Research Of Diagnostic Techniques Of Small Fiber Neuropathy

ObjectivesPart 1:To evaluate the relationship between clinical features, nerve conduction studies (NCS) and intraepidermal nerve fiber density (IENFD) in peripheral neuropathy with small fibers involvement and to determine the diagnostic value of 13-item small-fiber neuropathy and symptoms inventory questionnaire (SFN-SIQ) and neuropathy symptom score [lower limb] (NSS[LL]) in small fiber neuropathy (SFN).Part 2:To preliminarily establish normative reference value for contact heat evoked potentials (CHEPs).MethodsPart 1:34 consecutive patients with peripheral neuropathy accompanied by symptoms of small fibers damage resorting to Department of Neurology of Chinese PLA General Hospital were enrolled and divided into small fiber damage group and mixed (both small and large) fibers damage group. SFN-SIQ, NSS[LL] and neuropathy disability score [lower limb] (NDS[LL]) were performed. Nerve conduction studies and skin biopsy were conducted at the same side in the lower limb. The relationship between IENFD and SFN-SIQ, NSS[LL], NDS[LL] was assessed by partial correlation. Receiver operating characteristic curve (ROC) analysis was applied to evaluate the diagnostic value of SFN-SIQ and NSS[LL] in small fiber damage. Independent sample t test was used in the group of mixed fibers damage and small fiber damage group to compare various parameters, including IENFD, NSS[LL], NDS[LL], SFN-SIQ and VAS. Similar statistical method was used in IENFD abnormal and IENFD normal group to compare the clinical and electrophysiological parameters.Part 2:CHEPs were applied on 32 healthy volunteersat right volar fore arm, right side of C7, right side of T12 and position above right lateral malleolus. Then normative reference value of different age groups, including 20-29,30-39 and different genders was established. Independent sample t test and rank sum test were used to compare the parameters of different age groups (20-29,30-39) and genders. CHEPs parameters after different number of stimulus and after short-term interval were compared by paired sample t test and rank sum test.ResultsPart 1:According to the worldwide normative reference value of IENFD,13 patients were diagnosed with peripheral neuropathy with small fibers involvement. IENFD was moderately correlated with SFN-SIQ (r=0.437, P=0.012), and edge correlated with NSS[LL] (r=0.334, P=0.062). The diagnostic value of SFN-SIQ and NSS[LL] to small fiber damage was moderate (Az=0.753, P=0.012 for SFN-SIQ, Az=0.712, P=0.040 for NSS[LL]) and the best diagnostic indicator of each scale was 6. The value of NDS[LL] was apparently higher in the group of mixed fibers damage than in small fiber damage group (t=-5.605, P<0.001). The IENFD abnormal group had a much higher NSS[LL] value than that of the IENFD normal group (t=-2.047, P=0.049). The differences of electrophysiological parameters between IENFD abnormal and IENFD normal groups were not significant statistically.Part 2:The normative reference value of different age groups (20-29,30-39) and different genders was established. The differences of parameters in different genders were not ststistically significant and N-P amplitude was of significant difference between different age groups (20-29,30-39) (t=2.76, P=0.011 for right volar arm, t=2.743, P=0.012 for the right side of T12, t=3.731, P=0.001 for the position above right lateral malleolus). There was significant difference of N-P amplitude when different number of stimulations was applied (t=2.649, P=0.013 for the comparison of 3 and 5 stimulus, t=5.194, P=0.000 for the comparison of 3 and 10 stimulus). No significant difference was found of the parameters after 15-30mins.ConclusionPart 1:Chinese normative reference value of IENFD was desperately required in the diagnosis of small fiber neuropathy. SFN-SIQ and NSS[LL] had the potential to screen for small fiber neuropathy and were convenient in patient follow-up. Large sample studies were demanded in order to guarantee the clinical application of SFN-SIQ and NSS[LL].Part 2:The parameters of CHEPs were not related to gender, however, the N-P amplitude declined with growth of age. Latency was a more reliable parameter compared with amplitude, and N-P amplitude declined apparently after repetitive stimulation. CHEPs had good short-term repetitiveness.