Controlled thermocoagulation of trigeminal ganglion and rootlets for differential destruction of pain fibers

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Abstract
✓ The authors report their experience in the treatment of trigeminal neuralgia with controlled increments of radiofrequency heating from an electrode placed in the Gasserian ganglion or its posterior rootlets. Touch is preserved in some or all of a trigeminal zone rendered analgesic. The electrode tip is introduced through the foramen ovale and placed among the desired rootlets with the help of a combination of radiographs and the conscious patient's response to electrical stimulation with a square wave signal and gentle electrical heating. The degree of heat is measured by a thermister at the electrode tip. The patient's cooperation is maintained by the use of the neurolept anesthetic Innovar and the production of brief unconsciousness for the painful parts of the operation by methohexital (Brevital). Of 274 patients with facial pain so treated, 214 had trigeminal neuralgia; 91% of the latter group experienced relief of pain and 125 followed for 2½ to 6 years had a recurrence rate of 22%. In a total of 353 procedures, there has been no mortality and no neurological morbidity outside the trigeminal nerve. Only six of the patients with trigeminal neuralgia have complained significantly of postoperative paresthesias. The most serious undesired result has been the production of an anesthetic cornea in 28 patients, one of whom lost the sight of one eye due to corneal scarring. Correlating findings in our patients with those in studies by other authors, we conclude that the preservation of some touch is due to resistance to heating by the heavily myelinated A-beta fibers.