Objective: To prospectively evaluate microstructural abnormalities in sacral nerve roots in women affected by chronic pelvic pain associated with endometriosis.
Methods: We enrolled 30 women with an ultrasound diagnosis of endometriosis and moderate-severe chronic pelvic pain; 10 age-matched healthy women comprised the control group. All subjects underwent 3 T magnetic resonance imaging (MRI), including diffusion tensor imaging (DTI); the sacral roots were reconstructed by post-processing the DTI data with dedicated software. Mean fractional anisotropy (FA) values in the S1, S2 and S3 roots were quantified. Analysis of FA values was performed by two radiologists in order to evaluate the interobserver agreement.
Results: The sacral nerve roots in healthy subjects were clearly visualised. Most of the patients with endometriosis displayed abnormalities of S1, S2 and S3 bilaterally at tractography, including an irregular and disorganised appearance. FA values in the S1, S2 and S3 roots were significantly lower in patients than in controls (P < 0.0001, <0.05 and <0.02, respectively) for both observers. No significant difference was found between observers.
Conclusion: DTI with tractography is a non-invasive means of detecting changes in the microarchitecture of the sacral nerve roots. It can qualitatively and quantitatively reveal sacral root abnormalities in patients with endometriosis-associated pain.
Key points: • MRI is increasingly used for endometriosis and chronic pelvic pain (CPP). • Magnetic resonance tractography can demonstrate microarchitectural abnormalities in sacral nerve roots. • Tractography shows altered microstructure of sacral roots affected by endometriosis and CPP. • S1-S3 fractional anisotropy values are lower in endometriosis than in healthy women. • Sacral nerve root alteration may explain the nature of endometriosis-related CPP.