Quantitative assessment and correlation of sympathetic, parasympathetic, and afferent small fiber function in peripheral neuropathy

Abstract

We compared three neurophysiological methods for assessing small nerve fiber function in 40 patients with peripheral neuropathy to determine the various manifestation types of peripheral small fiber neuropathy. Heart rate variation tests were used to assess cardiac parasympathetic small fiber function. Cutaneous vasoconstrictor responses (sympathetic C fibers) induced by deep inspiration were examined with laser Doppler flowmetry. Cutaneous afferent C fiber function was assessed by measurement of axon reflex vasodilatation induced by histamine iontophoresis. All test parameters were significantly lower in patients with peripheral neuropathy than in control subjects. Comparison of the three small fiber systems revealed that functionally different systems are damaged independently, and isolated affection of each fiber type was frequently observed. The three tests are useful noninvasive tools with which to evaluate sympathetic, parasympathetic, and afferent small fiber function in patients with peripheral neuropathy. In many patients functionally different small fiber systems are affected selectively. To diagnose small fiber neuropathy and to evaluate the individual type of manifestation complementary testing of several small somatic and autonomic fiber systems is necessary.

Small fiber neuropathy: a common and important clinical disorder

“…Furthermore, in many patients, functionally different small fiber systems are affected selectively. In order to diagnose SFN and to evaluate the individual type of manifestation, complementary testing of several small somatic and autonomic fiber systems may be necessary [16]. Finally, all abnormal test results must be interpreted, taking into account the patient's history, previous treatments and other test results.…”

Postherpetic neuralgia: Topical lidocaine is effective in nociceptor–deprived skin

“…The peripheral function of cutaneous histamine sensitive C-fibres was assessed by measurement of the axon reflex flare [3,37]. Stimulation of cutaneous endings of these fibres produces impulses which travel both to the CNS leading to the sensation of itch and to axon collaterals in the skin to initiate vasodilatation and plasma extravasation due to release of peptides (i. e., axon reflex, antidromic vasodilatation, neurogenic inflammation).…”

Idiopathic restless legs syndrome:

“…In both groups the disturbance was distributed in a symmetrical manner, whereas the upper extremity was less or not affected. By combination of QST with a quantitative measurement of the peripheral C fibre axon reflex vasodilatation it is possible to decide if an impairment of temperature perception documented by QST is caused by deficit in central afferent processing [1,23].We found that flare response and vasodilatation was significantly reduced in the group of secondary RLS patients and normal in idiopathic RLS patients. In addition, in the secondary RLS group there was a negative correlation between flare response and vasodilatation and warm perception thresholds.…”