Do epilepsy and migraine share a genetic link?
“Epilepsy and migraine ‘could have a shared genetic link’”, reports BBC News.
This headline is based on a study of people with epilepsy who also had two or more close relatives with epilepsy.
Researchers were interested in whether having this type of family history increased the risk of participants experiencing migraines. If this was the case, it would suggest that epilepsy and migraines may have ‘shared genetic effects’.
The study found that participants with two or more first-degree relatives (parents, siblings or children) with epilepsy were more likely to suffer from migraine with aura (where the headache is preceded by warning signs such as visual problems), than participants with fewer additional affected relatives.
Overall, this study does not clarify whether there is a definite genetic link between epilepsy and migraine, it can only indicate an association in some groups of people.
Where did the story come from?
The study was carried out by researchers from Colombia University in New York. It was funded by the US National Institute of Neurological Disorders and Stroke.
The study was published in the peer-reviewed journal, Epilepsia.
This story was well-reported by the BBC, although it did not comment on the methods of this study or their limitations.
What kind of research was this?
This was a cohort study that aimed to determine whether there was a link between whether a person had a confirmed diagnosis of either generalised epilepsy (where a person loses consciousness during a seizure) or focal epilepsy (where a person does not lose consciousness during a seizure), and:
- the number of first-degree relatives who also had history of epilepsy or seizures (fits)
- the likelihood that the individual with epilepsy and a family history as described above also suffered from migraines
By seeing if individuals who have a greater number of family members affected by epilepsy (suggesting they may have genetic susceptibility) are more likely to suffer from migraines, the researchers aimed to strengthen the evidence for a genetic link between epilepsy and migraine.
Previous research into a possible link has produced inconclusive results – some studies found evidence of a link, others report finding no evidence.
What did the research involve?
The researchers recruited 730 participants aged 12 years or older with either focal or generalised epilepsy from 501 families containing two or more individuals with epilepsy of unknown cause. This meant that at least two siblings or a parent-child pair had to have epilepsy.
Participants were asked about their history of migraine using a standardised interview, and participants were classified as having had:
- no migraines
- migraine without aura
- any occurance of a migraine with aura (where the headache is preceded by warning signs such as visual problems including flashing lights or blind spots)
The researchers then asked participants about additional relatives affected with epilepsy or a seizure disorder. For each family, the researchers calculated the total number of relatives affected beyond the enrolled participants (referred to as ‘additional’ affected relatives) and the number of first-degree relatives of participants who were affected.
The researchers looked to see if a history of seizures in additional relatives increased the likelihood of migraine. The researchers controlled for age, sex, participant type (for example, whether the participant was the first enrolled person, a sibling or a parent), and epilepsy type (focal epilepsy or generalised epilepsy).
What were the basic results?
The prevalence of migraine in all participants was 25.2%. Women were more likely to have had a migraine than men: 31.5% of women had had a migraine, compared to 14.5% of men (odds ratio 2.4, 95% confidence interval 1.62 to 3.52).
The prevalence of migraine with aura increased when individuals had two or more additional first degree relatives with seizure disorder not enrolled in the study:
- 10% of patients with no additional relatives with seizure disorder had migraine with aura
- 11.3% of patients with one additional relative had migraine with aura
- 25% of patients with at least two additional relatives had migraine with aura
This meant that the odds of having a history of migraine with aura were 2.5 times higher if an individual had at least two additional relatives with a seizure disorder.
However, if more distant relatives were included, the association between number of affected relatives and migraine disappeared.
The prevalence of the other type of migraine, migraine without aura, did not vary with the number of additional first-degree relatives with seizure disorder.
How did the researchers interpret the results?
The researchers concluded that the “prevalence of a history of migraine with aura (but not migraine without aura) was significantly increased in enrolled participants with two or more additional affected first-degree relatives.” They go on to say that, “these findings support the hypothesis of a shared genetic susceptibility to epilepsy and migraine with aura.”
Conclusion
This paper suggests there is a link between the number of close relatives with a seizure disorder and the likelihood that an individual with epilepsy will also suffer from migraines with aura.
However, it seems that the researchers were only interested in what they term ‘additional’ family members, and did not take into account the fact that to be eligible for this study at least two siblings or a parent and child both had to suffer from epilepsy.
There seems to be the possibility that if, for example, four members of a family were enrolled in the study but the family had no further affected members, all members of this family would be classified as having no additional family members with seizure disorders.
It is unclear what would have been the effect on the results if only one member of each family had been studied and all other members of the family had been considered as relatives with seizure disorder.
The authors also identify limitations to their study:
- They did not collect data on family size. They consider that it is possible that families with more participants affected by seizure disorder may be larger, and that this is influencing the results. However, suffering from migraine might be independent of family size, and therefore this should not affect the results.
- The presence of seizure disorders in additional relatives was not confirmed, and the researchers were not able to assess the history of migraine in non-enrolled family members.
Overall, this study does not clarify whether there is a definite genetic link between epilepsy and migraine.
Though it does suggest an association, in some familes at least, which would seem to make the case for futher research.
Learning more about the genetics of both epilepsy and migraines could eventually lead to a theraputic breakthrough.
