Gut bacteria can cause big holes in the brain

Biome, or the collection of bacteria living in our bodies has been receiving belated and well deserved attention. The discovery that bacteria living in our intestines can cause cerebral cavernous malformations or CCM (see photo) is quite dramatic. But there is no need to panic since this is a rare condition. However, it does indicate that gut bacteria can have a major impact on our brains.

It was a serendipitous discovery by Dr. Mark Kahn, professor of medicine at U. Penn, who studied mice with CCM. He noticed that mutant mice prone to CCM stopped developing holes in their brains after being moved to a new building. The exception was mice who developed an abscess after having their intestines accidentally stuck with a needle during a routine injection. Dr. Kahn and his colleagues identified a specific bacterium, Bacteroides fragilis, which was responsible for the development of brain caverns.

This finding may explain why there is such a wide variety of presentations in people who have the familial form of CCM. Some have no lesions even when they are 70, while others have hundreds of them at age 10. Just like mutant mice, humans seem to need an additional trigger to start developing CCMs. This finding provides a clear path to developing an effective treatment and perhaps, just a simple probiotic could keep such patients healthy.

In fact, a probiotic containing 14 different strains of bacteria (Bio-Kult, made in UK) is effective in preventing migraine headaches, according to a study presented by Iranian doctors at the recent International Headache Congress in Vancouver. Fifty patients were recruited into this study with half taking the probiotic and the other half, placebo. After 8 weeks, patients on the probiotic had fewer days with migraine and the pain was milder when compared to those taking placebo.

The big question is, what other brain disorders are triggered or worsened by our gut bacteria. We have more bacterial cells living in our bodies (about 39 trillion) than we have of our own cells (about 30 trillion) and scientists are finally beginning to study them. I Contain Multitudes: The Microbes Within Us and a Grander View of Life, is a fascinating and well-written book by Ed Yong on this subject.