Study of nociceptive flexion reflex in healthy subjects and patients with chronic neuropathic pain syndrome.

Nociceptive flexion reflex was measured in healthy subjects and patients with chronic neuropathic pain (diabetic distal symmetric sensorimotor polyneuropathy). The study of nociceptive flexion reflex revealed reduction of subjective pain threshold and reflex threshold in patients compared with healthy persons reflecting deficit of descending antinociceptive influences in the CNS.

[The state of nociceptive and antinociceptive brain systems in patients with the pain form of diabetic polyneuropathy].

We studied 48 patients with the pain form of distal symmetric sensorimotor diabetic polyneuropathy (DPN) before and after polytherapy and 17 sex- and age-matched healthy people. Clinical/neurological, psychometric and neurophysiologic (recording of nociceptive flexor reflex (NFR) and exteroceptive suppression of involuntary muscle activity) methods were used. Lower NFR thresholds and coefficients pain threshold/reflex threshold (Pt/Rt) as well as the presence of moderately-severe depression and high anxiety level were found in patients with DPN. This reflects a lack of supraspinal and antinociceptive effects and a significant role of psychological factors in the formation of chronic neuropathic pain. The significant reduction of pain, increase of NFR thresholds and Pt/Rt coefficients were seen after the treatment with antidepressants (venlafaxine or pipofezine) in the combination with carbamazepine that suggests the strengthening of supraspinal and antinociceptive systems activity. Measuring of NFR parameters has a practical value for the assessment of the state of antinociceptive brain systems, intensity of pain syndrome, severity of comorbid anxiety-depression disorders and for the objectification of treatment efficacy in patients with DPN.