Cutaneous silent period in the assessment of small nerve fibers in patients on hemodialysis.

Aim: In hemodialysis patients renal disease may cause an impairment of central and peripheral nervous system. In most cases of the peripheral nervous system polyneuropathy is reported. The aim of this study was to evaluate the function of small A-delta nerve fibres, whose function is often overlooked.

Methods: The function of large diameter nerve fibers was performed by standard routine neurophysiological examination. Cutaneous silent period (CSP) was elicited by single electrical stimulations at the tip of digit II by the bipolar electrodes. The superficial electrodes were placed on the muscle belly of m. abductor pollicis brevis. The onset latency (L1) was recorded at the beginning of voluntary muscle activity suppression, the late latency (L2) at the start of new muscle activity. The difference between two latencies indicates the duration of CSP.

Results: The study included 38 consecutive patients (male/female - 21/17, median age 56.6±10.9 years) treated with hemodialysis (one month to 30 years) and 35 healthy subjects (male/female 23/17, age 47.4±10.1 years). The results of the conduction study demonstrated a significant prolongation of F-waves of the median and ulnar nerves, decreased motor and sensory velocities of both nervesin patients on hemodialysis (p less than 0.001). In patients with A-V fistulas a significant prolongation of the onset CSP latency L1 was obtained (p less than 0.001), whereas duration of CSP was not changed.

Conclusion: In hemodialysis patients the significant impairment of small nerve fibers was recorded. The evaluation of small nerve fibers contributes to the assessment of the whole peripheral nerve function.