Chapter 50 Ablative Neurosurgical Techniques in the Treatment of Chronic Pain: Overview Timothy R. Steel and Kim J. Burchiel Conservative nonsurgical treatment, including rehabilita- clude neuroma pain, postrhizotomy pain, anesthesia do- tion therapy, is the mainstay of the treatment of most pa- lorosa, postherpetic neuralgia, sympathetically maintained tients with chronic pain, whereas neuroablative surgery is pain, complex regional pain syndrome (CRPS) I and II, pain indicated only in a minority. It is the selection of the patients following brachial plexus avulsion, spinal cord injury pain, who will benefit from ablative procedures that is critical. and the thalamic pain syndrome. The pain often is described Appropriate management of patients with chronic pain re- as burning or crushing. Shocklike exacerbations occur and quires a combined approach between pain specialists, reha- may be spontaneous in most deafferentation syndromes but bilitation teams, and, when necessary, neurosurgeons. Some also may be triggered by cutaneous stimulation, as seen with patients will not be candidates for surgery at any time, causalgia or sympathetically maintained pains. Neuropathic whereas others may become candidates after maximal con- pain is incapacitating and is usually refractory to all conserv- servative therapies have been exhausted. ative measures. Narcotic analgesics characteristically provide The exact time course for pain to be classified as chronic is only minimal relief. Anesthetic blockade proximal to the le- a matter more of convention than of science. Chronic pain sion may relieve deafferentation pain temporarily; however, has been described as that which persists beyond 1 month neuroablative procedures rarely provide lasting relief and after the normal course of an acute illness or after a reason- may cause an even more widespread deafferentation pain able time for an injury to have healed.1 The International As- state. In selected conditions, good results can be achieved by sociation for the Study of Pain stated that chronic pain is destructive procedures. The poor results of sensory pathway any pain that persists beyond the “normal time of healing.”2 ablation suggest that structures other than the spinothalamic Bonica suggested that 3 months is the best time of separa- tract and somatosensory relay nuclei of the thalamus are in- tion between acute and chronic pain.1 Because long-standing volved in the pathogenesis of deafferentation pain. pain experienced by patients with cancer or other chronic Although surgical ablative procedures can be effective in disease states becomes an illness in itself, the pain syndrome the management of chronic pain, they often are discarded as warrants treatment as a specific disorder on its own, no mat- a treatment option by many physicians because historically ter what the time constraints. these procedures are associated with a relatively high com- Chronic pain can be divided broadly into two kinds: no- plication rate. These complications include the development ciceptive pain and neuropathic (deafferentation) pain. Noci- of new deficits as a result of the ablative procedure and mor- ceptive pain results from stimuli that damage or severely bidity associated with operative procedures on high-risk pa- deform tissue and cause the conscious experience of pain. tients, such as those with end-stage cancer. In patients un- Trauma, inflammation, visceral distention, and neoplastic dergoing ablative surgery for benign pain syndromes, the infiltration all cause nociceptive pain. Narcotic analgesics long-term difficulties with pain recurrence and the develop- generally provide relief for such patients, although the po- ment of deafferentation pain also have contributed to thera- tential for these patients to experience tolerance and habitu- peutic nihilism in this area. ation is high. Anesthetic blockade, somatic nerve or root sec- Over the last two decades, the administration of in- tion, and spinothalamic tract section typically will abolish traspinal and intraventricular morphine has both improved nociceptive pain. and simplified the management of pain from many malig- The distinguishing features of neuropathic pain are shared nant processes.3 Direct delivery of small doses of opiates to by many different chronic pain syndromes associated with spinal and ventricular cerebrospinal fluid (CSF) provides ef- peripheral or central nervous system (CNS) injury. These in- fective analgesia in most patients without the major side 633 Surgical Management of Pain. Burchiel. Thieme Medical Publishers, Inc., New York © 2002 634 SURGICAL PROCEDURES effects of sedation, nausea, or constipation. Reported com- tients who survive for longer periods (>6 months), tolerance plications are rare, with more than 90% of patients reporting may develop, requiring greater doses, which may cloud con- significant benefits until death or last follow-up.3 Drug de- sciousness and impair judgment.3 It is these patients who will livery systems of varied complexity and expense are avail- benefit most from neuroablative procedures.7 able. Few patients are truly too ill to undergo the minimally If the neurosurgeon can offer selective neurodestructive invasive surgery necessary for implantation. procedures with minimal or at least acceptable morbidity, This chapter first reviews the general principles of pa- and ideally no mortality, neurodestructive procedures can tient selection for neuroablative procedures and then fo- reliably improve the quality of life for these patients. In cuses on the procedures currently available. We shall dis- some cases, this means the patient can be narcotic free cuss which procedures are appropriate to consider in the for substantial periods of his or her remaining life. In cases management of specific pain syndromes and where in the of narcotic-resistant pain, limited destructive neurosurgical treatment paradigm they should be applied. For most con- procedures often can provide pain relief for the duration of ditions, ablative techniques still are considered second-line the patient’s life.3 The estimated length of survival of these therapy. Only in a minority of situations would an ablative patients is important in determining a treatment strategy. surgical procedure be considered the primary treatment. Loeser believes that patients with less than 3 months’ life expectancy should not be considered surgical candidates because of their higher risk of significant morbidity and GENERAL CONSIDERATIONS mortality.7 In general, patients with expected survival of more than 6 months constitute better candidates for surgical To consider a patient for an ablative procedure, conservative procedures. They typically have lower surgical risk, and the nonsurgical therapy must have been attempted, maximized, analgesia that is produced can markedly reduce or even and fully evaluated as to reasons for failure. Of course, eliminate dependence on narcotic analgesics.11 Patients with medical treatment must be individualized, but it generally cancer pain are also more likely to have good results from consists of a combination of analgesics, antidepressants, and ablative procedures because their pain derives from direct often anticonvulsants. Nonsurgical peripherally applied stimulation of pain receptors and is transmitted in pain neuroaugmentative and counterirritation techniques such pathways (i.e., nociceptive), which are eliminated by neu- as transcutaneous electrical nerve stimulation (TENS) and rodestructive procedures.7 These patients are also often un- acupuncture also may be of benefit,4–6 and these should be likely to survive long enough for the benefits of the proce- tried if indicated. For the purposes of this chapter, we shall dures to disappear or for new pain syndromes to develop. assume that best medical therapies have been instituted for Rehabilitation techniques can be of value in the manage- all conditions unless otherwise stated. ment of patients with cancer pain. TENS and acupuncture Neurosurgical options in the relief of chronic pain in- techniques have been used successfully for a variety of clude (1) the electrical stimulation of the brain, spinal cord, painful conditions associated with malignancy.12,13 Physical or peripheral nerves, (2) the implantation of devices to de- therapy with the use of joint manipulation, stretching exer- liver drugs to the CSF, and (3) the destruction or incision of cises, muscle strengthening, and massage can help control neural tissue.7 Many of the ablative neurosurgical options pain caused by contractures and other soft-tissue and joint for chronic pain treatment are depicted in Figure 50–1. complications due to inactivity.14,15 The application of heat and cold can also be used to treat various cancer pain Malignant Pain problems.12,14 Relaxation therapy also can be of benefit in improving pain control as well as general patient well- Pain is experienced by one third of cancer patients who re- being.13,14 By whatever means, the primary goal of treatment ceive active treatment and by three quarters of those with in such patients is to render them pain free for the duration advanced disease.8 Because cancer pain usually is associ- of their remaining life. Their restricted life span often makes ated with structural pathology, definitions of the extent of long-term rehabilitation planning unfeasible. Expecting pa- the disease and the nature of the specific underlying cause tients with malignant disease to attempt rigorous and ex- of the pain are essential in the assessment