Evaluation of the sacral nerve plexus in pelvic endometriosis by three-dimensional MR neurography.

PURPOSE: To investigate the feasibility of three-dimensional MR neurography (3D MRN) for the sacral plexus using sampling perfection with application-optimized contrasts using different flip angle evolution (SPACE) sequences, and to demonstrate structural abnormalities in the pelvic nerve of women with pelvic endometriosis.

MATERIALS AND METHODS: Twenty patients with pelvic endometriosis and 20 healthy controls were examined by contrast-enhanced 3D short time inversion recovery T2-weighted imaging (CE 3D STIR T2WI) SPACE sequences on 3 Tesla MRI. Image quality and diagnostic confidence of the sequences in identifying abnormalities of the sacral plexus were analyzed and compared with conventional three-plane images of 2D turbo-spin echo T2-weighted images (2D TSE T2WI). The changes in the sacral plexus caused by endometrial lesions were evaluated.

RESULTS: The sacral plexus was clearly revealed in both healthy controls and patients with endometriosis on 3D STIR SPACE images. A good agreement was reached in the evaluation of both imaging quality (Kappa value [κ] = 0.73-1.00) and diagnostic confidence (κ = 0.66-0.81) when compared between the two independent readers. Abnormalities caused by endometriosis were identified in 17 patients, unilaterally in 10 patients, and bilaterally in 7 patients. Nerve fiber abnormalities of lumbar 5 (L5) were detected in 11 patients, of sacral 1 (S1) in 14 patients and of sacral 2 (S2) in 9 patients.

CONCLUSION: CE 3D STIR SPACE sequences demonstrate its significant capacity to investigate and map the sacral plexus, and reveal the compression and adhesion of the sacral plexus nerve as a result of ectopic lesions.

LEVEL OF EVIDENCE: 3 J. Magn. Reson. Imaging 2017;45:1225-1231.