Rett syndrome (RTT) is a neurodevelopmental disorder that affects girls almost exclusively (about 1 in 10 000 females). It is characterized by normal early growth and development followed by a slowing of development, loss of purposeful use of the hands, distinctive hand movements, slowed brain and head growth, problems with walking, seizures, and intellectual disability. Herein, the inventors demonstrated that delivering a vector expressing a cholesterol 24-hydroxylase (CYP46A1) gene intravenously in a mouse model of RTT is able to prevent/correct the development of motor impairment, in a mild and an aggravated model of the disease both in male and female mice. In addition in males, the inventors demonstrated a prevention of the loss of Purkinje cells and an improvement of astrogliosis and microgliosis in the mild KO MECP2 model. Thus, the present invention relates to a vector for use in the treatment of Rett syndrome or related autism spectrum disorder, which vector comprises cholesterol 24-hydroxylase encoding nucleic acid.