الفهرس 
NORMAL AND RADIOLOGICAL ANATOMY OF THE SPINEOnly 14 pages are availabe for public view
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Abstract
T
he technical advantages of MR myelography over conventional myelography are well known (i.e. it is noninvasive, and does not use ionizing radiation or iodinated contrast agents). The quality of MR myelograms remains excellent over the entire length of the spinal canal even in the presence of a major obstruction showing blockage on conventional myelography. The severity of nerve root compression can be assessed adequately.
MR myelography was accepted rapidly by the clinicians. The number of conventional lumbar spine myelograms has decreased nowadays. If the clinician requests we can add the 4 MR myelographic views to the MR examination instead of performing a conventional myelogram. These images help the clinicians to understand the images better. In addition, we think that the additional images increase the level of confidence of the radiologist because of the rapid assessment of the thecal sac and the nerve roots. Only patients with ferromagnetic implants or claustrophobia are examined with conventional myelography.
MR myelography produces excellent delineation of cauda equina nerve roots using the brightness of CSF as a background to the hypointense nerve roots. Diffuse bulge of the outer fibers of the annulus fibrosus of disc material shows uniform decrease in signal intensity at that level while herniated disc produces focal loss of CSF signal indenting the adjacent ventral surface of the thecal sac with impingement on the adjoining nerve roots that usually shows buckling superiorly.
MR myelography results confirmed the diagnosis of disc herniation made on T1 / T2 weighted images especially thecal sac compression and / or amputation of nerve root sheathes. MR myelography appeared to be useful in migrated disc herniation or in abnormal origin of nerve roots more over it allowed full and panoramic visualization of the subarachnoid space and nerve root sheathes.
MR myelography complements conventional MR imaging by making it possible preoperatively to localize a herniated disc, which is seen as a defect or a mass, and showing the relationship to the nerve root sleeves and to the remaining of the subarachnoid space. It can also produce accurate diagnosis of conjoined nerve roots or associated perineural cysts and diagnose associated arachnoid adhesions. These findings were not adequately provided by conventional MR imaging and will avert the need for intrathecal contrast myelography.
The images obtained by MR myelography were similar in quality to those obtained by conventional myelography. When combined with some other conventional MR imaging techniques, this diagnostic techniques of imaging spinal disease is further enhanced.
In case of spinal block both the superior and inferior extents of the block are shown non invasively by Coronal MR myelography. Loss of CSF signal at the site of block probably represents valid anatomic changes and indicates severe compression of spinal contents.
MR myelography was found to be less reliable than MR imaging in detecting early changes of cord oedema and myelomalacia associated with intradural tumours and cystic masses, however, the relationship of an intradural tumor to the displaced or compressed signal cord was better shown with MR myelogram.
MR myelography was especially valuable in demonstrating abnormal intraspinal vascularity and in guiding patient treatment by providing detailed preoperative information about intradural masses and post traumatic and post operative diverticulum and meningocele.
Thus MR myelographic technique is a useful adjunct to MR imaging, especially in cases in which the more detailed information provided will be helpful in the analysis of complex intraspinal disease.