Not an expert on the technique, but if it's possible to "edit" a gene, how would the altered gene be propagated to billions of neurons (assuming that's where the gene has effect)? The idea of modifying the gene in situ is a technical issue that would seem awfully hard to resolve.
Of course the whole idea is predicated on having sufficient knowledge of the gene's effect. The reported finding awaits replication, and quite likely further refinement before practical applications are feasible.
I would assume editing In Situ would require a retrovirus or something similar. Seems incredibly risk, but then again, so was open-heart surgery until we figured out all the things that will go wrong.
There are more cells in a body than stars in the universe; I'm under the impression that the first CRISPR therapies will be on early-stage embryos where the number of cells is still manageable and we can feasibly edit all of them. Would be happy to hear more from someone who knows more about the latest in gene therapy though, my training here is getting a little dated.
Of course the whole idea is predicated on having sufficient knowledge of the gene's effect. The reported finding awaits replication, and quite likely further refinement before practical applications are feasible.