The sagittal images are best to delineate the herniation of the nucleus propulsus through the annulus fibrosis. The transverse images best define the compression of the thecal sac and the left S1 nerve root. Spinal Stenosis Spinal stenosis is due to circumferential narrowing of the spinal canal, usually secondary to degenerative disc disease. The canal is usually narrowed anteriorly by a bulging or herniated disc. This is frequently accompanied by posterolateral compression form hypertrophy of the facets and ligamenta flava.
Patients frequently have pain with bilateral extremity symptoms, often exacerbated by standing.
The most common sources of metastases to the spine are carcinomas of the prostate, breast, and lung. Metastatic tumors demonstrate decreased signal on T1-weighted images and are well seen when contrasted against the high signal fatty marrow in the vertebrae. Since the presence of metastases has such a great impact on the prognosis for a cancer patient, MRI is frequently used to further evaluate suspected lesions seen on x-ray or bone scan. MRI also serves a vital role in evaluating the cancer patient with suspected cord compression. Instead of subjecting a critically ill patient to a total myelogram, MRI can survey the entire spine in less than one hour with minimal discomfort to the patient.