Effective Connectivity of Beta Oscillations in Endometriosis-Related Chronic Pain During rest and Pain-Related Mental Imagery.

Using the EEG recordings of patients with endometriosis-related chronic pelvic pain, we have examined the effective connectivity within the cortical pain-related network during rest and during pain-related imagery. During rest, an altered connectivity was hypothesized between cortical somatosensory pain areas and regions involved in emotional and cognitive modulation of pain. During pain-related imagery, alterations in prefrontal-temporal connectivity were expected. The effective connectivity was estimated using the Directed Transfer Function method. Differences between endometriosis patients and controls were found in the beta band (14-25 Hz). During rest, endometriosis was associated with an increased connectivity from the left dorsolateral prefrontal cortex to the left somatosensory cortex and also from the left somatosensory cortex to the orbitofrontal cortex and the right temporal cortex. These results might be related to sustained activation of the somatosensory pain system caused by the ongoing pain. During pain-related imagery, endometriosis patients showed an increased connectivity from the left dorsolateral prefrontal cortex to the right temporal cortex. This finding might point to impaired emotional regulation when processing pain-related stimuli, or it might be related to altered memorization of pain experiences. Results of this study open up new directions in chronic pain research aimed at exploring the beta band connectivity alterations. PERSPECTIVE: This study examined the pain system's dynamics in endometriosis patients with chronic pelvic pain during resting-state and pain-related mental imagery. The results could contribute to the development of new therapies using guided mental imagery.

Experimental pain tolerance is decreased and independent of clinical pain intensity in patients with endometriosis.

OBJECTIVE: To investigate alterations in tactile, pain thresholds and pain tolerance thresholds in patients with endometriosis using a multimodality approach. DESIGN: Cross-sectional study. SETTING: Multidisciplinary referral center. PATIENT(S): Women with proven endometriosis (N = 35) and healthy controls (N = 38). INTERVENTION(S): Pain processing was tested using quantitative sensory testing (QST) to investigate sensation, pain, and pain tolerance thresholds for thermal, electrical, and pressure stimuli. MAIN OUTCOME MEASURE(S): Differences in QST measures in patients with endometriosis and in healthy controls on the endometriosis site and control sites, and the association between QST outcomes and patient characteristics. RESULT(S): We observed a significantly decreased pain tolerance in patients with endometriosis, independent of clinical pain intensity or revised American Society for Reproductive Medicine stage, compared with healthy controls. CONCLUSION(S): Increasing knowledge concerning mechanisms underlying the pain of women with endometriosis creates opportunities to develop new treatment options. More attention should be paid not only to treat endometriosis in a surgical or pharmacologic way, but also to desensitize by pain education or cognitive therapy.