Intrathecal baclofen and catheter tip inflammatory mass lesions (granulomas): a reevaluation of case reports and imaging findings in light of experimental, clinicopathological, and radiological evidence.

Two case reports recently appeared in the pain management literature that described magnetic resonance imaging (MRI) findings in three patients receiving intrathecal baclofen (ITB) therapy and who experienced loss of ITB clinical effects without any other neurological symptoms [1,2]. Although one of the reported patients was quadriplegic [1], the other two had post-stroke spasticity and multiple sclerosis, respectively—which would have allowed their physicians to detect new signs, symptoms, neurological deficits, or paralysis due to spinal cord compression or compromise—if those events had occurred [2]. The physicians in all cases made prompt and accurate diagnoses of catheter complications as the cause for loss of ITB effects, and they performed catheter revision or replacement procedures that restored therapeutic efficacy and returned the patients to their previous functional status. In summary, all three patients received timely intervention that led to optimal results. The controversial aspect of the reports was attribution of MRI findings to catheter tip inflammatory mass or “granuloma.” This phenomenon previously had been described only in patients or experimental animals exposed to intrathecal opioid drugs or pharmacy-compounded drug admixtures [3–5]. Consequently, the new reports generated questions and comments among practitioners who care for large numbers of patients on ITB therapy [6,7]. In this article, we will briefly review the state of the current knowledge about inflammatory mass (IM), explain the MRI findings associated with catheter complications in ITB patients, and clarify why the same inflammatory process observed in pain patients and animals exposed to intrathecal opioids is highly unlikely to occur during ITB therapy. In 2000–2001, one of us (RJC)—in cooperation with clinicians, researchers, and members of a consensus panel that included another of the present authors (TD)—performed the first comprehensive analysis of unpublished animal research, sporadic published reports, and unpublished cases pertaining to intrathecal catheter …