The Mosaic Brain: a New Diagnostic Approach in Focal Epilepsies

Overall, this observational cohort study aims to: 1. Improve our understanding of the genetic architecture of childhood focal epilepsies. 2. Develop a liquid biopsy of cerebrospinal fluid (CSF) and assess feasibility to detect cerebral mosaicism using cell-free DNA (cfDNA) analysis and evaluate its performance against brain tissue on the panel testing. 3. Develop a methodology to use trace tissue from Stereoelectroencephalography (SEEG) DNA and assess feasibility to detect cerebral mosaicism and evaluate its performance against brain tissue on the panel testing. 3\. Validate the use of the liquid biopsy and SEEG trace tissue for use in the English National Health Service clinical services and share with other Genomic Laboratory Hubs.