CUTANEOUS FIELD STIMULATION (CFS) - A NEW POWERFUL METHOD TO COMBAT ITCH

Scratching the skin, while instantly relieving itch, often aggravates itch over time due to skin injury. To relieve itch, without damaging t he skin, a new technique termed cutaneous field stimulation (CFS) was developed and tested on 21 subjects. CFS uses a flexible plate with ne edle-like electrodes (n = 16) to electrically stimulate nerve fibres i n the superficial skin. The electrodes were stimulated consecutively ( 4 Hz per electrode, pulse duration 1 ms, intensity 0.4-0.8 mA, 25 min) . CFS resulted in a pricking and burning sensation that usually faded rather quickly. The burning sensation was still present during a selec tive block of impulse conduction in myelinated fibres indicating that nociceptive C-fibres are activated by CFS. Furthermore, a flare reacti on developed around the CFS electrodes indicating activation of axon r eflexes in nociceptive C-fibres. Itch, elicited by transdermal iontoph oresis of histamine, was abolished within the skin area pre-treated wi th CFS, and was reduced to 14% of control 10 cm distally. Contralatera l effects were small or non-existent. After 4 h, itch was reduced ipsi laterally to 32% of control. In comparison, 2 h after transcutaneous e lectrical nerve stimulation (TENS; 10-20 mA, 100 Hz, 25 min) ipsilater al itch was reduced to 56% of control. In conclusion, CFS offers a pow erful new method for combating itch. It is suggested that CFS acts thr ough endogenous central inhibitory mechanisms that are normally activa ted by scratching the skin. (C) 1997 International Association for the Study of Pain.