Technology, Computing, and Simulation: Pain Medicine: Case Report
Intrathecal catheters may be placed to provide pain relief for intractable conditions unresponsive to conservative measures. Most of the available literature regarding outcomes of implanted catheter/pump systems is in the form of case reports or case series. Pain after spinal cord injury is often resistant to treatment (1). Known complications of spinal intrathecal catheter placement include infection, misplacement in associated areas (subdural, epidural), spinal cord or nerve injury, dural cerebrospinal fluid (CSF) leak, and spinal hematoma (2). Percutaneous and open procedures via laminectomy may be used depending on patient-associated factors or surgeon preference.
The performance of regional anesthetic techniques involving catheter introduction can be associated with neurological complications and may be more likely in anesthetized or insensate patients (3). Because of the extensive dissection required, many procedures for implantation of intrathecal catheter/pump systems are performed under general anesthesia, with monitored anesthesia care during catheter placement and general anesthesia during implantation. Patient ability to report the occurrence of a paraesthesia during catheter placement has been advocated to avoid neurological injury (4). Paretic patients, however, often receive spinal anesthetics below the level of their lesion for procedures, in part to prevent autonomic dysreflexia. There have been no case reports of spinal cord intraparenchymal catheter placements occurring during direct laminectomy placements.
A 45-yr-old man who sustained a T11/T12 burst fracture in 1977 when he was thrown from a pickup bed was diagnosed with a complete T12 motor and incomplete T10 sensory spinal cord injury with dysesthetic pain and burning in the legs. His spine was stabilized with Harrington rod fixation, which was subsequently removed. Multiple oral medication trials of opioids and adjuvant drugs for the management of neuropathic pain provided minimal relief. In 2000, the patient was evaluated for an intrathecal, opiate pump implant and had a “successful” epidural trial with morphine from which the patient had a significant (>50%) reduction in his pain. After a failed percutaneous attempt, an open procedure was performed under general anesthesia to ensure proper catheter placement. The T9/T10 level was selected for catheter placement. The dura was identified, incised, and elevated. A styletted catheter was advanced about 7 cm, and good CSF flow was reported from the distal catheter tip. The case was completed without complication.
At presentation to our clinic 18 months later, the patient complained of severe left-thoracic, abdominal, and flank pain with continued dysesthetic leg pain that had been present since the second intrathecal catheter/pump implant. The left-sided thoracic pain had become intolerable despite advances in both oral adjuvants and large increases in his intrathecal infusion. He was receiving 24 mg of hydromorphone (50 mg/mL) and bupivacaine 0.75% per day for a daily volume of 0.48 mL per day via his intrathecal pump. Despite this new pain in the thoracic area, there was no discussion of repeat imaging such as a magnetic resonance image (MRI) mentioned in the postoperative medical records. Physical examination was consistent with previous examinations except now the left T6-T12 dermatomal areas were hypersensitive and allodynic.
A new MRI demonstrated anterior wedging of T12 with obliteration of the central spinal canal. At T7/T8, there was extensive hemosiderin surrounding a catheter intrinsic to the spinal cord with lower thoracic cystic myelomalacia (Figs. 1 and 2). The intraspinal infusion was gradually reduced over 4 wk. At return for surgery 4 wk later, the patient’s left flank pain had resolved, but surgery was still advised because of the continuing risk of cord injury. The catheter was easily removed without incision of the spinal cord or complication. The patient was released to his home pain physician on oral opiates.
Implanted pump/catheter techniques have been available for more than two decades. The discovery of new problems, including catheter granuloma formation (5) has cast greater scrutiny on these procedures for patients with chronic benign pain. Catheter granuloma formation seems to be unpredictable, but is more often associated with large opioid concentrations (6). There have been no case reports of catheter migration into the spinal cord from a subarachnoid site. The initial placement may have been into the spinal cord parenchyma in this case. Without a documented syringomyelia, along with an initial report of good CSF flow, intraparenchymal placement seems unusual. However, because the patient reported this new pain immediately after the procedure, we believe the initial catheter placement was in the cord. The patient may have perceived a paresthesia had he been conscious during the initial catheter placement at T7.
The decrease of the patient’s thoracic pain as the pump flow was decreased suggests that a pressure/volume effect may have induced his pain symptoms. When pain is unresponsive to increases in medication, this effect should be considered.
Patients with postspinal cord injury pain are difficult to treat, and often present with unexplainable complaints. The thoracic spinal canal is technically challenging, given the combination of a narrow spinal canal and a critical vascular supply (7) A prompt MRI with standard precautions should be strongly encouraged to aid in the diagnosis when unexplained symptoms occur in these patients (5). Patient condition and prognosis should have a role in selection of implanted infusion devices. Consideration of performing staged procedures wherein catheters may be placed while patients are awake may help prevent complications.
In summary, we present a case of a paraplegic man receiving intrathecal infusion for intractable pain found to have his catheter within the spinal cord. Pain relief was obtained with cessation of infusion, yet surgical removal was recommended to minimize the risk of future injury to the spinal cord. Increased vigilance is warranted when caring for these patients.
1. Turner JA, Cardenas DD, Warms CA, McClellan CB. Chronic pain associated with spinal cord injuries: a community survey. Arch Phys Med Rehabil 2001;82:501–9.
2. Ben-David B. Complications of neuraxial blockade. Anesthesiol Clin North America 2002;20:669–93.
3. Bromage PR, Benumof JL. Paraplegia following intra-cord injection during attempted epidural anesthesia under general anesthesia [see comment]. Reg Anesth Pain Med 1998;23:104–7.
4. Krane EJ, Dalens BJ, Murat J, Murrell D. The safety of epidurals placed during general anesthesia [see comment]. Reg Anesth Pain Med 1998;23:433–8.
5. Hassenbusch S, Burchiel K, Coffey RJ, et al. Management of intrathecal catheter-tip inflammatory masses: a consensus statement. Pain Med 2002;3:313–3.
6. Yaksh TL, Hassenbusch S, Burchiel K, et al. Inflammatory masses associated with intrathecal drug infusion: a review of preclinical evidence and human data. Pain Med 2002;3:300–12.
© 2004 International Anesthesia Research Society
7. Panjabi MM, Takata K, Goel V, et al. Thoracic human vertebrae: quantitative three-dimensional anatomy. Spine 1991;16:888–901.