**6. Summary and future developments**

In summary, AAV vectors are a promising tool to transduce both the CNS and the spinal cord. Following a single systemic injection, AAV vectors cross the BBB and mediate widespread gene transduction throughout the brain, including the cerebral cortex, cerebellum, olfactory bulb, and brain stem. Recently, to obtain more efficient transduction, a new AAV vector serotype [27] or tyrosine mutant capsid [2] was developed. In addition, Rafi et al. succeeded in treating a mouse model of Krabbe disease (twitcher mice) by administering a combination of intracerebroventricular, intracerebellar, and intravenous injections of AAV vectors to neonates [28]. This suggests that administration of AAV vectors via several routes could prove highly useful for efficient and long-term overexpression or downregulation of genes through‐ out the CNS and spinal cord and could be a useful means of treating genetic neurological diseases.
