Botulinum toxin is a treatment option for adults with chronic migraine

Introduction

 

Botulinum toxin A was licensed specifically for the treatment of chronic migraine in July 2010 by the Medicines and Healthcare products Regulatory Agency (MHRA). It has not been shown to be effective for any other headache type (e.g. episodic migraine, tension-type headache, cluster headache) as yet. The information below outlines the evidence for the use of botulinum toxin in headache.

What is botulinum toxin?

Botulism - paralysis of muscles caused by high doses of botulinum toxin - was first described in 1817. The responsible bacterium, Clostridium botulinum, was not isolated until 1895. Seven different subtypes of botulinum toxin (A-G) are known. A highly dilute preparation of botulinum toxin type A (Botulinum Toxin®) was introduced in clinical practice in the 1970s and 1980s to treat squint and blepharospasm. Since then it has found uses in other areas of medicine including dystonia (including writer's cramp), post-stroke spasticity, and hyperhidrosis. Other botulinum toxin preparations are available, both of type A (Dysport and Xeomin) and type B (Neurobloc or Myobloc), but these have never been tested in headache disorders.

Botulinum toxin and headache

In the mid-1990s a number of people reported improvement in headaches in patients receiving botulinum toxin for other reasons. Clinical trials of botulinum toxin in various types of headache followed, but the results were disappointing, with no difference over placebo.Detailed analysis of the results suggested, however, that there might be a subgroup of patients with chronic migraine who could benefit, and further trials were undertaken.

Botulinum toxin in chronic migraine: the PREEMPT trials

Two Phase 3 Research Evaluating Migraine Prophylaxis Therapy (PREEMPT) trials recruited 1384 patients with chronic migraine, and randomised them to treatment with Botulinum Toxin A or placebo. These patients were suffering on average 20 days of headache each month, of which 18 were moderate or severe. Those randomised to Botulinum Toxin A received fixed-site, fixed dose injections every 12 weeks over 56 weeks. These injections covered seven specific areas of the head and neck, with a total dose of between 155-195 units. At six months, after two cycles of treatment, those treated with Botulinum Toxin A had on average eight less days of headache each month. After 12 months, 70% of those treated had ?50% the number of headaches that they had done originally. Botulinum Toxin A was well-tolerated, the commonest side effects being neck pain (6.7%), muscular weakness (5.5%), and drooping of the eyelid (3.3%). No serious irreversible side effects have ever been reported in trials of Botulinum Toxin A in headache.

How does botulinum toxin work in chronic migraine?

The simple answer is that we don't know. A recent study suggested that botulinum toxin inhibits pain in chronic migraine by reducing the expression of certain pain pathways thought to play a key role in the headache phase of a migraine attack.

Unlike many of the other conditions in which it is used, it is not thought to work by relaxing overactive muscles. Botulinum toxin has been shown to reduce pain in a number of disease states, including cervical dystonia, neuropathic pain, lower back pain, spasticity, myofascial pain, and bladder pain.

Is Botulinum Toxin® right for me?

Only patients with chronic migraine are eligible for treatment with Botulinum Toxin A. Chronic migraine is defined as headaches occurring on 15 or more days each month, at least half of which have migrainous features. There are, however, other treatments available to patients with chronic migraine, and it is important that patients have an informed discussion of their headaches and the options for treatment with Dr. Saif Sulaiman before a decision to use Botulinum Toxin A is taken.

On visiting the clinic a detailed history of the patient's condition will be taken, including symptoms, frequency of attacks and any medication tried in the past or currently taking. Keeping a diary can help with this.