Catheter-Tip Granulomas Associated with Intrathecal Drug Delivery: A Two-Center 20-Years' Experience Identifying 13 Cases

Background: Intrathecal (IT) drug therapy with implanted pumps is an effective treatment modality for chronic pain and/or spasticity, especially after noninvasive treatment has failed. Long-term use of intrathecal opioids may cause formation of inflammatory masses at the tip of intrathecal catheters, possibly leading to neurological deficits and/or catheter revision. We here aimed to identify risk factors for catheter-tip granuloma (CG) formation. Methods: We retrospectively reviewed patient data treated at two Swiss centers (Kantonsspital St. Gallen, Swiss Paraplegic Centre Nottwil) between January 1994 and October 2013. Collected data were age at operation, gender, smoking status, previous spinal operations, spinal level of catheter-tip, clinical symptoms, catheter testing with contrast agent, applied drugs, drug concentration, and cumulative daily drug dosages. Results: Thirteen patients with a mean age of 52.6 years and CG formation after a mean of 6.9 years of follow-up (FU) were identified and compared with 54 patients without CG of similar age (p = 0.535) and length of follow-up (p = 0.236). In the analysis of risk factors, catheter ending in the middle thoracic spine (Th4–8; 38.5 vs. 6.5%; p = 0.010), previous spinal surgery (75 vs. 41%; p = 0.051), and chronic pain as underlying primary symptom for IT drug therapy (100 vs. 56%, p = 0.003) were associated with CG formation. IT drug therapy for spasticity appeared to be much less associated with CG formation (0 vs. 44%, p = 0.003). As the symptomatology is closely related to the medical treatment applied, patients with CG were more likely to be treated with IT morphine (77 vs. 20%; p < 0.001), and as tendency with IT clonidine (54 vs. 26%; p = 0.092), and IT bupivacaine (46 vs. 20%; p = 0.077). Average in-pump morphine concentration (30.3 vs. 19.5 mg/mL; p = 0.05), as well as average daily dose of morphine (12.5 vs. 6.2 mg/d; p = 0.037) were significantly higher in the CG group. Smoking could not be identified as risk factor for CG formation (p = 0.693). Conclusions: Our patient cohort with catheter-tip granulomas differed in some features, of which some like catheter localization, choice, dosage, and the concentration of drugs are potentially modifiable. These results could contribute to prevention of CG in the future.