Distinguishing between scar and recurrent herniated disk in postoperative patients: value of contrast-enhanced CT and MR imaging.

Twenty patients with failed back surgery syndrome were analyzed prospectively with MR imaging. In addition, 10 of these patients were analyzed with high-dose contrast-enhanced CT or gadopentetate dimeglumine-enhanced MR imaging. Imaging results were compared with surgical and pathologic findings in all cases. In the 10-patient subset, abnormal epidural soft-tissue specimens were also assessed with light and electron microscopy for vascular density, size of the extracellular space, and collagen orientation and thickness. The average vascular density of epidural fibrosis on light microscopy was found to be 1.19%; the average size of the extracellular space on electron microscopy was 4.29%. Scar 4 months of age or less had a larger extracellular space than did older scar; high- (grade 4 or 5) intensity scar had a larger extracellular space than did less intense scar on long TR/short TE images. Scar 1 year old or less enhanced more intensely on CT than did older scar. The MR signal intensity and CT enhancement characteristics of epidural scar were also found to differ according to epidural location. The percentage of scar that was hyperintense on long TR/TE images was as follows: anterior, 82%; lateral recess, 70%; lateral, 47%; and posterior, 20%. However, no relationship was found between the degree of CT enhancement of scar and vascular density. Gap junction status and extracellular space size, therefore, are more important than vascular density in predicting the degree of enhancement. The accuracy of contrast-enhanced CT and unenhanced MR in separating scar from herniated nucleus pulposus is 80%. This accuracy is related to the partial overlap in imaging characteristics of scar and recurrent herniated nucleus pulposus.

Dural carcinomatosis: MR demonstration.

A case of pachymeningeal carcinomatosis is presented in which CT evaluation revealed an extraaxial, heterogeneous density over the left cerebral convexity. The finding was believed to be consistent with subdural hematoma, empyema, or meningeal thickening. Magnetic resonance evaluation demonstrated a similar crescentic lesion that was of intermediate signal intensity on both T1- and T2-weighted images. This was thought to be uncharacteristic of either subdural hematoma or empyema. The T2-weighted image showed CSF interposed between the cerebrum and the lesion, limiting the abnormality to the dura or subdural space.

Epidural fibrosis and recurrent disk herniation in the lumbar spine: MR imaging assessment.

Twenty patients were enrolled in a prospective study to evaluate MR imaging in the differentiation of epidural scar and herniated disk material. Fourteen patients had surgical verification of imaging findings. In 12 (86%) of these patients, the MR interpretations fully agreed with the observations at surgery. Careful integration of the findings on sagittal and axial T1-weighted images with more T2-weighted axial images was important for analysis. Anterior and lateral recess scars were hypo- or isointense on T1-weighted sequences and hyperintense on more T2-weighted sequences relative to the "parent" anulus intensity. Free fragments demonstrated a slightly hyperintense signal intensity on T1-weighted images relative to epidural fibrosis but had a similar hyperintense signal intensity on T2-weighted sequences. Prolapsed or extruded disk fragments were hypo- or isointense relative to the parent anulus on all sequences. Morphology, epidural location, mass effect, and often signal intensity were the important parameters by which scar and herniated disk could be differentiated with MR.

Abdominal aortic injury associated with transverse lumbar spine fracture--imaging findings.

The association of abdominal aortic injury with transverse fractures of the lumbar spine is not well recognized. Three cases are presented with description of a mechanism common to both injuries that may explain this association--that of distraction and hyperflexion, such as occurs in seat-belt injuries. Whenever a transverse lumbar spine fracture following such a mechanism of injury is recognized, the co-existence of an injury to the abdominal aorta should be excluded by aortography if there is any doubt concerning the integrity of the peripheral pulses. This is best performed prior to laparotomy for any associated intraperitoneal injuries. Repeated clinical examination may detect deterioration in those cases with initially normal pulses. Ultimately, detection of the aortic injury rests on a high index of suspicion.

Cervical radiculopathy: value of oblique MR imaging.

Eighteen patients with cervical radiculopathy were entered into a prospective study to compare the accuracy of surface coil magnetic resonance (MR) imaging with that of metrizamide myelography and computed tomography (CT) with metrizamide. All MR studies included tailored axial and oblique images as well as routine sagittal images. All imaging studies were evaluated for topography and type of disease. Nine of 18 patients subsequently underwent cervical surgery with an anterior interbody approach at 11 levels. The surface coil MR findings concerning disease topography and type concurred with the surgical findings at nine of 11 levels (82%). At three levels, the oblique view added important information not available on the sagittal images or clarified changes seen on the axial images. Metrizamide myelography with CT metrizamide myelography had findings concurrent with surgical findings at ten of 11 levels (91%).