Anil K. Sharma, MD
Spine and Pain Centers of NJ and NY
Nervous System Lesioning
Cryogenic lesioning relies upon cooling the tip of the probe to an extremely low temperature to freeze a region of tissue around the tip. These probes are larger in diameter and
the relief offered usually shorter in duration than with other modalities.
Ultrasound energy has been used since the 1950s for lesioning in the brain. It is difficult
to control the size of the lesion and also difficult to monitor the temperature.
Injection of alcohol, phenol or a glycerol has been used to destroy peripheral nerves.
The inability to control the flow of the injected material results in variably sized, irregular lesions. Moreover, this modality confers a significant chance of neuroma (neuritis)
Lasers have also been used to make lesions in the nervous system. Limitations of the
modality include difficulties in monitoring tissue temperature and controlling the extent
and rapidity of tissue destruction.
Radiofrequency lesioning has been used since the 1950s, initially using continuous radiofrequency energy in the 1 megahertz range. 1, 2 The radiofrequency generator is connected
to a needle electrode placed in the body. The current flows between the tissues. The active electrode generates heat, lesioning the target issue. The other electrode is simply a
grounding pad. The mechanism of tissue heating is primarily ionic. 3 The radiofrequency
voltage at the tip of the needle sets up electric fields in the space around the needle and the
heat is generated. The needle itself does not actually heat up. The tip has a temperature
sensor. The equilibrium is usually reached in about 60 seconds. The size of the lesion
depends on the length and diameter of the electrode tip and the temperature generated.
In radiofrequency denervation a Teflon-coated electrode with an exposed tip is inserted
close to a nerve. When a high frequency electric current is applied, it concentrates on the
exposed tip and heating and coagulating the immediate surrounding tissues.
Indications of Radiofrequency Denervation
Zygapophysial (facet) joints have been implicated as a source of chronic pain in 15% to
45% of patients with chronic low back pain. 4-11 Radiofrequency denervation is indicated
in the treatment of facet joint mediated back and neck pain. While physical examination
and imaging may suggest the facets joints as a possible pain generator, evidence suggest
their clinical specificity is quite low (is this ok?). The diagnosis of zygoaphophysial joint
pain can be further assessed with either by intra-articular injections or by anesthetizing the
medial branches of the dorsal rami that innervate them. Usually two sets of diagnostic
injections are done, and these should be medial branch blocks. Local anesthetics with
a different duration of action can be utilized. After each diagnostic injection, the patient