Botulinum toxin
Professor Michael P Barnes, Professor of Neurological Rehabilitation
Newcastle University
Open Door - February 2008 pages 12-13
Most people with multiple sclerosis will have heard of botulinum toxin and may have wondered if it might be something that could help them. Perhaps the best known use of botulinum toxin is for the management of wrinkle lines but it has been widely used for a whole variety of other purposes for about 20 years. Botulinum toxin has an interesting history. It was first developed at the Porton Down establishment in the South of England where the scientists needed to develop an antidote in case botulinum was used as an agent for chemical warfare. However, it was soon realised that it might have a role to play in medical science and the Porton Down scientific unit established a commercial 'spin off', Porton Products Ltd, to develop the toxin commercially.
The first use in man was in the United States when Professor Scott injected botulinum into the muscles surrounding the eye for some people with squint. Indeed, it is still occasionally used for the management of squint by the eye surgeons. These early studies showed that the toxin was safe to use and the number of uses has steadily increased ever since.
How does it work?
Botulinum toxin solution is injected into a muscle. Over a few days the toxin will spread within the muscle and block the impulse of the nerves that cause the muscle to contract. In chemical terms it blocks the release of the neurotransmitter, acetyl choline, which is needed for the transmission of the nerve impulse to the muscle. The end result of the injection is that the muscle becomes weakened. This effect lasts, on average, about three months and then the damaged nerve endings regrow and the muscle power returns to normal. If the injections have been helpful then they are simply repeated at three monthly intervals. Many people have now been having injections every three months for up to 20 years.
Are there different sorts of botulinum toxin?
There are now three brands of botulinum toxin type A available - Dysport, Botox and Xeomin. The last is not yet widely available but should be licensed in the UK early in 2008. There is also botulinum toxin type B, which is marketed as Neurobloc. There is very little practical difference between these different types of toxin and one does not really have any advantage over another.
Are the injections safe?
The injections are extremely safe. About 1% of people have a flu-like reaction which is usually quite mild. About one in a thousand people develop a short-lived skin rash. The botulinum injection can spread to surrounding muscles and occasionally these muscles are inappropriately relaxed. As an example, if injections are made around the neck for over active neck muscles then the injection can spread to relax the swallowing muscles. Swallowing difficulties occur in around 10% of people after neck injections. If injections are used around the eye then relaxation of the surrounding eyelid muscles can cause the eyelid to become droopy. However, in most cases relaxation of the surrounding muscles is not a problem and in the vast majority of people injections cause no side effects at all.
What are they used for?
The main use for people with MS is a relaxation of muscles that are over active. In other words it is used to treat the common problem of spasticity, which can cause muscles to become stiff and rigid and sometimes painful. A spastic muscle does not move normally and thus people with spasticity can have problems with walking and controlling their arms and hands, etc.
Spasticity is a very troublesome problem and historically it has been difficult to treat. There are a number of tablets that can be taken such as baclofen, dantrium, tizanidine and others, but there are often side effects. The advantage of botulinum toxin is that it can be injected into the muscles that need relaxing and it will not usually affect other muscles. Thus, it is a very useful agent for the management of spasticity.
Botulinum can also help those with a related condition called dystonia, which is characterised by muscle spasms in a few muscle groups such as around the neck (when it is called spasmodic torticollis) or around the eye (blepharospasm) or involving the facial muscles (hemi-facial spasm).
Botulinum can also help dry up saliva and sweat. It is used for people who have very excessive sweating (hyperhidrosis) and also those that have troublesome drooling of saliva. This sometimes occurs in MS but is more common in younger children with cerebral palsy or older people with Parkinson's disease.
In MS botulinum can sometimes help tremor - by simply damping down the movement in the muscles involved.
Our colleagues in urology also now inject botulinum to relax the bladder wall. This can sometimes be helpful for those with over active bladders causing such problems as urgency, frequency and incontinence.
There is also some early evidence that botulinum will help other conditions, such as tension headaches, migraine and back pain characterised by muscle spasms. However, in MS by the far the most common use is for the management of spasticity.
Who should give the injections?
Botulinum toxin is a prescribed drug and thus it is best injected by a medical consultant or a trained nurse or physiotherapist working within a botulinum clinic. In our centre in Newcastle we have a combination of doctors, nurses and physiotherapists working in the busy botulinum clinics. We also have a trained nurse and a physiotherapist who are able to visit people in their own home or in a nursing home.
However, the availability of botulinum toxin around the country is quite variable and is restricted in some parts of the UK. If the injections are useful they should be repeated every three months but in some centres it is not possible to offer appointments three monthly and people may have to wait four or even six months between injections. Regrettably the use of botulinum toxin is one of those really useful prescriptions that are subject to a 'postcode lottery'. Your GP or the local neurology service should certainly know the closest centre and should also know about the local availability of botulinum toxin.
Botulinum toxin has made a significant difference to how we can manage problems of muscle spasms and spasticity as well as an increasing variety of other neurological problems. It has been a very useful advance for some people with MS but it is a pity that availability is not uniform across the UK.
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