Send comments and feedback Somatic genetic epilepsies arise from mutations that occur early in fetal development. They are usually only detectable by genetic sequencing of tissue. For these epilepsies, the timing of the mutation is key: For example, research has shown that focal cortical dysplasia type IIB and hemimegaloencephaly are genetically the same disease, but arise from somatic mutations at different developmental time points. This relatively new area of research is discussed by Dr. A...