Researchers define new subtypes of common brain disorder

Roughly 4% of the population is affected by a congenital brain malformation that has eluded researchers’ efforts to find causes and treatments. For the condition, Chiari type-1 malformation, the diagnosis is straightforward: the lower part of the brain, known as the cerebellum, protrudes at least five millimeters through the gap in the skull that connects to the spinal cord.