbs. The tremor disappears when walking and is high frequency (14 to 20 Hz), affecting the same-side and opposite-side muscles together.
- Cerebellar tremor: This can either be a postural, intention, or action tremor with a relatively low frequency (3 to 4 Hz). It’s usually associated with unsteady movements and lack of precise coordination.
- Writing tremor: This is specifically noticeable during writing, unseen in other tasks requiring coordination. Considered a variant of focal hand dystonia (writer’s cramp).
- Psychogenic tremor: The tremor severity varies depending on the person’s emotional state related to stressful life events. Indicators to differentiate its psychogenic nature include sudden onset and spontaneous remission, larger variations of amplitude and frequency, and lesser severity. The tremors dissipate with distractions like alternate finger tapping or mental concentration. Additionally, the tremor’s frequency may change to match voluntary movements made by the opposite limb.
Making accurate diagnoses entails thoroughly understanding and considering these potential conditions.
What to expect with Essential Tremor
Essential tremor, a condition that causes involuntary shaking, usually becomes more noticeable over time. While some may not see a change in their tremors, it’s generally expected to gradually worsen. If your tremor isn’t getting worse, you might not have essential tremor at all. Instead, it could be a more intense version of a natural body shake or a tremor brought on by medication.
Although we don’t have much data looking at essential tremor over a long period, there’s a chance it could lead to Parkinson’s disease, which is another disorder affecting movement. However, it’s important to remember that having essential tremor does not shorten your life span. Despite this, it can affect your overall quality of life and may make daily activities more challenging.
