Imaging lumbosacral plexus using CT and MR: Anatomic and clinical correlations

Transcription

1 Imaging lumbosacral plexus using CT and MR: Anatomic and clinical correlations Poster No.: C-737 Congress: ECR 2009 Type: Educational Exhibit Topic: Neuro Authors: S. Belião, Á. Almeida; Lisbon/PT Keywords: ct, MR, lumbosacral plexus DOI: /ecr2009/C-737 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 21

2 Learning objectives To present the lumbosacral plexus regional anatomy using CT and MRI. To make a pictorial review of the main lumbosacral plexopathy. Background The complex anatomy of the lower lumbar spine and the diverse diseases affecting lumbosacral plexus are diagnostically challenging. Also, surgical/ medical management and operative technique depend on an accurate determination of the specific structures involved. In this context, imaging techniques can be useful in the evaluation of the diverse disorders affecting the lumbosacral plexus [1]. Pathologic conditions affecting the lumbosacral plexus were studied by reviewing CT and MR examinations performed at our institution on 100 patients with signs and symptoms possibly related to the lumbosacral plexus. Based on our clinical experience, we describe the abnormal radiologic findings in this population and the imaging methods applications in the evaluation of lumbosacral plexopathy. Imaging findings OR Procedure details Anatomy Understanding the relevant lumbosacral plexus is essential for the correct interpretation of imaging findings. The lumbosacral plexus is formed by the anterior branches of the lumbar and sacral spinal nerves and is anatomically located behind the psoas muscle. Its branches provide sensory and motor innervation to the lower limb. The branches of L1-L3 and part of L4 form the lumbar plexus. The obturator nerve and the femoral nerve originate from here, in addition to several short muscular branches. The lumbar plexus gives off direct short Page 2 of 21

3 muscular branches to the hip muscles, namely, to the greater and lesser psoas, the lumbar quadrate muscle and the lumbar intercostal muscles [2]. The remainder of the L4 nerve and L5 nerve join to form the lumbosacral trunk, which then unites with sacral branches S1-S3 to form the sacral plexus on the anterior surface of the piriform muscle, making it the key anatomic landmark for locating the sacral plexus and sciatic nerve. Contributions from the lower lumbar plexus and upper sacral plexus originate the sciatic nerve. This nerve passes through the sciatic foramen and descends the posterior aspect of the leg until it reaches the popliteal fossa, where it divides into the posterior tibial and common peroneal nerves. Branches from both the lumbar and sacral plexus also form the inferior and superior gluteal nerves innervating the lateral and posterior hip musculature. Branches from the sacral plexus alone converge to form the pudendal nerves, innervating the pelvic floor musculature and perineal sensation [3]. (Fig.1, 2) Page 3 of 21

4 Fig.: Figure 1:Simplified schema of the lumbosacral plexus[4] Page 4 of 21

5 Fig.: Fig.2: Simplified schema of the lumbosacral plexus[1] Lumbosacral Plexopathy Lumbosacral plexopathies usually present with diffuse weakness of the affected lower extremity, which can involve the femoral and sciatic territories depending upon whether the lumbar and sacral plexi are both involved. Weakness of the gluteal muscles will likely be present due to injury to fibers destined for the superior and inferior gluteal nerves. Sensory loss involving femoral, peroneal and tibial territories or lateral and posterior tight also can occur. The main lumbosacral plexopathies are resumed in the following table: Plexopathies Etiology Symptoms Traumatic injury Compressive lesions Radiation-induced injury - Rare lesions - Blunt or penetrating trauma; compression during delivery - Hematoma, abscess, tumour in retroperitoneum - May occur 2-20 years after radiation therapy - Clinical assessment can be difficult in these patients. - Profound weakness and sensory loss of the affected leg - Slowly progressive weakness and sensory loss affecting entire leg - Bladder and fecal incontinence Page 5 of 21

6 Diabetic amyotrophy Idiopatic lumbosacral plexitis - Poorly controlled diabetes - Perivascular inflammation and secondary nerve infarction involving L2,L3 and L4 roots - Associated with previous infection or trauma - Severe proximal leg and hip pain. - Progressive proximal weakness of the affected extremity - Severe pain is predominant - Weakness and atrophy of the affected leg - Sensory loss is limited Adapted from: Rutkove S. Overview of lower extremity peripheral nerve syndromes.2008 [3]. Imaging techniques MR Imaging MR imaging often determines whether a mass is intrinsic or extrinsic to the plexus and, for extrinsic masses, determines the site of the displaced and compressed nerve fibers before surgical intervention. Such information is valuable for benign as for malignant processes [6]. T1-weighted images display regional anatomy best. T2-weighted images are useful to detect pathologic changes within components of the plexus. Fat suppression is used because abnormal intraneural signal intensity may be obscured by adjacent fat signal intensity. Gadolinium contrast is useful for suspected neoplasm, radiation injury, inflammation, abscess and following peripheral nerve surgery [4]. Abnormal findings include loss of fat planes around all or part of plexus component, diffuse or focal enlargement of a component, hyperintensity on T2-weighted images and/or enhancement on T1-weighted images with fat suppression [4]. CT Imaging CT is an excellent imaging modality for visualizing most pelvic structures. However, it has limitations in individualizing the individual extradural peripheral nerves that form the lumbosacral plexus from the normal adjacent soft tissues. This method can be useful in patients with pacemakers or other conditions contraindicating MR. Also can give better information about bony elements and offers the advantage of providing guidance for percutaneous needle biopsy in appropriate cases. In our population, demonstrable lesions of the lumbosacral plexus include mass and infiltration. Metastatic lesions were the most common pathology found but other malignant tumours and benign lesions were detected. Traumatic injuries are rare but were also represented. TRAUMATIC INJURY Page 6 of 21

7 Injury to the lumbosacral plexus can result from blunt or penetrating trauma. Because of the stability of the pelvic girdle and lumbar spine, blunt traumatic injury is relatively uncommon, most often seen in high-velocity injuries. Conversely, a portion of the plexus that lies over the pelvic brim may be compressed during childbirth. Findings can be acute or chronic (Fig.3). Fig.: Fig.3. - Stress fracture of right sacral wing after traumatic injury in a 70-year-old female patient. CT coronal image show potential involvement of right sacral roots. MASS INVOLVING THE PLEXUS Neoplasms can arise primarily from the neural components of the lumbosacral plexus or involve it secondarily: 1. Nerve sheath tumours (Fig.4) 2. Metastases(Fig.5,6) 3. Direct extension of non-neurogenic primary tumour (Fig.7,8,9) 4. Lymphoma(Fig.10) The main benign conditions affecting the plexus are: hematoma, fibromatosis, lipoma, myositis ossificans, ganglioneuroma, hemangioma and lymphangioma. Page 7 of 21

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9 Fig.: Fig.4. - Malignant schwannoma in a 37-year-old male patient. Sagittal, coronal and axial T1 weighted MR images after IV administration of contrast material show the presence of a mass occupying the sacrum, with high signal intensity and heterogeneous enhancement. Page 9 of 21

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11 Fig.: Fig year-old female patient with metastatic colon carcinoma and metastasis involving sacral roots. Images show the presence of a soft tissue mass in the sacral spinal canal with an extra-compartimental component.a-axial enhanced with Gadolinium T1 MR imageb-sagittal T1 MR imagec-sagittal T2 TSE MR image Page 11 of 21

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13 Fig.: Fig.6. - Metastasis involving right lumbosacral plexus in a 56-year-old male patient with melanoma. Axial CT and coronal T2 TSE MR images show a metastatic lesion involving the pedicle and posterior arch of L3, right psoas muscle and lumbar roots. Fig.: Fig year-old female patient with leyomiosarcoma of pelvis and bilateral lumbosacral plexus involvement. Axial CT image shows an infiltrative soft tissue mass causing destruction of the sacroiliac joint, with synovial interruption. Page 13 of 21

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15 Fig.: Fig year-old male patient with multiple myeloma. Plain film and axial CT images show lytic lesions replacing most of the left iliac bone and sacroiliac joint, possibly invading ipsilateral lumbosacral plexus. Page 15 of 21

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17 Fig.: Fig.9. - Plasmocytoma in a 41-year-old female patient. Coronal and axial CT images show soft tissue paravertebral masses with extensive calcifications, involving bilaterally the psoas and lumbar roots. Page 17 of 21

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19 Fig.: Fig Bilateral lumbosacral plexus involvement in a 75-year-old female patient with lymphoma. These axial CT images demonstrate a soft tissue perivertebral mass and bone destruction, with a mixed sclerotic and osteolytic character. INFECTION Soft-tissue abscesses (Fig.11) and spondylodiscitis (Fig.12) can spread along normal anatomic pathways to affect the lumbosacral plexus. The psoas muscle, iliac muscle and iliac vessels provide potential routes for extension of abdominal infection into the pelvis. Gluteal abscesses can directly affect the proximal sciatic nerve and can reach the sacral plexus through the greater sciatic foramen. Fig.: Fig.11: Psoas abscess in a 35-year-old male patient with weakness of the right leg. Axial CT image shows a collection (arrow) in the right psoas. Page 19 of 21

20 Fig.: Fig.12: Multiple abscesses in a patient with tuberculous spondylodiscitis. Sagittal images show infection of a lumbar disk and adjacent vertebral bodies at L3-L4 level. Coronal image show bilateral paraspinal abcesses involving the psoas and lumbar roots. A, C- Sagittal and Coronal T1- weighted MR images after IV administration of contrast material.b- Sagittal T2- weighted MR image. Conclusion There is a wide spectrum of pathologic processes involving the lumbosacral plexus. Because of the complex regional anatomy it may be difficult to locate clinically with precision the level of pathological involvement. The detailed imaging with CT and MR in these patients can provide important information about the specific structures involved, facilitating careful treatment planning. Page 20 of 21

21 Personal Information Sara Belião Department of Radiology, Hospital S. Francisco Xavier - Lisbon, Portugal sara.beliao@clix.pt References [1] Blake LC, Robertson WD, Hayes CE. Sacral Plexus: Optimal Imaging Planes for MR Assessment. Radiology 1996; 199: [2] Kahle W. Colour Atlas of Human Anatomy vol 3: Nervous System and Sensory Organs 5 th Ed. Thieme: [3] Rutkove S. Overview of lower extremity peripheral nerve syndromes [4] Gebarski KS, Gebarski SS, Glazer GM, et al. The lumbosacral plexus: Anatomic-radiologicpathologic correlation using CT. Radiographics 1986; 3: [5] Gierada DS, Erickson SJ. MR Imaging of the Sacral Plexus: Abnormal Findings. AJR 1993; 160: [6] Bowen BC, Seidenwurm DJ; Plexopathy. American Journal of Neuroradiology 2008; 29: [7] Beatrous TE, Choyke PL, Frank JA. Diagnostic Evaluation of Cancer Patients with Pelvic Pain: Comparison of Scintigraphy, CT and MR Imaging. AJR 1990; 155: [8] Moore KR, Tsuruda JS, Dailey AT. The Value of MR Neurography for Evaluating Extraspinal Neuropathic Leg Pain: A Pictorial Essay. American Journal of Neuroradiology 2001; 22: Page 21 of 21