Cytokine expression in serum and cerebrospinal fluid in non-inflammatory polyneuropathies.
BACKGROUND
Pain is a common symptom in polyneuropathies (PNPs), although it is still not known why some PNPs are painful and others are painless. Increased pro-inflammatory cytokines have been found in conditions resulting in exaggerated pain states in animal studies. Recently, elevated pro-inflammatory cytokine levels have also been found in the cerebrospinal fluid (CSF) of patients suffering from complex regional pain syndrome. Pro-inflammatory cytokines have been shown to induce or increase inflammatory or neuropathic pain.


METHODS
Using chemiluminescent enzyme immunometric assays, cytokine levels in 36 patients with painful and painless non-inflammatory PNPs in serum and CSF were investigated. The severity of PNPs was measured with electroneurography (ENG). In subjects with normal results using conventional ENG, quantitative thermo-testing was performed to investigate small-nerve-fibre function.


RESULTS
Interleukin (IL)-6 and tumour necrosis factor (TNF)-alpha in serum or CSF did not differ between patients with (n = 18) or without (n = 18) painful PNPs, whereas patients with mechanical allodynia (n = 5) had elevated serum TNF-alpha levels compared to those without allodynia. TNF-alpha and IL-6 serum levels were higher in patients with severe (n = 21) compared to those with mild neuropathy (n = 15), and showed a positive correlation with severity of neuropathy.


CONCLUSIONS
Results suggest that nerve fibre degeneration and presence of mechanical allodynia in peripheral non-inflammatory neuropathy determine cytokine expression in serum.
Division of Neurological Pain Research and Therapy, Department of Neurology, Universitätsklinikum Schleswig-Holstein, Campus Kiel, Kiel, Germany. j.ludwig@neurologie.uni-kiel.de
J
J
Ludwig
A
A
Binder
J
J
Steinmann
G
G
Wasner
R
R
Baron
D003710:Demography; D003920:Diabetes Mellitus / Q000453:epidemiology; D004185:Disability Evaluation; D005260:Female; D006304:Health Status; D006801:Humans; D015850:Interleukin-6 / Q000097:blood* / Q000134:cerebrospinal fluid*; D008297:Male; D008875:Middle Aged; D010292:Paresthesia / Q000175:diagnosis / Q000453:epidemiology; D011115:Polyneuropathies / Q000097:blood* / Q000134:cerebrospinal fluid* / Q000453:epidemiology; D012720:Severity of Illness Index; D013832:Thiamine Deficiency / Q000453:epidemiology; D014409:Tumor Necrosis Factor-alpha / Q000097:blood* / Q000134:cerebrospinal fluid*; D014806:Vitamin B 12 Deficiency / Q000453:epidemiology; D026681:Vitamin B 6 Deficiency / Q000453:epidemiology
D015850:Interleukin-6; D014409:Tumor Necrosis Factor-alpha