Has your hand ever trembled while performing a really important task? Perhaps it was in a competition setting where time was rapidly running out, or during a delicate task like threading a needle.
Many of us would have experienced this type of tremor at one time or the other.
England-based consultant functional neurosurgeon Dr Ian Low says: “Tremor is normal. All of us have a tremor – it’s called a physiological tremor.
“It becomes pathological when it becomes very severe; and this is due to a breakdown in the feedback circuits to the tremor itself, but we don’t really know the exact mechanism.”
The Queen’s Hospital’s surgical lead for functional neurosurgery in London explains that a tremor is defined as a neurological condition characterised by involuntary oscillation of a part of the body – with emphasis on “involuntary”.
It can be caused by many conditions, including Parkinson’s disease, stroke, brain injury and metabolic disorders.
However, the condition that, by far, most commonly causes tremors is called essential tremor.
Dr Low notes that: “Essential tremor is the most common movement disorder in the world.
“In fact, it is much more common than Parkinson’s disease, but Parkinson’s disease gets all the attention and the funding.
“So this is actually a hidden condition, but its impact is very, very great.”
In Malaysia, there are about 15 new cases of Parkinson’s disease diagnosed every year for every 100,000 people in the population.
However, Dr Low says that essential tremor cases are between three to 20 times more frequent than Parkinson’s disease.
One of the reasons he thinks that it is not diagnosed as much as it should be is because many people think that getting a tremor is a part of old age, and thus, do not seek medical attention for it.
Another reason is more insidious; as alcohol tends to suppress essential tremors quite well in the initial stage, many people tend to self-medicate by drinking.
However, the worse the tremors get, the more they drink, and the more likely other people are to attribute their tremors to their alcohol addiction.
“So people then say if you have a tremor, it means you are an alcoholic.
“But actually, it was the tremor that caused the alcoholism, rather than the alcoholism being the cause of the tremor,” he says.
Types of tremors
According to Dr Low, there are three major forms of tremors: tremor at rest, postural tremor, and action or intention tremor.
A tremor at rest is a tremor that occurs even when you are not doing anything, while a postural tremor occurs when you stretch out your hands, he explains.
“And the final one is when you are actually trying to do something with a limb – usually the hand, and less commonly, the leg – that is called an action or intention tremor,” he says.
Dr Low notes that the tremor at rest is typically – although not always – associated with Parkinson’s disease.
A Parkisonian tremor looks like the patient is rolling a pin and only occurs at rest, disappearing as soon as the patient attempts to do something.
Meanwhile, postural or intention tremors are most likely due to essential tremor, he says.
Intention tremors are particularly disabling as the tremor gets worse the closer you get to the target of your action.
For example, if you are reaching out to take a sip of water, the tremor becomes increasingly worse the closer the hand gets to the cup, then subsides after grasping the cup. Then, the closer the cup comes to the mouth, the worse the tremor gets again.
“Action tremors are incredibly disabling as we use our hands to do a lot of things that need purposeful movements; action tremors prevent you from doing purposeful movements – you cannot write, you cannot hold a cup, you cannot do your buttons,” explains Dr Low.
“In very severe cases, they cannot feed themselves, they cannot clean themselves.”
He emphasises that: “The most important thing about the management of tremors is that you have to get the diagnosis correct, because there are many, many conditions that mimic essential tremors, for which the treatment is completely different.”
However, he says that essential tremor is a very difficult diagnosis to make, with neuro-logists likely to misdiagnose it in up to 20% of cases, according to the latest studies.
“Neurology is not actually an exact science, it is nothing but recognising patterns – there’s no black-and-white in neurology.
“And that’s why long-term follow-up is required because the tremor pattern will become more apparent with time – sometimes it may be very clear cut, but other times, it is not.”
When treatment is needed
The necessity for treatment really depends on the patient’s perception of how much their tremors affect their quality of life.
“Once you’ve decided what kind of tremor the patient has, the treatment varies depending on the severity of the condition, and also, the patient’s characteristics,” says Dr Low.
If the tremor is slight and the patient does not find it too disturbing, it can just be monitored.
If, however, the tremor is severe enough to significantly disturb the patient’s daily activities, then treatment according to the condition causing the tremor is indicated.
For Parkinsonian tremors, the treatment targets the Parkinson’s disease itself. Options include a number of drugs, including levadopa, which is the gold standard treatment, according to Dr Low.
He adds, however: “It has to be emphasised that the tremor of Parkinson’s disease is very difficult to control with medications, for reasons we don’t understand.
“So, if you have Parkinson’s where the main problem is tremor, medication is mainly effective in only about 30%-40% of cases.”
Drugs are also one option in the treatment of essential tremors.
According to Dr Low, these include beta-blockers like propanolol, which are effective in 50%-60% of cases, but cannot be taken by those with low blood pressure, heart problems, breathing difficulties and diabetes; primidone, which is very effective in controlling tremors, but tends to make patients feel disorientated, unsteady and unable to think properly; and other less effective drugs like topiramate, gabapentin and benzodiazepine, which only work in about 30% of cases and cause drowsiness.
If the tremor is localised to the head or vocal cords, Botox injections are an option.
Dr Low explains that these injections are impractical in other parts of the body, like the hands, as they would paralyse the muscles.
Other non-medical methods to help mitigate the effects of tremors include calming techniques, like meditation, as anxiety increases the severity of the tremors, and using assistive devices like weighted utensils to help counter the effect of the tremors.
The next option, once the tremors become too disruptive to the patient’s life, is surgery.
“There are two surgical methods for tremor: one is radiofrequency lesioning and the other is deep brain stimulation,” says Dr Low.
“Radiofrequency lesioning involves destroying the small part of your brain that controls the tremor.
“And this can be done by putting a wire into your brain and heating the end of the wire such that it burns a hole in the brain.”
The advantages of this procedure is that it is relatively cheap, quick, has been proven safe over the long term, and very effective, with relatively few side effects for a single-sided lesioning.
Dr Low notes that lesioning is not done on both sides of the brain as there is a very high chance of decrease in thinking function in such cases.
The procedure requires a very skilled neurosurgeon as “once you destroy that part of the brain, it is gone – there are no second chances”.
Also, both essential tremor and Parkinson’s disease progress with time; this means that after a few years, the tremor is likely to return, and another procedure would be necessary.
According to Dr Low, there are two other methods of lesioning that do not require opening up the brain, i.e. radiosurgery and magnetic resonance-guided focused ultrasound.
However, neither of these techniques are very effective.
The other surgical option is Dr Low’s particular area of expertise: deep brain stimulation.
“Deep brain stimulation is the most commonly accepted surgical technique for |tremor control in developed countries,” he says, noting that many developing countries that cannot afford this technique still use radiofrequency lesioning.
In deep brain stimulation, microelectrodes are passed through a five sen-sized hole in the brain to the area that controls the tremor.
Once it is in the right position, the neurosurgeon adjusts the electric current to stop the tremor, as well as to test for any side effects like double vision and one-sided muscular contractures.
“The ideal spot is the one that will stop the tremor and has no side effects.
“And that’s why the patient needs to be awake for this part,” he says, explaining that the patient needs to give feedback as to the side effects they may experience. The patient is under local anaesthetic at this point in the procedure.
Once the ideal spot is located, the neurosurgeon will then put in the permanent electrode, sending the patient for magnetic resonance imaging (MRI) to ensure that it is in the right place and that there is no bleeding in the brain.
Then the patient is given general anaesthesia so that the neurosurgeon can run the extension wire from the electrode under the skin to a neurostimulator, also called a brain pacemaker, placed just under the collarbone.
Dr Low says that the entire procedure usually takes approximately eight hours and the patient can return home the next day.
“Then we bring them back to the hospital in about two to four weeks’ time to check the wound, programme their neurostimulator and teach them how to use their own personal programmer,” he said.
He adds that the patient might need more than one programming session, but once they find the right programme – that is, the right pulse width, amplitude and frequency of the current – it usually stays unchanged for years.
On average, a patient undergoing deep brain stimulation will see a 74% reduction in their tremors, and research has shown that this will remain stable for at least 10 years.
“It is the most effective form of treatment for tremor-dominant Parkinson’s disease,” Dr Low adds.
In addition, it can be done on both sides of the brain, unlike radiofrequency lesioning, and any side effects can be managed instantly by adjusting the neurostimulator.
“But it is expensive and it needs follow-up,” says Dr Low, adding that in Britain, deep brain stimulation costs about £30,000 (RM166,314), while radiofrequency lesioning costs half of that.
Some of the other disadvantages of the procedure include having a foreign body (the electrode, wire and neurostimulator) in the body and needing to change the neurostimulator’s battery on average once every four years for Parkinson’s patients and six years for essential tremor patients,
These patients will also face limitations when it comes to undergoing an MRI and certain types of surgery, as well as if they require a cardiac pacemaker for heart problems.