Editor-in-Chief: Alaa Abd-Elsayed, MD, PhD
The utilization of intrathecal pumps is increasing as more practitioners are becoming familiar with their use, and as the applications of continuous intrathecal infusions increase. There are many potential risks with intrathecal pump implantation, which include the risk of infection, bleeding, nerve damage, as well as other potential issues. After prolonged usage, granuloma formation, medication tolerance, disease progression, mechanical failure, and arachnoiditis can also occur. Arachnoiditis has been associated with spinal disease, contrast media, preservatives in medications, infectious causes, hemorrhage, and more. The potential causes of arachnoiditis are many; however, it is infrequently associated with intrathecal pump infusates.
Morphine is commonly used in intrathecal pumps, either as a sole agent or in combination with other medications. Its role in arachnoiditis and catheter granuloma formation can be extrapolated from its effects on inflammation. In particular, it is well known that morphine causes mast cell activation and subsequent release of substance P and tryptase. In addition, morphine can sensitize the central nervous system to inflammatory effects as it can enhance the release of substance P from the dorsal root ganglia as well. Lastly, activation of µ receptors on lymphocytes can result in lymphocyte proliferation.
When arachnoiditis occurs in the setting of an intrathecal pump, there are several important considerations. These include the appropriate diagnosis of the cause as well as evaluation of potential treatment options. We report a case of intrathecal morphine-associated arachnoiditis that was diagnosed using both clinical and magnetic resonance imaging findings. This case describes a successful exchange of intrathecal morphine for intrathecal hydromorphone, with the subsequent improvement of the patient’s symptoms of arachnoiditis.
KEY WORDS: Adhesive arachnoiditis, arachnoiditis, cancer pain, complications, intrathecal catheter, intrathecal drug delivery system, intrathecal hydromorphone, intrathecal inflammation, intrathecal morphine, intrathecal pump, intrathecal opioid, intrathecal ziconitide