MECP2 and glycogen storage disease VI: Our prior work with CLN6 and CLN8 diseases (Cain et al., 2019; Johnson et al., 2021) has demonstrated that the ICV route of administration can be utilized efficaciously with substantially lower doses of virus (20- to 40-fold lower than the aforementioned studies using the AAV9-Mecp2 combination) while reducing potential toxicity issues encountered with high intravenous doses and the local trauma created by parenchymal injections (Garg et al., 2013; Bosch et al., 2016).