Tremors (shaking movements) are one of the most characteristic symptoms of Parkinson’s disease. They are so characteristic, in fact, that even those without the disease often associate the symptom with Parkinson’s. But there are a number of medical conditions other than Parkinson’s that could explain why a person may have tremors and bodily shakes.

One such condition is known as “essential tremor.” A person can be diagnosed with essential tremor but not Parkinson’s. And you can have both. Because the movements associated with essential tremor are similar to the shaking that occurs with Parkinson’s disease, it can be hard to tell the two apart.

Here is what you need to know about these two conditions so you can distinguish between them and understand your own diagnosis.

What Is a Tremor?

A tremor is a specific type of shaking that affects a particular area (or areas) of the body. It is unintentional, meaning that the person experiencing the tremor is not doing anything on purpose to cause the shaking.

Tremors are also rhythmic in nature. That is, the shaking in a tremor is not completely random. The movements actually have their own rhythm, almost like the beat of a piece of music. A tremor does not have to be exactly “on beat” to qualify as such. But some sort of repetitive, cyclical nature to the shaking can distinguish the movements.

How Are Essential Tremor and Parkinson’s Disease Connected?

For years, essential tremor and Parkinson’s disease were considered two entirely different conditions. However, more recent studies have suggested that having essential tremor raises a person’s risk level of developing Parkinson’s disease later on.

This connection is thought to be based on a number of factors. Abnormal proteins known as Lewy bodies have historically been associated with Parkinson’s disease. Lewy bodies have been found in the brains of 15 to 24 percent of people diagnosed with essential tremor. In addition, Parkinson’s disease seems to have a higher prevalence in people who have had essential tremor for a long time. Essential tremor also seems more likely to develop in people who have Parkinson’s disease in their family.

The exact relationship between the two conditions is unknown. Many people are diagnosed with essential tremor and never develop Parkinson’s, while others are diagnosed with Parkinson’s without ever experiencing essential tremor. It’s also possible to have them at the same time. More research is needed to understand how and why these two conditions are connected.

What Are the Similarities of Essential Tremor and Parkinson’s Disease?

The most significant similarity between essential tremor and Parkinson’s disease is their characteristic symptom: the presence of tremors. Both conditions are movement disorders with tremor as the primary symptom.

In both essential tremor and Parkinson’s disease, tremors are most common in the hands. With essential tremor, people may also experience head and voice tremors. In Parkinson’s, however, tremors can also be in the jaw or tongue, but almost never involve a person’s head or voice. In rare cases, essential tremor and Parkinson’s can also affect someone’s legs.

Tremors in both Parkinson’s disease and essential tremor both worsen during periods of high stress. Stressful situations can also result in more severe shaking or cause shaking in parts of the body that are not usually affected by tremors.

Both conditions and their symptoms can interfere with daily life, though the extent to which a person is affected may depend on the severity of their tremors. Larger, more grand tremors can make everyday tasks difficult and have a negative effect on a person’s quality of life.

The Diagnostic Process

Both Parkinson’s disease and essential tremor are diagnosed by doctors specializing in neurology. A neurologist will examine the tremors, other symptoms, and the results of a battery of tests. Doctors will also take a detailed medical history, including a family history of related medical problems.

It’s often difficult to distinguish between Parkinson’s disease tremor and essential tremor. There is no definitive diagnostic test, and a diagnosis is largely based on symptoms. Scientists are, however, researching diagnostic tests to see what can help. One possibility involves an imaging test called a dopamine transporter single photon emission computed tomography (DaT-SPECT) scan. The DaT-SPECT can measure the level of dopamine uptake in a person’s brain. People living with Parkinson’s disease have impaired dopamine uptake.

Another possible diagnostic test is an SN-TCS (or substantia nigra hyperechogenicity measured by transcranial sonography). An SN-TCS imaging scan is used to examine the neurons in the brain. Neurons often die or become impaired in those with Parkinson’s disease.

What Are the Differences Between Essential Tremor and Parkinson’s Disease?

There are a number of key differences between essential tremor and Parkinson’s disease.

When Does the Shaking Occur?

The most significant difference between essential tremor and Parkinson’s disease has to do with when a person’s tremorous movements occur. In someone with essential tremor, their shaking occurs when part of their body is active. (This is called an “active tremor” or “action tremor.”) In someone with Parkinson’s disease, their tremor occurs in parts of their body when those parts were otherwise at rest. (This is called a “resting tremor.”)

Imagine watching someone with a tremor while they are relaxing on the porch. In a person diagnosed with essential tremor, you may not know they have a tremor until they try to move the affected body part. For example, when they reach for their glass on the table, their hand may shake.

In a person with a tremor from Parkinson’s disease, you will see the tremor while they are at rest. Their hand may shake while it is on their lap or resting on the arm of their chair. When they reach for their glass, though, the tremor will stop until their hand is at rest again.

Other Differences in Tremor Features

There are a few other differences in the tremors experienced by those diagnosed with essential tremor and those diagnosed with Parkinson’s.

Parkinson’s Tremors Are Slower

While Parkinson’s tremors are still noticeable, they are slower than those associated with essential tremor.

Parkinson’s Tremors Are Bigger

The range of motion, or amplitude, of tremors experienced by those diagnosed with Parkinson’s is usually greater than those experienced by people diagnosed with essential tremor.

Parkinson’s Tremors Roll

A hand tremor in someone with Parkinson’s is likely to begin with a wrist movement and end with the fingertips rolling together. This is sometimes called a “pill-rolling tremor.”

Other Differences Between Parkinson’s Disease and Essential Tremor

Several other factors can be used to distinguish between essential tremor and tremors from Parkinson’s disease.

Family History

It is more likely for those with essential tremor to have a family history of the disease than those with Parkinson’s. More than half of people diagnosed with essential tremor have a family member with the same diagnosis or a related condition. In fact there’s a term for that — familial tremor. On the other hand, fewer than 10 percent of people diagnosed with Parkinson’s disease have it in their family tree.

Other Symptoms

In people diagnosed with essential tremor, the tremor is the primary symptom that they demonstrate. Parkinson’s disease involves its unique tremors, but it is also characterized by other symptoms. Those others include slow movements and general slowness (bradykinesia), stiff body motions and a stiff body overall, and balance or coordination problems.

Response to Alcohol

When people diagnosed with Parkinson’s disease consume alcohol, they usually will not see a change in their tremors or other symptoms. Those diagnosed with essential tremor, however, often experience a temporary reduction in their tremors after drinking alcohol (in moderation).

Response to Different Medications

The symptoms of Parkinson’s disease usually improve when treated with carbidopa/levodopa. But this combination drug does not affect those with essential tremor. Instead, those with essential tremor may see improvement when they take Inderal (propranolol) or Mysoline (primidone), though these do not work for everyone with the condition.

Condition Progression

Parkinson’s disease usually begins on one side of the body. While the disease typically progresses to the other side of the body, symptoms usually progress unevenly. Essential tremor, however, usually strikes both sides of the body at once, and it affects both sides in the same manner throughout the course of the condition.

Find Your Team Today

On MyParkinsonsTeam, the social network for people living with Parkinson’s disease and their loved ones, more than 83,000 members come together to ask questions, give advice, and share their stories with others who understand life with tremors and Parkinson’s disease.

Do you or a loved one experience tremors? Share your experience in the comments below, or start a conversation by posting on MyParkinsonsTeam.