Abstract: A method for delivering fluid to the brain of a subject using an intraparenchymal catheter, the method comprising the step of inserting the catheter 5 into the brain using a posterior to anterior approach and methods of treating neurodegenerative disorders using this delivery method, as well as methods for delivering fluid to an elongate structure of the brain using an intraparenchymal catheter, the method comprising the step of inserting a catheter into the brain along an insertion axis that is substantially aligned with a long axis of the elongate structure.