Texas Spine and Joint Hospital, Tyler, TX

Background: Subdural migration of epidural catheters is well known and documented. Subdural placement of intrathecal catheters has not been recognized. Twocases 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 monthsof 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) inthe cephalad portion of the thoracic spine. Over time, the tip became covered withtissue, 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 atT12-L1. At the time of surgical revision, the catheter was pulled back to L2. Repeatimaging showed it to be entirely subarachnoid, and analgesia was restored.Conclusions: These cases differ from others in the literature because the catheterwas apparently subdural at the time of initial implantation. As these 2 cases demonstrate, this placement may manifest immediately, but it may remain undetected for aprolonged period. Initial subdural placement should be considered along with catheter migration into the subdural space in the differential of a malfunctioning pump.Key words: intrathecal catheter, subdural, migration