Application Of HRCT Reconstruction In 5th Lumbar Nerve, Sacral Plexus, The Proximal Sciatic Nerve And Related Diseases

BackgroundThere was a wide variety of lumbosacral neurological diseases, including congenital variation of nerve root, Protrusion (bulging) of lumbar intervertebral disc, trauma, primary or metastatic tumors, nerve root sheath cysts, tuberculosis, hypertrophy of transverse process of L5 vertebra, piriformis syndrome, etc. These lesions were often direct or indirect oppression and invasion lumbosacral nerve, thus producing complex clinical symptoms. Light diseases could cause limb sensory or motor dysfunction, severe cases could lead to loss of nerve function, limb paralysis and other serious consequences to patients themselves and their families a great deal of pain and burdens. How quickly and effectively to help the clinical diagnosis and then take the best means of treatment was vital. However, many diseases were often found outside of the spinal canal causing spinal nerve compression, invasion, injury, etc. The conventional CT, MRI showed nerve section, often not recognized, mainly rely on clinical symptoms and signs of neuropathy to largely determine the sites of lesions, resulting in adverse clinical consequences of misdiagnosis, mistreatment and so on. The L5 nerve traveled quite a long distance outside of the spinal canal and had complex adjacent anatomy. It located in the lumbosacral junction, which was the boundary of travelling down of spinal biomechanics, so lumbar vertebral degeneration and other diseases easily lead L5 nerve compression or injury. sciatica of nerve trunk was a common symptom of piriformis syndrome, most scholars believed that piriformis syndrome was a nerve entrapment syndrome characterized by the entrapment of the sciatic nerve and its nutrient vessels by piriformis muscle edema, hypertrophy, inflammation, degeneration or contracture. the sciatic nerve in the infrapiriformis foramen was entrapped by edematous and contractural piriformis muscle when the sciatic nerve and the piriformis presented anatomical variation that a part of sciatic nerve passing through the piriformis muscle. However, some academics had suggested stenosis of pelvic outlet of sciatic nerve, that is the sciatic nerve was entrapped in the pelvis outlet due to increasing interstitial fluid pressure caused local pathological changes in adhesion, edema, venous congestion and dilation. It was by far lack of radiologic evidence in pelvic outlet segment of sciatic nerve. Conventional CT cross-sectional scans and three-dimensional reconstruction was difficult to identify or difficult to show neural anatomical structure because nerve cord was the cable structure and vary small passing through the complex soft tissue and vascular plexus space in extra-vertebral canal. Inside the nerve cord was solid-like structure composed of nerve fibers, so The traditional myelography was so difficult to introduce a contrast agent for artificial contrast that only display the spinal nerve roots. In recent years, many studies of magnetic resonance neurography in peripheral nerves had high requirements for equipment and imaging parameters, it had long scan time and contraindication to metal internal fixation operation. After the advent of high resolution computed tomography, it greatly improved the organization and spatial resolution, also provided the possibility for displaying small nerve. Therefore, we hoped to reconstruct the course, morphology, branches and relationship with adjacent tissues of normal L5 nerve, sacral plexus and the proximal sciatic nerve by multiple-plane reconstruction techniques at the same slice, and hoped to provide intuitionistic imaging evidence for clinical diagnosis and treatment of lumbosacral nerve disorders.Part I The anatomical study of HRCT in normal L5 nerve, sacral plexus, the proximal sciatic nerveObjectiveTo investigate the value of multiple-plane reconstruction techniques at the same slice in displaying normal L5 nerve, sacral plexus and the proximal sciatic nerve sciatic nerve and study the course, morphology, branches and relationship with adjacent tissues of normal L5 nerve, sacral plexus and the proximal sciatic nerve.Materials and MethodsThe imaging of 20 normal adults (12 men,8 women; aged 20～69 years with a mean of 51.85±11.90) of no low back and leg pain and normality by scanning with pelvic CT were collected at the Navy General Hospital form January 2013 to December 2014.8 cases of normal adults were scanned with Light Speed 64-slice spiral CT (GE Company) and 12 cases with Philips Brilliance iCT (256-slice) in routine posture of the lumbar vertebrae. All original images were reconstructed and observed on Extended Brilliance workstation (EBW 4.0) of Philips Brilliance iCT (256-slice) with multiple-plane reconstruction techniques at the same slice. According to normal anatomy of L5 nerve, sacral plexus and the proximal sciatic nerve, we would perfectly show morphology and length of nerves as much as possible and save imaging with DICOM. All reconstructed images were observed by two experienced radiologist.ResultsThe L5 nerve, sacral plexus and the proximal sciatic nerve were clearly showed with multiple-plane reconstruction techniques at the same slice.20 cases (100%) normal L5 nerve were symmetrically displayed from starting point to margin of psoas major and 16 cases (80%) to upper sacroiliac joint in oblique coronal plane.20 cases (100%) L5 nerve were displayed from starting to sacroiliac joint plane and 6 cases (30%) were showed to sacral plexus or the proximal sciatic nerve in internally rotating oblique coronal plane.SI-S3 nerves were exited from the same sequence of sacral foramen and formed slight enlargements of ganglion intraforaminal. The nerves passed through the posterolateral wall of pelvic cavity and in front of sacroiliac joint, sacrum and piriformis after exiting from sacral foramen. S1-S3 nerves displayed arc towards to posterior inferior and lateral on the edge of piriformis. S1-S3 nerves collected acute angle and form sacral plexus in front of piriformis. It could be displayed separately every sacral nerve and longer length in internally rotating oblique sagittal plane.20 cases (100%) could be displayed full-length of S1 and S2 nerves in this plane, but 3 cases (15%) of S3 nerve could not be reconstructed the whole length, only appeared intraforaminal portion.Sciatic nerve that had low density septa of fat and fiber passed through infrapiriformis foramen and displayed flat type in front of piriformis. It showed infrapiriformis foramen of the triangle acme outward, which upper bound was the lower edge of piriformis, lower bound was superior gemellus muscle and medial bound was sacrotuberal ligament in 20 cases.6 cases could be appeared the full length of L5 nerve to the proximal sciatic nerve.6 cases (30%) of sciatic nerve presented variation in 20 cases, in which there were a divided sciatic nerve passing through and below the piriformis muscle in 2 cases (Type Ⅱ), and left type Ⅱ variation in 3 cases, right variation in 1 case.Conclusion1 It could display the course, morphology, branches and relationship with adjacent tissues of normal L5 nerve, sacral plexus and the proximal sciatic nerve by multiple-plane reconstruction techniques at the same slice and show a higher rate of extraspinal nerve.2 L5 nerve, sacral plexus and the proximal sciatic nerve had a complex course and relationship with adjacent tissues. It displayed the longest nerve in fine-tuning of internally rotating oblique coronal plane.PartⅡThe clinical applications of HRCT reconstruction in L5 nerve, sacral plexus, the proximal sciatic nerve correlated diseasesObjective42 patients with the L5 nerve, sacral plexus and the proximal sciatic nerve extraspinal diseases were performed with multiple-plane reconstruction techniques at the same slice.The relationship between these nerves and diseases and morphology of nerves were analyzed by reconstructed images to explore the clinical application of multiple-plane reconstruction techniques at the same slice in above nerves correlated diseases.Materials and MethodsThe imaging of 42 patients(23 men,19 women; aged 23-76 years with a mean of 53.16+13.16) of low back and leg pain at the Navy General Hospital and PLA General Hospital, and all patients had to undergo a clinical examination and treatment diagnosis or pathologically confirmed.11 cases of normal adults were scanned with Light Speed 16-slice spiral CT (GE Company) and 31 cases with Philips Brilliance iCT (256-slice) in routine posture of the lumbar vertebrae. The scanning range included the whole lesions as much as possible. All the image post-processing was same to Part I. According to normal imaging of L5 nerve, sacral plexus and the proximal sciatic nerve, it was observed that course, shape, angle changes of above nerves and relationship with disease. We would perfectly show morphology of nerves and the relationship with diseases as much as possible and save imaging with DICOM.ResultsIt was clearly displayed that travel direction and tension status change of spinal nerve and relationship with disease in 42 cases of extraspinal lumbosacral nerve lesions with multiple-plane reconstruction techniques at the same slice.1 The L5 nerve extraspinal compression in 33 cases (45 sides)1.1 L5-S1 lateral intervertebral disc herniation with bone hyperplasia in 12 cases (14 sides):The L5 nerve was compressed by L5-S1 intervertebral disc herniation and bone hyperplasia, showed traveling deviation from the normal anatomy of the nerve, eminence and thickening locally, most of nerves atrophy, higher density and adhesion with adjacent tissue.1.2 The L5 nerve was compressed by hypertrophy of transverse process of L5 vertebra in 6 cases (7 sides):L5 nerve was atrophy and trapped by new bone formation arising from a pseudarthrosis which was present between the hypertrophy of transverse process of L5 vertebra and the sacral ala, and adipose connective tissues adjacent to L5 nerve was less or disappearance.1.3 L5 spondylolysis in 8 cases (16 sides):L5 nerve which enclosed intervertebral disc herniation and laterally vertebral body was eminence and compressed in the side of vertebral body. It showed "right angle" sign when vertebra was obvious slippage.1.4 L5 vertebral compression fracture in 3 cases (3 sides):L5 nerve was vague and deviation from normal anatomy pathway or interrupt, atrophy1.5 Lumbosacral tumors in 4 cases (5 sides):It clearly showed the site of affected nerve and the degree of compression. L5 nerve passed into tumor and showed "submersion sign" and local thickening.2 The lesions of sacral plexus in 5cases (5 sides)2.1 Benign tumors of pelvic cavity in 4 cases (4 sides):It showed that sacral plexus was compressive deformation, displacement, partly ill-defined and together with compression and displacement of vessels adjacent the sacral nerve. Sacral plexus bypassed the margin of the tumor and increased tension.2.2 Sacral plexus cyst in 1 case (1 side):It clearly showed size, quantity and location of cyst and relationship with sacral nerve. Cyst located in the sacral plexus presented "hanging sign".3 The lesions of sciatic nerve in 4 cases (6 sides):It showed vascular tortuosity and expanded into lumps, which was indistinct boundary with sciatic nerve below infrapiriformis foramen, it was no significant changes in size and shape of piriformis.Conclusion1 It could clearly display the entrapment of L5 nerve, sacral plexus and the proximal sciatic nerve, the compression and displacement of nerve in the lesions, whether or not be wrapped in neoplastic diseases with multiple-plane reconstruction techniques at the same slice. And it can supply more direct and integrated images for clinical diagnosis and treatment of lumbosacral nerve disorders.2 It should observe extraspinal nerve whether compressed with multiple-plane reconstruction techniques at the same slice for patient that had severe low back pain but lumbosacral nerve root normal with conventional examination.3 Given the exclusion of other causes of sciatic, gluteal vascular compressive sciatic nerve below infrapiriformis foramen was suspected.