First of all, let’s recap the take home points from part 1:
- Migraines happen in normal brains
- Migraines are the result of a malfunction in pain processing, or specifically pain processing in reverse
- Migraines are weird.
So we’ve established that, with migraine, everything is thrown on its head. Pain doesn’t mean what we normally expect it to mean. It’s not signaling any threat to our health and survival, but rather is the result of our brain’s pain centers being flipped on by the migraine mechanism itself.
Like a cough or a sneeze, migraine is a stereotyped sequence of physiological events that are set in motion by specific stimuli. Unlike coughing or sneezing, however, migraine appears to serve no adaptive purpose. Once the migraine process is activated inside the brain, it may result in a myriad of symptoms. It’s a process with many potential moving parts, and the specific symptoms you experience with any migraine depends on how many of those parts are switched on. When they are all set in motion, then the result is a migraine in its most classic form, which is typically broken up into 4 different phases.
Migraine Phase 1: the Prodrome
The very first symptoms of a classic migraine may be recognized hours, even up to two days prior to the onset of head pain. Astute migraineurs who experience the prodromal phase can often use these symptoms to predict that a migraine is on its way. Symptoms that folks consistently report as part of the prodrome include sleepiness, malaise, excessive thirst, food cravings, changes in bowel or bladder function, depression, irritability, and even euphoria. In an upcoming post we’ll discuss the deeper significance of these symptoms.
Migraine Phase 2 – the Aura
Perhaps as concerning as the excruciating pain of a migraine headache is the experience of the aura that precedes it. Auras are a temporary disturbance in neurological function. Typically lasting between 20 and 45 minutes, auras can manifest as virtually any neurological deficit. The most common auras are visual in kind: shimmering and expanding crescents, perceptual distortions, or even complete loss of vision are but some of the possible symptoms folks may experience. Beyond visual disturbances, tingling and numbness in the face, arm, or leg, disruption of speech, weakness or inability to move a limb or limbs, and vertigo are all well documented aura phenomenon.
In the brain, the aura correlates to a wave of “spreading depression” of brain cell activity that marches along the cerebral cortex. Where that wave decides to go determines the particular aura symptoms experienced.
Migraine Phase 3 – the Pain
Not surprisingly, it is the pain phase that steals all the attention when it comes to migraine. Classically defined, the pain of a migraine is one-sided (“unilateral”), oftentimes localized to around the eye (but certainly not always), and throbbing in character. It is aggravated by bright lights, loud noises, and physical activity, and it can be accompanied by nausea and vomiting. It often persists until it is interrupted by medication or a good night’s rest. The pain phase itself can last from hours to days, and in rare cases months or years.
Migraine Phase 4 – the Postdrome
Even after the pain is gone, things aren’t yet back to normal, as the brain must still recover and return to its physiologic baseline. During this period, the most prominent symptom is usually fatigue, typically lasting up to 24 hours. In the postdrome, the migraine threshold is reduced, meaning that it doesn’t take much for the whole process to be triggered again.
Cruelly, migraines beget migraines.
What has been described here is the classic, textbook definition of migraine. It is what happens when the migraine process unfolds in its entirety in the brain. A migraine fully realized.
Many times, however, things aren’t quite so straightforward. In the next post, we’ll cover migraine’s many disguises.