Department of Obstetrics and Gynecology, Faculty of Medicine, University of Calgary
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Jarrell, J. Demonstration of Cutaneous Allodynia in Association with Chronic Pelvic Pain. J. Vis. Exp. (28), e1232, doi:10.3791/1232 (2009).
Pelvic pain is a common condition that is associated with dysmenorrhea and endometriosis. In some women the severe episodes of cyclic pain change and the resultant pain becomes continuous and this condition becomes known as Chronic Pelvic Pain. This state can be present even after the appropriate medical or surgical therapy has been instituted. It can be associated with pain and tenderness in the muscles of the abdomen wall and intra-pelvic muscles leading to severe dyspareunia. Additional symptoms of irritable bowel and interstitial cystitis are common. A common sign of the development of this state is the emergence of cutaneous allodynia which emerges from the so-called viscero-somatic reflex. A simple bedside test for the presence of cutaneous allodynia is presented that does not require excessive time or special equipment. This test builds on previous work associated with changes in sensation related to gall bladder function and the viscera-somatic reflex(1;2).
The test is undertaken with the subject s permission after an explanation of how the test will be performed. Allodynia refers to a condition in which a stimulus that is not normally painful is interpreted by the subject as painful. In this instance the light touch associated with a cotton-tipped applicator would not be expected to be painful. A positive test is however noted by the woman as suddenly painful or suddenly sharp. The patterns of this sensation are usually in a discrete pattern of a dermatome of the nerves that innervate the pelvis.
The underlying pathology is now interpreted as evidence of neuroplasticity as a consequence of severe and repeating pain with changes in the functions of the dorsal horns of the spinal cord that results in altered function of visceral tissues and resultant somatic symptoms(3).
The importance of recognizing the condition lies in an awareness that this process may present coincidentally with the initiating condition or after it has been treated. It also permits the clinician to evaluate the situation from the perspective that alternative explanations for the pain may be present that may not require additional surgery.
In most cases the areas of cutaneous allodynia will be identified in the dermatomes of the abdomen and perineum that innervate the intra-pelvic structures – T11-L1 and S3,4,5 respectively. The term allodynia refers to the presence of a painful sensation as a consequence of a stimulus that is not normally painful, in this case a cotton-tipped culture stick.
The presence of cutaneous allodynia indicates the woman has had severe pain in the past to the extent that neuropathic changes have occurred. Although the problem may have originated from dysmenorrhea or endometriosis, a new condition has emerged – Chronic Pelvic Pain. The original condition may be active or quiescent. Recognition of this new development is important for patient education and to initiate processes of rehabilitative care. Recognition of the development of this state may also permit the clinician to explore other options and avoid potentially unnecessary surgery – particularly if the original condition has been treated.