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

Abstract

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.

Comparison of vibrotactile threshold and suprathreshold responses in men and women

“…The growth of sensitivity to vibration on the hand. This finding differs from that of Goff et al (1965), who showed that women were generally more sensitive than men, but it is consistent with other reports that vibrotactile sensitivities for the two sexes were approximately equal (Plumb & Meigs, 1961;Steinberg & Graber, 1963;Verrillo & Ecker, 1977). In a recent study (Verrillo, in press), the author measured vibration thresholds in five groups of subjects ranging in mean age from 10 to 65 years.…”

“…Men, on the other hand, were found to have stable thresholds to 45 years of age before sensitivity decreases. A number of studies, however, found no differences between men and women with respect to vibrotactile threshold measurements (Plumb & Meigs, 1961;Steinberg & Graber, 1963;Verrillo & Ecker, 1977).…”

Vibrotactile adaptation on the face

“…Not until frequency exceeded 400 Hz did threshold begin to drop abruptly. There is no sign in Barlow's shallow function of Verrillo and Ecker's (1977) Uvshaped branch.…”

“…This phenomenon, previously studied almost exclusively on the hand, is here shown for the first time to occur on the face as well. Adaptation is then used analytically to determine that the two-branched thresholdversus-frequency function obtained on the face by Verrillo and Ecker (1977) represents the activity of two distinct mechanisms. Action spectra of vibrotactile adaptation reveal the presence of both mechanisms even in subjects whose unadapted threshold function (like that reported by Barlow, 1987) shows no sign of duplexity.…”

“…Verrillo and Ecker (1977), in the course of a study of tic douloureux, examined the facial vibrotactile sensitivity of a control group of neurologically normal subjects, and found it to be a two-branched function of frequency. Threshold was essentially independent of frequency below 40 Hz, but at higher frequencies, threshold began to decline at a rate of about 6 dB/octave, reaching a minimum in the neighborhood of 200 Hz.…”