Effects of root or nerve destruction on vibrotactile sensitivity in trigeminal neuralgia

Vibrotactile thresholds were determined at 7 frequencies between 25 and 300 Hz at the medial edge of the cheek in 11 patients who had been or were currently being treated for major trigeminal neuralgia, tic douloureux. A control group, comparable in age but without neural pathology, was also tested. Results indicate essentially no difference between normal and affected sides of the face prior to surgery. The drug carbamazepine (Tegretol), commonly used to control pain of trigeminal neuralgia, did not affect vibrotactile thresholds. Infraorbital neurectomy resulted in an initial loss of sensitivity at all frequencies, followed by a gradual return of sensation which reached preoperative levels at approximately one year. The return of sensitivity was followed by the return of neuralgia. Following alcoholic gasserian rhizolysis, low-frequency thresholds were elevated considerably as after neurectomy, but sensation above 100 Hz was lost completely. A return of high-frequency sensitivity accompanied the recurrence of pain in some patients who had been injected up to 13 years prior to testing. The results are discussed in terms of recent anatomical, electrophysiological, and clinical findings.