Introduction

Botulinum toxin is a powerful neurotoxin produced by the bacteria, Clostridium Botulinum. The toxin works by blocking the release of the chemical acetylcholine from nerve fibers, resulting in relaxation of the muscles it is injected into.

These injections were initially used only for therapeutic purposes, such as the treatment of various movement disorders and neurological problems. Recently, botulinum toxin is also used for cosmetic indications such as to smoothen wrinkles in the face.

At the NNI, the botulinum toxin clinic focuses on the therapeutic uses of this medication. The most common conditions treated by these injections include:

• hemifacial spasm (twitching of one side of the face)
• dystonia (sustained contraction or spasms of muscles that may involve one or more body parts, e.g. both eyes, jaws, neck, arms, writer's cramps)
• spasticity (muscles stiffness or increased muscle activity after a stroke or head injury)

Hemifacial Spasm.

Hemifacial spasm is a neuromuscular disorder characterised by frequent sudden involuntary twitching of muscles in the face. It often starts with an intermittent twitching of the eyelid muscles that can lead to forced closure of the eye and involvement of the other facial muscles on one side. Most often, it is caused by a blood vessel pressing on the facial nerve in the brain resulting in irritation and activation of the nerve that gives rise to facial twitching. This condition can result in visual problems because of the eye closure and can cause a considerable amount of embarrassment to patients.

There are essentially three modes of treatment for this condition:

• Oral medications

Medications such as clonazepam and carbamazepine may help to relax the muscles and reduce the frequency of facial twitching. These medications may not always work and may be associated with side-effects such as sleepiness.

• Botulinum toxin injections

These are the most effective means of treatment for this condition by relaxing the muscles it is injected into. The injections are focused only on the affected areas with hardly any side-effects on the rest of the body.

• Surgical decompression

As the cause of hemifacial spasms is thought to be related to facial nerve irritation, microvascular decompression surgery maybe performed in the brain to insulate the responsible blood vessel(s). This treatment offers the best chance of a cure for this condition. The operation is done under general anaesthesia with careful monitoring of the nerves being operated on. However, it carries a small risk of complication such as hearing loss, stroke and other complications associated with major surgery.

Dystonia

Dystonia isa neurological movement disorder characterized by involuntary muscle contractions which force certain parts of the body into abnormal, sometimes painful, movements or postures These dystonic movements are usually aggravated by voluntary movement.

Dystonia can affect any part of the body. It may affect the eyes, called blepharospasms, that result in increased blinking or inability to open the eyelids. It can also affect the muscles of the face, jaws, voice, neck, upper limbs and/or lower limbs. At times these spasms occur on performing a specific task, e.g. writer's cramps, which occurs during writing.

Such patients need to be clinically evaluated by a specialist to detect and treat any underlying cause, if present. Treatment for this condition involves a combination of medications such as benzhexol, benzodiazepines, baclofen, and tetrabenazine, together with botulinum toxin injections in suitable patients. Botulinum toxin injections are injected into the affected muscles to relax them and relieve the spasms and contractions. The suitability for these injections depends on the site of dystonia, the muscles involved, as well as the size and number of muscles affected.

Spasticity

After a stroke or injury to the brain or spinal cord, patients may develop spasticity. Spasticity refers to the stiffness or increased muscle activity that can develop a few weeks after an individual suffers a stroke. In some situations, spasticity may, overtime, cause harm by impairing limb function, cause painful cramps and spasms, or give rise to contractures and bony deformities.

Botulinum toxin is useful in carefully selected patients to improve function of the affected limb, relieve pain or improve ability to administer care The evaluation of a patient's suitability for these injections is best done in consultation with the treating physician, caregivers and physiotherapist. After each injection, it is important for regular follow-up physiotherapy to maximise the effects of each treatment.

Botulium Toxin

Patients with these conditions need to be evaluated first at the Movement disorders clinic or by a neurologist to assess their suitability for these injections. If suitable, minute doses of botulinum toxin are injected inframusculary at various sites into the affected muscles using small needles. No anesthesia.

The effects of botulinum toxin can be observed four to seven days an injection and the effects usually last three to four months. Botulinum toxin injections are not a cure for any of the above condition and repeated injection will be necessary when the symptoms recur. Botulinum toxin is generally a safe medication and has been used worldwide since 1989.

Side-effect are rare and related to the injection or medication injection related side-effect include pain, bleeding or bruising at the injection site. Medication related side-effects include excessive weakness of muscles to or close to the injection site, flu-like symptoms or generalized fatigue.

Botulimun toxin should not be used in certain neuromuscular conditions or in pregnancy. In Singapore, the medication is available in two brands Botox@ and Dysport@ the cost of each injection ranges for about S$120 to more than S$500 depending on the amount of botulinum toxin used.