MEN1 and periventricular nodular heterotopia: In 2019, Montier et al. conducted a pioneering study that identified a somatic mutation with a high VAF (16.7%) in the MEN1 gene from the DNA extracted from trace tissues adhering to SEEG electrodes in a patient with focal epilepsy and bilateral periventricular nodular heterotopia.22 A second case report study identified a KCNT1 mutation at a mosaic level of ∼25% from one patient with non-lesional focal epilepsy.23 Both studies were conducted on whole genome-amplified DNA and pooled SEEG electrodes.