Analgesic Efficacy of Dry Needling in Fibromyalgia Patients.Influence of Catastrophism in the Successful Intervention

Fibromyalgia syndrome (FS) is currently classified as chronic widespread pain with widespread allodynia (Coster et al., 2008). These symptoms are accompanied by other disorders, such as sleep disturbance, headaches, morning stiffness, irritable bowel syndrome, interstitial cystitis, dyspareunia, mood disturbances and depression (Gerwin, 2005). The World Health Organization recognized FS as a disease in 1992, basing its decision on the diagnostic criteria of the American College of Rheumatology (ACR) which has recently been criticized and updated (Wolfe et al., 2011; Wolfe et al., 2010; Wolfe and Hauser, 2011). Depending on the diagnostic criteria used, the prevalence is from 2% to 8% of the population increasing with age, with highest values attained between 60 and 70 (Stahl, 2009). In Spain, was estimated that 2.4% of the population over 20 years old presents the disease, and it is higher in females than in males (ratio 21:1) (Cordero, 2011).

A central sensitivity syndrome could be the most plausible explanation for chronic widespread pain affecting people with fibromyalgia syndrome. Although it was suggested this condition was the sole cause (Yunus, 2007), central sensitization of the nervous system causes the phenomena of hyperalgesia and allodynia in the individual suffering from chronic pain (Butler and Moseley, 2003) .

The subject with chronic pain has an altered alarm system; this alteration could be initiated by a peripheral sensitization (Sarzi-Puttini et al., 2011) activated by the release of various chemical substances such as substance P, serotonin and bradykinin (Yunus, 2007). Myofascial trigger points (MTrPs) are able to maintain this peripheral sensitization (Affaitati et al., 2011; Ge et al., 2010) by triggering the spontaneous pain patterns experienced by a patient with fibromyalgia syndrome (Ge et al., 2011).

MTrPs contain algogenic substances capable of generating changes in the intensity of pain. Differences in the concentration of these substances between healthy muscle and MTrPs (Shah et al., 2005) have been shown. One of the most effective techniques for the treatment of MTrPs is dry needling (Mayoral, 2010), because it alters the chemical environment of the MTrPs, thus decreasing their sensitization (Dommerholt, 2011). However, there are as until no few studies that have examined the effectiveness of this technique in patients with FS (Chou et al., 2008; Staud, 2006). Moreover, in these patients the perception of pain during and after treatment can be influenced not only by central sensitization, but also by psychosocial variables.

Catastrophization, considered to be the basic psychological construction concerning the perception of pain intensity, is a cognitive and emotional process encompassing magnification of pain-related stimuli, feelings of helplessness, and a generally pessimistic orientation (Labus et al., 2003; Rodero et al., 2010). This catastrophization, understood as a set of negative emotions and cognitive processes, is a risk factor in fibromyalgia and leads to an increase in symptoms, health status warning, symptoms of helplessness and pessimism (Alegre de Miquel and Sellas Fernandez, 2008; Sullivan et al., 2001).