In many migraine sufferers, there is a problem with the membranes that surround and protect the brain. These membranes are called meninges and are sensitive to pain, in much the same way the membranes of the eye can be irritated by dust or chemicals. This makes our eyes itch and become inflamed, a natural healing response.
In a migraine there is activation of pain reflexes in the nerves supplying the meninges. The nerve most affected is the trigeminal nerve which responds by releasing pain- and inflammation-causing chemicals. This inflammation results from changes in the blood vessels in the brain, making them relax (the more accurate term is dilate).
In the healing process, inflammation allows our immune system to fix a cut, or fight a bug. In a migraine however this inflammation is not helpful, it causes redness, heat, swelling and pain, caused by certain proteins and chemicals leaving the bloodstream and surrounding the nerves.
As a consequence, the trigeminal nerve continues to sense pain even after the initial migraine trigger has passed; this inflammation can persist into a long-standing or chronic state. This is believed to cause increased sensitivity to pain and making further migraines more likely to happen i.e. chronic migraines.
Acetaminophen is commonly used for mild to moderate pain. It works by reducing or blocking the production of chemicals called prostaglandins that cause inflammation which leads to its pain relieving and anti-fever effects. These chemicals are normally produced by the body in a pathway that helps with infection and clotting. With less inflammatory chemicals released in the nerves supplying the meninges in the brain, there is less redness, heat, and swelling. This can reduce the level of pain that a patient experiences.
Acetaminophen is proposed to act in two ways:
- It has pain relieving effects similar tonon steroidal anti-inflammatory drugs (NSAIDs).
- It acts on other pain receptors that are not yet defined.
The combination of the two mechanisms helps to relieve migraine symptoms once a migraine starts to appear.
