PVL is sequle of hypoxic/ischemic insult to brain during birth and I disagree with the improvement you had noticed after using stramonium - the process of delayed myelination in your child seems non progressive and has tendency to improve in course of time, by itself, little by little although not totally. Moreover, datura is relatively a poisonous substance and I had seen in India doctors prescribe in higher doses to patients which we neurologists strongly disagree . A regular physiotherapy
with combined occupational therapy
programme is all that is needed and don't ever go for non-scientific ways of treatment which are not yet proved to be beneficial.