Some migraine sufferers experience a bizarre symptom at the onset of headaches, according to a new study. When their migraines begin these people report having hallucinations involving their sense of smell.
In other words, they smells scents that are not there.
“It’s uncommon, but distinctive,” said Matthew Robbins, leader of a study conducted at the Montefiore Headache Center in New York.
Although visual disturbances associated with migraines, known as aura, have been widely studied, scent disturbances, known as olfactory hallucinations, have yet to be covered by researchers, Robbins notes.
The study followed more than 2,100 patients over the course of a 30 month period. Fourteen people, or less than 1 percent, claimed that they suffered from olfactory hallucinations immediately preceding the onset of their headaches.
“The most common was of the burning or smoke variety,” Robbins said.
Some subjects described the scent as one of something burning, while others were more specific, saying they smelled cigar smoke, wood smoke, and even burned popcorn.
The second most common smell reported was “decomposition” odor including garbage and sewage.
Although it is unclear what causes this hallucinatory sensation, it could be the result of something called "cortical spreading depression." The phenomenon, which has been implicated in the cause of aura symptoms, takes place during a migraine when there is a wave of increased electrical activity in the nerve cells of the brain, followed closely by a wave of decreased activity, according to Robbins.