Catheter-Associated Masses in Patients Receiving Intrathecal Analgesic Therapy

A cohort of seven patients receiving intrathecal analgesic drug therapy for chronic intractable pain underwent radiocontrast myelography and computed tomography (CT) scanning to screen for catheter-associated intrathecal masses. Three of seven patients examined had intraspinal masses associated with the tip of the drug infusion catheter after a total of 118 mo of therapy. The index case presented with exacerbation of neuropathic pain and paralysis of the left lower extremity. The two additional cases detected by CT myelography were asymptomatic at the time the catheter-associated mass was assessed. The mean duration of therapy before diagnosis of the catheter-associated mass was 19.6 mo, with a range of 16–25 mo. An intergroup comparison of demographic and treatment variables between patients, with and without catheter-associated masses, demonstrated that patients with masses were younger and were receiving a larger morphine dose than patients without masses. The differences were statistically significant (P = 0.05). In one patient with an asymptomatic catheter-associated intrathecal mass, regression of the mass was observed after cessation of therapy. In a second asymptomatic patient, the mass remained stable over 1 yr of continued treatment after substitution of hydromorphone for morphine without interruption of therapy. Neither asymptomatic patient has subsequently developed additional neurologic findings or injury after detection of occult catheter-associated intrathecal masses and clinical intervention. We suggest that all patients receiving long-term intrathecal analgesia should undergo periodic radiographic surveillance to further define their risk of developing occult catheter-associated masses and to allow intervention before neurologic injury can develop.