Neurologic Sequelae of Intraspinal Drug Delivery Systems: Results of a Survey of American Implanters of Implantable Drug Delivery Systems

Implantable Drug Delivery Systems and Foreign Body Reaction: Traversing the Current Clinical Landscape

Precise delivery of therapeutics to the target structures is essential for treatment efficiency and safety. Drug administration via conventional routes requires overcoming multiple transport barriers to achieve and maintain the local drug concentration and commonly results in unwanted off-target effects. Patients’ compliance with the treatment schedule remains another challenge. Implantable drug delivery systems (IDDSs) provide a way to solve these problems. IDDSs are bioengineering devices surgically placed inside the patient’s tissues to avoid first-pass metabolism and reduce the systemic toxicity of the drug by eluting the therapeutic payload in the vicinity of the target tissues. IDDSs present an impressive example of successful translation of the research and engineering findings to the patient’s bedside. It is envisaged that the IDDS technologies will grow exponentially in the coming years. However, to pave the way for this progress, it is essential to learn lessons from the past and present of IDDSs clinical applications. The efficiency and safety of the drug-eluting implants depend on the interactions between the device and the hosting tissues. In this review, we address this need and analyze the clinical landscape of the FDA-approved IDDSs applications in the context of the foreign body reaction, a key aspect of implant–tissue integration.

The effects of long-term intraspinal infusion therapy with noncancer pain patients: evaluation of patient, significant-other, and clinic staff appraisals

Objective. This study examines, in a retrospective fashion, the effects of intraspinal infusion therapy, primarily using opioids, in the treatment of recalcitrant noncancer pain in a sample of 29 consecutive patients. Patients were, on average, 58 years of age having had one surgery, with a pain duration of 221 months. Mean follow-up duration was 31 months. Telephone interviews by a disinterested party were used to obtain follow-up data from patients and their significant others. In addition, clinic staff rated patient improvement. Results. The patients reported an average of 63.4% improvement in pain; 45.5% improvement in activity level; and a 53.8% improvement in "ease" of performing activities. Average pain level on a numerical rating scale decreased from 8.91/10 to 5.03/10. The number of patients reporting a pain level of 5/10 or less increased from 1/29 to 15/29. Patients generally reported long-term benefit to be equal to or greater than that realized during the intrathecal trial. Approximately 86% of patients reported a "good" or "excellent" outcome. Significant-other ratings of improvement correlated more highly with clinic staff than with patients. No statistically significant differences were observed when worker's compensation (WC) patients were compared with nonworker's compensation (NWC) patients. Nearly 50% of the patients reported some type of transient or persistent side effect, mostly related to the infused substance. No mechanical failure of the DAS system was observed. Conclusion. These results in part replicate those from previous studies examining the long-term effects of infusion therapy. Side effects remain fairly common and require continued attention. Their presence, however, did not appear to deter from the patient's overall sense of satisfaction. Acquiring information from significant others and clinic staff may be a useful adjunct in interpreting the overall outcome.

Intramedullary placement of intrathecal catheter. Report of a rare complication of intrathecal therapy

A rare complication of intrathecal drug therapy-inadvertent insertion of the intrathecal catheter into the matter of the spinal cord-is presented. The patient developed signs of progressive monoparesis immediately after implantation of an intrathecal drug delivery system. The underlying problem was diagnosed with computed tomographic (CT) myelography and magnetic resonance imaging. The symptoms resolved after the catheter was removed. The article discusses probable mechanism of the complication and possible ways of its prevention. The usefulness of CT myelography in determining the intrathecal catheter position relative to the spinal cord is emphasized.

Spinal cord compression secondary to intrathecal catheter-induced granuloma: a report of four cases

Objective: The management of nonmalignant pain by morphine pump implantation has become an effective and increasingly frequent strategy of care. We report a rare complication of intrathecal granuloma formation adjacent to the intrathecal catheter tip resulting in spinal cord compression in four patients undergoing intrathecal treatment for chronic pain.

Methods: Four patients presented with chronic back pain and lower extremity pain and weakness and were treated with morphine pump implantation (Fig 1). Each patient developed a mass at the level of the intrathecal catheter tip resulting in increased back pain and diminished neurological function. Following clinical examination and x-ray workup, the patients underwent surgical resection of the mass and removal of the intrathecal catheter. One patient received conservative saline therapy first, and another patient had granuloma resection first and removal of the intrathecal catheter at a later date. Pathological analysis showed granulation tissue with extensive necrosis and chronic inflammation, with negative culture results. No evidence of neoplasm was found.

Results: Patients showed varying degrees of improvement following removal of the intrathecal mass. Two patients had moderate pain reduction following resection of the granuloma; a third had minimal pain improvement; and a fourth had significant pain improvement but continued lower extremity weakness.

Conclusions: The formation of granulomas caused by intrathecal catheter implantation is a rare but serious complication. Imaging studies including magnetic resonance imaging with contrast and computed tomography with myelogram should be used to follow up a neurological examination consistent with spinal cord compression. Timely surgical intervention may result in marked improvement of symptoms.

Intrathecal catheter-tip inflammatory masses: an intraparenchymal granuloma

The authors report the case of a 54-year-old woman who presented with an intraparenchymal granuloma in her lower thoracic spinal cord. On imaging studies there was an intramedullary enhancement at the left dorsal aspect of the cord immediately adjacent to the tip of an intrathecal arachnoid catheter used for intraspinal drug therapy. At surgery, it was apparent that once this superficial component of the catheter and inflammatory mass was removed, there was a granulomatous component that extended into the spinal cord. A 5-mm caseating chalklike granuloma was carefully dissected away. To the authors' knowledge, this is the first reported case of an intrathecal catheter-tip granuloma growing inside the spinal cord parenchyma.

[Punctate midline myelotomy for the treatment of oncologic visceral pain: analysis of three cases]

INTRODUCTION

A new midline posterior column pathway related to visceral pain has been recently discovered.

OBJECTIVE

To present its interruption by a punctate midline myelotomy providing significant visceral oncologic pain relief.

METHOD

Three patients with abdominal cancer refractory pain from opiate analgesics were treated by a punctate midline myelotomy through thoracic laminectomy.

RESULTS

Complete pain control was achieved in two patients, one had no more narcotics and the other one had significant lowering of opiate intake doses. The third patient was intolerant to narcotics having 80% relieving pain. There were no postoperative neurological deficits.

CONCLUSION

The present report reaffirms the existence of a dorsal column midline pathway related to visceral pain in humans, and its interruption ameliorates abdominal pain due to cancer.

Programmable intrathecal opioid delivery systems for chronic noncancer pain: a systematic review of effectiveness and complications

OBJECTIVES

We conducted a systematic review of the literature on the effectiveness and complications of programmable intrathecal opioid and ziconotide drug delivery systems (IDDS) for patients with chronic noncancer pain.

METHODS

We searched MEDLINE, Cochrane, and other bibliographic databases to identify English-language journal articles reporting programmable IDDS complications or effects on pain or functioning. Additional study methodology criteria were applied for the effectiveness review. Two authors independently abstracted data from each included article.

RESULTS

Six articles met the inclusion criteria for the effectiveness and complications reviews, and 4 others met the criteria only for the complications review; none were randomized trials or of ziconotide. All 6 articles reviewed for effectiveness reported improvement in pain and functioning on average among patients who received a permanent IDDS. Two articles reported the proportion of patients with > or =50% improvement in pain at 6 months (38%, 56%) and 2 at longer follow-ups (30%, 44%). Intrathecal morphine-equivalent doses increased over time. The most commonly reported permanent IDDS drug side effects were nausea/vomiting (mean rate weighted by sample size=33%), urinary retention (24%), and pruritus (26%). Catheter problems were also reported commonly. Rare but serious complications included intrathecal catheter tip granulomas.

CONCLUSIONS

The studies reviewed found improvement in pain and functioning on average among patients with chronic noncancer pain who received permanent IDDS. However, their methodologic limitations preclude conclusions concerning the effectiveness of this technology long-term and as compared with other treatments. Drug side effects and hardware complications were common. Suggestions are made for methodologic improvements in future studies.

Neurologische Komplikationen und Wirkverlust unter intrathekaler Schmerztherapie

In a new guideline issued by the German Association for the Study of Pain, intrathecal opioid therapy is described as proven to be effective with relatively few side effects. We reviewed this statement by analysis of the available literature and critical evaluation of the clinical course in a few of our own patients (n=3). In these cases (as well as in a further eight patients), explantation and a switch to oral opioids led to distinctly better alleviation of pain and abatement of the unwanted effects. The problems we discuss do not appear to be rare instances, but by all means complications that are frequently described. The long-term efficacy of intrathecal opioids has not been adequately verified; moreover, their potency is not high. The frequency of undesired events is comparable to that of oral opioid medication, but serious neurological complications are possible. To avoid dose escalations and to recognize neurological complications in time, diligent monitoring by the surgeon or an experienced pain center is essential.

Inflammatory masses associated with intrathecal drug infusion: a review of preclinical evidence and human data

OBJECTIVES

The phenomenon of inflammatory masses at the tips of intrathecal drug administration catheters was the subject of a recent case-compilation report and a number of animal studies. We sought to synthesize current clinical and preclinical data to formulate hypotheses about the etiology of catheter-tip masses.

METHODS

We reviewed the published human clinical data, new unpublished clinical data, and the results of preclinical studies in two mammalian species, beagle dogs and sheep.

RESULTS

Intrathecal morphine sulfate studies in beagle dogs suggested that the observed inflammatory reaction was dose or concentration dependent. Masses occurred after 28 days in one of three animals at 1.5 mg/day (the lowest morphine dose tested); in two of three animals at 3 and 9 mg/day; and in three of three animals at 12 mg/day. The addition of various amounts of clonidine to 1.5 mg/day of morphine revealed no mass formation when the clonidine dose was>0.25 mg/day. A morphine sulfate study that was performed in sheep using a commercially marketed drug administration system found catheter tip masses in two of three animals that received 12 or 18 mg/day of morphine, the highest doses tested. Human cases have occurred only in pain patients who received intrathecal opioids, alone or mixed with other drugs, or in patients who received investigational agents (such as superoxide dismutase or the partial micro-opioid-receptor agonist, tramadol) that were not labeled for long-term intrathecal use.

DISCUSSION/CONCLUSIONS

The evidence suggests that the long-term administration of opioids, especially morphine, caused the masses that were observed in humans and in two species of animals. A relationship probably exists between mass formation and intrathecal morphine doses or concentration. Other factors remain to be investigated.

Intrathecal opioid treatment for chronic non-malignant pain: a 3-year prospective study

Intrathecal (IT) opioid therapy is a treatment alternative for patients with severe chronic non-malignant pain. Several uncontrolled retrospective and prospective outcome studies have suggested a benefit in chronic non-malignant pain patients, but uncertainties about patient selection in these studies weaken the results. This study evaluated long-term outcome of IT opioid therapy in chronic non-malignant pain prospectively, and included two comparative groups to improve understanding of selection criteria and relative severity of intrathecal pump recipients (PRs). The study subjects included 38 PRs while the comparative groups included 31 intrathecal candidates who either had an unsuccessful trial, or declined the IT therapy, and another group of 41 newly referred patients. The following data were analyzed at study entry, and at 6 monthly intervals for a 3-year period: Symptom Check List 90 (SLC-90), SF-36 Health survey, Beck Depression Inventory, McGill Pain Questionnaire (short form), Oswestry Disability Index, Pain Drawings and Pain rating on visual analogue scale. Data analysis suggests the study group of PRs had improvements in pain, mood, and function from baseline to 36 months. These same parameters improved among new referrals (less severe patients receiving conservative pain management) while non-recipients significantly worsened. Although PRs improved, they were still worse off at 36 months than new referrals were at baseline. The study showed that when patients with extremely severe pain problems are selected as pump candidates, they will likely improve with the therapy, but their overall severity of pain and symptoms still remains high.

Spinal cord lesion after long-term intrathecal clonidine and bupivacaine treatment for the management of intractable pain

Long-term intrathecal drug administration using implanted pumps is increasingly used in the treatment of chronic refractory pain [Anderson and Burchiel 1999, Neurosurgery 44 (1999) 289; Krames 2002, Best Pract Res Clin Anaesthesiol 16 (2002) 619; Wallace 2002, Neurology 59 (2002) S18]. Extensive clinical experience over the last 15 years suggests that in selected cases the technique is safe, although infections, system malfunction and drug-related complications have been reported. In most cases, drug-related spinal cord injuries have resulted from the compression of a spinal inflammatory mass or abcess rather than from a direct neurotoxic effect. We report on a case of toxic spinal cord lesion occurring after more than 3 years of uneventful continuous infusion of a mixture of bupivacaine and clonidine.

Catheter-associated masses in patients receiving intrathecal analgesic therapy

A cohort of seven patients receiving intrathecal analgesic drug therapy for chronic intractable pain underwent radiocontrast myelography and computed tomography (CT) scanning to screen for catheter-associated intrathecal masses. Three of seven patients examined had intraspinal masses associated with the tip of the drug infusion catheter after a total of 118 mo of therapy. The index case presented with exacerbation of neuropathic pain and paralysis of the left lower extremity. The two additional cases detected by CT myelography were asymptomatic at the time the catheter-associated mass was assessed. The mean duration of therapy before diagnosis of the catheter-associated mass was 19.6 mo, with a range of 16-25 mo. An intergroup comparison of demographic and treatment variables between patients, with and without catheter-associated masses, demonstrated that patients with masses were younger and were receiving a larger morphine dose than patients without masses. The differences were statistically significant (P = 0.05). In one patient with an asymptomatic catheter-associated intrathecal mass, regression of the mass was observed after cessation of therapy. In a second asymptomatic patient, the mass remained stable over 1 yr of continued treatment after substitution of hydromorphone for morphine without interruption of therapy. Neither asymptomatic patient has subsequently developed additional neurologic findings or injury after detection of occult catheter-associated intrathecal masses and clinical intervention. We suggest that all patients receiving long-term intrathecal analgesia should undergo periodic radiographic surveillance to further define their risk of developing occult catheter-associated masses and to allow intervention before neurologic injury can develop.

IMPLICATIONS

Catheter-associated intrathecal masses were detected in three of seven patients receiving long-term intrathecal analgesia. In the two asymptomatic patients, timely clinical intervention was associated with the avoidance of subsequent neurologic injury and spontaneous resolution of one of the occult masses.

Epidural and intrathecal analgesia for cancer pain

The three-step analgesic ladder approach developed by the World Health Organization works well in treating the vast majority (70-90%) of patients suffering from pain related to cancer. In those patients who do not get pain relief by this three-step approach, intraspinal agents can be a fourth step in managing pain of malignant origin. Although morphine is the only opioid approved by the US Food and Drug Administration for intraspinal use, many different opioid analgesics are used intraspinally, including hydromorphone, fentanyl, sufentanil, meperidine and methadone in the treatment of cancer pain. Many non-opioid agents have also been used intraspinally either alone or in combination with opioids in the treatment of intractable cancer pain. This chapter summarizes the clinical use of these agents with some practical points.

Management of Intrathecal Catheter-Tip Inflammatory Masses: A Consensus Statement

OBJECTIVES

In a companion article, we synthesized current clinical and preclinical data to formulate hypotheses about the etiology of drug administration catheter-tip inflammatory masses. In this article, we communicate our recommendations for the detection, treatment, mitigation, and prevention of such masses.

METHODS

We reviewed published and unpublished case reports and our own experiences to find methods to diagnose and treat catheter-tip inflammatory masses in a manner that minimized adverse neurological sequelae. We also formulated hypotheses about theoretical ways to mitigate, and possibly, prevent the formation of such masses.

RESULTS

Human cases have occurred only in patients with chronic pain who received intrathecal opioid drugs, alone or mixed with other drugs, or in patients who received agents that were not labeled for long-term intrathecal use. Most patients had noncancer pain owing to their large representation among the population with implanted pumps. Such patients also had a longer life expectancy and exposure to intrathecal drugs, and they received higher daily doses than patients with cancer pain. Clues to diagnosis included the loss of analgesic drug effects accompanied by new, gradually progressive neurological symptoms and signs. When a mass was diagnosed before it filled the spinal canal or before it caused severe neurological symptoms, open surgery to remove the mass often was not required. Anecdotal reports and the authors' experiences suggest that cessation of drug administration through the affected catheter was followed by shrinkage or disappearance of the mass over a period of 2-5 months.

CONCLUSIONS

Attentive follow-up and maintenance of an index of suspicion should permit timely diagnosis, minimally invasive treatment, and avoidance of neurological injury from catheter-tip inflammatory masses. Whenever it is feasible, positioning the catheter in the lumbar thecal sac and/or keeping the daily intrathecal opioid dose as low as possible for as long possible may mitigate the seriousness, and perhaps, reduce the incidence of such inflammatory masses.

Implantable devices for pain control: spinal cord stimulation and intrathecal therapies

Untreated chronic pain is costly to society and to the individual suffering from it. The treatment of chronic pain, a multidimensional disease, should rely on the expertise of varying health care providers and should focus not only on the neurobiological mechanisms of the process but also on the psychosocial aspects of the disease. Implantable devices are costly and invasive, and such efficacious therapies should be used only when more conservative and less costly therapies have failed to provide relief of pain and suffering. Spinal cord stimulation provides neuromodulation of neuropathic, but not nociceptive, pain signals and when used for appropriate indications in the right individuals provides approximately 60-80% long-term pain relief in 60-80% of patients trialled for efficacy. Intrathecal therapies with opioids such as morphine, fentanyl, sufentanil or meperidine--or non-opioids such as clonidine or bupivacaine--provide analgesia in patients with nociceptive or neuropathic pain syndromes. Baclofen, intrathecally, provides profound relief of muscle spasticity due to multiple sclerosis, spinal cord injuries, brain injuries or cerebral palsy.

Outcome of intrathecal opioids in chronic non-cancer pain

Eighty-eight patients (58 women and 30 men; mean age 53.4 years) with chronic non-cancer pain present on average for 9.8 years were evaluated following treatment with intrathecal opioids for an average duration of 36.2 months. Outcome measures were global pain relief, physical activity levels, medication consumption, work status, intrathecal opioid side-effects, proportion of patients who ceased therapy and patient satisfaction. The most common diagnosis in this group was lumbar spinal or radicular pain after failed spinal surgery (n= 55, 63%). At the time of follow-up, mean pain relief was 60% with 74% of patients (36 of 49) reporting increased activity levels. Oral medication intake was significantly reduced (Medication Quantification Scale Score prior to implantation 31.0+/-2.6 and at follow-up 12.7+/-1.4; n= 48; p< 0.0001). These gains were not accompanied by a change in work status (43 of 50 working age patients not working at follow-up). There were frequent reports of opioid side-effects, including sexual dysfunction and menstrual disturbance. Technical complications occurred with the drug administration device, most often catheter related, requiring at least one further surgical procedure in 32 patients (40%). Patient satisfaction with intrathecal opioids was high, with 45 of 51 (88%) reporting satisfaction. Mean intrathecal morphine dose increased from 9.95+/-1.49 mg/day (mean+/-SEM) at 6 months to 15.26+/-2.52 mg/day 36 months after initiation of therapy. Drug administration systems were permanently removed in five patients (6%). Intrathecal opioid therapy appears to have a place in the management of chronic non-cancer pain. Therapy does not seem to be significantly inhibited by the development of tolerance.

Inflammatory mass lesions associated with intrathecal drug infusion catheters: report and observations on 41 patients

OBJECTIVE

Several reports have described inflammatory mass lesions at the tip of intraspinal drug administration catheters. We evaluated the number of patients reported with this condition and whether data support hypotheses that have been put forth regarding the cause of these lesions.

METHODS

Information that was reported in the medical literature, and by Medtronic, Inc., to the United States Food and Drug Administration as of November 30, 2000, was reviewed.

RESULTS

Forty-one cases were identified, including 16 from the literature and 25 that were not published previously in the literature. Because of voluntary reporting and other methodological limitations, the actual number of cases must be higher than reported. All of the patients had chronic pain. The mean duration of therapy was 24.5 months. Most masses were located in the thoracic region. Intrathecal drugs included morphine or hydromorphone, either alone or mixed with other drugs, in 39 of 41 cases. No masses were reported in patients who received baclofen as the only intrathecal medication. Thirty patients underwent surgery to relieve spinal cord or cauda equina compression. Eleven patients were nonambulatory at last follow-up, and one died of a pulmonary embolus. Surgical specimens revealed noninfectious chronic inflammation, granuloma formation, and fibrosis or necrosis.

DISCUSSION

The most plausible hypothesis with regard to the cause of intrathecal catheter tip mass lesions implicates the administration of relatively high-concentration or high-dose opiate drugs or the use of drugs and admixtures that are not labeled for intrathecal use.

CONCLUSION

Patients who require high-dose intraspinal opioid therapy and those who receive drugs or admixtures that are not approved for intrathecal use should be monitored closely for signs of an extra-axial mass or catheter malfunction. Prompt diagnosis and treatment may preserve neurological function.