Cutaneous silent period in the evaluation of small nerve fibres.

INTRODUCTION: High intensity cutaneous stimulus transiently suppresses tonic voluntary muscle activity resulting in cutaneous silent period (CSP). AIM: The aim of our study was to evaluate the normal values of an onset latency L1, a late latency L2 and a duration of CSP after stimulating sensory fibres of the median nerve. MATERIAL AND METHODS: This prospective study was performed at the Neurology Department, Clinical Center of Sarajevo University in period from January 1st 2013 to December 1st 2013. In our study we examined 61 subjects. The group included our relatives, coworkers and friends. The informed consent from testing subjects was obtained. RESULTS: The origin of silent period is stimulation of small A-delta nerve fibres. The pre-synaptic or post-synaptic interruption of the electrical volley to motor neurons is discussed. Median values of muscle activity suppression in healthy female is 55.0 ms (45.0-74.0) and 59.0 ms (52.0-67) male subjects. There is a correlation between the onset latency L1 and the late L2 latency (p < 0.03). In the on-going study it seems that delay of L1 and shorter muscle activity suppression might provide a sign of small nerve fibres involvement. CONCLUSION: The use of CSP improves the value of neurophysiology examination.

A neurophysiological study of large- and small-diameter nerve fibers in the hands of hemodialysis patients.

PURPOSE: Polyneuropathy in patients with advanced clinical kidney disease is a very disabling condition. The aim of this study was to evaluate neurophysiological abnormalities of large- and small-diameter nerve fibers in the hands of hemodialysis patients. METHODS: A total of 38 hemodialysis patients and 38 healthy control subjects underwent a conventional electrophysiological examination. The function of small nerve fibers was assessed using cutaneous silent period (CSP) measurement. RESULTS: Slower median nerve motor conduction velocities were recorded in patients with fistula (p < 0.0001) and without fistula (p < 0.001). Sensory median and ulnar nerve conduction velocities were slower in both patient groups compared with the control group (p = 0.001). Median sensory nerve action potential amplitudes were lower in patients with fistulas (p = 0.009) and without fistulas (p = 0.005) compared with the control group. Significantly prolonged F-wave latencies of the median (p = 0.002) and ulnar nerves (p = 0.023) in patients with fistulas hands were observed. In 12/38 (32 %) patients, the onset latencies of CSPs were significantly delayed (p = 0.001). There was an inverse correlation of ß2-microglobulin and decreased conduction velocities of the median nerves, while Kt/V was associated with improved sensory nerve conduction velocity of the median nerve. An inverse correlation between motor velocity of both nerves and hemodialysis duration was observed in the patient groups. CONCLUSIONS: The measurement of CSPs provides a useful method for assessing small nerve fibers. The role of A-delta fibers is often overlooked.