Intractable cancer pain, as well as chronic intractable benign
pain, has been troublesome to the pain practitioner because of the
short life span of conventional nerve blocks. Neurolytic agents have
been in use since the turn of the 20th century for this particular
group of pain patients for prolonged pain relief.
Neurolysis encompasses interruption of painful pathways by placement
of a needle in the proximity of a nerve or plexus, either by injecting
destructive chemicals or creating nerve obliteration by cold (cryotherapy)
or heat energy (radiofrequency ablation).
This chapter focuses on the properties of the neurolytic agents
and their clinical applications; separate chapters are dedicated
to the other two techniques: cryotherapy and radiofrequency.
The first report of neurolysis was in 1863 by Luton, who injected
subcutaneous irritant substances into painful areas and found that
sciatic neuralgia was responsive to such therapy.1 Hartel reported
the first use of caustic agents on nerve roots to interrupt pain
fibers in 1914,2 and Doppler reported the use of
phenol to destroy nerve tissues in 1926.3 Putnam
and Hampton, in 1936, reported the first use of phenol as a neurolytic
agent for gasserian ganglion block.4 In 1931, Dogliotti
described the first use of alcohol for subarachnoid neurolysis to
achieve prolonged relief.5 The first use of phenol
for subarachnoid neurolysis was reported by Maher in 1955.6 Today,
ethyl alcohol and phenol are the most widely used compounds; yet
hypertonic saline, glycerol, ammonium salts, and chlorocresol have
also been used.
Proper selection of patients for neurolytic blocks is the key
to success of these potentially harmful procedures. After successful
diagnostic local anesthetic blocks, a neurolytic block can be considered
with reference to the cause and localization of the pain.7 If
the patient is too debilitated, or the logistics of a procedure
would not allow a trial local anesthetic block, diagnostic blocks
can be combined with a neurolytic agent at the practitioner’s
discretion. Clear communication of alternative techniques, outcomes,
complications, expectations, and disease progression with the patient
and the family is important prior to a neurolytic procedure.
A multidisciplinary approach, including an aggressive trial of
opioids and adjuvant medications, along with temporary nerve blocks
and psychological support are the mainstays of therapy.8 If
these measures result in inadequate pain control or excessive nausea,
sedation, or constipation, a neurolytic block should be strongly
A thorough medical examination, including laboratory testing
and imaging studies if appropriate, is necessary before performing
a neurolytic block. Active infection, tumor involvement of the needle
entry site, bleeding disorders, or concomitant anticoagulation therapy
may be relative contraindications.
Currently, nerve stimulation techniques are widely used with
all peripheral neurolytic blocks. Computed tomography (CT) or biplanar
fluoroscopic guidance is common for neuroaxial and sympathetic neurolytic
procedures. As in all invasive procedures, adherence to strict sterile
technique is mandatory. Cardiovascular monitoring during and ...