Small fiber neuropathy associated with hyperlipidemia: utility of cutaneous silent periods and autonomic tests

Background. Established electrophysiological methods have limited clinical utility in the diagnosis of small fiber neuropathy.Thecutaneous silent period (CSP) may be useful as a method for the evaluation of smaller and unmyelinated fiber dysfunctions.Hyperlipidemia is a very rare cause of small fiber neuropathy. In this study, hyperlipidemia and small fiber neuropathy insymptomatic patients with normal nerve conduction studies were evaluated with autonomic tests and cutaneous silent periods.Methods. Twenty-five patients with clinically suspected small fiber neuropathy and 23 healthy volunteerswere included. CSP latencyand duration, as well as CSP latency difference of the upper and lower extremities, were examined. Two tests were used to assess theautonomic nervous system, namely, the R-R interval variation test in basal and profound breath conditions and the sympatheticskin response. Results. Twenty-five patients with clinically suspected small fiber neuropathy and normal nerve conduction studieswere compared with 23 controls. In the upper extremities, patients had prolonged CSP latencies (?? = 0.034) and shortened CSPdurations (?? = 0.039), whereas in the lower extremities, patients had shortened CSP durations (?? = 0.001). The expiration-toinspirationratios were also reduced in patients groups. There was no significant difference between sympathetic skin responselatencies and amplitude of the case and control groups. Conclusion. Our findings indicate that CSP may become a useful techniquefor the assessment of small fiber neuropathy in hyperlipidemic patients