(208) Arachnoiditis Associated with Intrathecal Analgesic Administration

Abstract

Intrathecal analgesic administration via implanted drug infusion system has become a popular method of treating otherwise intractable pain. Drug reactions are known to occur but are typically similar to side effects that occur with systemic administration of the same drug and are reversible upon discontinuation of drug delivery. Symptoms consistent with arachnoiditis have been reported to occur with intrathecal infusion of high concentration bupivacaine but not for other agents, to our knowledge, and there are no reports describing arachnoiditis attributable to an indwelling intrathecal catheter. We treated a 47 year-old woman, with multiple drug allergies, who had complex regional pain syndrome II. She responded favorably to several single injections of intrathecal clonidine, had a successful trial with continuous intrathecal infusion of clonidine/morphine, and underwent implantation of a Medtronic 8617 pump and Model 8709 catheter. Approximately 2 weeks post-implant, she developed back and leg pain, numbness, and paresthesias throughout the distribution of the cauda equina. Evaluation revealed possible catheter migration into the subdural space. The catheter was revised and the daily dose of intrathecal clonidine/morphine was reduced with subsequent improvement of these symptoms. Several weeks later, she had the onset of progressively worsening back and leg pain and spasms (which became severe), cramping, numbness, and paresthesias in distribution of the cauda equina. Catheter studies, MRI, and CSF studies were normal. Drug infusion was discontinued with no improvement in symptoms. The infusion system was explanted due to concern about possible arachnoiditis induced by the silicone rubber catheter. We do not have proof of arachnoiditis in this case but the symptoms were classic for arachnoiditis, silicone rubber is known to produce an inflammatory reaction in some individuals, and we are not aware of any reports of arachnoiditis being associated with the infusion of either morphine or clonidine. There exists one other documented (not published) case in which a silicone rubber intrathecal catheter was felt to have induced arachnoiditis. This is a very rare occurrence but should be considered in the differential diagnosis of individuals with intrathecal infusion systems who develop symptoms of arachnoiditis.