THE VALUE OF QUANTITATIVE MEASUREMENT OF PAIN SENSATION
Keywords:
neuropathic pain, painful neuropathy, peripheral neuropathy, chronic pain, nerve fibers, sinusoidal transdermal stimulation, skin biopsyAbstract
Objective: The value of quantitative measurement of pain sensation after C nociceptor activation with transdermal sinusoidal current wave stimulation protocol and skin biopsy.
Methods: 30 healthy volunteers aged 20-30 years (17 females 18 males) participated after having given their informed consent. Half-sine wave pulses of 0.5sec duration (1Hz) were generated at intensities of 0.2 to 1 mA by a constant current stimulator. Apart from half-sine wave stimulation, sine wave pulses of 60sec duration (4Hz) were generated at intensity of 0.2mA also by the constant current stimulator (Digitimer Ltd, Welwyn Garden City, UK) controlled by DAPSYS 8 (www.dapsys.net). Moreover, we performed 3-mm skin punch biopsies 10 cm above the lateral malleolus of the leg and in the middle of the volar side of the forearm to the volunteer’s group.
Results: We demonstrate that delivering transdermal sinusoidal half sine wave when trying to stimulate mechano-sensitive C fibers, when the amplitude of the delivered wave is increased from 0.2mA to 1mA considering our protocol, pain sensation is also increased following the same scheme. If we observe a different scheme of activation in C fibers, may be a sign of neuropathic pain. Concerning the mechano-insensitive C fibers of pain, when trying to stimulate them we expect increasing pain sensation and then familiarization, desensitization and reduction of pain sensation. As a result, if this scheme isn’t observed when sine wave is delivered transdermal with 1 min of duration, and we observe a different scheme there may be a involved a C fiber neuropathy and neuropathic pain. Concerning the skin biopsies, a correlation between pain sensation, of sine wave (delivered transdermal to stimulate mechano-insensitive C fibers of pain on the forearm), was observed and the nerve fiber density. A correlation between the bifurcated fibers of the biopsy site and the pain sensation was observed when mechanosensitive and mechano-insensitive fibers are stimulated, which needs further investigation. Also, a correlation between the remnant nerve fibers of subepidermal nerve plexus and mechano-insensitive nerve fibers of pain is observed that also needs further investigation.
Conlclusion: Skin biopsy and transdermal electrical stimulation are very promising available tools of diagnosing C fiber neuropathies and assessing neuropathic pain.
