Rationale for Medical Use of Botulinum Toxin A (Botox®)
Health Canada has approved the use of Botox for the treatment of chronic migraine in 2011. The clinical trials proved its efficacy and safety for the treatment of chronic migraine. Botox should be offered as a treatment to people who live with chronic migraine.
INDICATIONS AND USAGE
BOTOX (onabotulinumtoxinA) for injection is indicated for the prophylaxis of headaches in adult patients with chronic migraine
(≥15 days per month with headache lasting 4 hours a day or longer).
Blepharospasm and Strabismus
BOTOX is indicated for the treatment of strabismus and blepharospasm associated with dystonia, including benign essential blepharospasm or VII nerve disorders in patients 12 years of age and above.
How does Botox work?
Nerves communicate by releasing molecules to their targets: the muscles, the sweat glands but also the sensory organs of the skin. The molecules released bind to receptors and induce actions: muscle contraction, sweat production, sensory modulation. Botox prevents nerves from communicating with their targets. If the target is a muscle, it will stop contracting. If the target is a sweat gland, it will stop producing sweat.
In chronic migraine, we know now that sensory nerves become inflamed and hypersensitive. The inflammation is caused by different molecules that may be released by the sensory nerves. Botox blocks this, and that has a «calming» effect on the pain. There are studies done on animals showing that Botox modifies the electric activity of the pain network of the face and neck.
Should Botox be used for any person with migraine?
No. Botox is approved only for Chronic Migraine. Chronic migraine is the most severe form of migraine. 1 to 2% of the population suffers from chronic migraine. These people have more than 15 days of headaches a month for at least three months, 8 or more of which are migraines. The other days can be «tension type», as the severity of headache varies in Chronic Migraine.
Unfortunately, Botox does not work for people who have a less severe form of migraine called episodic migraine. Studies on people with episodic migraine were negative. You may want to see a headache specialist to discuss if Botox would be right for you.
What are the expected benefits of Botox therapy?
We look for an improvement of more than 50% in the frequency and intensity of migraines. If you have 20 days per month, your 50% response would be 10 days per month (not zero).
In studies nearly 50% of patients achieved this goal after 6 months of treatment (2 sets of injections). Some people improve more than others (responders). 23% of patients in the studies improved by 75% (super responders). If you start at 20 days, you would go down to 5.
Other potential Benefits:
The attacks are less severe
The attacks are easier to control with acute treatments
The «baseline headache» or «baseline neck pain» are less intense
The tolerance to triggers is higher
The person functions better overall
Some of those effects may be seen earlier with the first treatments, before the impact on the frequency appears. Always use a headache diary!
How long should I try Botox before making a decision?
A trial of 3 cycles (or 9 months) is reasonable. The effect over the first treatments seems to be cumulative. 10% of people will notice an improvement only at the third treatment, especially if the situation was very severe to start with.
Could Botox work if other preventives do not?
Yes. Botox has a different mechanism of action than oral preventives. Studies have demonstrated a benefit in patients who had tried other preventives. In real life, Botox is covered only after previous trials, and improvements are observed.
Is the effectiveness of Botox sustained over time?
Yes. For most people who respond to Botox, the benefit are sustained over time. Remember that migraine is a fluctuating disease and that even if Botox is effective for you, you may have better phases and more difficult ones.
CONTRAINDICATIONS - You should not have Botox if you have:
Hypersensitivity to any botulinum toxin preparation or to any of the
components in the formulation (4.1, 5.3, 6.2)
Infection at the proposed injection site (4.2)