OBJECTIVE : Several reports have described inflammatory mass lesions at the tip of intraspinal drug administration catheters. We evaluated the number of patients reported with this condition and whether data support hypotheses that have been put forth regarding the cause of these lesions.
METHODS : Information that was reported in the medical literature, and by Medtronic, Inc., to the United States Food and Drug Administration as of November 30, 2000, was reviewed.
RESULTS : Forty-one cases were identified, including 16 from the literature and 25 that were not published previously in the literature. Because of voluntary reporting and other methodological limitations, the actual number of cases must be higher than reported. All of the patients had chronic pain. The mean duration of therapy was 24.5 months. Most masses were located in the thoracic region. Intrathecal drugs included morphine or hydromorphone, either alone or mixed with other drugs, in 39 of 41 cases. No masses were reported in patients who received baclofen as the only intrathecal medication. Thirty patients underwent surgery to relieve spinal cord or cauda equina compression. Eleven patients were nonambulatory at last follow-up, and one died of a pulmonary embolus. Surgical specimens revealed noninfectious chronic inflammation, granuloma formation, and fibrosis or necrosis.
DISCUSSION : The most plausible hypothesis with regard to the cause of intrathecal catheter tip mass lesions implicates the administration of relatively high-concentration or high-dose opiate drugs or the use of drugs and admixtures that are not labeled for intrathecal use.
CONCLUSION : Patients who require high-dose intraspinal opioid therapy and those who receive drugs or admixtures that are not approved for intrathecal use should be monitored closely for signs of an extra-axial mass or catheter malfunction. Prompt diagnosis and treatment may preserve neurological function.