Imaging in extraspinal sciatic neuropathy

Transcription

1 Imaging in extraspinal sciatic neuropathy Award: Winner Poster No.: P-0081 Congress: ESSR 2012 Type: Scientific Exhibit Authors: T. Moritz, G. Kasprian, D. Prayer, G. Bodner ; Vienna/AT, Wien/AT Keywords: Trauma, Inflammation, Edema, Diagnostic procedure, Ultrasound, MR, Neuroradiology peripheral nerve DOI: /essr2012/P-0081 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. Page 1 of 30

2 Purpose The purpose of this educational exhibit is to: 1) Describe the Ultrasound Anatomy of the sciatic nerve 2) Describe typical Ultrasound signs of nerve pathology 3) Present exemplary Ultrasound cases of extraspinal sciatic disease. Methods and Materials Anatomy The sciatic nerve derives from the L4-S3 branches of the lumbosacral plexus. It passes through the greater sciatic foramen from where it passesbelow the piriform muscle and enters the thigh between the ischial tuberosity and the greater trochanter of the femur, benath the gluteus maximus muscle. It then descends lying on the adductor magnus muscle, being crossed by the long head of the biceps femoris muscle (see Figure 1 and 2). Sonomorphology of peripheral nerves Nerves are cable-like structures that consist of axons surrounded by myelin-sheaths and Schwann-cells. Several of these nerves form a fascicle, several fascicles form a nerve. The fascicles are surrounded by the epineurium. The echostructure of a nerve can be seen in Figure 3. Pathology Different factors such as external pressure, trauma, dissection, immobilisation or metabolic changes can lead to the dysfunction of a peripheral nerve. The mechanical mechanisms of nerve injury have been classified by Seddon (see also Figure 4): Neuropraxia: Temporary loss of conduction without loss of axonal continuity Page 2 of 30

3 Axonotmesis: Loss of continuity of axon and myelin sheath, epi-/perineural structures preserved Neurotmesis: Disruption of the entire nerve fiber Important features to look for in suspected peripheral nerve pathology are: Fascicular swelling Increase in nerve diameter Nerve discontinuity Increased intraneural vascularisation Disturbed mobility in relation to the surrounding tissue Altered contact to the surrounding tissue (e.g. scarring) Correlation with patient symptoms (e.g. positive Tinel sign). Common sciatic nerve pathology: The most common extraspinal sciatic diseases are of traumatic origin, most frequently caused by surgery. Pelvic and femoral fractures, as well as hematoma in the pelvic and gluteal region may lead to nerve dissection, compression or ischemia (disturbance of the blood flow in the vasa vasorum). Other causes may be of infectious or of tumoral origin, as well as compression by surrounding structures as in the case of the piriformis-syndrome. Images for this section: Page 3 of 30

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5 Fig. 1: Anatomy of the dorsal thigh region (Gluteus maximus and medius removed). Fig. 2: Axial Ultrasound image in the gluteal region. The sciatic nerve marked in yellow colour. GM=Gluteus maximus mucle, VL=Vastus lat. Muscle, AD=Adductor magnus muscle, ST=semitendinosus muscle, FB= Femoral bone Fig. 3: Ultrasound morphology of a large peripheral nerve (the median nerve in this case). It is easy to depict the nerve fascicles (1) and the surrounding epineural stuctures (2) Page 5 of 30

6 Fig. 4: Classification of nerve injury according to Seddon. Upper left: Normal nerve; Upper right: Neuropraxia; Lower left: Axonotmesis; Lower right: Neurotmesis Page 6 of 30

7 Fig. 5: Scheme of important structural changes of peripheral nerves. Page 7 of 30

8 Results We present 6 cases of patients with extraspinal sciatic disease. Ultrasound (US) images were obtained on Logiq e9 (GE) and IU22 (Philips) machines. MRI images were obtained on a 3T Philips Achieva scanner. Case 1 A 13 year-old boy complains about electrizising pain in the innervation area of the sciatic nerve after prolonged treatment in the intensive care unit because of a spontaneous brain stem bleeding. For images of this case see Figures 6 to 8 on the right. Imaging findings showed unilateral swelling and edema of the right sciatic nerve, most likely due to a focal neuritis. Symptoms and swelling diminished after repeated ultrasound-guided perineural cortisone injection. Case 2 A 45 year-old woman is referred because of a quickly growing mass in the distal thigh and popliteal region. The patient complained of a burning sensation on the plantar pedis. The patient is otherwise healthy. For images of this case see Figures 9 to 13 on the right. Histological evaluation after Ultrasound-guided biopsy of the lesion showed a (very rare) diffuse B-cell lymphoma of the sciatic/tibial nerve. Case 3 A 34-year-old male is referred to imaging procedures because of increasing pain in the innervation area of the sciatic nerve, especially while sitting. He had a major pelvic trauma about 15 years ago with necrosis and resection of the Gluteus maximus muscle and a Latissimus-Flap in the gluteal region. Page 8 of 30

9 For images and a video of this case see Figures 14 to 17 on the right. Th patients symptoms were thought to be caused by the exposure of the sciatic nerve due to the missing of the Gluteus maximus muscle. The patient improved with supportive measures avoiding to compress the sciatic nerve while sitting. Case 4 A 45-year-old male is referred to sonographic evaluation because of sciatica after a gunshot-injury two months ago. For images of this case see Figures 19 to 23 on the right. During the operation a penetration injury to the sciatic nerve and an incomplete Neurotmesis were found (see Figures 22 and 23). Case 5 A hobby athlete in preparation for a marathon is complaining about pain in the gluteal and dorsal thigh region reaching to the poplitea. For video of this case see Figure 24 on the right. The changes were thought to be caused by a focal neuritis of the sciatic nerve and diminished after ultrasound-guided perineural cortisone injections. Case 6 A 25-year-old patient is referred to a US examination because of a slowly growing mass in the distal thigh-region. For images of this case see Figures 25 to 26 on the right. Histologic workup after the surgical resection showed that the lesion was a fibrolipoma of the sciatic nerve. Page 9 of 30

10 Images for this section: Fig. 6: Case 1: Ultrasound images obtained in the gluteal region shows marked sidedifference in the nerve diameter of the sciatic nerve. Page 10 of 30

11 Fig. 7: Case 1: Short T1 Inversion Recovery (STIR-) Sequence of the posterior thigh region in a coronal plane. Edema and swelling of the sciatic nerve on the right side (black arrowheads) compared to the left hand side (white arrowheads) Fig. 8: Case 1: Comparison between Ultrasound findings and axial T1-weighted 3D fast GRE MRI sequence. Page 11 of 30

12 Fig. 9: Case 2: Panoramic view ultrasound image obtained in the sagittal plane demonstrates a large mass in the course of the sciatic nerve continuing into the tibial nerve. Some fascicles can be followed through into the mass. Fig. 10: Case 2: Composed ultrasound image in the sagittal plane demonstrates the large mass in the course of the sciatic nerve continuing into the tibial nerve. The mass is outlined by the blue lines, the sciatic/tibial nerve is marked by yellow lines. Page 12 of 30

13 Fig. 11: Case 2: Doppler sonographic image demonstrates hypervascularity of the mass. Page 13 of 30

14 Fig. 12: Case 2: Unenhanced T1-weighted Turbo-spin-Echo (TSE) sequence in a sagittal plane demonstrating the mass in the course of the sciatic and tibial nerve in the popliteal region. Note: MRI images were obtained approx. 4 weeks prior to Ultrasound Page 14 of 30

15 Fig. 13: Case 2: Unenhanced axial T1-weighted TSE-sequence and axial STIRsequence demonstrating the mass in the course of the sciatic and tibial nerve in the popliteal region Note: MRI images were obtained approx. 4 weeks prior to Ultrasound Fig. 14: Case 3: Due to the resection of the gluteus maximus muscle, the sciatic nerve is running superficially. The fascicular pattern can be very well delineated. Page 15 of 30

16 Fig. 15: Case 3: Axial CT image demonstrating the superficial course of the sciatic nerve (white arrow) Page 16 of 30

17 Fig. 16: Case 3: Axial CT series demonstrating the missing Gluteus maximus muscle, the Latissimus-flap and the exposed sciatic nerve (see also Figure 15) Page 17 of 30

18 Fig. 17: Case 3: A division of the sciatic nerve can be seen with one portion running around the semitendinosus tendon Page 18 of 30

19 Fig. 18: Case 3: Video following the sciatic nerve from distal to proximal showing the division and reunion of the sciatic nerve. Page 19 of 30

20 Fig. 19: Case 4: Video sequence of the US images acquired in the sagittal plane. Three nerve lesions can be identified, marked with arrows Page 20 of 30

21 Fig. 20: Case 4: US-examination in the sagittal plane following the sciatic nerve from proximal to distal. Two of the three hypoechoic structural alterations of the nerve can be seen, representing traumatic neuroma. Page 21 of 30

22 Fig. 21: Case 4: US images in the axial plane moving from proximal to distal showing a central hypoechoic defect in the sciatic nerve in one of the neuroma found in the sagittal plane. This turned out to be a gunshot penetration injury of the sciatic nerve (also see Figure 22) Page 22 of 30

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24 Fig. 22: Case 4: Intraoperative image showing the gunshot penetration defect demonstrated in Figure 21. Fig. 23: Case 4: Intraoperative image of the on of the nerve defects demonstrating incomplete Neurotmesis of the sciatic nerve. Page 24 of 30

25 Fig. 24: Case 5: Axial MRI STIR-sequence demonstrates edema of the right sciatic nerve and the surrounding tissue including the biceps, adductor magnus and semitendinosus muscle. Page 25 of 30

26 Fig. 25: Case 6: Left: US shows an oval-shaped and well defined mass within the sciatic nerve. Right: A T1-weighted TSE MRI sequence demonstrates the fat-like signal characteristics of the lesion Page 26 of 30

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28 Fig. 26: Case 6: Intraoperative view demonstrating the fatty tissue structure of the lesion. Histologic workup after surgical resection showed the lesion to be a fibrolipoma of the sciatic/tibial nerve. Page 28 of 30

29 Conclusion MRI and US have great potential in detecting and characterising peripheral nerve pathology. Both techniques have their unique value and strongly complement each other in this respect. Therefore, both modalities should be combined for the diagnosis and treatment planning in suspected peripheral nerve pathology. References Ergun, T., & Lakadamyali, H. (2010). CT and MRI in the evaluation of extraspinal sciatica. The British journal of radiology, 83(993), Silvestri, E., Martinoli, C., Derchi, L., Bertolotto, M., Chiaramondia, M., & Rosenberg, I. (1995). Echotexture of peripheral nerves: correlation between US and histologic findings and criteria to differentiate tendons. Radiology, 197(1), 291. Simmons, D. N., Lisle, D. A., & Linklater, J. M. (2010). Imaging of peripheral nerve lesions in the lower limb. Topics in magnetic resonance imaging : TMRI, 21(1), Peer, S., Kovacs, P., Harpf, C., & Bodner, G. (2002). High-resolution sonography of lower extremity peripheral nerves: anatomic correlation and spectrum of disease. Journal of ultrasound in medicine : official journal of the American Institute of Ultrasound in Medicine, 21(3), Konstantinou, K., & Dunn, K. M. (2008). Sciatica: review of epidemiological studies and prevalence estimates. Spine, 33(22), Bianchi, S., Martinoli, C., & Derchi, L. E. C. (2007). Ultrasound of the musculoskeletal system (p. 974). Springer Verlag. Peer, S., & Bodner, G. (2008). High-Resolution Sonography of the Peripheral Nervous System (p. 201). Springer Verlag. Personal Information Thomas Moritz, MD is a resident at the Department of Radiology, Medical University of Vienna. His main area of interest is both the diagnostic and therapeutic use of High Resolution Ultrasound in peripheral nerves and musculoskeletal applications. Page 29 of 30

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