As described by those who live with them, migraine headaches are intensely painful and are often accompanied by other debilitating symptoms such as nausea, visual disturbances, and sensitivity to light and noise. These attacks can be incapacitating—migraine headaches are one of the world’s leading causes of disability.

Despite their prevalence, migraine headaches are still diagnosed and treated based solely on a patient’s description of symptoms. Migraine treatment is pretty much guesswork, said Robert Cowan, MD, a clinical professor of neurology who specializes in headache research.

Recently, Cowan led the largest study to date to categorize migraine patients using a brain imaging technique known as functional MRI. The study, which was published in the journal Cephalalgia, used fMRI to identify two biological subtypes of migraine. Jaiashre Sridhar, a data analyst at Stanford Medicine, is lead author on the study, and Cowan is senior author.