Essential Tremor: Causes, Treatments & How It Differs From Parkinson's Disease

If someone were to ask, "What disease causes tremors?" would your first thought be Parkinson's disease? You wouldn't be wrong, but several movement disorders cause tremors that can be just as disabling, including essential tremor. Essential tremor is often confused with Parkinson's disease, even though the condition is eight times more common, according to the International Essential Tremor Foundation.

Essential tremor can make completing everyday tasks extremely difficult. While there is no cure, several treatments can help ease the condition. We spoke with a neurosurgeon specializing in treating movement disorders to understand more.

What is essential tremor?

Essential tremor is a movement disorder that causes parts of the body to tremor or shake in a rhythmic fashion. People don't have control of the tremor, and while any part of the body can be affected, it most often affects the hands and arms.

"Essential tremor is a condition where patients have an action tremor related to movement," says Dr. Amir Faraji, a functional neurosurgeon at Houston Methodist. "Usually, it's a hand or arm tremor, like taking a glass of water and holding it; they can't drink, and they spill. They have to use two hands to brace a pencil or pen. They can't hold a tray or button a button. It can also be associated with a body tremor, like a head and neck tremor, leg tremor or even voice tremor. It's a condition where one side is frequently worse, but both sides can be impacted."

Dr. Faraji says the tremor can also occur when someone holds their affected hand or limb in a pose, like outstretching to shake someone else's hand. The condition affects each person differently, and its intensity can vary.

"It impacts different people to different degrees," Dr. Faraji says. "Some patients have isolated voice tremors. Some patients have head or neck tremors, and the hands are quieter. There are patients whose hand tremor is more pronounced with the head and neck quiet. There are rating scales that we can use to quantify tremor and to have an idea of how severe the condition is."

The tremor often comes on gradually and becomes more and more noticeable over time.

"Usually, it's not sudden," Dr. Faraji says. "Patients will come in and say, 'Oh, I've been shaking for five years, 10 years, even 20 years.' They may not think anything of it at first, and it finally gets just annoying enough that they say, 'This the final straw. Let's do something about it.'"

Dr. Faraji also says that if a tremor starts suddenly, it is important to seek care in case it is related to other conditions, such as a neurological disorder or even reactions to medications.

As the years pass, essential tremor can worsen, and begin to affect quality of life.

"It's quite disabling," Dr. Faraji says. "Eight million people in the U.S. have the condition, and 50% or more of patients don't even get to a neurologist's office."

Who is at risk for essential tremor?

Essential tremor has historically been known by different names. Two of these — familial and hereditary tremor — describe the genetic component of potentially developing the condition.

"We don't exactly know the cause, but it may run in families," Dr. Faraji says. "So if your mom or aunt had it, you can be at risk. It can also be sporadic, and they may develop a tremor as they age."

Dr. Faraji says the condition usually impacts older people, ages 40 and up. The condition can develop at any age, and those with a family history of the condition may be more likely to develop it at younger ages.

How is essential tremor different from Parkinson's disease and other conditions with tremors?

"There are different forms of tremor that are not the same as essential tremor and can be related to an event, such as post-stroke or post-trauma, anxiety or as a side effect of medicines," Dr. Faraji says. "That's why seeing an appropriate professional is important to parse out what the tremor is from. Is it really ET, or is it something different?"

Dr. Faraji says that a movement disorder specialist or neurologist can differentiate tremors associated with other conditions from essential tremor based on the fluidity of movement and whether there's a tightness in the arm. The tremor associated with Parkinson's disease also has unique characteristics.

"In particular with Parkinson's, a big distinction is the tremor," Dr. Faraji says. "In general, a Parkinson's tremor starts as unilateral and a resting pill-rolling type tremor in their fingers, but may then progress to being on both sides. It may impact the arm or leg more on one side, but usually that's associated with rest, not activity. So that there's a difference there in terms of diagnosis."

According to Dr. Faraji, Parkinson's disease also has a constellation of symptoms that aren't present in essential tremor, including rigidity, stiffness, slowness, and sometimes balance issues and a shuffling gait.

"Sometimes it's difficult deciding what is essential tremor or Parkinson's," Dr. Faraji says. "There is a spectrum to this. And so again, having a provider vet them would be an important process. There are some radiographic studies, like a nuclear medicine scan, that can give some indication radiographically if it is Parkinson's or not."

One such scan, the noninvasive DaTscan, takes an image of a person's brain after they are injected with a medicine that helps assess the dopamine-containing neurons that control movement in our bodies. Additionally, Dr. Faraji says what's known as a levodopa challenge test can also aid in diagnosing Parkinson's disease.

"You give the patient a pill form of dopamine (levodopa), and if they get better, then they likely have Parkinson's," Dr. Faraji says. "If they don't get better, they probably don't have Parkinson's. It's very much a clinical diagnosis. And most Parkinson's patients in the United States don't even see a movement disorder neurology specialist, but instead work with a general neurologist or even a primary care doctor."

What treatments exist to manage essential tremor?

There are two mainstay medicines to treat essential tremor: propranolol, a beta blocker that can help manage heart issues but can improve tremor; and primidone, an anti-seizure medicine.

People with essential tremor often complete regimens of both medications before they find one that helps quiet the tremor. Should the medicines fail to ease symptoms, only then are patients presented with surgical options, according to Dr. Faraji.

"There are a couple of procedures that can be done ranging from noninvasive to an actual surgery with device implantation," Dr. Faraji says.

The most common surgery for essential tremor is deep brain stimulation, where a neurosurgeon implants an electronic device in the thalamus, which controls movement in the body. The first deep brain stimulation electrode to target a central tremor was implanted in a patient in France in 1988, showing that tremor for Parkinson's disease and essential tremor could be "turned off." The U.S. Food and Drug Administration approved the implant in 1997, and the technology has continued to improve significantly in the following decades, according to Dr. Faraji.

"The surgery has gotten safer over the past couple decades," Dr. Faraji says. "We have directional lead programming. We have good rechargeable batteries. We have smaller batteries. The wires are more elastic and less prone to breakage. We have advances in imaging and surgical robotics to improve the accuracy of lead placement. The technology and surgery of today is far better than it was twenty years ago."

Another type of surgery is thalamotomy, or lesioning, in which heat is applied to the thalamus to create a lesion in the brain circuit causing the tremor. Dr. Faraji says this procedure is less frequently used.

According to Dr. Faraji, other noninvasive options include gamma knife radiosurgery, where the thalamus is slowly treated with highly focused radiation. Over time, the tremor improves as a lesion develops. Another noninvasive option is focused ultrasound.

"A patient undergoing focused ultrasound needs to shave the whole head so that we can put a water bath over the head and not trap air bubbles," Dr. Faraji says. "You have several ultrasonic elements around the top of the water bath. It creates sound wave vibrations that can then pass through the skull if the skull density is appropriate. These sound waves can be targeted deep within the center of the brain to the same target that we use for DBS and lesioning. We can heat and monitor that target in an MRI scanner to create a lesion that stops tremors. We do one side and then the other side nine months later if needed."

Dr. Faraji says people with essential tremors should consult their neurologist and neurosurgeon to determine the best procedure.

"So the first decision point is — how bad is your tremor? If it's disabling or causes quality of life issues, we can do something about it," Dr. Faraji says. "The second decision tree point is whether you benefit from medicines. And if the answer is yes, but not enough benefit, or no, then we move into discussing a surgical procedure, such as deep brain stimulation or focused ultrasound."

Dr. Faraji says nuances regarding who makes a good surgical candidate are based on the person's exact level of symptoms, disability, medical history and suitability to undergo anesthesia.

If you notice a tremor, don't be afraid to get help

Dr. Faraji says that one of the barriers to getting care for essential tremor can be the fear regarding treatment options. He says a nuanced conversation with a surgeon can help answer individualized questions to understand the options better.

"I know patients are scared of having a brain procedure," Dr. Faraji says. "Most of the time, their fears are related to the uncertainty of the actual risk-benefit between the procedures. An individualized discussion with a surgeon is important because that may answer some of their fears regarding the need for a procedure. Don't be afraid to contact a physician to understand your treatment options so that you can put your tremor behind you."