Gene therapy is a very powerful tool that is currently being explored to combat disorders with underlying genetic causes. Within the field of neurological diseases, there is great interest looking at rare diseases of monogenic origin with the hope of developing disease-modifying gene therapies, as opposed to treatments for symptom management. Therefore, using relatively tunable systems like recombinant AAVs (rAAVs), scientists are also exploring in vivo gene delivery in parallel to ex vivo.