Subdural intrathecal catheter placement: experience with two cases.

BACKGROUND Subdural migration of epidural catheters is well known and documented. Subdural placement of intrathecal catheters has not been recognized. Two cases of sudural placement of intrathecal catheters are presented. OBJECTIVE The possibility of subdural migration of epidural catheters and its manifestations has been well documented. The following 2 cases demonstrate that intrathecal catheters can enter the subdural space upon placement. CASE REPORTS The first case is a 52-year-old male with multiple sclerosis receiving a pump for intrathecal baclofen. It worked well for 10 years, but after 2 months of inadequate relief despite a 2-fold increase in baclofen, the catheter was imaged. The catheter pierced the arachnoid in the lower thoracic spine and tunneled subdural. It then pierced the arachnoid again, re-entering the cerebrospinal fluid (CSF) in the cephalad portion of the thoracic spine. Over time, the tip became covered with tissue, preventing direct CSF communication and causing subdural drug sequestration. The second case is a 54-year-old male with chronic bilateral lower extremity pain having a pump placed for pain control. Because of inadequate relief after implantation, the catheter was imaged. It pierced the arachnoid at L4-L5 but became subdural at T12-L1. At the time of surgical revision, the catheter was pulled back to L2. Repeat imaging showed it to be entirely subarachnoid, and analgesia was restored. CONCLUSIONS These cases differ from others in the literature because the catheter was apparently subdural at the time of initial implantation. As these 2 cases demonstrate, this placement may manifest immediately, but it may remain undetected for a prolonged period. Initial subdural placement should be considered along with catheter migration into the subdural space in the differential of a malfunctioning pump.