One in six people will have a migraine at some point

British scientists believe the severe headaches are caused by an abnormal brain reaction rather than a consequence of key changes inside the head.

Their controversial theory suggests migraines are caused by brain cells not behaving as they should.

One in 20 people suffer from migraines at least once a month and one in six at some point in their life.

Brain cells

Previous studies have suggested migraines may be triggered by blood vessels contracting.

This, they suggested, occurred when blood was prevented from reaching the membrane around the brain, where pain sensing neurons are located.

The brain is somehow misreading signals Dr Peter Goadsby

In recent years, scientists have started to believe the problem may have more to do with brain cells or neurons rather than blood vessels.

But Dr Peter Goadsby, at the Institute of Neurology in London, has taken this theory further by proposing the problem lies in the brainstem.

The brainstem connects the brain to the spinal cord, allowing signals to flow through.

Dr Goadsby believes migraines are triggered when the brainstem reacts abnormally to these signals.

Although the signals are no stronger than usual, they somehow cause a major reaction within the brainstem.

This, he says, causes the brainstem to generate pain from almost nothing.

"The concept takes the disorder away from being a pain problem to being a sensory disturbance," he told New Scientist magazine.

"Migraine is primarily a disorder of sensory processing, not a disorder of pain at all."

'Leap of faith'

Dr Goadsby acknowledges his theory is somewhat controversial.

"To say the pain is not really happening is quite a leap of faith," he said.

But he suggests his theory can perhaps be explained by the often strange symptoms that can precede migraines.

Sufferers often complain of lights being too bright, sounds being too loud or smells being unpleasantly strong prior to an attack.

Dr Goadsby says these are just sensory changes.

The light is not stronger, he says.

"So maybe it's not hard to believe that there's not really any worse pain, but that the brain is somehow misreading signals."