Destructive interventions on the nervous system are a valuable method to obtain control of otherwise intractable pain. Before the relatively recent development of augmentative techniques, such as intrathecal drug delivery and electrical neurostimulation (both peripheral and central), these were the mainstay of neurosurgical pain treatment. Options exist for lesioning the nervous system at multiple levels, including the brain and brainstem, cranial nerves, spinal cord, and peripheral nerves. Although the rise of these newer therapies has pushed aside many ablative procedures, these are still valuable components of the neurosurgical armamentarium.
The interruption of peripheral or central nervous system (CNS) pathways carrying pain has always seemed the most direct and logical manner to solve the problem of medically intractable pain, whether benign or malignant in origin. The targets for these interventions include the peripheral nerves and ganglia, the ascending spinothalamic tract and central aspects of the spinal cord, and the trigeminothalamic tract. Supratentorial structures such as the thalamus and cingulate gyrus have also been destroyed in the quest for pain control. Unfortunately, the results of these interventions have not been as straightforward as the theories behind them use, again demonstrating that the physiology underlying the development and maintenance of chronic pain is more complex than we understand.
Several methods have been used to lesion the nervous system. The easiest is a simple mechanical interruption via avulsion, transaction, or resection of a peripheral nerve, a cranial nerve branch, a ganglion, or a segment of the spinal cord. Thermocoagulation or radiofrequency (RF) lesioning has been most often used in the CNS, including the creation of ganglionic, spinal cord, and intracerebral lesions. Cryoablation found some favor in the mid 20th century but is rarely used today. Other alternatives include laser, radiation, and focused ultrasound.
Patients selected for these procedures should have chronic pain that has failed to adequately respond to multiple other conservative nonsurgical treatments. These prior treatments should include rehabilitation, oral medications (anti-inflammatories, opioids, anticonvulsants, antidepressants), and injections. Given the advances in neurostimulation and intrathecal drug delivery, it is also reasonable to conduct a trial of these therapies before considering ablative procedures. This is true both for patients with pain from late stage malignancies (because of their higher medical risk in undergoing surgery) and those with pain from nonmalignant causes (because of the risk of permanent neurologic morbidity from the procedures).
It is just as important to carefully select the correct ablative procedure for the patient, considering both the etiology of the pain and its location within the nervous system, so as to maximize the chance of achieving pain relief. For instance, central neuropathic pain is not expected to respond well to a peripheral neurectomy or dorsal root ganglion lesion.
This chapter reviews the published experience with several neuroablative procedures, beginning with those that are still most commonly in use. Certain destructive procedures (e.g., trigeminal ...