PTEN and isolated focal cortical dysplasia type II: Type 2 Focal Cortical Dysplasia (T2FCD), which is the human pathology associated with PTEN somatic mosaicism, is an important cause of intractable focal epilepsy48,49, and it is also characterized by disturbances of sleep EEG and by the presence of characteristic ‘brushes’ formed by transient episodes (10–100 s) of regular firing50,51.