Short-term effect of glucocorticoid injection into the superficial masseter muscle of patients with chronic myalgia: a comparison between fibromyalgia and localized myalgia.

The aim of this study was to investigate whether the treatment effect of intramuscular glucocorticoid injection differs between patients with fibromyalgia and those with localized myalgia of the masseter muscle concerning pain, tenderness to digital palpation, pressure pain threshold, pressure pain tolerance level, maximum voluntary occlusal force, or intramuscular temperature. Twenty-five patients with fibromyalgia and 25 patients with localized myalgia of the masseter muscle were first asked to assess their pain on a visual analogue scale; afterward, a routine clinical examination, including tenderness to digital palpation, was performed. For each patient, the pressure pain threshold, pressure pain tolerance level, and maximum voluntary occlusal force, as well as the intramuscular temperature, were recorded. Finally each patient received an injection of glucocorticoid. The examination and glucocorticoid treatment were repeated after approximately 2 weeks, and a follow-up was performed after another 5 weeks. In the fibromyalgia group, there was a reduced tenderness to digital palpation in response to the treatment. The localized myalgia group responded with a general improvement of symptoms as well as a significant reduction of pain intensity and tenderness to digital palpation. The results of this study indicate that patients with fibromyalgia and localized myalgia in many respects show a similar response to local glucocorticoid treatment.