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Pain


Intrathecal Drug Delivery for Neuropathic Pain David E Jamison, MD,1


Indy M Wilkinson, MD2


and Steven P Cohen, MD3


1. Assistant Professor, Uniformed Services University of the Health Sciences and Walter Reed National Military Medical Center; 2. Resident in Anesthesiology, National Capital Consortium; 3. Professor of Anesthesiology, Uniformed Services University of the Health Sciences, and Associate Professor, Johns Hopkins School of Medicine


Abstract


Neuropathic pain represents a substantial burden on society. The treatment of neuropathic pain is challenging and typically involves multiple medication classes such as anticonvulsants, antidepressants, and opioids. The advent of intrathecal medication delivery in the late 1970s provided an additional option for the treatment of refractory neuropathic pain. This article presents a review of the evidence regarding intrathecal medications for neuropathic pain. There is strong evidence to support the use of intrathecal opioids in malignant pain of mixed characteristics, and moderate evidence for their use in non-malignant, neuropathic pain. The use of baclofen is strongly supported for spasticity, but there is only intermediate-level evidence for its use in neuropathic pain. With respect to clonidine and ziconotide, there is moderate evidence to support their use for neuropathic pain, although the effectiveness of the latter agent is limited by the high incidence of adverse effects. For steroids, there is weak evidence in favor of its use in neuropathic pain, predominantly in combination with opioids. The evidence is moderate to strong for the use of steroids in post-herpetic neuralgia, which must be weighed against the possibility of neurotoxicity if depot steroids are injected.


Keywords


Intrathecal, neuropathic pain, spinal analgesia, ziconotide, baclofen, morphine, clonidine, methylprednisolone, post-herpetic neuralgia, failed back surgery syndrome


Disclosure: The authors have no conflicts of interest to declare. Acknowledgment: The opinions or assertions contained herein are the private views of the authors and are not to be construed as official or as reflecting the views of the Department of the Army or the Department of Defense. Received: October 28, 2011 Accepted: November 7, 2011 Citation: US Neurology, 2011;7(2):154–62 Correspondence: Steven P Cohen, MD, 550 North Broadway, Suite 301, Baltimore, MD 21029. E: scohen40@jhmi.edu


Neuropathic pain may arise from a variety of causes involving either the central or peripheral nervous system, and is typically challenging to treat. The annual incidence of neuropathic pain is estimated to be 1 %, with the burden likely to increase as the population ages.1


When


traditional mainstays of treatment fail to provide relief, more advanced interventions such as neuromodulation and intrathecal therapy may result in symptom palliation.


The practice of introducing medication into the intrathecal space can be traced to the accidental spinal anesthetic performed by the neurologist J Leonard Corning in 1885.2


the spinal fluid for analgesia as well as anesthesia. This presumption was borne out in animal models and eventually human cancer patients. Early intrathecal analgesia focused on the use of opioids for the treatment of cancer pain, but this soon evolved to include treatment for non-malignant pain and spasticity. In addition to opioids, medications that can be injected into the subarachnoid space to provide analgesia include alpha-2 adrenergic agonists, calcium channel blockers, gamma-aminobutyric acid agonists, local anesthetics, and corticosteroids.


Corning’s intention was to inject


cocaine solution onto a dog’s lumbar nerve roots, but the needle inadvertently pierced the dura with resultant lower-extremity paresis. He subsequently applied this technique in the treatment of neurologic disorders in humans. The first use of spinal anesthesia was in 1899 by Augustus Bier after he and his assistant took turns performing spinals on each other.3


Shortly thereafter, Bier reported a series of six lower-extremity surgeries performed under spinal anesthesia.4


The discovery of opioid receptors in the central nervous system in the early 1970s led to the proposal that medications could be introduced into


154


• • •


The decision to proceed with intrathecal therapy is based on a number of criteria:


• • • •


chronic pain condition refractory to more conservative therapy; no medical contraindication to implantation surgery; no psychological or sociological contraindication to surgery;


constant or near-constant pain requiring around-the-clock medication administration;


no tumor encroachment on the thecal sac; life expectancy greater than three months;


no practical issues that might interfere with pump placement, refill, or maintenance (morbid obesity or cachexia, impending move from


© TOUCH BRIEFINGS 2011


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