Last week I had a migraine. To some that won't mean much, but fellow sufferers will know that it means hours, or even days, of nausea, light sensitivity, sound sensitivity, and crushing, pulsing pain. The kind of pain that makes you think (in the moments when you can think at all) that self- trepanation with the rusty drill from the understairs cupboard might be a viable option. Eventually - minutes, hours, or days, later - the pain subsides. For me the days following a migraine are filled with a mixture of relief and mental exhaustion. My head is sore and my brain is tired.

It feels kind of like a mental hangover - like being drugged. Sometimes the migraine lasts for days and when it finishes I want to make up for lost time. I want to function. And somehow somehow I just can't. For a day or more after a severe migraine, I feel like I'm working through a mental fog, one so heavy that even routine tasks take on an otherworldly quality.

What is this feeling AFTER the pain? I knew I would face skepticism at best and outright disbelief at worst when I talked to people about it. And I even began to doubt myself. Maybe I was just tired? Finally I decided to look for a study. Is this real, or am I just imagining things?

It turns out that what I experience is called the migraine postdrome. Migraine can occur in four possible stages, and each patient may experience one, some, or all of them. First is the prodrome, the period before the migraine, consists of a variety of possible symptoms which seem to have very little in common: irritability, depression, yawning, gastrointestinal disturbance, food cravings, stiff muscles, even hot ears. Not all patients get this, but it occurs hours to days before an attack, and is often the only warning they get. The second phase is the Aura. This phase can come immediately before or during the actual migraine pain phase, and can consist of visual disturbance (many people talk about blind spots or zigzags), or of other changes in perception, such as a pins and needles feeling. And then there's the third phase. The pain phase. This can last from 4-72 hours and includes pain (usually, but not always localised to one side of the head), nausea, vomiting, and intense sensitivity to light or sound.



And finally, after the pain, the postdrome. The symptoms here are less dramatic than the pain, the auras, and the vomiting, but can still impair quality of life. Instead of pain or nausea there is fatigue, difficulty concentrating, dizziness, weakness, and decreased energy. They don't sound like much, but patients report a decreased ability to work, decreased interactions with family and friends, and what is often most frustrating, a feeling of cognitive impairment. These feelings can be maddening and depressing. When you're supposed to be feeling better, you end up almost feeling worse.

Not only are the symptoms themselves exasperating, the postdrome itself is a relatively new and unexamined phenomenon. While reports of and treatments for migraine go back millennia, studies of migraine postdrome itself go back only to 2004. Patients generally complain of similar symptoms. But the causes of migraine postdrome, like the migraines themselves, remain a mystery.

No one knows what causes migraine. It's a strange pile of symptoms: auras, light sensitivity, gastrointestinal disturbance, pain, exhaustion. Some people may exhibit all symptoms, some almost none. Some feel repetitive pulsing pain, some feel crushing pain, and some have light sensitivity, auras, and vomiting, without any pain at all. Some people have clear triggers, such as food or smells, that can bring on a migraine. But a food or a smell isn't a direct cause. It's only a trigger. Many have a postdrome, but some do not.

There are many hypotheses. People who experience aura before migraines show a spreading depression of cortical activity in the brain. But then, there are many migraineurs who don't experience aura at all. Some hypothesize that dilation of the blood vessels in the scalp produces the throbbing pain that goes with each heartbeat. But some migraneurs don't even experience pain, and some experience pain that does not throb. Many drugs that are used to treat migraine act on the neurochemical serotonin, a chemical which plays a role in mood as well as pain, and which can also control the dilation of blood vessels. But there are many migraineurs who don't respond to these drugs. Some scientists think that there is an underlying brain dysfunction. But there is no evidence.

All these hypotheses were in place before the acknowledgement of a "postdrome". Though the idea of a postdrome may be a relief for patients, to have their experience acknowledged as reality, it can seem to complicate the migraine issue. Yet another weird symptom to add to the pile. Another aspect of migraine that the final cause must encompass and explain. Maybe it's better to focus on the "bigger" aspects, the pain and the auras, and let the postdrome go, until we have a good working theory.

There are several reasons that the migraine postdrome has remained unstudied and ignored. First of all, there's no pain. The seriously debilitating symptoms of migraines are the pain, the light sensitivity, the auras. Compared to these, a little mental fog in the few days after seems like the least of our concerns. Secondly, what is the point in studying the postdrome? These cognitive symptoms and decreased energy may be debilitating, but they only complicate the issue of what may be causing the main symptoms. Finally, what if it doesn't exist? A significant number of patients report the symptoms, but so far, there are no biological indications.

Not every migraine sufferer experiences postdrome, but I'm certainly not alone. While my feelings of cognitive impairment may not sound like much, they can be intensely frustating, undermining my confidence and affecting my daily performance. And there is another good reason to study the postdrome: while my feelings of "mental hangover" are one more symptom of the inscrutable condition of migraine, it's possible that no one symptom is going to reveal the underlying causes. Migraine is not one thing, it's a collection of symptoms, and we need to consider that whole collection when coming to a hypothesis of what it's about. Maybe no single piece will solve the puzzle, but by fitting together a group of symptoms, we may see a clear picture of migraine.

Scicurious has a PhD in Physiology and is a postdoctoral researcher. Her work has appeared in three years of The Open Laboratory: the Best of Science Blogging (2008, 2009, 2010), and on the Scientific American Guest Blog. She blogs at Neurotic Physiology

References

Kelman, L "The postdrome of the acute migraine attack" Cephalagia, 2006

Kelman, L "The Premonitory Symptoms (Prodrome): A Tertiary Care Study of 893 Migraineurs" Headache, 2004

Cady et al "Primary Headaches: A Convergence Hypothesis" Headache, 2002

Pascual, J "Migraine Postdrome" Headache, 2011

Dodick, DW "Examining the Essence of Migraine—Is it the Blood Vessel or the Brain? A Debate" Headache, 2008

Alrumani, U "Calcitonin Gene-Related Peptide and Migraine: Implications for Therapy, 2004