A rapid exchange microcatheter for accessing the intracranial neurovasculature. A side opening through the sidewall is located a first distance proximal to the distal-most tip. A proximal opening located proximal to the side opening is a second distance from the distal-most tip. A distal, reinforced catheter portion extends between a distal end region to a point near the side opening. A proximal, reinforced catheter portion extends a distance from a point near the side opening towards the proximal end of the catheter body. The side opening is positioned within a gap between a proximal end of the distal reinforced catheter portion and a distal end of the proximal reinforced catheter portion. A payload of a cerebral treatment device is housed within the lumen proximal to the side opening. Related devices, systems, and methods are disclosed.