Imaging and clinical features of sciatic nerve entrapment syndrome
Objective To investigate the common causes and imaging characteristics of sciatic nerve entrapment syndrome and provide imaging basis for its clinical treatment.Methods The medical history,clinical features and imaging data of 35 clinically confirmed patients with 40 sides of the sciatic nerve entrapment syndrome were retrospectively analyzed in the Second Affiliated Hospital of Shandong First Medical University from March 1st,2016 to December 31st,2022.The thickness of the pelvic outlet of the sciatic nerve and the piriformis muscle were measured also.Results Totally 35 cases with 40 sides of sciatic nerve pelvic presented outlet stenosis,and the transverse and anteroposterior diameters of sciatic nerve pelvic outlet were about(15.20±2.27)mm and(4.98±1.63)mm,respectively.Among them,17 cases(sides)were pelvic wall metastasis,4 cases(8 sides)were adhesion after radiotherapy,6 cases(sides)were chronic inflamma-tion,4 cases(5 sides)were piriformis muscle development variation,and 4 cases(sides)were caused by pelvic malignant tumor destruction.Five cases were bilateral and 30 cases were unilateral,of which 18 cases were on the left side and 12 cases were on the right side.In 4 cases(side),the piriformis muscle were significantly thinner about(10.85±3.91)mm,which were caused by the rapid growth of malignant tumors adjacent to the pelvis,and MR signal were uniform,muscle fibers were tortuous and slender.The piriformis muscle were thickened in 36 sides about(22.61±5.06)mm,of which 31 sides were caused by metastatic tumor invasion,radiotherapy and chronic inflammation.MR muscle signal were heterogeneous,showing low signal on T1WI and high signal on T2WI,slightly heterogeneous signal and thickening of the surrounding fascia.On CT imaging,the muscle fiber density were increased,the edge were blurred,and the thickness of the fascia were uneven.The other 5 sides of thickened piriformis muscle were caused by developmental variation and showed uniform or localized thickening on imaging,which were no obvious abnormal enhancement in signal intensity and density after contrast enhancement.Conclusions Sciatic nerve entrapment syndrome was often secondary to pelvic wall tumors,piriformis muscle development variation,adhesion and inflammation after radiotherapy,which compress the pel-vic segment of the sciatic nerve and cause entrapment syndrome.Sciatic nerve entrapment due to primary sciatic nerve dis-ease was relatively rare.
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