How does Botox work in Migraines?

Botox is a radically different way of treating migraines. When administered correctly it can stop migraines for the period it is active in relaxing targeted muscles, and is helping to shed new light on how migraines start.  Before I talk about the theory on how Botox works, I will run through the existing understanding and theories.

What Is A Migraine?  Simply put, Migraines are caused by a misfiring of the nervous system. There is an overwhelming build-up of nerve cell activity in the brain stem at the base of the brain and the effect of this spreads in a cascade to produce the migraine headache that lasts for several hours to a day or more before it gradually recedes. The misfiring can spread to other parts of the brain to produce visual distortions, pins and needles in the face and strange tastes before the headache starts. Some sufferers may recognise that they are building up to an attack days before it starts. Different sufferers have many different patterns of symptoms and this has produced a plethora of competing theories, and treatments, and has lead to a degree of competition between some doctors who believe that they have the better explanation/treatment. The reality is that they are all right, or at least partially so!

Trigger Zones  It has been recognised for years that Migraine sufferers have trigger zones, the most common ones being at the back of the head, over the eyes, and over the temples. These correlate to the distribution of the Occipital Nerve and the Ophthalmic Branch of the Trigeminal Nerve. Interestingly both these nerves have their roots in the same part of the brain, where migraines start, and they carry not just ordinary sensory fibres of touch and pain etc but also fibres of the sympathetic nervous system, a more primitive system that controls many body functions such as breathing and blood pressure. The intimate linking of the two apparently separate nerves covering different areas is illustrated in some people who are aware of sensations above their eye when the back of their neck is pressed. As it happens, both these points are also acupuncture points. Occipital Nerve blocks have been used at the back of the head for many years, with varying success, and dentists have talked about the TemporoMandibular Jaw joint being a cause of migraines, and treated jaw misalignments, again with varying success.

Seeing Inside The Brain  More recently a special brain scan called a Functional MRI Scan has enabled doctors to visualise the brain activity as a migraine is actually happening and you can see the build-up of nerve cell activity as the migraine occurs. More specifically, for those who have a well define trigger zone over one eye you can see that the ophthalmic branch of the Trigeminal Nerve is thickened as it comes out from behind your eye over the bone and up on to your forehead. This is the place that sufferers press to relieve the headache in a migraine attack, though in reality pressing there works in part by distracting you from the migraine because it is so unpleasant to do, even when you’re not having an attack!!

Botox For Migraines This is where Botox comes in. It had been observed for years that some migraine sufferers found their migraines disappeared when they had botox for their wrinkles. Research in the USA has shown that up to 95% of sufferers get a positive effect. British doctors have been slower, but National Institute for Clinical Excellence (NICE), an NHS linked research organisation, now also accept that Botox is effective enough for them to recommend it for severely disabled migraine sufferers. However it is also recognised by the NICE researchers that for some sufferers the migraines can disappear completely for the period the Botox is working. This is explored in greater detail by other research in the USA and Germany that NICE have not used

So how does Botox work?  When a migraine is beginning there is a cascade of increasing stimulation of the brain stem.

  • There is no single trigger but there are well known factors such as diet, particularly food such as red wine, cheese and chocolate, hormonal changes during a woman’s menstrual cycle, and stress, that help precipitate an attack. Another part of the cascade appears to be related to the trigger zones covered by the Occipital and Trigeminal Nerves and even in diet/hormone related migranes, the trigger zones appear to play a part. Mechanical stimulation of these nerves has been recognised for years  in many theories and has lead to nerve blocks and surgery to reduce this, though the results have not been conclusive. The Supra-Orbital branch of the Trigeminal Nerve is unusual because it passes through the Corrugator muscle rather than around it as usually the case so is easily irritated.
  • The Corrugator is the main muscles that makes us frown, so when we do frown it also constricts the nerve. The Corrugator is one of the muscles we want to weaken when we use Botox to get rid of wrinkles. Botox is a potent and effective in paralysing muscles in very localised areas and this partial weakening is enough to stop mild migraines in some people.
  • A theory to explain it’s action is that the paralysis in the Corrugator muscle in the place it surrounds the Supra-Orbital branch results in less irritation of the sympathetic system fibres within the nerve that go back to the brain stem. It is not necessarily that this stimulation is the only cause of the migraine to start, for botox is not always 100% effective. However by reducing one part of the stimulation process you can prevent some of the early waves of excessive nerve cell activity from developing into a full-blown migraine. For some this may be that they have no attacks at all and for others it may be a much appreciated reduction in the severity and frequency of attacks.
  • If you remove the Corrugator by surgery from around the Supra-Orbital Nerve so that it is no longer mechanically irritated then the relief is as effective as the temporary paralysis with Botox, illustrating that it is  the reduced irritation and not direct action of Botox on the nerve that is helping. Research has shown that Botox is an effective test of whether surgery is going to work.