Standardized measurement of the piriformis muscle and the proximal portion of the sacral nerve roots using transvaginal ultrasound
Ultraschall in der Medizin, vol.47, no.01, pp.61-67, 2026 (SCI-Expanded, Scopus)
- Publication Type: Article / Article
- Volume: 47 Issue: 01
- Publication Date: 2026
- Doi Number: 10.1055/a-2521-9321
- Journal Name: Ultraschall in der Medizin
- Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
- Page Numbers: pp.61-67
- Keywords: deep endometriosis, pelvic anatomy, piriformis muscle, sacral nerve roots, transvaginal sonography
- Acibadem Mehmet Ali Aydinlar University Affiliated: No
Abstract
Objective To identify the sonomorphological appearance and to measure the thickness of the piriformis muscle (PM) and the proximal portion of the sacral nerve roots S1-S3 in healthy premenopausal women. Materials and Methods This prospective multicentric observational study included a consecutive series of women undergoing transvaginal sonography (TVS) at 2 tertiary gynecological referral centers. Standardized assessment of the pelvic organs was performed, followed by an attempt to visualize the right and left PM and sacral nerve roots S1-S3 at their origin in proximity to the sacral neuroforamen. Visualization rates, diameters of the muscle and nerve thickness, and the time needed to identify the PM were recorded. Results 305 patients were included in the study. In 293 women (96.1%), the PM was identified bilaterally. The median diameter of the PM was 18.3mm on the right side and 18.4mm on the left side. S1 nerve roots were successfully identified bilaterally in 224 (73.4%) patients. Their right and left median diameters were 4.8mm. Both S2 nerves were successfully identified in 215 (70.5%) patients. Their median diameter were 4.3mm on both sides. S3 nerve roots were successfully identified in 203 (66.6%) patients. Their median diameter were 3.2mm on both sides. Conclusion We describe methods which allow consistent and rapid identification of the PM and the S1-S3 sacral nerve roots using TVS. Visualization of the PM and the proximal portion of the sacral plexus may be useful regarding identification of pathological changes in PM thickness and could help to distinguish perineural cysts from other gynecological pathologies.