[Pre- and postoperative quantitative measures of facial sensitivity in tic douloureux]

Electrical stimulation was used for quantitative assessment of facial sensibility before, during and after percutaneous electrocoagulation of the Gasserian ganglion in 19 patients with tic douloureux. A portable stimulator was of a constant current type, which generated rectangular monophasic pulses of 0,2 ms in length and 100 Hz in frequency. The bipolar electrode consisted of saline-soaked felt discs with a surface of 1 cm2 and an interpolar distance of 1 cm. The thresholds for perception and pain were measured over six regions of each side of the face. Additionally, maximal pain tolerance was measured in the painful area and its corresponding healthy area. Shortlasting intravenous anesthesia with Brietal was given before each electrocoagulation. As soon as the patient began to react to speech, the threshold for pain was measured in the painful and the corresponding healthy area. Preoperatively, the measurements showed that the average threshold for perception was 2,5 mA and for pain 3,5 mA. The average maximal pain tolerance was 10,8 mA. There were no differences between the painful and the healthy sides. Electrocoagulations were stopped when the thresholds for pain in the trigger area had become twice as high as that on the contralateral side. The postoperative measurements showed that the average thresholds for perception and pain had doubled, measuring 4,8 and 8,0 mA, respectively. The average pain tolerance had risen from 10,8 to 22,5 mA. A marked rise of both thresholds was also seen in the ipsilateral areas adjacent to the trigger zone. There was good correlation between a heavy sensory deficit and a favourable clinical result.(ABSTRACT TRUNCATED AT 250 WORDS)