Neuropathic pain in endometriosis

Chronic pelvic pain is one of the main symptoms of endometriosis which affects 1 in 10 women of reproductive age. Historically, despite the prevalence of this condition and the impact it has on those affected, endometriosis-associated pain (EAP) has been poorly understood. In this thesis I explore endometriosis-associated pain, specifically the presence of neuropathic pain (pain due to lesion/disease of the somatosensory system). To do this, I use a variety of different techniques including questionnaires, functional magnetic resonance imaging (fMRI) and quantitative sensory testing (QST). To determine the prevalence of neuropathic pain in a large population is difficult. In this thesis I use an online questionnaire on patient support websites to give an estimation of the proportions of women experiencing neuropathic pain. I investigate differences between those with and without neuropathic pain with respect to pain symptoms, psychological and cognitive function, number of surgeries to the abdomen and duration of pain. I also sub-divided women further based on their sensory symptom profiles. I replicate these findings in a novel cohort and relate them to treatment response. Central nervous system changes have been demonstrated in people with neuropathic pain. In this thesis I investigate the association between neuropathic pain features and functional connectivity of the brain in women with endometriosis-associated pain. Sensory testing is an important aspect of neuropathic pain research and in this thesis I use QST to investigate sensory perception. A range of stimuli are used to determine whether there are changes in sensory processing in women with endometriosis-associated pain. Overall, the aims of the research described in this thesis are to advance knowledge regarding the prevalence of neuropathic pain in endometriosis; how women can be stratified using questionnaires and whether that relates to treatment response; what changes associated with neuropathic pain can be seen in the activity of the brain at rest; and the sensory profiles of women with EAP. Research in the area of EAP is critical to inform clinical practice and improve treatment.