Magnetic resonance evaluation of recurrent disc herniation: is gadolinium necessary?

STUDY DESIGN: Evaluation of magnetic resonance images (MRIs) with surgical reference standard. OBJECTIVES: To determine whether the addition of contrast-enhanced MRI scans increases diagnostic efficacy in the evaluation of recurrent disc herniation. SUMMARY OF BACKGROUND DATA: Many centers now routinely use gadolinium-enhanced examinations in the evaluation of recurrent disc herniation. Others, noting the additional expense of contrast injection, advocate a more limited role for contrast injection and emphasize the importance of T2-weighted axial sequences. METHODS: The study included 165 consecutive patients who were referred to the authors' outpatient imaging center and had a history of previous lumbar discectomy and recurrent back and/or leg pain. The scanning protocol included sagittal and axial T1-weighted spin-echo pre- and postcontrast injection images and sagittal and axial T2-weighted fast spin-echo images. Twenty-eight patients (32 vertebral levels) had subsequent surgical exploration of a disc margin that had previously undergone discectomy. The surgical findings formed the reference standard. Three spine radiologists interpreted the MRI examinations without knowledge of the surgical results. They first interpreted the unenhanced studies, indicated whether they felt contrast injection would be helpful in further evaluation, and then (regardless of this determination) read the postcontrast study. RESULTS: On pre- and post-contrast examinations Reader 1 had a sensitivity of 95% (20/21), a specificity of 100% (10/10), and an accuracy of 97% (30/31). Reader 2 had a sensitivity of 95% (20/21), a specificity of 90% (9/10), and an accuracy of 94% (29/31). Reader 3 had a sensitivity of 90% (19/21), a specificity of 100% (10/10), and an accuracy of 94% on the precontrast examinations. His postcontrast performance demonstrated a sensitivity of 86% (18/21), a specificity of 100% (10/10), and an accuracy of 90% (28/31). In the nine interpretations wherein the readers thought that a contrast-enhanced examination might provide useful additional information, they did not change their interpretations in three cases, improved their interpretations in two, and made their interpretations worse in four on the basis of addition of the enhanced images. CONCLUSIONS: Routine use of contrast-enhanced examinations in patients who have had prior lumbar surgery probably adds little diagnostic value and may be confusing.

Magnetic resonance imaging evaluation of the adolescent patient with idiopathic scoliosis before spinal instrumentation and fusion. A prospective, double-blinded study of 140 patients.

STUDY DESIGN: This was a prospective, double-blinded study of the magnetic resonance imaging findings in the neural axis of 140 neurologically normal typical adolescents with idiopathic scoliosis who were scheduled for scoliosis surgery. OBJECTIVE: To detect the prevalence of spinal cord and neural axis abnormalities in this select population. SUMMARY OF BACKGROUND DATA: No similar study exists, although a few related studies were published. METHODS: Full-length neural axis magnetic resonance imaging studies were reviewed independently by two radiologists who specialize in the spine. RESULTS: Only four patients had a definite abnormality-one a small thoracic syrinx and the other three with a Chiari malformation. None of these required neurosurgery. All 140 patients had their scoliosis surgery without necrologic compromise. CONCLUSION: Routine magnetic resonance imaging evaluation of neurologically normal, typical adolescents with idiopathic scoliosis is not warranted, based on this study.

The natural history of asymptomatic thoracic disc herniations.

STUDY DESIGN: Magnetic resonance imaging was used to determine the natural history of asymptomatic thoracic disc herniations. OBJECTIVES: To determine whether thoracic disc herniations change in size over time. SUMMARY OF BACKGROUND DATA: Based on previous work by the authors of the present study, the incidence of asymptomatic thoracic disc herniations is approximately 37%. The natural history of thoracic disc herniations is unknown. The natural history of lumbar and cervical disc herniations in symptomatic individuals who become asymptomatic has been shown in multiple studies frequently to result in a decrease in size of the herniation. METHODS: Twenty patients with 48 asymptomatic thoracic herniations previously diagnosed with magnetic resonance imaging underwent repeat magnetic resonance imaging using sagittal T1-weighted spine echo and axial multiplanar gradient refocused images at each thoracic disc level from T1 to T12 for a mean follow-up period of 26 months. Midsagittal canal diameter was recorded, and disc herniation square area was measured using a computer-assisted digitizing program. Disc herniations were categorized according to percentage of canal compromise. The change in size of the disc herniations over time was analyzed. RESULTS: All patients remained asymptomatic during the follow-up period. A total of 48 disc herniations were identified from the original magnetic resonance images. There were 21 small (0-10% canal compromise) disc herniations, 20 medium (> 10-20%) disc herniations, and seven large (> 20%) disc herniations. Of the 21 small disc herniations, 18 showed no significant change in size, whereas three showed a measurable increase in size. Of the 20 medium-sized disc herniations, 16 showed either a small or no change in size, one showed a significant increase in size, and three showed a significant decrease in size. Of the seven large disc herniations, three demonstrated no change in size, and four demonstrated a significant decrease in size. In addition, five new disc herniations were detected in four patients; one was small, and four were moderate in size. CONCLUSIONS: Based on the results of this study, the authors believe that asymptomatic disc herniations may well exist in a state of relative flux, yet exhibit little change in size and remain asymptomatic. There was a trend, however, for small disc herniations either to remain unchanged or increase in size and for large disc herniations often to decrease in size.

Vertebral body MRI related to lumbar fusion results.

The evaluation of continued pain after a technically successful posterolateral lumbar spine fusion is often challenging. Although the intervertebral disc is often a source of low back pain, abnormal endplates may also be a focus of pain, and possibly a source of continued pain after a posterolateral fusion. MRI allows noninvasive evaluation for disc degeneration, as well as for abnormal endplates and adjacent vertebral body marrow. Previous studies have found inflammatory marrow changes, adjacent to abnormal endplates, associated with disc degeneration in low back pain patients. In this study, preoperative MRI scans in 89 posterolateral lumbar fusion patients were reviewed, by an independent radiologist, to determine whether vertebral body marrow changes adjacent to the endplates were related to continued pain. Independent chart review and follow-up telephone interview of all patients at a 4-year follow-up (mean) formed the basis for the clinical results. Vertebral body MRI signals consistent with inflammatory or fatty changes were found in 38% of patients, and always occurred adjacent to a degenerated disc. Inflammatory MRI vertebral body changes were significantly related to continued low back pain at P = 0.03. We conclude that posterolateral lumber fusion has a less predictable result for the subset of degenerative disc patients with abnormal endplates and associated marrow inflammation. More research is needed to determine the biological and biomechanical effects of posterolateral fusion upon the endplate within the fused segments. If indeed further study supports the hypothesis that abnormal endplates associated with inflammation are a source of pain, then treating the endplates directly by anterior fusion may be a preferred treatment for this subset of degenerative patients.

Lumbar disc high-intensity zone. Correlation of magnetic resonance imaging and discography.

STUDY DESIGN: This study correlated a specific lumbar disc abnormality described as the high-intensity zone observed on high-field magnetic resonance imaging with discography. OBJECTIVES: To analyze the significance of high-intensity zones in lumbar discs of symptomatic patients with low back/radicular pain. SUMMARY OF BACKGROUND DATA: Aprill and Bogduk described an 86% incidence of concordantly painful discography in lumbar discs exhibiting a posterior high-intensity zone on T2-weighted magnetic resonance imaging studies performed on back pain sufferers. They assert that the high-intensity zone is a reliable marker of discogenic pain in symptomatic subjects. METHODS: Consecutive cases of lumbar spine high-field magnetic resonance imaging using T2-weighted images on symptomatic patients followed by discography at all high-intensity zone levels and at non-high-intensity zone control levels were reviewed until 100 high-intensity zone discs in 63 patients were found. Seventeen lifelong asymptomatic (for low back/radicular pain) adults were also scanned as magnetic resonance imaging controls. All magnetic resonance scans and discograms were agreed on by at least two of the radiologist authors. RESULTS: Eighty-seven of 100 of the high-intensity zone discs proved concordantly painful at discography. All 87 painful and concordant discs exhibited abnormal morphology with anular tears extending either well into or through the outer third of the anulus fibrosus. Sixty-five of 67 non-high-intensity zone control discs were nonconcordant and of lower sensation intensity than the high-intensity zone discs. Only one high-intensity zone was found in the control subjects. CONCLUSIONS: In patients with symptomatic low back pain, the high-intensity zone is a reliable marker of painful outer anular disruption.

Magnetic resonance imaging of the thoracic spine. Evaluation of asymptomatic individuals.

We reviewed magnetic resonance imaging studies of the thoracic spines of ninety asymptomatic individuals to determine the prevalence of abnormal anatomical findings. This group included sixty individuals who had no history of any thoracic or lumbar pain and thirty individuals who had a history of low-back pain only. In addition, we reviewed imaging studies of eighteen patients who had an operatively proved herniation of a thoracic disc and studies of thirty-one patients who had been seen with thoracic pain. Sagittal T1-weighted spin-echo and axial multiplanar gradient refocused images at each disc level were interpreted by us (two neuroradiologists and two orthopaedic spine surgeons); we had no clinical information about the patients. Sixty-six (73 percent) of the ninety asymptomatic individuals had positive anatomical findings at one level or more. These findings included herniation of a disc in thirty-three subjects (37 percent), bulging of a disc in forty-eight (53 percent), an annular tear in fifty-two (58 percent), deformation of the spinal cord in twenty-six (29 percent), and Scheuermann end-plate irregularities or kyphosis in thirty-four (38 percent). This study documents the high prevalence of anatomical irregularities, including herniation of a disc and deformation of the spinal cord, on the magnetic resonance images of the thoracic spine in asymptomatic individuals. We emphasize that these findings represent roentgenographic abnormalities only, and any clinical decisions concerning the treatment of pain in the thoracic spine usually require additional studies.

Imaging evaluation of patients with spinal deformity.

CT myelography and MRI provide the best means of preoperatively assessing patients with spinal deformities. Owing to its noninvasive nature and its superior soft-tissue contrast, MRI represents the single best modality in the evaluation of a patient with any deformity. MRI allows complete preoperative surgical planning and obviates the need for any additional studies. Screening of the entire cord in a patient with a deformity is best accomplished with sagittal and coronal (as needed) T1W images. These images allow assessment of the cord for compression, tethering, syrinx, enlargement, and Arnold-Chiari malformation. Evaluation of cord compression at the apex of a curve is the single most important consideration other than the diagnosis of intrinsic cord abnormality. Subsequent sagittal or axial T2W images may be helpful if specific abnormalities are noted on T1W screening images. Coronal images are particularly helpful in patients with prominent curves or in those with vertebral anomalies. Additionally, coronal images may be useful in assessing patients with suspected diastematomyelia. Advances in hardware and software design have resulted in marked improvements in the ability to satisfactorily image all aspects of patients with spinal deformities. New phased array coils allow rapid imaging of larger portions of the spine. For instance, a complete MRI of the spine can be performed in a child in the same length of time that would have been necessary for a single lumbar examination when MRI was in it's infancy. The use of fast spin-echo imaging also permits more rapid acquisition times. CT myelography remains useful for those patients who cannot undergo MRI or for those with specific abnormalities such as multilevel central spinal stenosis when dynamic information obtained during the myelogram might be helpful. CT myelography represents the only means of assessing the central spinal canal of patients with metallic instrumentation in place. With the exception of these limited applications, MRI has replaced CT myelography as the imaging study of choice in the evaluation and examination of patients with spinal deformities.

Juvenile discogenic disease.

This study was undertaken to document an association of degenerative lumbar disc disease in patients with thoracolumbar Scheuermann's disease. During a 3-month period, 9% of 1419 of the persons referred to our center for magnetic resonance imaging of the lumbar spine demonstrated changes of both thoracolumbar Scheuermann's disease and degenerative disc disease in the lower lumbar spine. The disease was less commonly detected on computed tomography (2% of 1522 patients). The patients were relatively young: 81% were younger than 40 years and 9% were younger than 21 years. We theorize that the thoracolumbar Scheuermann's disease and the associated degenerative disc disease of the lower lumbar spine are manifestations of an intrinsic defect of the discs and/or cartilaginous end plates, which results in inadequate nutrition and structural weakness or a combination of both, and early degeneration.

Epidural hematoma of the lumbar spine: 18 surgically confirmed cases.

The authors report 18 cases of surgically proved spontaneous epidural hematoma of the lumbar spine. The clinical findings in spontaneous epidural hematoma were identical to those in acute disk herniation. Underlying disk abnormalities were common; the majority of hematomas (14 of 18, 78%) were associated with small concomitant disk herniations or underlying annular tears. The magnetic resonance imaging and computed tomographic findings were similar to those in extruded/free-fragment disk herniation. The strong coincidence between epidural hematoma and underlying disk disruption (annular tear or herniation) leads the authors to postulate that spontaneous epidural hematoma results from tearing of fragile epidural veins lying adjacent to the displaced anulus or nucleus.

Changes in vertebral rotation after Harrington and Luque instrumentation for idiopathic scoliosis.

This study was carried out to analyze the three-dimensional and in particular the rotational correction obtained after spine instrumentation for idiopathic scoliosis. Preoperative and postoperative radiographs and computed tomographic scans with single axial cuts through each vertebral level were obtained for 14 patients: 4 Harrington, 7 Luque, and 3 Harrington-Luque. Rotation of vertebrae relative to the spinal axis and rotation between vertebrae (segmental rotation) were measured from computed tomographic scans of instrumented and uninstrumented segments. The derotation and changes occurring after surgery were calculated. Before operation, rotation was maximal at the apex, and close to 0 at the end vertebra; segmental rotation was greatest at the end of the curve, and minimal at the apex. After Harrington instrumentation the apical vertebrae showed a median derotation of 16%, after Luque instrumentation it was 12% and after Harrington-Luque instrumentation it was 13%. Segmental derotation did not uniformly occur. Major derotation was obtained at the end vertebrae and 39% of the total derotation occurred outside of the instrumented levels of the spine.

Intraspinal abnormalities and congenital spine deformities: a radiographic and MRI study.

Forty-two patients with congenital spinal deformity were studied by magnetic resonance imaging (MRI). Sixteen patients had intraspinal abnormalities consisting of a tethered cord in 10, diastematomyelia in four, diplomyelia in three, syringomyelia in four, a low lying conus in three, and a teratoma of the sacrum in one patient. In seven patients, intraspinal anomalies were suspected based on routine spinal radiographs and physical findings. We recommend MRI in patients undergoing spinal stabilization procedures and in all patients with lumbosacral kyphosis and those with pain, neurologic findings, or cutaneous hairy patch.

The diagnosis of temporomandibular joint disease: two-compartment arthrography and MR.

The reliability and accuracy of two-compartment temporomandibular joint (TMJ) arthrography was compared with MR imaging on the basis of an analysis of surgical findings obtained from joints that had been studied preoperatively with arthrography or MR or, in some cases, both procedures. Seven hundred forty-three consecutive TMJ arthrograms were successfully obtained in a total of 443 patients by using a single 27-gauge needle and a two-compartment technique in each joint. There was a 100% correlation with surgical findings in 218 radiologically abnormal joints operated on within 90 days of arthrography with respect to the presence or degree of meniscus displacement and normal or abnormal disk morphology and function. In 604 patients 1052 TMJs were studied with high-field-strength surface-coil MR. Surgical findings were available for correlation in 170 of the joints studied. Forty-three joints were studied with both two-compartment arthrography and MR. Eight operated joints had been imaged successfully with both two-compartment arthrography and MR. Both methods of evaluation provided highly reliable and accurate information regarding meniscus position and shape. Arthrography was superior to MR in detecting capsular adhesions and the presence or absence of perforation of the disk or meniscus attachments. Simple meniscectomy (with or without insertion of a temporary Silastic TMJ implant) was the most frequently performed surgical procedure in the series, followed by meniscus repositioning procedures. Joint effusions, failed TMJ implants, and avascular necrosis were demonstrated best with MR. Soft-tissue lesions, including intrinsic degeneration of the meniscus, anomalous muscle development, muscle atrophy, tendinitis, and injuries such as contusions and hematomas, were demonstrated only with MR. Partial-flip-angle GRASS (gradient-recalled acquisition in the steady state) techniques permit both fast scanning and study of functional joint dynamic. Joint fluid may appear as high signal intensity on GRASS images because of T2*-weighting. We recommend MR as the procedure of choice for diagnosis of uncomplicated internal derangements of the TMJ. Two-compartment arthrography with videofluoroscopy is an important ancillary procedure that should be performed whenever capsular adhesions or perforations are suspected and not demonstrated with MR and whenever MR is inconclusive.

Three-dimensional computed tomography in maxillofacial surgical planning.

Fifty-four maxillofacial three-dimensional computed tomographic examinations were performed during a 12-month period for the purpose of surgical planning. Pathologic entities in the series included trauma, neoplasia, cleft palate, and other developmental anomalies. Computer-assisted mandibular disarticulation was performed routinely after each study to permit direct viewing of the mandible or maxilla in isolation. Three-dimensional computed tomography is a useful technique for maxillofacial surgical planning.

Temporomandibular joint: MR imaging of internal derangements and postoperative changes.

Nineteen abnormal temporomandibular joints (TMJs) imaged with high-field-strength surface-coil MR are presented to illustrate specific changes associated with disk derangement, trauma, and previous surgery. Cases were selected from a series of 248 TMJ MR studies in 144 patients (9-68 year old, 130 females and 14 males) performed during a 5-month period. Surgical findings were available for correlation in 44 of the 248 joints studied. Increased signal caused by myxoid degeneration within the degenerating meniscus was seen, as were pathologic changes including atrophy, fibrosis, and contracture of masticatory muscles occurring with internal derangements. Advantages and limitations of MR are discussed with reference to arthrography and videofluoroscopy. High-resolution and partial-flip-angle images of a normal joint are provided for comparison. In most clinical circumstances, MR is the procedure of choice when examining the TMJ, because it provides contrast resolution of soft-tissue structures superior to that of conventional imaging techniques.

CT evaluation of the failed back surgery syndrome.

Inadequate low back care has now been clearly identified as perhaps the greatest single waste of health care resources in the United States. Low back care failure represents a particularly frustrating and challenging entity. Statistics suggest that 25,000 to 50,000 FBSS cases occur each year. This is a public health problem that should be of the highest level of concern. Modern understanding and technical prowess allow us to study past therapeutic failures and thus gain the knowledge necessary to do better in the future. We sincerely hope that our colleagues will give careful consideration to the material presented here.

High-resolution computed tomography of the lumbar spine.

High-resolution computed tomography (CT) has dramatically expanded the understanding of lumbar spine anatomy. The procedure provides accurate preoperative assessment of bony and soft tissue pathology; directly visualizes the pathologic processes affecting the spine; and furnishes direct evidence of nerve root involvement by bony stenosis, herniated disc, and postoperative perineural fibrosis. The bony spinal and intervertebral nerve root canals and soft tissues can be imaged, herniated and sequestered discs identified, and causes of postoperative pain syndrome differentiated. High-resolution CT defines nerve root entrapment more accurately than any other imaging method currently used in the study of lumbar spine disease. Because it can provide complete preoperative information regarding bone and soft tissue pathology, the procedure can reasonably be expected to significantly reduce the incidence of "failed back surgery syndrome."

Causes of failure of surgery on the lumbar spine.

An interinstitutional study on the failed back surgery syndrome (FBSS) has determined that failure to recognize or adequately treat lateral stenosis of the lumbar spine with resultant nerve irritation and/or compression comprised the primary etiology in 57% to 58% of patients. Other common causes were recurrent or persistent disk herniation and lumbosacral adhesive arachnoiditis. The diagnosis of stenosis was made either by high-resolution CT scan of the lumbar spine or by directly testing lateral canal and for animal patency at the time of surgery. It is now appreciated that the process of degenerative disk disease, particularly when enhanced by diskectomy, results in progressive loss of intervertebral disk volume and predisposes to future ipsilateral or contralateral lateral spinal stenosis. Degenerative disk disease is ultimately a bilateral process and therefore surgical exposure should be bilateral. The direct and indirect costs of FBSS to patients and to society as well as the toll in human suffering are very high. This is particularly a matter of concern when it is realized that for many FBSS patients, surgery could have been avoided in the first place by preventive care or by innovative conservative treatment. When surgery is indicated, adequate diagnostic tests and the execution of appropriate procedures based upon this information should largely prevent the failed back surgery syndrome.