High-Definition and Three-Dimensional Volumetric Ultrasound Imaging of the Sciatic Nerve

Fig. 18.1

Anatomical illustration showing the formation of the lumbosacral plexus by the union of the anterior primary rami of the L4, L5, S1, S2, S3, and S4 spinal nerves

Fig. 18.2

Rendered sagittal oblique MRI image from the level of the greater sciatic foramen, demonstrating the sacral plexus and the parasacral relations of the sciatic nerve. Note that the sciatic nerve exits the pelvis through the greater sciatic foramen lying deep to the piriformis muscle

Fig. 18.3

Sagittal sonogram at the level of the greater sciatic foramen (parasacral scan) showing the sacral plexus and the sciatic nerve as it exits the pelvis to enter the infra-piriformis fossa. Note the close relationship of the sacral plexus to the pelvic peritoneum (hyperechoic), and the hypoechoic perineural space deep to the piriformis muscle and posterior to the sciatic nerve

Fig. 18.4

Sagittal sonogram showing the sciatic nerve as it exits the greater sciatic foramen between the piriformis muscle and the gemelli muscles and the tendon of the obturator internus. Note the hypoechoic perineural space between the sciatic nerve and the piriformis muscle posteriorly. The sciatic nerve is also seen to continue distally to enter the subgluteal space between the gluteus maximus posteriorly and the quadratus femoris anteriorly

Fig. 18.5

Transverse sonogram of the gluteal region showing the sciatic nerve between the gluteus maximus and the gemelli muscles, immediately distal to the greater sciatic foramen (parasacral position)

Fig. 18.6

A transverse iSlice display of the sciatic nerve, rendered from a three-dimensional (3D) ultrasound volume of the parasacral region, in color (sepia tone) mode. In this figure, 16 contiguous transverse cuts of the acquired sciatic nerve volume (0.8–0.9 mm apart) are displayed. The iSlice mode allows display of the acquired volume similar to a CT scan, and this can be done in all three planes (transverse, sagittal, and coronal). By varying the thickness of the slice, one can accurately delineate changes in the anatomy of the volume as one navigates through it. The distance covered by a single sweep with the volume linear array transducer used (VL13, 13–5 MHz, (Philips Healthcare, Andover, MA, USA) is 42 mm

Fig. 18.7

Multiplanar anatomy (rendered from the Visible Human data set) of the sciatic nerve at the subgluteal space. The reference marker (green crosshair) has been placed over the sciatic nerve in the transverse view and its corresponding position in the sagittal and coronal images can be seen. AM adductor magnus, BF biceps femoris, GI gemellus inferior, GM gluteus maximus, GS gemellus superior, IT ischial tuberosity, OI obturator internus, PF piriformis, QF quadratus femoris, VL vastus lateralis (Courtesy of the Visible Human Server at Ecole Polytechnique Fédérale de Lausanne, Visible Human Visualization Software (http://visiblehuman.epfl.ch)

Fig. 18.8

Figure highlighting the anatomical structures that are insonated during a transverse ultrasound scan for the sciatic nerve at the subgluteal space, between the greater trochanter and ischial tuberosity. The plane of the ultrasound beam has been superimposed over the anatomy imaged (rendered from the Visible Human data set) (Courtesy of the Visible Human Server at Ecole Polytechnique Fédérale de Lausanne, Visible Human Visualization Software (http://visiblehuman.epfl.ch)

Fig. 18.9

Transverse (axial) CT image showing the subgluteal space between the gluteus maximus muscle posteriorly and the quadratus femoris muscle anteriorly, at the level of the greater trochanter and ischial tuberosity

Fig. 18.10

Transverse (axial) MRI scan demonstrating the subgluteal space between the gluteus maximus muscle posteriorly and the quadratus muscle anteriorly, at the level of the greater trochanter and ischial tuberosity. Note the tendons of the semitendinosus and biceps femoris at the medial end of the subgluteal space

Fig. 18.11

Transverse sonogram of the gluteal region between the greater trochanter and ischial tuberosity, demonstrating the hypoechoic subgluteal space between the hyperechoic epimysium of the gluteus maximus muscle posteriorly and the quadratus femoris muscle anteriorly. The sciatic nerve is seen as a hyperechoic nodule in the medial aspect of the subgluteal space. Also note the origin of the tendon of the biceps femoris from the ischial tuberosity

Fig. 18.12

A multiplanar 3D ultrasound image of the sciatic nerve at the subgluteal space between the greater trochanter and ischial tuberosity. The “reference maker” (green crosshair) has been placed over the sciatic nerve, and corresponding views of the sciatic nerve in the (a) transverse, (b) sagittal, and (c) coronal planes can be seen. Also note the hypoechoic subgluteal space in the transverse and sagittal sonograms. GT greater trochanter, IT ischial tuberosity

Fig. 18.13

A multiplanar (niche view) 3D ultrasound image of the sciatic nerve between the epimysium of the gluteus maximus and the quadratus femoris muscle at the subgluteal space