Cine MRI during spontaneous cramps in women with menstrual pain

Abstract

Background: The lack of noninvasive methods to study dysmenorrhea has resulted in poor understanding of the mechanisms underlying pain, insufficient diagnostic tests, and limited treatment options. To address this knowledge gap, we have developed a magnetic resonance imaging-based strategy for continuously monitoring the uterus in relationship to participants' spontaneous pain perception.

Objective: The study objective was to evaluate whether magnetic resonance imaging can detect real-time changes in myometrial activity during cramping episodes in women with dysmenorrhea, with a handheld squeeze bulb for pain reporting.

Study design: Sixteen women with dysmenorrhea and 10 healthy control women both on and off their menses were evaluated with magnetic resonance imaging while not taking analgesic medication. Continuous magnetic resonance imaging was acquired using half-Fourier acquisition single-shot turbo spin echo sequence along with simultaneous reporting of pain severity with a squeeze bulb. Pearson's coefficient was used to compare results between reviewers. Proportional differences between women with dysmenorrhea and controls on/off menses were evaluated with a Fisher exact test. The temporal relationships between signal changes were evaluated with Monte Carlo simulations.

Results: Spontaneous progressive decreases in myometrial signal intensity were more frequently observed in women on their menses than in the absence of pain in the same women off their menses or participants without dysmenorrhea (P < .01). Women without reductions in myometrial signal intensity on their menses either had a history of endometriosis or were not in pain. Observations of myometrial events were consistently reported between 2 raters blinded to menstrual pain or day status (r = 0.97, P < .001). Episodes of cramping occurred either immediately before or 32-70 seconds after myometrial signal change onset (P < .05).

Conclusion: Transient decreases in myometrial uterine T2-weighted signal intensity can be reliably measured in women with menstrual pain. The directionality of signal change and temporal relationship to pain onset suggest that cramping pain may be caused by a combination of uterine pressure and hemodynamic dysfunction.

Keywords: dysmenorrhea; endometriosis; magnetic resonance imaging; pain; uterus.

Conflict of interest statement

Conflicts of interest: The authors report no conflict of interest

Copyright © 2018 Elsevier Inc. All rights reserved.

Figures

Figure 1. Temporal profile of spontaneous cramps

The 25th, 50th, and 75th percentile pain scores are shown for visually identified cramps (a). The reported level of pain (0–10) was determined by self-report of baseline pain and the scaled level of squeeze-bulb pressure. Consecutive cramps were profiled relative to visually identified onset (gray dashed line). The profiles of squeeze-bulb pressure were generated similarly (b) suggesting a threshold of 40% could detect 75% of all spontaneous cramps.

Figure 2. Example measurements of myometrial signal

Shown is a representative image from a continuous series of HASTE scans (a). The red line indicates the cross section defined for the continuous assessment. An enlarged cross section (b) is shown over 10 minutes to demonstrate the stability and specificity of change to the myometrial layer (black arrow). Dynamic changes in myometrial signal were charted (beneath in blue) by the change in average signal intensity in the myometrial layer of the uterus. Bulb-squeezing indicative of cramping pain is indicated by a red line beneath the cross section.

Figure 3. Example images of a healthy participant without menstrual pain on her menses

The red line indicates the position of the cross section defined for the continuous assessment (a). Unlike the participant with dysmenorrhea (Figure 2), the cross-sectional signal was stable over a ten-minute period (b).

Figure 4. Menstrual cramps occurred more frequently immediately before, and up to 40 seconds after, a myometrial event

The average HASTE signal intensity in the myometrial layer over time was determined across all dysmenorrhea participants with myometrial events (a). The blue line indicates the median signal intensity across all images in all women with myometrial events. Error bars indicate the standard error of the mean. The median bulb-squeeze pressure (b) is highest immediately before and 32–70 seconds after the myometrial event onset. The dotted line indicates the upper 95% confidence interval for above average pressure. Thus, pressure levels above the dotted line indicate levels of pain more than anticipated by chance (p 40% pressure) for each time point relative to a myometrial event was calculated (c). Whereas pressure levels indicate pain severity (b), frequency of cramping indicates likelihood of cramping at each time point (c). The dotted line indicates the upper 95% confidence interval for the number of spontaneous cramping episodes expected by chance.