A Perspective on the Migraine Mind
Visual depictions of auras offer an inside peek into the sensory chaos that lies behind a migraine’s debilitating pain.
A few centuries ago, people who described an episode of strangely skewed vision followed by a throbbing headache might be told they had received a message from heaven, or else they had been possessed by an evil spirit. A generation ago, similar tales of hallucinations and pain were often received with neither fear nor awe but simply exasperation. The writer Joan Didion found that her accounts of migraine sometimes met with reactions little short of disdain, “for I had no brain tumor, no eyestrain, no high blood pressure, nothing wrong with me at all. I simply had migraine headaches, and migraine headaches were, as everyone who did not have them knew, imaginary.”
On the contrary, those who have experienced them know that migraines are all too real. Making sense of them is a major challenge, however. They are made even more baffling by the fact that the headache is not their only manifestation. Migraines are often preceded or accompanied by visual hallucinations. Arriving suddenly out of a clear blue sky, a migraine aura—a set of shimmering, flashing, weird perceptions—is bound to seem inexplicable, even frightening. This was certainly the case for eminent neurologist Oliver Sacks, whose first migraine occurred when he was only three or four years old. The incident left an indelible memory:
“I was playing in the garden when a brilliant, shimmering light appeared to my left—dazzlingly bright, almost as bright as the sun. It expanded, becoming an enormous shimmering semicircle stretching from the ground to the sky, with sharp zigzagging borders and brilliant blue and orange colors. Then, behind the brightness, came a blindness, an emptiness in my field of vision, and soon I could see almost nothing on my left side. I was terrified—what was happening? My sight returned to normal in a few minutes, but those were the longest minutes I had ever experienced.“
Fortunately for young Oliver, his mother immediately recognized the condition. As a migraine sufferer herself, and a trained physician, she could assure him he would soon be good as new. She explained he had experienced “a sort of disturbance like a wave” passing across a part of his brain, temporarily distorting his senses.
Years later, Oliver Sacks wrote a book, Migraine, and a number of related articles that greatly increased the public understanding of migraine—not just the headache but also the aura and other characteristic symptoms—as an illness, and a fairly common one at that. According to figures from the World Health Organization, as many as 11 percent of all adults suffer from this condition, which affects their quality of life and interferes with work and social activities. The toll on the affected individual amounts to an estimated 1.3 years lost to disability over a lifetime.
In trying to identify the cause of migraines and the sensory havoc that comes with them, patients and healthcare professionals have pointed to a great variety of factors: coffee, red wine, aged cheese, sunlight, exercise or lack of exercise, fluctuating hormone levels, chronic stress. Although a discrete episode of migraine might be triggered by any of these, or even by no apparent factor at all, the underlying susceptibility to migraines seems to be encoded in the genome. In studies focusing on the so-called classic manifestation, migraine with aura, researchers have identified mutations in several genes that are involved in the release and uptake of two important signaling molecules in the synapses between brain cells.
One of these chemical signals, or neurotransmitters, is serotonin, which helps regulate sleep and mood and is also involved in the perception of pain. The other neurotransmitter, glutamate, serves as an excitatory signal, enabling the physical processes in the brain that underlie learning and memory. Too much excitement can be dangerous, however: Although under normal circumstances glutamate acts as the “on” signal for many brain activities, over-exposure to glutamate may cause receptor cells to shut down altogether for a time, or even die.
A recent study in Nature Genetics suggests that if neurons at the receiving end of a glutamate signal do not perform efficiently, an accumulation of glutamate in the synapses may help bring on migraine attacks. The wave of hyper-excitement followed by inactivity spreads across the cerebral cortex and gradually disperses like ripples on the surface of a pond, in a feature known as cortical spreading depression. Depending on which regions of the brain it affects, cortical spreading depression can wreak mischief on the senses in myriad ways, in addition to the most common visual auras. Journals of neurology abound with case histories of hallucinatory sounds, illusory odors (usually unpleasant, alas), dizziness, tingling, numbness, or out-of-body experiences.