Do your hands sometimes shake uncontrollably? Is it a sign of Parkinson’s disease or something else?

It could be a medical condition called essential tremor, and a new study by Singapore’s National Neuroscience Institute has found a link for this, gene variations and structural changes in the brain.

You could be holding a spoon when you notice your hand is shaking and spilling the soup that you're trying to bring to your mouth. Or you could be using a laser pointer during a presentation – and realise that the red dot on the screen isn’t going where you want it to go.

These could very well be signs of essential tremor (ET), a medical condition that causes shakiness usually in the hands, but they can also occur in other parts of the body, according to Singapore’s National Neuroscience Institute (NNI).

“Hand tremors affect both the young and the old. It is not only socially embarrassing but impacts one’s quality of life,” said Professor Tan Eng King, the deputy chief executive officer of academic affairs, and a senior consultant with NNI’s Department of Neurology.

“Some patients also develop voice and head tremors. While some medical conditions can cause tremors, the exact cause of ET is unknown,” he said.

But now, there are new findings in this area by NNI’s experts that sheds light on just what is going on when you have these uncontrollable shakes.

WHAT’S CAUSING THE TREMORS?

Published in the journal Movement Disorders this year, the NNI study looked at the brain scans and genetic data of 33,000 adults to identify genetic variations associated with ET as well as their links with structural changes in the brain. In doing so, the study also sheds light on new potential drugs to treat the condition.

The team, headed by Prof Tan, found that genes with differences were linked to specific parts of the brain involved in tremors. For example, there is a specific set of genes that are related to the outer region of the brain (thinner cortex) and the hind brain (smaller cerebellum), the part of the brain involved in balance and movement.

What lets you keep still or move your hands is a neural pathway known as the tremor network that links up those areas of the brain. In the illustration below, you can see the pathway connects the brain’s motor cortex (A), thalamus (B) and cerebellum (C) to regulate movement. According to NNI, this pathway needs to be clear before signals can be sent to the muscles in the hands, triggering them to take the action you want.

But in those with ET, faulty proteins are detected. “Normally, the body is able to dispose of the faulty proteins but we found that this ‘quality control’ system is faulty in tremor-related parts of the brain,” said Dr Thomas Welton, NNI’s principal investigator and the first author of the paper.

“This may affect cell function and disrupt the flow of messages along the key neural pathway between the cerebellum, thalamus and motor cortex, and result in uncontrollable shaking of the hands," said Dr Welton.

HOW COMMON IS ESSENTIAL TREMOR?

ET tends to affect the elderly from ages 65 and above, according to NNI. “Worldwide, the prevalence of ET is more than 60 million. However, many cases of ET go unreported because not all will feel the need to seek medical attention,” said Prof Tan, who noted that the condition is more common in men than women in Singapore.

“ET is more common as one ages,” added Prof Tan. “However, we see peaks in patients seeking medical treatment for ET at ages 20 years and 60 years old.”

The top risk factor is a family history as 40 per cent to 50 per cent of ET patients have a parent or sibling with ET or a history of tremors. “Other environmental factors such as type of work and activity levels may play a role but no links have been identified at present,” said Prof Tan.

Other factors can include certain medications, especially psychiatric medications; alcohol consumption; and medical conditions such as hyperthyroidism, said Prof Tan.

WHAT ARE THE SIGNS THAT YOU HAVE ESSENTIAL TREMOR? HOW ARE THEY DIFFERENT FROM PARKINSON'S DISEASE?

In ET, the tremors tend to occur during specific postures or actions such as drinking a beverage, said Prof Tan, which is the reason why such shakes are known as action tremors. These shaky actions can make tasks such as writing or brushing teeth difficult.

And it’s not only the hands. Sometimes, the tremors may be accompanied with a quivering sound in your voice, uncontrollable head-nodding and in some instances, tremors in your legs or feet.

“In ET, it is common for tremors to occur in multiple parts of the body at the same time,” said Prof Tan. “Around 10 per cent to 25 per cent of ET patients also experience head tremors, and 10 per cent experience voice tremors.” 

Meanwhile, in Parkinson’s disease, “the tremors occur even when at rest, for example, when the hand is resting on a table or lap (called a rest tremor) as well as during specific actions or postures”, according to Prof Tan.

ET usually occurs in both hands, while the tremors of Parkinson's disease can start from just one side. “Both types of tremors can be aggravated by stress and anxiety,” he said, adding that ET is 20 times more prevalent than Parkinson’s disease.

CAN HAVING ESSENTIAL TREMOR INCREASE YOUR RISK OF PARKINSON’S DISEASE?

“ET patients have a very small but higher risk of being diagnosed with Parkinson’s as compared to the general population,” said Prof Tan.

“Some genetic variants related to ET are also related to neurodegenerative diseases, which suggests overlaps in the mechanism causing Parkinson’s and ET, and the way the brain is affected, resulting in tremors.”

WHAT ARE THE TREATMENTS AVAILABLE?

Almost everyone experiences hand tremors at some point in their life due to stress, lack of sleep, too much caffeine and other triggers. “Such tremors are normal and can usually be managed by identifying and removing the triggers,” said Prof Tan.

"Not everyone diagnosed with ET will be prescribed medications," he said. "There are relaxation and non-drug approaches to manage the condition such as getting enough rest, having regular meals, and reducing the consumption of caffeine-enriched drinks such as coffee and tea."

But if the tremors persist and are affecting your daily life, you should seek a doctor’s help. “When medications are prescribed, a common first-line treatment is propranolol,” said Prof Tan. “Propranolol works as a ‘beta-blocker’ to block the release of certain hormones such as adrenaline and noradrenaline in some parts of the body, which can help reduce tremors.”

Other medications can also be prescribed for ET, depending on the individual’s symptoms and other health conditions they may have, he said.

Sometimes, botox injections may be used to quell ET symptoms for a few months at a time, said Prof Tan. Yes, the same botulinum toxin type A that is injected into the face to soften wrinkles is used to prevent the release of acetylcholine, a chemical that carries messages from your brain to your body through nerve cells. In turn, muscle movements are reduced.

Botox injections may be carried out in the forearm muscles to help manage hand tremors, according to Medical News Today. For head tremors, jabs may be made into the deep muscles on each side of the neck.

In severe cases, a surgery known as Deep Brain Stimulation (DBS) may be considered. “In DBS, a small electrode is accurately placed inside the brain, which provides a targeted electrical signal that shuts down tremors,” explained Prof Tan.

CAN LIFESTYLE CHANGES HELP?

Eating a healthy diet and exercising can do heaps of good for your brain, and in turn, your tremors. “There are many possible mechanisms for this, including a reduced inflammation of nerve cells, and an improved ability of the brain to generate new nerve connections and blood vessels,” said Prof Tan.

Healthy living can also help your brain to “properly dispose of waste”, he added, and guard against neurodegenerative diseases.