Classifying Migraine Subtypes

Migraine symptoms are heterogeneous, and no single symptom is diagnostic. A classification scheme for migraine subtypes could help improve diagnosis and target therapies.

The investigators used results from a cross-sectional survey of a general population, the Korean Sleep-Headache Survey, to analyze associations between migraine symptoms. These associations were used to define distinct classes of migraines.

There were 2501 participants who completed the survey. Of these, 1186 experienced a headache during the previous year, and 125 received a diagnosis of migraine.

The symptoms identified by the subset of participants with migraines were sorted by patterns into 3 classes using a modeling technique called latent class analysis. The symptoms examined were from the International Classification of Headache Disorders diagnostic criteria for migraines as well as additional characteristics that were outside these criteria.

The investigators were able to divide migraines into 3 classes:

• Class 1—Mild and low frequency. This was the most common class, with 52% of participants.
• Class 2—Photophobia and phonophobia. This class had an intermediate headache frequency and intensity but the highest frequency of photophobia and phonophobia. One-third of people were in this class.
• Class 3—Severe and high frequency. This class had the highest headache frequency and intensity. It was the least common class, with 14.4% of participants.

Other symptoms were associated with the classes at different frequencies. Unilateral pain was common in Class 1 but not in Class 3, the class with the worst pain and frequency. The opposite was true for the symptom of aggravation by routine physical activity. Osmophobia, intolerance of smells, was most frequent in Class 2, “photophobia and phonophobia.”

The investigators noted that photophobia and severe headache intensity were less common in their study and in other studies from Asian countries compared with reports from Western countries for unknown reasons.

One difference between the classifications made in this study with those conceived in previous studies is the unique photophobia and phonophobia class. A previous model for classifying migraines proposed groups that seemed to correspond to Class 1 and Class 3 and a class with visual aura. The visual aura group did not include phonophobia in that model.

Some limitations of the study are that it does not capture variations in headache types within one individual and that the participants were not using daily diaries to track headaches.

The investigators suggested that their classification groups may help generate hypotheses about the pathophysiologic mechanisms of migraines. For example, the fact that photophobia, phonophobia, and osmophobia frequently occur together suggests that these symptoms may stem from a common mechanistic origin that causes hypersensitivity to sensory input. Similarly, headache intensity and headache frequency were of similar severity within classes and may therefore have similar causes.

“Other approaches of migraine subtyping including genetic, biochemical and neuroimaging studies are needed to verify our findings,” the investigators stated.

Source

Lee W, Min IK, Yang KI, et al. Classifying migraine subtypes and their characteristics by latent class analysis using data of a nation-wide population-based study. Sci Rep. 2021;11:21595.