Chapter 77: Neurolytic Blocks

INTRODUCTION

Dogliotti¹ first described the technique of subarachnoid chemical neurolysis using alcohol for the treatment of sciatic pain more than 80 years ago. That same year, Suvansa² described intrathecal carbolic acid for the treatment of tetanus. A quarter of a century later, Maher^3,4 in his 2 landmark articles described his experience with hyperbaric phenol and silver nitrate for subarachnoid neurolysis, stating, “It is easier to lay a carpet than to paper a ceiling,” an obvious reference to his understanding of the baricity properties of alcohol and phenol (carbolic acid). Over the ensuing years, however, lack of experience with either technique and fear of the anticipated complications resulted in underuse of this neurolysis, especially when applied to the subarachnoid space. Better understanding and increased use of neuraxial opiates for cancer pain since the 1980s have decreased the use of subarachnoid chemical neurolysis even further. Nonetheless, because of the physical separation of the sensory and motor roots of spinal nerves within the spinal canal, intrathecal dorsal rhizotomy (more appropriately called rhizolysis) is the only neurolytic procedure that allows sensory block without concomitant motor block. Because of this and because of the relative precision with which the affected nerve roots can be blocked, the technique is particularly useful for treating cancer pain in an extremity, where preservation of motor function is so important. In short, the physical separation of motor and sensory fibers in the subarachnoid space preserves forever a small but unique role for subarachnoid neurolysis in the management of cancer pain in carefully selected patients. The present chapter will describe the techniques of:

• Trigeminal neurolysis

• Lumbar sympathetic (LSNB)

• Celiac plexus (CPB) neurolysis

• Ganglion impar and superior hypogastric plexus neurolysis

• Sacroiliac joint (SIJ) neurolysis

• Spinal and epidural including transforaminal neurolysis

INDICATIONS

Neurolysis may be used to manage recalcitrant pain syndromes of both a malignant as well as benign etiology. Techniques have been described for blocking different types of pain:

• Pain from the cranial nerves (particularly the trigeminal nerve; CN V)

• Pain originating in the major plexuses (brachial and lumbar)

• Pain associated with sympathetic-medially pain (especially the celiac plexus, lumbar sympathetic ganglia, ganglion impar, and superior hypogastric plexus)

• Pain originating in the periphery (sacroiliac joints)

Before considering the use of chemical or thermal neurolysis, however, it behooves the clinician to ascertain that every alternative means of providing analgesia has been investigated with the patient. By virtue of their irretrievable nature, chemical neurolytics are exceedingly unforgiving when placed in contact with nonintended, nontargeted tissues. For these reasons, a caveat to the successful use of neurolytic blocks is a predetermined analgesic response, which is unequivocal following a local anesthetic block of the same targeted structure(s).

AGENTS

• In general, absolute alcohol or phenol may be selected for chemical neurolysis.

• Alcohol has been the drug of choice for ...