Central Awareness in Women With Endometriosis

Endometriosis is a chronic benign condition characterised by the presence of endometrial cells within the uterine wall and/or in anatomical locations outside the uterus; 1 in 10 women of reproductive age are affected. Various symptoms are associated with endometriosis: dysmenorrhoea, chronic pelvic pain, peri-ovulatory pain, dyspareunia, dyschezia, dysuria. Chronic pelvic pain (CPD) is one of the most common symptoms of clinical manifestation of endometriosis; 71% to 87% of women surgically diagnosed with endometriosis suffer from it. Therapies have focused on hormone therapy and surgery; although they can control the extent of the disease, most patients fail to resolve DPC. It has therefore been suggested to consider a polycentric chronic pelvic pain (DPC) origin perspective, as suggested by the myofascial and central sensitisation syndrome, which seem to contribute to pain through activation of different trigger points.

In central sensitisation (CS), peripheral nociceptive signal transmission pathways (such as those due to the presence of endometriosis lesions) can lead to adaptive changes in neurons of the central nervous system, including presynaptic effects (e.g. changes in neurotransmitter release) and postsynaptic effects (e.g. increased calcium entry into N-methyl-D-aspartate channels). This leads to a reduction in the activation threshold of central neurons and consequently to a hypersensitisation to pain associated with symptoms of hyperalgesia and allodynia. Together with pain, other symptoms of central sensitisation may occur, such as fatigue, depression, hypersensitivity. While the direct innervation of endometriotic lesions results in the activation of visceral nociception and peripheral sensitisation, CS creates a pain-feeding circuit that is independent of the underlying pathology. In some women with endometriosis, hyperalgesia, allodynia, psychological comorbidities and extension of receptor zones have been observed. Neuroimaging studies have identified changes in the grey matter in women with endometriosis and chronic pelvic pain, further supporting the hypothesis of a central component in women with endometriosis.

CS in some pathologies has led to the definition of a true algic syndrome, called Central Sensitisation Syndrome (CSS). For the identification of this syndrome in clinical practice, the Central Sensitisation Inventory (CSI) has been proposed. It takes the form of a screening tool, based on the patient's completion of a questionnaire, and helps to determine the severity of the symptoms characteristic of this syndrome, enabling its diagnosis. The CSI has been studied and validated for the diagnosis of CSS in patients suffering from fibromyalgia, irritable bowel syndrome and migraine.

Despite the practicality and applicability of the CSI, there appears to be only one study in the literature evaluating its application in women with endometriosis. In particular, this study analyses the correlation between the CSI score and two symptoms characteristic of endometriosis: deep dyspareunia and bladder and/or pelvic floor pain. To date, there appear to be no studies in the literature reporting the prevalence of CSS in patients with endometriosis.