Intrathecal drug delivery pumps can aspirate cerebrospinal fluid (CSF) when the drug reservoir is empty or at other times to maintain a continuous or cyclic fluid flow through the pump and the delivery catheter. This addresses the potential need for continuous infusion to maintain an un-occluded fluid pathway to the intrathecal space by providing an “active port” that aspirates and expels CSF to keep fluid flow going without infusing a drug or requiring saline to fill the pump. If drug refill visits are missed, CSF could be used to keep the pump mechanism functional rather than having it run dry requiring replacement or requiring saline injections to keep the pump mechanism functioning. In addition, by having the pump aspirate CSF into the body of the pump, it would be possible to monitor biomarkers using systems in the fluid pathway and pressure differences for possible issues related to CSF management.