Study On Normal Value Of Current Sense Threshold Of 166 Healthy People

Background:Cutaneous nerve fibers are typically classified into three varieties according to cross sectional diameter. They are the larger myelinated A-beta fibers (5 to 15 um diameter), lightly myelinated A-delta fibers (1 to 4 um diameter) and the unmyelinated C fibers (0.5 to 1.5 um diameter). Recently, it has become possible to obtain direct quantitative sensory evaluation by CPT (current perception threshold) device. It achieves differential neuro-excitatory effects by applying different frequencies of an electrical sine wave stimulus. Evidence suggested that 2000 Hz,250 Hz,5 Hz stimulus measures respectively reflected function of A-beta, A-delta, C fibers. Up to now, the clinical normative value of CPT based on data from large sample study of Chinese population is rare. Besides, the influence of factors such as age, gender on the test result of CPT is still controversial.Objectives:This study aimed to clarify the influencing factors of CPT through analyzing data from healthy volunteers and establish practical normative value range suitable for subjects with different clinical characteristics based on the effects of different factors.Methods:20 healthy volunteers recruited publicly combining 146 subjects taking CPT test in the census of the national project cardiovascular and cerebrovascular diseases in rural areas of China from 2013 to 2015 were analyzed. The inclusion criteria were no history of neuropathy, no complaints of sensory abnormalities and normal neurological examination. The past medical history and demographic characteristics such as age, gender, and occupation were collected. The distal phalange of left index finger (or the back of the left hand) and right hallux were tested. Fully automated, double-blinded CPT procedure was performed for each subjects, and CPT values of 2000Hz,250Hz,5Hz at both sites were recorded for statistics analysis.Results:For all subjects included,2000Hz,250Hz,5Hz CPT of test region (X±S):index finger were 226.8±63.7,100±34.8,57.2±21.8; hand back were 136.8±37.8,39.8±11.7, 19.9±8.0; hallux were 287.7±72.1124.0±47.0,71.4±34.9.CPT of hand back was lower than that of hallux for each of the three frequencies (p<0.001), and significant difference between CPT of index finger and that of hallux was only showed in 2000Hz(p<0.01).Gender differences were showed at 2000Hz CPT of hand back and hallux (p<0.01), and male subjects had higher CPT. Age had positive correlation with 250Hz CPT of index finger (p<0.05),2000Hz CPT of hand back (p<0.001) and index finger (p<0.05). Manual workers had higher 250Hz CPT of hallux than mental workers (p<0.01).Conclusions:The study determined the impact of different factors on CPT test and provided normative values for different conditions according to the impact of subject characteristics.