What is essential tremor

Essential tremor also known as benign essential tremor, familial tremor or hereditary tremor, is a nervous system or neurological disorder that causes involuntary and rhythmic shaking (tremor) that you can’t control and can affect almost any parts of your body (hands, head, voice, legs or trunk), but the tremor happens most often in your hands ¹, ², ³, ⁴, ⁵, ⁶, ⁷, ⁸, ⁹. The tremor is typically most noticeable when holding your outstretched hands or making fine hand movements, such as holding a cup, drinking from a glass, using a spoon, writing or tying shoelaces ². The tremor usually stops if your hands or arms are completely relaxed, such as when resting in your lap. Anxiety, fatigue or stress often makes the tremor temporarily worse.

Essential tremor is distinguished from tremor that results from other disorders or known causes, such as Parkinson’s disease or head trauma.

When doctors diagnose essential tremor, they analyze the way the tremors happen. Two key components of tremors are their frequency and their amplitude. The following example explains these terms and what they look like in a hand tremor ¹⁰:

• Amplitude: The amplitude of a tremor is the end-to-end distance your hand travels during a tremor. The larger the distance, the greater the tremor’s amplitude. The tremor amplitude usually increases as the essential tremor progresses and may vary in certain circumstances such as with action or posture.
• Frequency: Each shake of your hand is one tremor cycle. The frequency of a tremor is how many cycles you have in one second. The international unit for cycles per second is a Hertz (abbreviated Hz). Essential tremor usually causes 4 to 12 tremor cycles per second (4 to 12 Hz), but this usually slows down as tremor amplitude increases and can vary from person to person.

Essential tremor is a common disorder. Essential tremor is the most common neurological cause of postural or action tremor, affecting up to 10 million people in the United States. Estimates of its prevalence vary widely estimated prevalence of up to 10% of the population in the US because several other disorders, as well as other factors such as certain medications, can result in similar tremors. In addition, mild cases are often not brought to medical attention, or may not be detected in clinical exams that do not include the particular circumstances in which an individual’s tremor occurs. Severe cases are often misdiagnosed as Parkinson disease. The worldwide estimated prevalence of essential tremor is up to 5% of the population ¹.

Essential tremor may appear at any age, but the age of onset for essential tremor has a bimodal distribution, dividing  essential tremor into young onset vs. old onset essential tremor ¹¹. Essential tremor most common in people age 40 and older with an average age of onset of 35-45 years old. Young onset essential tremor cases are more likely to have a family history of tremor ¹², whereas old onset essential tremor cases often have faster disease progression ¹³. If a person were to have essential tremor, the disease would be prominent by 65 years of age, and virtually almost always present by 70 years old. Some studies have suggested that people with essential tremor have a higher than average risk of developing neurological conditions including Parkinson disease or sensory problems such as hearing loss, especially in individuals whose tremor appears after age 65.

Essential tremor affects both sexes equally. However, the site of involvement of the tremor is different depending on different gender. Head tremor may be more frequent in women while postural hand tremor is more frequent in men.

Sometimes essential tremor can be a familial disorder, in which a strong family history is seen. It is then called familial essential tremor or familial tremor. Essential tremor can be passed through generations in families, but the inheritance pattern varies. In most affected families, essential tremor appears to be inherited in an autosomal dominant pattern, which means one copy of an altered gene in each cell is sufficient to cause the disorder, although no genes that cause essential tremor have been identified. In other families, the inheritance pattern is unclear. Essential tremor may also appear in people with no history of the disorder in their family.

In some families, some individuals have essential tremor while others have other movement disorders, such as involuntary muscle tensing (dystonia). The potential genetic connection between essential tremor and other movement disorders is an active area of research.

Essential tremor usually occurs alone, without other neurological signs or symptoms. However, some experts think that essential tremor can include additional features, such as mild balance problems.

Essential tremor usually occurs with movements and can occur during many different types of activities, such as eating, drinking, or writing. Essential tremor can also occur when the muscles are opposing gravity, such as when the hands are extended. It is usually not evident at rest.

In addition to the hands and arms, muscles of the trunk, face, head, and neck may also exhibit tremor in essential tremor; the legs and feet are less often involved. Head tremor may appear as a “yes-yes” or “no-no” movement while the affected individual is seated or standing. In some people with essential tremor, the tremor may affect the voice (vocal tremor).

The exact mechanism of essential tremor is unknown ¹⁴, ¹⁵ . It is thought that certain pathways in the brain are affected where the control of fine movement occurs. However, no pathology has been identified with essential tremor.

Essential tremor does not shorten the lifespan, but essential tremor typically worsens over time and can be severe in some people. However, essential tremor may interfere with fine motor skills such as using eating utensils, writing, shaving, or applying makeup, and in some cases these and other activities of daily living can be greatly impaired. Symptoms of essential tremor may be aggravated by emotional stress, anxiety, fatigue, hunger, caffeine, cigarette smoking, or temperature extremes.

Are there different kinds of tremor?

Yes, many things can cause tremor. Not all tremors are essential tremors. For example, Parkinson’s disease causes tremor that you might notice when your hands are resting in your lap or at the sides of your body. A stroke can cause tremor that gets worse when you reach for something. Thyroid problems or low blood sugar can cause mild tremor. Tremor can be caused by some medicines. These include heart medicines, decongestants, medicines for breathing problems, and tricyclic antidepressants. Drinks that contain caffeine also may cause a tremor.

Essential tremor is just one kind of tremor. Other things that can cause a tremor (non essential tremor) include:

• Parkinson’s disease
• Multiple sclerosis (MS)
• Fatigue after exercise
• Extreme emotional stress, brain tumors
• Some prescription medicines
• Alcohol or drug withdrawal.

Is essential tremor a form of Parkinson’s disease?

No. Essential tremor is about 10 times more common than Parkinson’s disease. Unlike essential tremor, the hand tremor of Parkinson’s disease is most obvious when a patient’s hands are relaxed and not when they are being used for activities also known as resting tremor. Other signs of Parkinson’s disease, but not essential tremor, include slowness of movement (bradykinesia), shuffling gait, rigidity or stiffness and slowness and poverty of movement (hypokinesia), e.g. loss of facial expression and arm swing, difficulty with fine movements.

Is essential tremor contagious?

Experts don’t know exactly why essential tremor happens or if there are triggers that cause them to happen. However, essential tremor isn’t contagious, and you can’t catch it from or spread it to other people.

How long does essential tremor last, and can it go away?

Essential tremor is a permanent, life-long condition once it starts. It’s not curable, and it doesn’t go away on its own.

Essential tremor starts small and usually only affects your hands at first. Over time, usually many years, the tremors may spread to affect your arm and head. As the condition progresses, you may begin to struggle with certain activities and may need help to do them.

People with more severe tremors struggle with activities such as cooking, using kitchen utensils, drinking from a cup, hygiene activities, grooming and dressing. Some people who have essential tremor eventually can’t live independently and need to live with family or in an assisted living or skilled nursing facility setting.

Essential tremor vs Parkinson’s disease

Many people associate essential tremor with Parkinson’s disease, but the two conditions differ in key ways ¹⁶, ¹⁷:

• Timing of tremors. Essential tremor of the hands usually occurs when you use your hands also called an action tremor. Tremors from Parkinson’s disease are most prominent when your hands are at your sides or resting in your lap also called resting tremor.
• Associated conditions. Essential tremor doesn’t cause other health problems, but Parkinson’s disease is associated with stooped posture, slow movement (bradykinesia) and shuffling gait. However, people with essential tremor sometimes develop other neurological signs and symptoms, such as an unsteady gait (ataxia).
• Parts of body affected. Essential tremor mainly involves your hands, head and voice. Parkinson’s disease tremors usually start in your hands, and can affect your legs, chin and other parts of your body, and patients with Parkinson’s disease rarely have head or voice tremor.

The characteristics listed in the table below can help differentiate between Parkinson’s disease and essential tremor, but a medical professional should be consulted for proper diagnosis.

Many differences exist between essential tremor and Parkinson’s disease with essential tremor being at least eight times more common than Parkinson’s disease. Up to 20% of patients with essential tremor may develop Parkinson’s disease, and 10% report a family history of Parkinson’s disease. Some studies have shown a higher proportion of patients with essential tremor developing Parkinson’s disease than would be expected, ranging from 3.1 to 20.8% of those included in these studies ¹⁸, ¹⁹, ²⁰, ²¹. In one study, which followed patients with and without essential tremor for several years, patients with essential tremor were four times as likely to develop Parkinson’s disease (3.0% of essential tremor patients versus 0.7% of patients without essential tremor) ¹⁸. Several families have been noted to have members with both essential tremor and Parkinson’s disease ²². In one study, patients with Parkinson’s disease were more likely to have a family history of essential tremor ²³. Another study compared patients with and without Parkinson’s disease, and those with Parkinson’s disease were over 7 times as likely to have a tremor 10 years before their diagnosis, although it’s unclear if this tremor was essential tremor or an early isolated tremor ²⁴. Both essential tremor and Parkinson’s disease can have similar “non-motor” features, such as thinking and memory changes, mood issues, and dream-enactment behavior ²⁵. However, whether essential tremor is a risk factor for Parkinson’s disease remains an unresolved and somewhat controversial issue ²⁶.

As essential tremor progresses, tremor frequency (number of repetitions per second) may decrease; however, tremor amplitude (magnitude/strength) may increase. Increased amplitude is associated with a decreased ability to manage fine, discrete motor tasks.

In those with Parkinson’s disease the most disabling symptoms are generally slowness, stiffness and problems with walking and balance, although tremor can also cause some disability. In Parkinson’s disease, writing often becomes very small (micrographia) and therefore difficult to read.

The severity of essential tremor and level of disability can vary greatly among patients. Some patients have a very mild tremor and therefore minimal to no disability. Others who have a severe tremor often cannot perform the majority of their daily activities and require help.

The writing of a person with essential tremor tends to be large and tremulous rather than slow and small as in Parkinson’s disease.

Anxiety can increase both essential tremor and Parkinson’s disease.

Clarifying the relationship between essential tremor and Parkinson’s disease is challenging as there is no specific diagnostic test or biomarker that reliably differentiates these two conditions ¹⁷. Many studies looking at the rates of Parkinson’s disease in patients with essential tremor are “retrospective”, meaning that they gather data from looking in the past through patients’ charts. Data that is more reliable comes from “prospective” studies that follow groups over time, but these studies are often difficult to undertake ¹⁷. Complicating matters further, essential tremor patients can sometimes have parkinsonian symptoms such as rest tremor, slowness of movement and loss or balance ²⁷. If someone develops a rest tremor, it can sometimes be difficult to say whether their essential tremor is getting worse or whether they are beginning to show signs of Parkinson’s disease ¹⁷. In a detailed review of 300 patients followed at the Parkinson’s Disease Center and Movement Disorders Clinic, Baylor College of Medicine in Houston, Texas, 26% had evidence of associated Parkinson’s disease ¹⁷.

If there is any concern for symptoms of Parkinson’s disease, the first step is to seek out evaluation from an experienced neurologist, and preferably one with additional training in movement disorders ¹⁷. The diagnosis of Parkinson’s disease can typically be made by listening to a patient’s history and performing a physical examination, where the neurologist will look closely at your type of tremor and see if you have any slowness, stiffness, changes in your walking, or other signs of Parkinson’s disease ¹⁷. However, if there is any uncertainty about the diagnosis, the neurologist may order a DaTscan (Dopamine Transporter Scan – a diagnostic imaging procedure that visualizes the dopamine system in the brain using a radioactive tracer and a SPECT scanner) to look for evidence of decreased dopamine neurons, which would be suggestive of Parkinson’s disease.

In addition to medications and botulinum toxin, deep brain stimulation (DBS) and focused ultrasound have been used for patients with disabling tremor due to essential tremor or Parkinson’s disease ²⁸, ²⁹.

Essential tremor is often associated with a strong family history known as familial tremor, but no specific essential tremor-related gene has been identified.

Table 1. How Essential tremor differ from Parkinson’s disease

Parkinson’s disease tremor signs and symptoms	Essential tremor signs and symptoms
High amplitude. Lower, slower frequency.	Low amplitude. Amplitude is more variable, ranging from barely perceptible tremor to a high amplitude tremor. Higher, faster frequency.
Mostly seen at rest.	Mostly seen during action.
Generally involves slow movements (bradykinesia), rigidity (stiffness), and problems with walking or balance.	Tremor is primary symptom – slowness, stiffness, walking and balance problems are not commonly seen.
Rarely a family history (<10%).	Family history of tremor reported in the majority of patients (>50%).
Resting and postural (re-emergent); postural tremor observable after mean latency of 5 seconds; rarely kinetic.	Postural, kinetic; postural tremor immediately observable; resting tremor less common.
Onset generally at ages between 55-65.	Onset most common in middle age but can occur at any time in the lifespan.
Usually starts on one side of the body and progresses to the other side; usually remains asymmetrical.	Usually affects both sides of the body initially (bilateral; symmetrical).
No effect from consumption of alcohol.	Alcohol often improves tremor.
Usually improves with levodopa treatment.	Improves with primidone and propranolol in some cases.
Hands affected more than legs, voice and head almost never affected.	Hands predominantly affected, but tremor also present in the head and voice; rarely in the legs.
Worsens with emotional stress.	Worsens with emotional stress.

Essential tremor causes

The causes of essential tremor are unknown ¹, ², ³⁰, ³¹, ³², ³³, ³⁴. About 50-70% of essential tremor cases appear to result from a genetic mutation, although a specific gene hasn’t been identified ³⁵, ³⁶, ³⁷. This form is referred to as familial tremor. It isn’t clear what causes essential tremor in people without a known genetic mutation.

Researchers are studying several areas (loci) on particular chromosomes that may be linked to essential tremor, but no specific genetic associations have been confirmed. Several genes as well as environmental factors likely help determine an individual’s risk of developing this complex condition. Current studies suggest an autosomal dominant inheritance pattern with low penetrance in familial essential tremor, and a non‐Mendelian pattern, for example, multifactorial inheritance in sporadic essential tremor ³⁸. Inherited neurological channelopathies may also contribute to disease pathogenesis, supported with recent functional data ³⁹. The presence of complex non‐Mendelian inheritance patterns or environmental confounding may be contributing factors.

Researchers think essential tremor develops in your brain, but patients’ brain scans appear normal. The specific changes in the nervous system that account for the signs and symptoms of essential tremor are unknown. Some reports suggest that the neuropathology of essential tremor is localized in the brainstem at the locus coeruleus and cerebellum ⁴, ⁴⁰, ⁴¹, ⁴², ⁴³, ⁴⁴, but the presence of cerebellar pathology is controversial ¹.

It is believed that essential tremor is a risk factor for the development of Parkinson disease. Up to 20% of patients with essential tremor may develop Parkinson’s disease, and 10% report a family history of Parkinson’s disease. Some studies have shown a higher proportion of patients with essential tremor developing Parkinson’s disease than would be expected, ranging from 3.1 to 20.8% of those included in these studies ¹⁸, ¹⁹, ²⁰, ²¹. In one study, which followed patients with and without essential tremor for several years, patients with essential tremor were four times as likely to develop Parkinson’s disease (3.0% of essential tremor patients versus 0.7% of patients without essential tremor) ¹⁸. Several families have been noted to have members with both essential tremor and Parkinson’s disease ²². In one study, patients with Parkinson’s disease were more likely to have a family history of essential tremor ²³. Another study compared patients with and without Parkinson’s disease, and those with Parkinson’s disease were over 7 times as likely to have a tremor 10 years before their diagnosis, although it’s unclear if this tremor was essential tremor or an early isolated tremor ²⁴. Both essential tremor and Parkinson’s disease can have similar “non-motor” features, such as thinking and memory changes, mood issues, and dream-enactment behavior ²⁵. However, whether essential tremor is a risk factor for Parkinson’s disease remains an unresolved and somewhat controversial issue ²⁶.

In addition, there has also been an association between essential tremors and dystonic movements.

Figure 1. Familial tremor autosomal dominant inheritance pattern

Environmental and Lifestyle factors

Nongenetic factors may have significant effects on essential tremor, suggested by the high prevalence of essential tremor cases without family history or affected relatives, together with reported 60–63% concordance in monozygotic twins in twin studies ⁴⁵, ⁴⁶

Lifestyle and environmental factors are known to play an important role in other neurological disorders. Earlier studies in essential tremor have investigated effects of dietary factors including beta‐carboline alkaloids, meat, caffeine, and alcohol intake, as well as smoking habits and occupational toxin exposures of pesticides and solvents.

Diet

Diet is a key component of life. The effects of beta‐carboline alkaloids found in meat and dietary antioxidants have been studied with no clear conclusion. New evidence suggests that ethanol (drinking alcohol), previously thought to have tremor‐relieving effects, may be a risk factor as a cerebellar toxin. Evidence on the protective effects of caffeine consumption remains inconclusive. The studies on dietary components in essential tremor have been summarized (Tables 2 and 3 below).

Table 2. Dietary exposure case‐control studies in essential tremor

Categories	Authors	Year	Sample size	Country	Exposure	Results
Antioxidants	Scarmeas & Louis 47	2007	148 essential tremor, 250 controls	USA	Mediterranean diet	Higher adherence to diet was associated with lower odds for essential tremor [0.78 (0.61–0.99); P = 0.042]. Compared to lowest adherence tertile, middle tertile [0.41 (0.16–1.05)], and highest tertile [0.29 (0.10–0.82)] had a lower essential tremor odds [P for trend 0.021]
	Louis et al. 48	2005	156 cases, 220 controls	USA	Vitamin E, vitamin C	No significant difference in vitamin E and C consumption between essential tremor cases and controls
Meat (harmane)	Louis et al. 49	2008	125 cases, 125 controls	USA	Meat consumptions, meat doneness level	Higher total current meat consumption was associated with essential tremor (OR = 1.006, P = 0.04) only in male essential tremor cases. Male cases had higher odds of being in the highest than lowest quartile of total current meat consumption (adjusted OR = 21.36, P = 0.001). No significant difference between meat doneness level in cases and controls.
	Louis et al. 50	2005	106 cases, 161 controls	USA	Blood harmane concentration, animal protein intake	Higher log (blood harmane concentration) in essential tremor cases than controls. Similar amounts of animal protein consumption and caloric intakes in essential tremor cases and controls.
Harmane	Louis et al. 51	2013	130 cases, 138 controls	Spain	Blood harmane concentration	Blood harmane concentrations higher in essential tremor compared to controls, but did not reach statistical significance
	Louis et al. 52	2013	70 cases, 27 controls	USA	Brain harmane concentration	Mean brain harmane concentration was higher in essential tremor than controls. Mean concentration was 35% higher in essential tremor cases compared to controls after adjustment for postmortem interval and freezer time.
	Louis et al. 53	2008	150 cases, 135 controls	USA	Blood harmane concentration	Higher Log (blood harmane concentration) in essential tremor compared to controls (OR adjusted 1.56, 95% CI 1.01–2.42, P = 0.04) Higher odds of essential tremor OR 1.90 (95% CI 1.07–3.39, P = 0.029) in highest vs. lowest log (blood harmane concentration) tertile.
	Louis et al. 54	2002	100 cases, 100 controls	USA	Blood harmane concentration	Higher mean log (blood harmane concentration) in cases than controls. Median harmane = 5.21 g(−10)/mL in cases and 2.28 g(−10)/mL in controls) (P = 0.005).
Caffeine	Prakash et al. 5566	2006	79 cases, 100 controls	Singapore	Caffeine consumption	Caffeine consumption in essential tremor patients higher than control group (nonsignificant in multivariate analysis). No significant correlation with disease duration or total tremor score in essential tremor patients
	Louis et al. 56	2004	130 cases, 175 controls	USA	Caffeine consumption	No correlation between daily caffeine intake in milligrams and disease duration, total tremor score, or performance‐based test score in essential tremor cases.

Footnotes: Odds ratio (OR) is a statistical measure that quantifies the strength of association between an exposure and an outcome. Odds ratio (OR) represents the odds of an event happening in one group compared to the odds of the same event happening in another group, typically used in case-control studies ⁵⁷:

Odds Ratio = (odds of the event in the exposed group) / (odds of the event in the non-exposed group)

• An OR = 1 means there’s no association between the exposure and the outcome; the odds are the same in both groups.
• An OR > 1 suggests a positive association; the odds of the outcome are higher in the exposed group.
• An OR < 1 suggests a negative association; the odds of the outcome are lower in the exposed group

[Source ³² ]

Table 3. Studies on alcohol in essential tremor

Authors	Year	Study type	Sample size	Country	Exposure	Results
Nicoletti et al. 58	2011	Case‐control	83 cases, 245 controls	Italy	Wine	Negative association between essential tremor and wine consumption preceding the onset of disease OR = 0.23 (0.08–0.64) with a significant dose effect 1–2 glass of wine per day: OR 0.32 >3 glass of wine per day: OR 0.14
Louis & Michalec 59	2014	Case‐control	354 cases, 370 controls	USA	Ethanol	No significant difference in average daily ethanol intake between cases and controls. Among cases, there was no correlation between average daily ethanol intake and tremor severity.
Louis et al. 60	2009	Prospective cohort study	3285 (76 essential tremor cases)	Spain	Ethanol	Baseline number of drink‐years was marginally associated with a higher risk of incident essential tremor (RR = 1.003) Highest baseline drink‐year quartile doubled the risk of incident essential tremor (RR = 2.29), with decreasing RR down the quartiles With each higher drink‐year quartile, the risk of incident essential tremor increased an average of 23%.
Jiménez‐Jiménez et al. 61	2007	Case‐control	142 cases, 284 controls	Spain	Ethanol	Increased exposure to alcohol was significantly associated with higher age of essential tremor onset. Time of exposure to alcohol was correlated with age at onset of essential tremor Total consumption of alcohol was not correlated with age at onset of essential tremor
Louis et al. 56	2004	Case‐control	130 cases, 175 controls	USA	Ethanol	No significant difference in ethanol intake between essential tremor cases and controls

Footnotes:

Odds ratio (OR) is a statistical measure that quantifies the strength of association between an exposure and an outcome. Odds ratio (OR) represents the odds of an event happening in one group compared to the odds of the same event happening in another group, typically used in case-control studies ⁵⁷:

Odds Ratio = (odds of the event in the exposed group) / (odds of the event in the non-exposed group)

• An OR = 1 means there’s no association between the exposure and the outcome; the odds are the same in both groups.
• An OR > 1 suggests a positive association; the odds of the outcome are higher in the exposed group.
• An OR < 1 suggests a negative association; the odds of the outcome are lower in the exposed group

Relative risk (RR) is a ratio of the probability of an event occurring in the exposed group versus the probability of the event occurring in the non-exposed group. Relative risk (RR) is essentially a ratio of probabilities, quantifying the effect of exposure on the outcome ⁶². For example, the relative risk of developing lung cancer (event) in smokers (exposed group) versus non-smokers (non-exposed group) would be the probability of developing lung cancer for smokers divided by the probability of developing lung cancer for nonsmokers. If a study shows smokers have twice the risk of lung cancer compared to non-smokers, the relative risk (RR) would be 2. The relative risk (RR) does not provide any information about the absolute risk of the event occurring, but rather the higher or lower likelihood of the event in the exposure versus the non-exposure group ⁶³, ⁶⁴.

• An RR of 1 indicates that the risk of the event is the same in both groups.
• An RR > 1 means the exposed group has a higher risk of the event than the unexposed group.
• An RR < 1 means the exposed group has a lower risk of the event than the unexposed group, suggesting a protective effect of the exposure.

[Source ³² ]

Smoking

The protective effect of smoking has been reported by a series of Spanish case‐control studies (Table 4). A Spanish population‐based study reported that ever‐smokers had half the risk of essential tremor compared to never‐smokers. A dose‐dependent response was reported in the same study, with smokers in the highest pack‐year having only one‐third the risk of essential tremor compared to never‐smokers ⁶⁵. In the same cohort, smoking was associated with slightly lower risk of incident essential tremor, and adjusted Cox proportional hazards model analysis supported a similar dose‐dependent association ⁶⁶. Another Spanish study reported a correlation between increased period of smoking exposure and earlier age of essential tremor onset, although there were no significant associations with the amount of smoking exposure ⁶¹.

To date, the protective effect of smoking on essential tremor has been shown in studies limited to Spain and within a similar cohort ³². Studies from other populations are lacking. We cannot exclude the possibility that the protective effect of smoking may be specific to genetic or other environmental factors limited to this selected Spanish population ³². Future prospective studies in other cohorts and countries would be useful in confirming the generalizability of these findings.

Table 4. Studies on environmental exposures in essential tremor

Authors	Year	Study type	Sample size	Country	Exposure	Results
Louis et al. 66	2008	Prospective cohort study	3348 (77 essential tremor cases)	Spain	Smoking	The highest baseline pack‐year tertile was associated with lower risk of incident essential tremor. Cases in the highest pack‐year tertile were only one‐third as likely to develop essential tremor compared with nonsmokers (RR 0.29, 95% CI 0.09–0.90, P = 0.03)
Benito‐Leon et al. 65	2008	Case‐control	221 cases, 663 controls	Spain	Smoking	Ever‐smokers are less likely to have essential tremor than the never‐smokers (OR 0.58, 95% CI 0.40–0.84, P = 0.004). Inverse association between number of pack‐years and essential tremor (adjusted OR 0.991, 95% CI 0.984–0.997, P = 0.005). Ever‐smokers in the highest pack‐year tertile were one‐third as likely to have essential tremor than the never‐smokers (adjusted OR 0.39, 95% CI 0.22–0.69, P = 0.001).
Jiménez‐Jiménez et al. 61	2007	Case‐control	142 cases, 284 controls	Spain	Smoking	Time of exposure to smoking was correlated with age at onset of essential tremor. No associations found with total amount of smoking.
Azevedo & Meyer 67	2017	Case‐control	51 cases, 204 controls	Portugal	Pesticide exposure	Exposure to 16 to 16.9 years of pesticide use had highest odds of essential tremor (ORadj 4.60; 95% CI: 1.29–16.41) No significant correlation of essential tremor with other durations of pesticide exposure, no clear dose‐response trend.
Yao et al. 68	2015	Cross‐sectional	5932 (216 essential tremor cases)	China	Pesticide exposure	Past pesticide exposure was found to be greater in essential tremor compared to controls.
Dogu et al. 69	2007	Case‐control	105 cases, 105 controls	Turkey	Lead exposure	Higher median blood lead concentration in essential tremor cases (2.7 microg/dL) compared to controls (1.5 microg/dL)
Louis et al. 70	2006	Case‐control	136 cases, 144 controls	USA	Pesticide exposure	No significant difference in serum concentrations of organochlorine pesticides between essential tremor cases and controls.

Footnotes:

Odds ratio (OR) is a statistical measure that quantifies the strength of association between an exposure and an outcome. Odds ratio (OR) represents the odds of an event happening in one group compared to the odds of the same event happening in another group, typically used in case-control studies ⁵⁷:

Odds Ratio = (odds of the event in the exposed group) / (odds of the event in the non-exposed group)

• An OR = 1 means there’s no association between the exposure and the outcome; the odds are the same in both groups.
• An OR > 1 suggests a positive association; the odds of the outcome are higher in the exposed group.
• An OR < 1 suggests a negative association; the odds of the outcome are lower in the exposed group

Relative risk (RR) is a ratio of the probability of an event occurring in the exposed group versus the probability of the event occurring in the non-exposed group. Relative risk (RR) is essentially a ratio of probabilities, quantifying the effect of exposure on the outcome ⁶². For example, the relative risk of developing lung cancer (event) in smokers (exposed group) versus non-smokers (non-exposed group) would be the probability of developing lung cancer for smokers divided by the probability of developing lung cancer for nonsmokers. If a study shows smokers have twice the risk of lung cancer compared to non-smokers, the relative risk (RR) would be 2. The relative risk (RR) does not provide any information about the absolute risk of the event occurring, but rather the higher or lower likelihood of the event in the exposure versus the non-exposure group ⁶³, ⁶⁴.

• An RR of 1 indicates that the risk of the event is the same in both groups.
• An RR > 1 means the exposed group has a higher risk of the event than the unexposed group.
• An RR < 1 means the exposed group has a lower risk of the event than the unexposed group, suggesting a protective effect of the exposure.

[Source ³² ]

Pesticides and farming

Pesticide exposure, particularly organochlorine pesticides, has been linked to tremors. However, current evidence has been inconclusive. There was no difference in serum concentrations of six organochlorine pesticides in essential tremor cases compared to controls ⁷⁰. A similar lack of association with self‐reported pesticide exposure was reported by two case‐control studies in Spain and Singapore ⁶¹, ⁵⁵.

In contrast to these earlier studies, a large study cohort in China reported a positive association between self‐reported pesticide exposure and essential tremor ⁶⁸. Another study in Portugal reported significantly higher pesticide exposure in essential tremor ⁶⁷. Although this study reported that having 16–16.9 years of exposure led to highest essential tremor risk, there was no significant dose‐dependent trend noted across the range of exposure durations reported ⁶⁷, making it difficult to interpret these results in the context of other studies. A major limitation of these two studies is that they were not published in English, hence details of the study could not be assessed. Larger studies are needed to reassess the effect of pesticide exposure in essential tremor, and more quantitative methods of assessing pesticide exposure are required. Self‐reported values may not be sufficiently sensitive to detect differences between essential tremor and controls. Future studies may consider the use of surrogate measures such as occupational exposures or serum biomarkers together with self‐reported exposures.

Lead and heavy metals exposures

Exposure to heavy metals, specifically lead and manganese, has been studied in a small number of studies. Lead exposure has been shown to cause neurological disorders with tremors. essential tremor patients had higher blood lead concentrations compared to controls, reported in studies conducted in New York ⁷¹ and Turkey ⁶⁹. The effect of lead toxicity may be explained by its destructive effects on cerebellar tissue and Purkinje neurons. Subsequently, no new studies have investigated the effects of lead exposure in essential tremor.

Besides lead, the role of exposures to other metals and solvents in essential tremor is inconclusive. Case‐control studies have found no significant difference in occupational exposure to manganese and organic solvents ⁷² or iron–manganese alloys ⁶¹ in essential tremor cases compared to controls, although iron–manganese alloy exposure was associated with increased age of essential tremor onset ⁶¹.

There is a lack of studies evaluating these toxic exposures, likely due to the difficulties in quantifying these exposures accurately. The use of serum biomarker levels may be more reliable markers of such exposures as opposed to questionnaires.

Risk factors for essential tremor

Known risk factors for essential tremor include:

• Genetic mutation. The inherited variety of essential tremor (familial tremor) is an autosomal dominant disorder. A defective gene from just one parent is needed to pass on the condition. If you have a parent with a genetic mutation for essential tremor, you have a 50 percent chance of developing the disorder yourself.
• Age. Essential tremor is more common in people age 40 and older.

Genetic mutation

The genetics basis of essential tremor has been supported by evidence of heredity in familial essential tremor. Linkage studies have mapped susceptibility loci at gene regions on chromosome 3q13 (ETM1) in Icelandic families ⁷³, chromosome 2p22‐25 (ETM2) in American families ⁷⁴ and chromosome 6p23 in North American families (ETM3) ⁷⁵. Genome‐wide association studies identified mutations in the Leucine‐rich repeat and Ig domain‐containing Nogo receptor interacting protein‐1 gene (LINGO1) ⁷⁶ and solute carrier family 1‐glial affinity glutamate transporter‐member 2 (SLC1A2) gene ⁷⁷. Exome sequencing studies identified mutations in the fused in sarcoma/translated in liposarcoma (FUS/TLS) gene in a Canadian family ⁷⁸, the HTRA2 gene in a Turkish family ⁷⁹ and variants of TENM4 gene in the Spanish population ⁸⁰.

Essential tremor pathophysiology

The pathophysiology of essential tremor has been debated. Some studies establish evidence of a degenerative process, while others suggest functional dysregulation of neuronal transmission ³². Postmortem studies report two main subgroups of pathology, one with the presence of Lewy bodies in the brainstem, and the other without Lewy bodies but with degenerative changes of the cerebellum, marked by Purkinje cells loss and axonal swelling ⁸¹, ⁸². Some hypothesized that Purkinje cell pathology may be part of the cellular cascade leading to essential tremor, causing remodeling of the cerebellar cortex leading to cerebellar degeneration ⁸³.

The presence of Lewy bodies and protein aggregation in brain tissue supports an anatomical basis for clinical similarities between essential tremor and Parkinson’s disease such as common feature of tremor ⁸⁴, although Lewy bodies are reported only in a small proportion of essential tremor patients ⁸⁵. Essential tremor patients are more likely to develop Parkinson’s disease compared to healthy individuals ¹⁸, suggesting that early cellular degenerative changes may be common to both diseases. Neuroimaging has demonstrated iron accumulation in basal ganglia of essential tremor patients ⁸⁶, a finding that has been similarly observed in other neurodegenerative diseases including Parkinson’s disease.

Essential tremor prevention

Doctors don’t know exactly what causes essential tremor, so it can’t be prevented. If your doctor determines you tremor is caused by medicine or caffeine, you may be able to avoid essential tremor in the future by avoiding those substances.

Essential tremor symptoms

The key symptom of essential tremor is shaking — usually your hands — when you’re trying to use them. That shaking can take different forms and usually happens under certain circumstances.

• Action tremor: This is a form of essential tremor that happens during actions, such as reaching for an object.
• Postural tremor: This is shaking that happens when you hold part of your body in a specific pose, such as holding a hand outstretched and keeping it at the same height.

Essential tremor signs and symptoms:

• Begin gradually. They usually are more noticeable on one side of the body.
• Worsen with movement
• Usually occur in the hands first, affecting one hand or both hands
• Can include a “yes-yes” or “no-no” double nodding or shaking motion of the head.
• Quivering voice
• Tremors worsen with purposeful movement
• Rest helping to relieve tremors.
• Tremors may be aggravated by emotional stress, fatigue, caffeine, certain medications, low blood sugar, or temperature extremes.

Often, tremors are the only symptom you have when you have essential tremor. Other conditions that cause tremors come with other symptoms.

Essential tremor almost always affects both sides of your body but often affects one side more than the other. In addition to your hands, tremors can affect other parts of your body such as your head, voice, face and trunk.

The tremor itself isn’t dangerous, but it can cause problems with everyday activities as the condition worsens. Eventually, people with essential tremor may have trouble with activities such as eating with utensils and drinking from a glass, dressing themselves and writing.

Essential tremor complications

Essential tremor isn’t life-threatening, but symptoms often worsen over time. If the tremors become severe, you might find it difficult to:

• Hold a cup or glass without spilling
• Eat normally
• Put on makeup or shave
• Talk, if your voice box or tongue is affected
• Write legibly

Essential tremor diagnosis

Diagnosing essential tremor involves reviewing your medical history, family history and symptoms and conducting a physical examination.

There are no medical tests to diagnose essential tremor. Diagnosing it is often a matter of ruling out other conditions that could be causing your symptoms. To do this, your doctor may suggest the following tests:

Neurological examination

In a neurological examination, your doctor surveys your nervous system functioning, including checking your:

• Tendon reflexes
• Muscle strength and tone
• Ability to feel certain sensations
• Posture and coordination
• Gait

Laboratory tests

Your blood and urine may be tested for several factors, including:

• Thyroid disease
• Metabolic problems e.g. Wilson’s disease
• Drug side effects
• Alcohol levels
• Levels of metals like lead or manganese that may cause tremor
• Genetic testing. This tests for gene changes if there is a known family history of Parkinson’s disease or if you have familial tremor.
• Alpha-synuclein test. Alpha-synuclein test also called an alpha-synuclein seed amplification assay, detects Parkinson’s disease before symptoms begin. Alpha-synuclein clumps are a hallmark sign of Parkinson’s disease. Doctor can test for Parkinson’s disease in the skin or spinal fluid. Alpha-synuclein is found in Lewy bodies. It forms clumps that the body can’t break down. The clumps spread and damage brain cells. In a 2023 study, researchers tested the spinal fluid of more than 1,000 people to look for clumps of the protein alpha-synuclein. The alpha-synuclein test accurately identified people with Parkinson’s disease 87.7% of the time. Alpha-synuclein test also was highly sensitive for detecting people at risk of Parkinson’s disease. This study of the alpha-synuclein seed amplification assay was the largest so far. Some researchers say the study may be a breakthrough for Parkinson’s disease diagnosis, research and treatment trials. But larger studies are needed. There’s hope among researchers that in the future, the alpha-synuclein test could be done using blood samples rather than spinal fluid.

Imaging tests

These imaging tests can help rule out other conditions:

• Computerized tomography (CT) scan. A head CT (computed tomography) scan, also known as a CAT scan, is a medical imaging technique that uses X-rays to create detailed 3D images of the brain, skull, and surrounding structures, helping to diagnose various conditions like strokes, tumors, and injuries. These scans provide a more detailed view than a regular X-ray and can be used to diagnose a wide range of conditions.
• Magnetic resonance imaging (MRI). An head MRI (Magnetic Resonance Imaging) scan is a non-invasive medical imaging technique that uses strong magnetic fields and radio waves to create detailed images of the body’s internal structures. Your doctor can order MRI of your brain and surrounding nerve tissue inside your head using MRI.
• Positron emission tomography (PET) scan. A positron emission tomography (PET) scan is a nuclear medicine imaging technique that uses radioactive tracers to visualize and measure changes in metabolic processes within the body. These scans can help diagnose diseases, monitor treatment effectiveness, and assess organ function. Your doctor may order a PET scan to check for signs of brain disorders such as brain tumors, epilepsy, dementia and Alzheimer’s disease.
• A specific single-photon emission computerized tomography (SPECT) scan called a dopamine transporter (DAT) scan. This can help support the suspicion that you have Parkinson’s disease and help identify different types of tremor. But it is your symptoms and the results of your neurological exam that determine your diagnosis. Most people do not require a DAT scan.

Performance tests

To evaluate the tremor itself, your doctor may ask you to:

• Drink from a glass
• Hold your arms outstretched
• Write
• Draw a spiral

If your doctor is still unsure if your tremor is essential tremor or Parkinson’s disease, he or she might order a dopamine transporter scan (DaTscan). This can tell the difference between the two types of tremor. A special picture or scan of the brain that measures the uptake of dopamine, such as DaTscan, can help to differentiate between essential tremor and Parkinson’s disease tremor. Dopamine is depleted in patients with Parkinson’s disease but not in patients with essential tremor; therefore, scans showing depletion in dopamine are most likely Parkinson’s disease and normal scans would suggest a more likely diagnosis of essential tremor. These scans are used as a tool to help the physician make an accurate diagnosis in difficult cases.

Essential tremor diagnostic criteria

The Movement Disorders Society diagnostic criteria include ²⁷, ⁸⁷:

• Tremor is bilateral, symmetrical, and postural
• The tremor involves the forearms and hand
• Is persistent and visible
• It may be associated with isolated head tremor
• The absence of other neurological signs, such as dystonia, ataxia, and parkinsonism.

While these criteria provide useful research guidelines, it is increasingly recognized that 54–85% patients who otherwise fit the essential tremor diagnostic criteria have above-mentioned neurological signs (e.g., dystonia, ataxia, and parkinsonism) and some experts categorize this group of patients with a controversial term: essential tremor-plus ⁸⁸, ³¹.

Essential tremor treatment

Some people with essential tremor don’t require treatment if their symptoms are mild and early treatment does not stop or slow essential tremor symptomatic progression. But if your essential tremor is making it difficult to work or perform daily activities, discuss treatment options with your doctor. Only consider starting medication treatment when the tremor affects your daily activities or causes problems for you.

Essential tremor medications

• Beta blockers. Normally used to treat high blood pressure, beta blockers such as propranolol (Inderal) help relieve tremors in some people. This is the most common medication used for treatment of essential tremor. Multiple studies have shown that propanolol improves the symptoms ranging from 50-70% of the patients. However, no long term study has been conducted regarding the effect of propanolol in essential tremor. Other beta-blockers include atenolol, metoprolol, sotalol and nadolol. Beta blockers may not be an option if you have asthma or certain heart problems. Side effects may include fatigue, lightheadedness or heart problems.
• Anti-seizure medications. Epilepsy drugs, such as primidone (Mysoline), may be effective in people who don’t respond to beta blockers. The exact mechanism is unknown. Other medications that might be prescribed include gabapentin (Gralise, Neurontin) and topiramate (Topamax, Qudexy XR). However most of these anticonvulsants are not well studied – only small and short trials have been done to evaluate their effectiveness. Side effects include drowsiness and nausea, which usually disappear within a short time.
• Tranquilizers (benzodiazepines). Doctors may use drugs such as alprazolam (Xanax) and clonazepam (Klonopin) to treat people for whom tension or anxiety worsens tremors. Side effects can include fatigue or mild sedation. These medications should be used with caution because they can be habit-forming (addictive).
• OnabotulinumtoxinA (Botox) injections. Botulinum toxin is injected into the muscles that cause the tremor, temporarily weakening the muscle to reduce the tremor. Botox injections might be useful in treating some types of tremors, especially head and voice tremors. Botox injections can improve tremors for up to three months at a time. However, if Botox is used to treat hand tremors, it can cause weakness in your fingers. If it’s used to treat voice tremors, it can cause a hoarse voice and difficulty swallowing.

Essential tremor natural remedies

Lifestyle changes are often recommended to prevent the tremor from getting worse. Your doctor will ask you to avoid caffeine, cold medicines and certain other medicines if they seem to make your tremor worse. These medicines won’t make your tremor go away. However, the medicine may control the tremor enough to allow you to do normal activities without frustration or embarrassment.

To reduce or relieve tremors:

• Avoid caffeine. Caffeine and other stimulants can increase tremors.
• Use alcohol sparingly, if at all. Some people notice that their tremors improve slightly after they drink alcohol, but drinking isn’t a good solution. Tremors tend to worsen once the effects of alcohol wear off. Also, increasing amounts of alcohol eventually are needed to relieve tremors, which can lead to alcoholism.
• Learn to relax. Stress and anxiety tend to make tremors worse, and being relaxed may improve tremors. Although you can’t eliminate all stress from your life, you can change how you react to stressful situations using a range of relaxation techniques, such as massage or meditation.
• Make lifestyle changes. Use the hand less affected by tremor more often. Find ways to avoid writing with the hand affected by tremor, such as using online banking and debit cards instead of writing checks. Try voice-activated dialing on your cellphone and speech-recognition software on your computer.

Physical therapy

Doctors might suggest physical or occupational therapy. Physical therapists can teach you exercises to improve your muscle strength, control and coordination.

Occupational therapists can help you adapt to living with essential tremor. Therapists might suggest adaptive devices to reduce the effect of tremors on your daily activities, including:

• Heavier glasses and utensils
• Wrist weights
• Wider, heavier writing tools, such as wide-grip pens.

Nerve stimulation devices

A wearable electronic peripheral nerve stimulation device (Cala Trio, Cala kIQ) is a newer treatment option for people with essential tremor. The device is worn as a wristband for 40 minutes twice a day. It works by stimulating nerves and muscles to create a muscle response that reduces tremors. Studies have found that the device can bring some improvement for tremors.

Focused ultrasound thalamotomy

Focused ultrasound thalamotomy is a non-invasive neurosurgical procedure that uses focused ultrasound waves that travel through the skin and skull to target and destroy specific areas of the thalamus, a part of the brain involved in motor control, to reduce or eliminate tremors, particularly those associated with essential tremor or Parkinson’s disease ⁸⁹, ⁹⁰. During a focused ultrasound thalamotomy procedure a surgeon uses Magnetic Resonance Imaging (MRI – a medical imaging technique that uses strong magnetic fields and radio waves to create detailed, cross-sectional images of the body’s internal structures) to target the correct area of the brain and to be sure the sound waves are generating the exact amount of heat needed for the procedure.

Focused ultrasound thalamotomy is done on one side of the brain. The surgery affects the other side of the body from the one where it’s done. For example, focused ultrasound thalamotomy on the right thalamus affects the left side of your body. This is due to a phenomenon called contralateral control, where nerve pathways cross over in the brainstem, connecting the brain hemispheres to the opposite sides of the body where the left side of your brain generally controls the right side of your body, and the right side of your brain controls the left side of your body.

Focused ultrasound thalamotomy creates a lesion that can result in permanent changes to brain function. Some people have experienced altered sensation, trouble with walking or difficulty with movement. However, most complications go away on their own or are mild enough that they don’t interfere with quality of life.

Deep brain stimulation (DBS)

Deep brain stimulation (DBS) might be an option if your tremors are severely disabling and you don’t respond to medications ⁹¹. The surgical procedures are stereotactic thalamotomy or thalamic deep brain stimulation. Excellent results have been reported from these surgeries.

In deep brain stimulation, doctors insert a long, thin electrical probe into the portion of your brain that causes your tremors (thalamus). A wire from the probe runs under your skin to a pacemaker-like device (neurostimulator) implanted in your chest. This device transmits painless electrical pulses to interrupt signals from your thalamus that may be causing your tremors.

Side effects of surgery can include equipment malfunction; problems with motor control, speech or balance; headaches; and weakness. Side effects often go away after some time or adjustment of the device.

Figure 2. Deep brain stimulation

Coping and support

For many people, essential tremor can have serious social and psychological consequences. If the effects of essential tremor make it difficult to live your life as fully as you once did, consider joining a support group like International Essential Tremor Foundation (https://www.essentialtremor.org/).

Support groups aren’t for everyone, but you might find it helpful to have the encouragement of people who understand what you’re going through. Or see a counselor or social worker who can help you meet the challenges of living with essential tremor.

Essential tremor prognosis

Essential tremor is not a life-threatening condition. Survival in essential tremor does not differ from the general population ¹, ². Although there is no associated death rate, it can cause significant inconvenience to the patients and the overall quality of life can be significantly impaired with essential tremor ². This is due to the social and functional embarrassment that usually occur in activities of daily living such as employment, normal outing activities such as difficulty writing, eating, and drinking, attending parties, shopping alone, etc. As much as 85% of the patients with essential tremor reported that this condition affected their lifestyle in certain ways. Essential tremor symptoms are typically progressive and potentially disabling, often forcing patients to change jobs or seek early retirement ⁹², ⁹³, ⁹⁴, ⁹⁵.

Although prospective longitudinal data are limited, the usual course of essential tremor is one of slow, gradual progression ⁹⁶, ¹. The average rate that arm or hand tremors get worse is between 1.5% and 5% a year. As essential tremor progresses, tremor frequency (number of repetitions per second) may decrease; however, tremor amplitude (magnitude/strength) may increase. Increased amplitude is associated with a decreased ability to manage fine, discrete motor tasks. Essential tremor starts small and usually only affects your hands at first. Over time, usually many years, the tremors may spread to affect your arm and head. As the condition progresses, you may begin to struggle with certain activities and may need help to do them.

Essential tremor may remain stable in a minority of patients. However, a stable course should raise suspicion for an alternative diagnosis such as an enhanced, physiologic tremor or drug-induced tremor rather than an essential tremor ¹. While prospective data are limited, essential tremors may be associated with an increased risk for developing Parkinson disease ¹.

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