Ultrasound Image Characteristic Analysis of Sciatic Nerve and Main Branches in Third Trimester

Abstract

The pathogenesis and clinical characteristics of sciatica caused by pregnancy were summarized to reduce the incidence of misdiagnoses and missed diagnoses. The sciatic nerve, tibial nerve, common peroneal nerve, sural nerve, superficial peroneal nerve, saphenous nerve, and lateral femoral cutaneous nerve were examined using ultrasonography for 7 imaging features, including the shape and internal structure of the peripheral nerves of the lower extremities. Randomly selected healthy pregnant women and pregnant women without peripheral nerve damage in the third trimester were examined using a Philips iU22 color Doppler ultrasound scanner with a L12-5 high-frequency probe. The probe was moved anatomically along the peripheral nerves of the lower extremities, including the sciatic nerve, tibial nerve, superficial peroneal nerve, saphenous nerve, and lateral femoral cutaneous nerve. The nerve morphology, structural characteristics, and accompanying blood vessels, tendons, muscles, bones, and other tissues and structures were examined. To determine the site at which to measure the cross-sectional area of the target nerve, we selected places with obvious body surface signs (e.g., popliteal fossa, medial malleolus), less nerve position variation (e.g., neurology start, nerve bifurcation), ultrasound-visible features (e.g., popliteal arteriovenous, fibula head). Ultrasound examination showed that the cross-sections of the peripheral nerves of the lower limbs were triangular, circular, quasicircular, quasitriangular, oval, broad bean-shaped, and drop-shaped. When viewing the same measurement site, the nerve shape was similar and the shape variation was small. However, at different measurement sites, large differences were seen in the shape of the nerves. Hyperechoic shadows are present around the nerves, which make the nerves and adjacent tissues clearly visible. Inside the nerves, at the proximal end of the limbs and in the nerves with larger cross-sections, echo images of varying heights were seen. The arrangement was uniform and regular, and the high echo images were arranged in dots or lines, interlayered with the low echo images to form a honeycomb-like structure. The high and low echo images were arranged uniformly and densely in the distal limbs or inside the small nerves with a small cross section. Arranged in a dot pattern, the structure of nerve walking and accompanying tissues is consistent with the anatomy and is characteristic. We found no significant differences in the peripheral nerve cross-sectional area between the left and right legs but did find a positive correlation with body mass index and age.