Differentiation between postoperative scar and recurrent disk herniation: prospective comparison of MR, CT, and contrast-enhanced CT

Twenty-five symptomatic postlumbar surgery patients had findings on lumbar spinal noncontrast CT that were equivocal for distinguishing recurrent disk herniation from postoperative epidural fibrosis (scar). Contrast-enhanced CT and lumbar MR imaging were performed to differentiate these two conditions. Of the 14 levels, surgically explored, the diagnosis of scar or recurrent disk herniation was correct with contrast-enhanced CT at 10 levels and with MR imaging at 11 levels. At the levels operated on less than 2 years prior to MR imaging, scar more frequently demonstrated intermediate than low signal intensity. Scar older than 2 years most often showed low signal intensity. These preliminary findings suggest that MR may be useful in differentiating postoperative fibrosis from recurrent disk herniation in a significant proportion of patients whose unenhanced CT scans are equivocal.     

Magnetic resonance imaging of the lumbar spine with CT correlation

The results of magnetic resonance (MR) imaging and computed tomography (CT) in 18 patients with known degenerative disk disease of the lumbar spine were compared. In 60 intervertebral disk levels studied, there were 17 disks with degeneration and disk bulge, and 15 herniated disks. Final diagnoses were based on several factors, with surgical confirmation in five patients. There was good correlation between the two methods at 51 of the 60 levels studied. However, there were major discrepancies in interpretation at nine intervertebral disk levels. These included three false-positive MR imaging interpretations of a herniated disk and one false-negative herniated disk on MR imaging. MR imaging detected one case of disk herniation that was missed prospectively on CT. There were also four presumed degenerated disks seen on MR scans that appeared normal on CT. The conus medullaris was imaged in 16 of 18 patients. The sagittal view proved best for demonstrating both disk abnormality and the conus medullaris. The transaxial view was sometimes helpful in localizing a disk herniation, but partial-volume averaging in the 7-mm slice thickness limited its usefulness. There were five disk herniations that could not be accurately localized on the MR scan. MR imaging proved more sensitive than CT in detecting early disk disease, which appeared as decreased signal intensity within the disk. In three postoperative cases, MR imaging was better able to distinguish between recurrent disk herniation and postoperative scar formation. CT, on the other hand, was more specific in distinguishing herniated disk from disk bulge and proved far superior to MR imaging in localizing disk herniation.(ABSTRACT TRUNCATED AT 250 WORDS)     

The value of MR in differentiating subligamentous from supraligamentous lumbar disk herniations.

PURPOSETo determine the value of MR criteria in differentiating subligamentous from supraligamentous lumbar disk herniations.METHODSA retrospective review of surgical reports and MR images of 50 patients undergoing first-time lumbar surgery was performed. Three MR imaging criteria were assessed: the presence and integrity of a low-signal-intensity line posterior to the disk herniation, the size of the disk herniation in comparison with the size of the spinal canal, and the presence of disk fragments. Correlation was made with surgical findings to determine the value of these MR criteria in differentiating subligamentous from supraligamentous disk herniations.RESULTSFor determining subligamentous disk herniations: the presence of a continuous low-signal-intensity line posterior to the disk herniation was 29% sensitive, 65% specific, and 42% accurate; disk herniation size less than 50% of the size of the spinal canal was 64% sensitive, 47% specific, and 58% accurate; and the absence of disk fragments was 88% sensitive, 12% specific, and 62% accurate. Combinations of individual MR criteria did not improve diagnostic accuracy.CONCLUSIONSFor differentiating subligamentous from supraligamentous lumbar disk herniations, none of the MR imaging criteria assessed was reliable.     

Magnetic resonance-diskography correlation for the therapeutic approach of lumbar herniated disk

In order to evaluate MR reliability in the therapeutic approach to lumbar disk herniation, 51 patients were examined. MR images revealed disk herniation with integrity of posterior longitudinal ligament in 25 subjects. These patients were then examined with diskography, that confirmed MR diagnosis in 23/25 cases. Percutaneous diskectomy according to Onik was successfully performed in 23/25 patients. MR imaging appears as a non-invasive method which allows exhaustive analysis of all components of lumbar spine, yielding reliable information for choosing the appropriate treatment.     

MR imaging of epidural hematoma in the lumbar spine

OBJECTIVE: To bring attention to the MR imaging appearance of epidural hematoma (EDH) in the lumbar spine as a small mass often associated with disk herniation or an acute event. This paper will show our experience with this entity and describe criteria for its MR imaging appearance. DESIGN AND PATIENTS: Thirteen cases of prospectively diagnosed EDH of the lumbar spine were compared with 12 cases of prospectively diagnosed prominent epidural extrusion. Our criteria were retrospectively evaluated by the two authors for their presence or absence in each case. The chi-square test for nominal data was applied. MR imaging criteria utilized to distinguish EDH from disk herniation at our institution include: (1) signal different from disk, (2) high signal on T1-weighted images, either centrally or peripherally, (3) teardrop- or egg-shaped mass, in the sagittal plane, (4) size greater than half the vertebral body height in a craniocaudal dimension, (5) primarily retrosomatic epidural location, (6) plasticity - the mass is seen to conform closely to the contours of bone (e.g., in the lateral recess), (7) little or no disk space narrowing unless associated with disc herniation. RESULTS: Chi-square analysis demonstrated each criterion to significantly differentiate between EDH and extrusion. Only six of 13 EDH cases went to surgery in spite of their relatively large size. Two of six patients were diagnosed as having epidural clot consistent with hematoma at the time of surgery. The four patients who were not diagnosed at surgery revealed only small disk herniations or fragments of disk. CONCLUSIONS: The occurrence of EDH is more frequent than previously suspected. Spontaneous EDH is frequently associated with disk herniation and acute events such as sneezing or coughing. Most cases of spontaneous EDH will resolve prior to surgery with only the minority becoming chronic in order to be seen at surgery as an encapsulated mass. MR imaging can reliably identify EDH and distinguish between EDH and large disk extrusions.     

Gadopentetate dimeglumine-enhanced MR imaging of the postoperative lumbar spine: comparison of fat-suppressed and conventional T1-weighted images.

OBJECTIVE. Gadopentetate dimeglumine-enhanced T1-weighted MR imaging has been used to distinguish epidural fibrosis from recurrent disk herniation in the postoperative lumbar spine. Potential interpretative difficulties relate to detection of subtle contrast enhancement and distinction of enhanced tissue from surrounding epidural fat. The objective of this study was to evaluate the utility of fat-suppressed T1-weighted imaging in improving the depiction of postoperative abnormalities. SUBJECTS AND METHODS. Forty-one patients with recurrent signs and symptoms after previous laminectomy and diskectomy were examined with conventional and fat-suppressed T1-weighted imaging before and after IV administration of gadopentetate dimeglumine. MR images were analyzed for the presence or absence of an epidural soft-tissue mass located anterior and/or lateral to the thecal sac. When such masses were identified, their contrast enhancement behavior was characterized according to the volume, intensity, and pattern of enhancement. Epidural fibrosis was diagnosed by using established MR imaging criteria. In patients with evidence of recurrent disk herniation, diagnosis was based on surgery in six patients and on MR imaging findings in the remainder. RESULTS. Soft-tissue masses were present at 32 of the 43 levels operated on, representing epidural fibrosis (n = 21) or disk herniation (n = 11). Fat suppression improved depiction of contrast enhancement associated with sites of epidural fibrosis. The extent, intensity, and homogeneity of enhancement was greater with fat suppression than with conventional imaging, although the ability to distinguish epidural fibrosis from recurrent disk herniation was not improved. CONCLUSION. Use of the fat-suppression technique results in increased relative intensity and homogeneity of contrast enhancement associated with sites of epidural fibrosis. However, it does not result in significant improvement in the ability to differentiate fibrotic tissue from recurrent disk herniation. Fat suppression does not appear to be indicated for routine use in imaging of the postoperative lumbar spine, but may be useful as a problem-solving tool in selected patients.     

Lumbar disk herniation: do MR imaging findings predict recurrence after surgical diskectomy?

PURPOSE: To retrospectively evaluate if the degree of disk degeneration and disk herniation volume at magnetic resonance (MR) imaging are risk factors for recurrent disk herniation. MATERIALS AND METHODS: The institutional review board permits such retrospective studies, and individual informed consent was not required. MR imaging findings obtained before initial diskectomy in 30 patients (mean age, 42.8 years; 10 women, 20 men) with recurrent disk herniation (study group) and 30 patients (mean age, 42.2 years; nine women, 21 men) without recurrence for at least 2 years after surgery (control group) were compared. Disk degeneration was assessed on T2-weighted sagittal MR images with a five-point grading system (grade I indicated no degeneration; grade II, horizontal hypointense bands within disk; grade III, inhomogeneous disk with intermediate signal intensity; grade IV, no distinction between inner and outer parts of disk; and grade V, collapsed hypointense disk). Disk herniation was classified as representing protrusion, extrusion, or sequestration. The volume of both the affected intervertebral disk and the herniated disk material was measured. Qualitative and quantitative analyses were performed by two readers. The chi(2) test was used for comparison of categorical variables. For comparison of disk degeneration and volumes between patients with and those without recurrence, a paired two-tailed t test was used. Odds ratios based on the extent of disk degeneration were calculated for the entire sample. RESULTS: Advanced disk degeneration (grades IV and V) was significantly less frequent in the study group than in the control group (P < .006). The risk of recurrent disk herniation decreased by a factor of 3.4 for each increase in grade of disk degeneration (odds ratio: 3.58; 95% confidence interval: 1.3, 9.6; P = .011). Mean disk herniation volume as a percentage of intervertebral disk volume was 10.59% +/- 3.41 in the study group and 11.56% +/- 3.84 in the control group. This difference was not significant (P = .31). CONCLUSION: Minor disk degeneration but not herniation volume represents a risk factor for the recurrence of disk herniation after diskectomy.     

Hyperintense basal ganglia on T1-weighted MR imaging

OBJECTIVE: This study was designed to evaluate the safety, MR imaging characteristics, and clinical response to intrathecal gadopentetate dimeglumine (gadolinium) administration in human patients. SUBJECTS AND METHODS: Eleven adult patients were included in this prospective study. Via lumbar puncture, a single dose of either 0.2 ml, 0.5 ml, or 1.0 ml of gadolinium (500 mmol/l) mixed with 5 ml of previously removed CSF was slowly injected into the lumbar subarachnoid space. Immediate and delayed MR imaging were subsequently carried out using a 1.0-T magnet. RESULTS: No patient manifested gross behavioral changes, neurologic alterations, or seizure activity. The intrathecal gadolinium-enhanced MR myelography revealed disk herniation (n = 4), posttraumatic spinal stenosis (n = 3), postsurgical noncommunicating cyst (n = 1), myelitis (n = 1), intradural extramedullary mass formation (n = 1), and intradural vascular malformation (n = 1). CONCLUSION: This pilot study shows the relative safety and feasibility of low-dose intrathecal gadolinium administration. The potential clinical applications include the evaluation of obstructions and communications of the subarachnoid space, spontaneous or traumatic CSF leaks, and CSF dynamics. Additional animal and human studies must be performed to further evaluate the long-term safety and to prove the clinical applications of this procedure in a larger number of subjects.     

The postoperative lumbar spine: enhanced MR evaluation of the intervertebral disk.

PURPOSETo document the pattern of enhancement and morphologic changes on MR images that occur in the intervertebral disk and adjacent vertebral bodies after diskectomy and to correlate the presence of intervertebral disk enhancement with the preoperative and postoperative clinical findings.METHODSPreoperatively, and at 3 months and 6 months after surgery, 94 adults who had first-time surgery for a herniated lumbar intervertebral disk that was associated with radiculopathy, expressed as leg symptoms or signs (with or without lower back pain), were asked to respond to a questionnaire regarding pain, were given serial physical examinations, and were examined with contrast-enhanced MR imaging. The measures of clinical outcome that were evaluated included the straight leg raise sign, radicular pain, and lower back pain. Type of disk herniation, intervertebral disk enhancement, disk space height, and degenerative end-plate changes were also assessed.RESULTSOf the 94 patients evaluated, 19 (20%) had postoperative intervertebral disk enhancement that was not present on the preoperative study. The pattern of enhancement was remarkably consistent, with 18 of the cases showing linear enhancement within the intervertebral disk, manifested as two thin bands paralleling the end plates. End-plate enhancement was present in 7 (37%) of the 19 patients with disk enhancement. There were no significant associations between disk enhancement and specific clinical symptoms before or after surgery.CONCLUSIONOur group of asymptomatic postoperative patients had anular enhancement (curette site), disk enhancement, and vertebral end-plate enhancement on MR images without evidence of disk space infection. This finding points out the need to understand asymptomatic postoperative changes that are sequelae of surgery and not necessarily indicators of infection.     

Gradient-echo MR imaging of the lumbar spine: comparison with spin-echo technique

Gradient-echo (GRE) magnetic resonance (MR) imaging has been advocated as the imaging modality of choice for evaluating radiculopathy in the cervical spine. Axial GRE images of the lumbar spine in 50 patients were compared with similar images obtained using spin-echo (SE) technique on a 1.5 T MR system. The SE images were superior to GRE images in the evaluation of the neural foramina, epidural fat, and disk herniation. The GRE images obtained were inadequate for lumbar spine imaging due to an unacceptable level of chemical shift artifacts. The GRE technique does provide the advantages of rapid acquisition of T2* images and decreased motion artifact. Axial GRE images may play an increasingly important role in lumbar spine imaging with continued changes in software and improvements in technology.     

Lumbar disk herniation: correlation of histologic findings with marrow signal intensity changes in vertebral endplates at MR imaging

PURPOSE: To compare findings at preoperative magnetic resonance (MR) imaging with data for tissue composition of herniated disks in patients after microsurgical removal of herniated material. MATERIALS AND METHODS: Fifty-one patients underwent MR imaging before microsurgical removal of extruded lumbar disk herniation material. Marrow signal intensity changes along the cartilaginous endplates were classified according to Modic types 1-3. Severity of changes was evaluated with respect to extension along the endplate in the anteroposterior diameter (0%, <33%, 33%-66%, >66%). The existence of a dorsal vertebral corner defect was evaluated in relation to the existence of hyaline cartilage in the disk extrusion material. RESULTS: Mean tissue composition of herniated material in all patients was 63% anulus fibrosus, 30% nucleus pulposus, and 8% cartilaginous endplate. Twenty-five of the 51 patients had hyaline cartilaginous material in the extrusion (range, 5%-50%). Patients without marrow signal intensity changes along the cartilaginous endplate showed significantly less cartilaginous material in the extruded disk (P =.023, Fisher exact test). Mean percentage hyaline cartilage in patients without changes was 2% +/- 4 (SD) (Modic type 1, 16% +/- 15; type 2, 10% +/- 12). When the changes extended 33% of the vertebral endplate, there was cartilaginous endplate material in the extruded disk (P =.006). Cartilage from the endplate was present in the extruded disk material in 40% (16 of 40) of patients without a vertebral corner defect and in 82% (nine of 11) of patients with a vertebral corner defect (P =.019). CONCLUSION: Avulsion-type disk herniation seems to be common, and vertebral endplate marrow signal intensity changes on MR images are indicative of cartilaginous material in the extruded disk herniation material.     

Association of vertebral end plate fracture with pediatric lumbar intervertebral disk herniation: value of CT and MR imaging

A retrospective review of the radiologic findings in 31 patients less than 21 years old who underwent laminotomy for lumbar disk herniation revealed six cases of associated avulsion fracture of the vertebral end plate, a prevalence of 19%. All fractures were found in the 14-17-year-old subgroup (six of 19), a prevalence of 32%. In four patients, plain radiographs did not reveal the fracture. Computed tomographic (CT) findings were diagnostic in all six cases. Magnetic resonance (MR) images, obtained in three patients, demonstrated the avulsed cortical fragment and what are assumed to be the attached Sharpey fibers. On sagittal MR images, these structures had a configuration with the appearance of a "Y" or "7". Four of these six patients underwent bilateral laminotomies. The need for more extensive surgical resection may not be apparent at plain radiography or myelography but can be predicted with CT and MR imaging.     

MR imaging of the postoperative lumbar spine: assessment with gadopentetate dimeglumine

This study defines the accuracy of gadopentetate-dimeglumine-enhanced MR imaging in patients with failed back surgery syndrome by comparing the imaging studies with surgical findings in a large patient population. From June 1988 to March 1989, 193 postoperative patients had MR imaging of the lumbar spine both with and without contrast administration. Of this group, 27 had repeat surgery at 31 levels: these patients comprise the study group. Postcontrast MR diagnoses were as follows: scar only (n = 4), disk only (n = 13), scar and disk (n = 9), and no aberrant epidural tissue (n = 5). Surgical diagnoses differed from the MR diagnoses in two patients at two levels. In one patient, disk was diagnosed on MR while osteophyte was present at surgery. In the other patient, scar only was diagnosed by MR but disk and scar were present at surgery. These data, when combined with the authors' previous experience, give pre- and postcontrast MR a 96% accuracy in differentiating scar from disk in 44 patients at 50 reoperated levels. For patients 6 or more weeks past surgery, sagittal and axial T1-weighted MR imaging before and after administration of gadopentetate dimeglumine is an effective method of evaluating the postoperative lumbar spine.     

MR imaging of the postoperative lumbar spine: assessment with gadopentetate dimeglumine

This study defines the accuracy of gadopentetate-dimeglumine-enhanced MR imaging in patients with failed back surgery syndrome by comparing the imaging studies with surgical findings in a large patient population. From June 1988 to March 1989, 193 postoperative patients had MR imaging of the lumbar spine both with and without contrast administration. Of this group, 27 had repeat surgery at 31 levels: these patients comprise the study group. Postcontrast MR diagnoses were as follows: scar only (n = 4), disk only (n = 13), scar and disk (n = 9), and no aberrant epidural tissue (n = 5). Surgical diagnoses differed from the MR diagnoses in two patients at two levels. In one patient, disk was diagnosed on MR while osteophyte was present at surgery. In the other patient, scar only was diagnosed by MR but disk and scar were present at surgery. These data, when combined with the authors' previous experience, give pre- and postcontrast MR a 96% accuracy in differentiating scar from disk in 44 patients at 50 reoperated levels. For patients 6 or more weeks past surgery, sagittal and axial T1-weighted MR imaging before and after administration of gadopentetate dimeglumine is an effective method of evaluating the postoperative lumbar spine.     

Significance of thoracic disc herniation demonstrated by MR imaging

The thoracic spines of a group of 48 oncology patients were examined with high field (1.5 T) magnetic resonance (MR) imaging. Sagittal T1-weighted sections were obtained in all patients. Even using this single sequence an unexpectedly high prevalence of thoracic disk herniation (14.5%) was demonstrated. Thoracic disk herniation shown by MR may not be related to the patients' symptoms.     

Thoracic disk herniation: MR imaging

The authors undertook a retrospective study to assess the role of magnetic resonance (MR) imaging in thoracic disk herniation. The initial MR images were interpreted independently of other findings. These interpretations were compared with the findings of plain and computed tomography (CT) myelography and surgery, when available. Sixteen thoracic disk herniations were confirmed with plain and CT myelography and/or surgery. Plain myelography was performed on 14 patients and showed focal ventral filling defects in nine. Results of CT myelography were equivalent to those of MR imaging with three pulse sequences (sagittal T1 and T2 weighted, axial T1 weighted) in the identification of all the abnormal levels. In two patients, the signal from the herniated disk was so low on all sequences that thoracic disk herniation had to be inferred from the mass effect on the spinal cord. Precise location of the abnormal level with body coil MR images was achieved in six of 13 patients.     

Measuring diffusion of solutes into intervertebral disks with MR imaging and paramagnetic contrast medium.

BACKGROUND AND PURPOSEExperimental studies have shown that solutes diffuse more slowly into degenerated intervertebral disks than into normal disks. A noninvasive clinical study of diffusion in intervertebral disks is not generally available. Our purpose was to evaluate contrast-enhanced MR images to study diffusion in normal and degenerated lumbar intervertebral disks.METHODSThe change in signal intensity (as a proportion of baseline signal intensity) was calculated in lumbar intervertebral disks on MR images obtained before and after injection of intravenous contrast medium in 15 patients with low back pain. The intervertebral disks were classified as normal or degenerated on the basis of the MR appearance. Postoperative disks and degenerative intervertebral disks with a "high-intensity zone" were excluded. The changes in signal intensity as a proportion of baseline signal intensity were compared in degenerated disks and normal disks and the differences tested for statistical significance.RESULTSAfter intravenous administration of a gadolinium complex, signal intensity in normal intervertebral disks increased an average of 36% of baseline. In intervertebral disks with signs of degeneration, it increased an average of 21% of baseline. The difference was significant.CONCLUSIONThe study shows that diffusion into normal human lumbar intervertebral disks can be evaluated with MR imaging combined with intravenous contrast medium. With suitable MR techniques, the relationship between diffusion and disk degeneration, and the effect of trauma, drugs, and nutrition on disk degeneration can be studied noninvasively.     

Minimally invasive oxygen-ozone therapy for lumbar disk herniation

BACKGROUND AND PURPOSE: Oxygen-ozone therapy is a minimally invasive treatment for lumbar disk herniation that exploits the biochemical properties of a gas mixture of oxygen and ozone. We assessed the therapeutic outcome of oxygen-ozone therapy and compared the outcome of administering medical ozone alone with the outcome of medical ozone followed by injection of a corticosteroid and an anesthetic at the same session. METHODS: Six hundred patients were treated with a single session of oxygen-ozone therapy. All presented with clinical signs of lumbar disk nerve root compression, with CT and/or MR evidence of contained disk herniation. Three hundred patients (group A) received an intradiscal (4 mL) and periganglionic (8 mL) injection of an oxygen-ozone mixture at an ozone concentration of 27 micro g/mL. The other 300 patients (group B) received, in addition, a periganglionic injection of corticosteroid and anesthetic. Therapeutic outcome was assessed 6 months after treatment by using a modified MacNab method. Results were evaluated by two observers blinded to patient distribution within the two groups. RESULTS: A satisfactory therapeutic outcome was obtained in both groups. In group A, treatment was a success (excellent or good outcome) in 70.3% and deemed a failure (poor outcome or recourse to surgery) in the remaining 29.7%. In group B, treatment was a success in 78.3% and deemed a failure in the remaining 21.7%. The difference in outcome between the two groups was statistically significant (P <.05). CONCLUSION: Combined intradiscal and periganglionic injection of medical ozone and periganglionic injection of steroids has a cumulative effect that enhances the overall outcome of treatment for pain caused by disk herniation. Oxygen-ozone therapy is a useful treatment for lumbar disk herniation that has failed to respond to conservative management.     

Evaluation of the role of magnetic resonance myelography in lumbar spine imaging

The purpose of our study was to evaluate the accuracy of MR myelography in depicting disc herniation in the lumbar spine when compared with conventional MRI in patients presenting with clinical evidence of disc herniation. One hundred patients referred for conventional MR imaging of the lumbar spine also had coronal MR (TR 9000 ms, TE 272 ms eff, NEX 3, echo train length 32) myelography performed. Three experienced observers compared magnetic resonance myelography (MRM) with conventional lumbar spine MR using the following variables: visibility of thecal sac and nerve roots, and the presence, location and severity of disc herniation. Disc protrusions were seen at 110 disc space levels on conventional MR images as opposed to 93 on MRM. However, only 72 % of lesions seen on conventional MR were diagnosed by MRM. Similarly, only 63.8 % of nerve root compression abnormalities seen at conventional MR were visualized when compared with conventional MRM. The sensitivity, specificity and accuracy of MRM when compared with conventional MR was 72, 93 and 85 %, respectively. The MRM technique yields images that resemble conventional myelography and may be used to help confirm abnormalities seen on conventional MR in selected cases; however, the large number of false-positive and false-negative examinations indicates that caution should be used in interpreting MRM images. Received: 16 February 1998; Revision received: 25 May 1998; Accepted: 30 September 1998