A possible neural mechanism for photosensitivity in chronic pain.

Patients with functional pain disorders often complain of generalized sensory hypersensitivity, finding sounds, smells, or even everyday light aversive. The neural basis for this aversion is unknown, but it cannot be attributed to a general increase in cortical sensory processing. Here, we quantified the threshold for aversion to light in patients with fibromyalgia, a pain disorder thought to reflect dysregulation of pain-modulating systems in the brain. These individuals expressed discomfort at light levels substantially lower than that of healthy control subjects. Complementary studies in lightly anesthetized rat demonstrated that a subset of identified pain-modulating neurons in the rostral ventromedial medulla unexpectedly responds to light. Approximately half of the pain-facilitating "ON-cells" and pain-inhibiting "OFF-cells" sampled exhibited a change in firing with light exposure, shifting the system to a pronociceptive state with the activation of ON-cells and suppression of OFF-cell firing. The change in neuronal firing did not require a trigeminal or posterior thalamic relay, but it was blocked by the inactivation of the olivary pretectal nucleus. Light exposure also resulted in a measurable but modest decrease in the threshold for heat-evoked paw withdrawal, as would be expected with engagement of this pain-modulating circuitry. These data demonstrate integration of information about light intensity with somatic input at the level of single pain-modulating neurons in the brain stem of the rat under basal conditions. Taken together, our findings in rodents and humans provide a novel mechanism for abnormal photosensitivity and suggest that light has the potential to engage pain-modulating systems such that normally innocuous inputs are perceived as aversive or even painful.

Pelvic Floor and Urinary Distress in Women with Fibromyalgia.

Fibromyalgia (FM) patients were recently found to have more symptom burden from bothersome pelvic pain syndromes that women seeking care for pelvic floor disease at a urogynecology clinic. We sought to further characterize pelvic floor symptoms in a larger sample of FM patients using of validated questionnaires. Female listserv members of the Fibromyalgia Information Foundation completed an online survey of three validated questionnaires: the Pelvic Floor Distress Inventory 20 (PFDI-20), the Pelvic Pain, Urgency and Frequency Questionnaire (PUF), and the Revised Fibromyalgia Impact Questionnaire (FIQR). Scores were characterized using descriptive statistics. Patients (n = 204 with complete data on 177) were on average 52.3 ± 11.4 years with a mean parity of 2.5 ± 1.9. FM severity based on FIQR score (57.2 ± 14.9) positively correlated with PFDI-20 total 159.08 ± 55.2 (r = .34, p < .001) and PUF total 16.54 ± 7 (r = .36, p < .001). Women with FM report significantly bothersome pelvic floor and urinary symptoms. Fibromyalgia management should include evaluation and treatment of pelvic floor disorders recognizing that pelvic distress and urinary symptoms are associated with more severe FM symptoms. Validated questionnaires, like the ones used in this study, are easily incorporated into clinical practice.