Despite the lack of large epidemiologic studies to date, increased reporting of the inflammatory mass phenomenon as a consequence of scientific presentations and “Dear Doctor” letters to physicians, as well as the availability of new preclinical data, motivated the organization of a consensus panel. This panel’s goal was to formulate hypotheses about the etiology of catheter-tip masses and to provide recommendations for clinicians about the detection and treatment of this complication.1,2Together, these papers provide a comprehensive review of the preclinical and clinical data available regarding the incidence, etiology, and clinical features of inflammatory masses associated with intrathecal drug infusion and provide recommendations for screening, detection, diagnosis, treatment, and prevention of these masses. These recommendations emphasize the need for physician awareness, attentive patient follow-up, and maintaining intrathecal opioid dose and concentration as low as possible for as long as possible while still achieving adequate analgesia.
It remains that inadequately treated chronic pain is a serious condition that is associated with its own risks and morbidity. In that context, the risk of catheter-tip mass development as a consequence should remain acceptable provided the treatment is effective. The authors thank Drs. McMillan and Aldrete for their interest and their comments. We share Dr. McMillan’s view on the importance of defining the true incidence and risk of inflammatory mass formation. It is clear that the incidence of granuloma formation is underestimated because of the voluntary nature of reporting and the unknown incidence in asymptomatic patients. The authors believe, however, that imaging of all patients on intrathecal therapy for chronic pain is not supported by the current literature. Given the serious adverse impact of this complication and the likely increase in its incidence with long-term intrathecal opioid administration in noncancer pain populations, the authors believe that the same goals can be reached if physicians maintain a low threshold for ordering imaging studies in patients perceived to be at risk. Even subjective or relatively minor symptoms in a patient receiving long-term or high-dose intrathecal opioid therapy may justify an imaging study to rule out the possibility of a catheter-tip mass. Contrast-enhanced magnetic resonance imaging is the imaging modality of choice, although computed tomography–myelography is less costly and also effective in confirming the diagnosis.
* The University of Texas M.D. Anderson Cancer Center, Houston, Texas. firstname.lastname@example.org