EFFECT OF LOCAL GLUCOCORTICOID INJECTION ON MASSETER MUSCLE LEVEL OF SEROTONIN IN PATIENTS WITH CHRONIC MYALGIA

The aim of this study was to compare the effects on the level of serot onin (5-MT) in the masseter muscle by intramuscular glucocorticoid (GC ) administration in patients with fibromyalgia (FM) and localized myal gia (LM), as well as to determine associated changes in pain, tenderne ss, and microcirculation. The study comprised 22 patients with pain an d tenderness in the masseter muscle region. Ten patients (all women) h ad FM. and 12 (1 man and 11 women) had LM involving the temporomandibu lar system. The patients were examined clinically and by microdialysis at 2 visits 2-3 weeks apart and received local glucocorticoid treatme nt at the first visit. The ratio (S1/S2) between die initial level of 5-HT (S1) and steady state level (S2) was used as a relative measure o f the intramuscular release of 5-HT. This ratio decreased significantl y after treatment in the FM group. In the FM group there was also a ne gative correlation regarding changes between visits of 5-HT and change s of intramuscular temperature. 11 the LM group there was a negative c orrelation regarding changes between visits of 5-HT and changes of pre ssure pain threshold and pressure pain tolerance level. This study ind icates that there is a reduction of the ratio between initial 5-HT and steady state level in the painful masseter muscle after intramuscular GC administration to FM patients, a reduction not present in the LM p atients. In addition, 5-HT seems to be involved in the modulation of l ocal muscle microcirculation in FM patients and in hyperalgesia in LM patients.