Essential tremor (ET) is one of the most common movement disorders in the world, affecting approximately 24.9 million people as of 2020, yet many cases go unrecognized or misdiagnosed. Unlike Parkinson's disease, essential tremor causes a distinctive action tremor (trembling during movement or when holding a position) without the rigidity or slowness of movement that characterizes Parkinson's. The condition typically starts in one hand and gradually spreads to both arms, and may eventually affect the head, voice, jaw, or face in 30 to 40 percent of patients .

What Exactly Is Essential Tremor and How Does It Differ From Parkinson's?

Essential tremor is fundamentally different from Parkinson's disease in several key ways. While both are movement disorders involving tremor, ET produces an action tremor, meaning the shaking occurs when you're actively using your limbs or holding them in a position against gravity. Parkinson's disease, by contrast, causes a resting tremor that happens when your muscles are relaxed. Additionally, Parkinson's involves rigidity (stiffness), bradykinesia (slowness of movement), and other motor symptoms that do not occur in classic essential tremor .

The condition is diagnosed clinically based on specific criteria. A person must have a tremor that has been present for at least three years, affects both upper limbs primarily, and occurs during voluntary movement or when maintaining a posture. Importantly, there should be no other neurological signs such as dystonia (involuntary muscle contractions), ataxia (loss of coordination), or parkinsonism present .

Why Are Doctors Now Recognizing "Essential Tremor-Plus" as a Distinct Category?

For decades, essential tremor was considered a purely motor disorder affecting only tremor. However, recent research has revealed that many patients experience additional neurological symptoms beyond the tremor itself. In response, the International Parkinson and Movement Disorders Society released revised diagnostic guidelines in 2018 that introduced a new category called essential tremor-plus (ET-Plus) to capture this clinical reality .

ET-Plus is defined as essential tremor that occurs alongside other "soft" neurological signs of uncertain clinical significance. These additional symptoms can include mild gait impairment, rest tremor of lesser severity than the action tremor, mild memory impairment, mild slowness of movement, or questionable dystonic posturing. The distinction between ET and ET-Plus is important because it recognizes that essential tremor is not always a simple, single-symptom disorder. This new framework helps researchers create more homogeneous groups for studies and may eventually lead to better treatment strategies tailored to different patient subtypes .

How Common Is Essential Tremor Across Different Age Groups?

Essential tremor prevalence increases dramatically with age. In people younger than 20 years, the prevalence is approximately 0.04 percent. However, this rises sharply to 2.87 percent in those aged 80 years and older . The condition can begin at any age, though some research suggests two peaks in age at onset: early adulthood and later life. Earlier-onset cases are often associated with a positive family history, meaning relatives also have the condition.

Men and women are affected at similar overall rates, though some differences exist in how the tremor manifests. Head and voice tremors may be more common in women, while postural hand tremor may be more pronounced in men. Childhood-onset essential tremor may be more frequent in boys than in girls .

What Role Do Genetics Play in Essential Tremor?

Essential tremor is familial in 50 to 70 percent of cases, meaning it runs in families. When it does run in families, it typically follows an autosomal dominant inheritance pattern with incomplete penetrance, which means that inheriting the gene doesn't guarantee you'll develop the condition. Three susceptibility gene loci have been identified that increase the risk of developing essential tremor:

• 3q13 (ETM1): One of the first identified genetic locations associated with familial essential tremor
• 2p25-22 (ETM2): Another chromosomal region linked to the inherited form of the condition
• 6p23 (LINGO1 gene): A variant of this gene has been identified as a risk factor for familial essential tremor

Interestingly, in some families, postural tremor may be an alternative phenotype of a mutation that typically causes levodopa-responsive parkinsonism, suggesting a genetic overlap between these movement disorders .

Beyond genetics, environmental factors also appear to play a role. Harmane, a neurotoxin often found in the human diet, has been found in elevated blood concentrations in patients with essential tremor. However, research suggests that the elevated levels result from alterations in how the body metabolizes harmane rather than from increased dietary intake .

What Happens in the Brain When Someone Has Essential Tremor?

The exact cause of essential tremor remains poorly understood, but researchers believe it involves abnormalities in specific brain circuits. The tremor is likely generated by an abnormally functioning central oscillator located in the Guillain-Mollaret triangle near the brainstem, which involves the inferior olivary nucleus. The tremor also involves circuits connecting the cerebellum, brainstem, thalamus, and cerebral cortex .

Positron emission tomography (PET) scan studies have identified increased glucose consumption in the medulla and overactivity of cerebellar circuitry in patients with essential tremor. This suggests that the brain regions responsible for coordinating movement and balance are working abnormally, leading to the characteristic tremor .

Is Essential Tremor a Neurodegenerative Disease?

There is ongoing debate among neurologists about whether essential tremor is a neurodegenerative disease, meaning whether it involves progressive loss of nerve cells. Evidence supporting the neurodegenerative hypothesis includes postmortem findings of pathologic abnormalities in the brainstem and cerebellum, such as loss of Purkinje cells (specialized brain cells involved in coordination) and the presence of Lewy bodies (abnormal protein deposits) in the locus ceruleus. Clinical studies also show associations with cognitive and gait changes, which could suggest a neurodegenerative process .

However, conflicting evidence argues against this theory. Some studies have found a lack of prominent Lewy bodies in essential tremor patients, no gray matter volume loss on imaging studies, and improvement of gait abnormalities with alcohol, which is not typical of a neurodegenerative process. These contradictions suggest that essential tremor may not be a true neurodegenerative disease, or that it may represent multiple different conditions grouped under one name .

Regarding mortality, essential tremor was traditionally thought to have the same mortality rate as the general population. However, a longitudinal prospective study of patients aged 65 and older from three communities in central Spain found that the risk of mortality in persons with essential tremor was increased compared to the general population. Further research is needed to understand this finding and determine whether the increased mortality is directly caused by essential tremor or related to associated conditions .

How to Recognize Essential Tremor and When to Seek Medical Evaluation

If you notice a tremor in your hands or other parts of your body, understanding the key features of essential tremor can help you determine whether medical evaluation is warranted. Here are the important signs and considerations:

• Action-based tremor: The tremor occurs when you're actively moving (kinetic tremor) or holding your arms outstretched against gravity (postural tremor), not when your muscles are at rest
• Bilateral involvement: The tremor affects both sides of your body, typically starting in one hand and eventually involving both arms
• Duration: The tremor has been present for at least three years and is slowly progressive, gradually worsening over time
• Absence of other neurological signs: You do not have rigidity, slowness of movement, or other symptoms characteristic of Parkinson's disease or other movement disorders
• Family history: One or more relatives have a similar tremor, since 50 to 70 percent of essential tremor cases are familial
• Potential spread: Be aware that head and voice tremors may develop in 30 to 40 percent of patients after the initial arm tremor appears

Essential tremor is a clinical diagnosis, meaning your doctor will diagnose it based on your symptoms and medical history rather than a specific blood test or imaging finding. If you experience a tremor that matches these characteristics, consulting with a neurologist can help confirm the diagnosis and rule out other movement disorders like Parkinson's disease .

The recognition of essential tremor-plus as a distinct category also means that if you have tremor alongside other mild neurological symptoms such as memory problems or gait changes, your doctor may classify your condition differently and may recommend different monitoring or treatment approaches. Understanding these distinctions can help ensure you receive appropriate care tailored to your specific presentation .