Introduction
Ataxia and tremor are among the most difficult MS symptoms to treat. Commonly tried treatments involve drug therapy along with rehabilitation.
Another approach, which is much less commonly used, involves brain surgery.
Drug treatments
Many different medicines have been suggested to be useful for tremor and ataxia over the past 25 years. Surprisingly however, only a few have been tested by randomised controlled clinical trials, which is usually considered to be the best method of assessing the effectiveness of any particular treatment. This makes recommendation of many of the treatments difficult.
Ataxia and tremor are among the most difficult MS symptoms to treat.
Only one drug, called isoniazid (sometimes known as INH), has been shown to have a modest effect on tremor in randomised controlled clinical trials.
However, the trials involved only a small number of subjects. Isoniazid was actually developed in the 1950’s to treat tuberculosis. It can have side effects on the liver and potentially causes damage to the peripheral nerves (the nerve endings in the arms and legs) and so must be taken with vitamin B6 (pyridoxine) to prevent this. A typical dose of isoniazid, when used for tremor, would be 1,200 mg per day.
There are two drugs which have been shown to be unhelpful for either ataxia or tremor in MS. The first is cannabis and the cannabis-based medicines.
There have been several clinical trials of cannabis for a wide variety of MS symptoms but all the trials agreed that it had no beneficial effect on tremor.
The second drug is baclofen, which is commonly used to treat spasticity, spasms and cramps in MS. Unfortunately, improving spasticity does not appear to help unsteadiness or ataxia.
This leaves the other drug treatments in the undecided category; we are simply not sure of their effectiveness because they have been inadequately tested. Such drugs include anti-epileptic drugs such as levetiracetam, gabapentin and carbamazepine. A group of medicines known as the 5HT3 antagonists, which include ondansetron and dolasetron, have shown some early promise, but larger controlled trials are needed to prove their effectiveness. These drugs are usually used to treat nausea in cancer patients and work by reducing the action of serotonin (a chemical transmitter in the brain). There are some treatments which are known to be effective in tremor caused by other conditions (notably essential tremor) such as beta-blockers or even alcohol, but their effectiveness in MS tremor remains unclear.
Surgical treatment
Two types of brain surgery can be used to treat MS tremor. Both involve altering the activity of the nerve cells in a part of the brain called the thalamus. In the first type of procedure, a thalamotomy, a wire is inserted into the thalamus and the tip of the wire is heated (or made very cold) in order to permanently disrupt the nerve cells there. The second type of procedure is called deep brain stimulation and similarly involves insertion of a wire into the thalamus connected to a pacemaker device under the skin near the collarbone. A small electric current is passed which temporarily blocks the nerve cells.
The amount of stimulation can subsequently be adjusted or turned off.
In the short term, the results of such procedures can be very effective in reducing tremor. However, there are several drawbacks. First, there are potentially serious risks with the surgery including brain haemorrhage, stroke or even death.
Secondly, it is only effective in certain types of tremor and the person with MS has to be otherwise well enough to undergo the operation.
This means that the surgery is by no means an option for every case of MS tremor. Thirdly, the effects of thalamotomy or deep brain stimulation can wear off in around six months, and there may not be any improvement in overall disability for the person with MS. For these reasons, very careful consideration has to be given by the person with MS, their neurologist and the neurosurgeon about whether surgery would be a suitable treatment option for that individual.
Conclusion
Tremor and ataxia are probably among the most treatment-resistant and yet disabling symptoms in MS. There is little evidence that any current treatment has good long-term effectiveness. That is not to say there is no hope that such a treatment will be found, particularly as both new drugs and surgical techniques are developed and tested, and as the understanding of the cause of ataxia and tremor increases.
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