DNIC's efficacy across de menstrual cycle in women with fibromyalgia

Abstract

Fibromyalgia syndrome (FMS) is a widespread disorder of unknown aetiology affecting 2-4% of the general population in which women are about nine times more likely to develop fibromyalgia than men.1 Nonetheless, several hypotheses have been advanced to explain the onset of symptoms. One of these supports a reduction of diffuse noxious inhibitory controls (DNIC) in fibromyalgics.2 Another hypothesis comes from the fact that the higher prevalence of FMS in women should be related to sex hormones (SH). The goal of this study was to examine DNIC's efficiency in relation to the menstrual cycle of women with FMS. We measured DNIC recruitment and blood level of testosterone (T), estrogens (E) and progesterone (P) at three phases (lutheal, ovulation and menstrual) of a regular menstrual cycle in women with FMS. DNIC were activated by the persistent pain stimulation (PPS) procedure, which consists in a continuous nociceptive heat stimulation using a constant temperature thermode for two minutes (at the forearm) producing temporal summation of pain.3 DNIC activity was then indexed by comparing temporal summation effects recorded before and after a two minutes immersion of the contralateral arm in cold water (12°C). FMS patients reported similar pain ratings before and after the immersion procedure in menstrual (low E and P) and ovulation phases (high E, low P). However, they reported less pain after the immersion procedure during the lutheal phase (low E, high P). This pain diminution showed the analgesic effect caused by the activation of the DNIC. Moreover, SH analysis showed that FMS patients have normal levels of T, E and P. These results suggest that endogenous pain control mechanisms in FM female patients are modulated by menstrual cycle. (1. Wolfe, J Musculoskelet Pain, 1993; 2. Julien, Pain, 2005; 3. Tousignant-Laflamme, Brain Research, 2008.) Fibromyalgia syndrome (FMS) is a widespread disorder of unknown aetiology affecting 2-4% of the general population in which women are about nine times more likely to develop fibromyalgia than men.1 Nonetheless, several hypotheses have been advanced to explain the onset of symptoms. One of these supports a reduction of diffuse noxious inhibitory controls (DNIC) in fibromyalgics.2 Another hypothesis comes from the fact that the higher prevalence of FMS in women should be related to sex hormones (SH). The goal of this study was to examine DNIC's efficiency in relation to the menstrual cycle of women with FMS. We measured DNIC recruitment and blood level of testosterone (T), estrogens (E) and progesterone (P) at three phases (lutheal, ovulation and menstrual) of a regular menstrual cycle in women with FMS. DNIC were activated by the persistent pain stimulation (PPS) procedure, which consists in a continuous nociceptive heat stimulation using a constant temperature thermode for two minutes (at the forearm) producing temporal summation of pain.3 DNIC activity was then indexed by comparing temporal summation effects recorded before and after a two minutes immersion of the contralateral arm in cold water (12°C). FMS patients reported similar pain ratings before and after the immersion procedure in menstrual (low E and P) and ovulation phases (high E, low P). However, they reported less pain after the immersion procedure during the lutheal phase (low E, high P). This pain diminution showed the analgesic effect caused by the activation of the DNIC. Moreover, SH analysis showed that FMS patients have normal levels of T, E and P. These results suggest that endogenous pain control mechanisms in FM female patients are modulated by menstrual cycle. (1. Wolfe, J Musculoskelet Pain, 1993; 2. Julien, Pain, 2005; 3. Tousignant-Laflamme, Brain Research, 2008.)