A method for determining the status of a catheter of an implanted infusion system, where the catheter is intended to deliver a fluid composition to CSF of a patient, includes monitoring catheter pressure, developing a pressure modulation profile based on the monitored pressure, and comparing the developed pressure modulation profile to a predetermined pressure profile. The predetermined pressure profile may be a profile of cerebrospinal fluid or a bolus infusion or withdrawal profile for the catheter. A determination of catheter status, such as properly functioning, occluded or leaky, can be made based on the comparison.