Inhibition by transcutaneous electrical stimulation of noxious heat elicited in human Gasserian ganglion.

During percutaneous thermocoagulation of the Gasserian ganglion for trigeminal pain, the pain perception threshold was established in a series of 25 awake patients by measuring the temperature at the electrode tip within the ganglion during slow increase of the radiofrequency current. Between 42 and 48 degress C pain perception was regularly reported by the patients. A cutaneous-stimulating system was then applied to the trigeminal area which was reported to be painful during the heating. The external stimulation attempted to preferentially stimulate the A afferent nerve fibres. When external stimulation was applied during the heating of the Gasserian ganglion, the pain perception threshold was enhanced in about half of the cases. A transcutaneous electrical stimulation of part of the body not related with the investigated pain sensation did not produce the same inhibitory action in 3 out of 5 cases.