Evaluation of degenerative disease of the lumbar spine: MR/MR myelography versus conventional myelography/post-myelography CT

Resurgence of the Role of Computed-Tomography Myelogram in the Era of MRI for Surgical Decision-Making of Lumbar Degenerative Disc Disorder

BACKGROUND

Since the introduction of magnetic resonance imaging (MRI) into clinical practice in the mid-1980s, the role of computed tomography myelography (CTM) has become less important in spinal diagnostics but remains a method that is probably even superior to MRI for special clinical issues. The study aims to report the diagnostic utility of CTM as an adjunct to MRI in lumbar degenerative disc disorder (DDD).

METHODS

Included were 20 patients who presented with symptomatic DDD but with MRI findings that did not correlate with the clinical features. These patients underwent CTM as an additional imaging technique to aid preoperative surgical decision-making. Both imaging modalities were compared for the identification of the impinging pathology as well as the number of levels of compression.

RESULTS

MRI revealed compression and/or impingement at 38 levels, whereas CTM revealed these at 29 levels. Of 20 patients, 18 underwent surgery, and a total of 29 levels were decompressed as localized in the CTM. The visual analog scale (VAS) score for back pain and leg pain at baseline were 6 ± 0.7 and 7 ± 0.4, respectively, and at 6 months postintervention (surgical/conservative) were 2 ± 0.8 and 0.3 ± 0.1, respectively. The Oswestry Disability Index scores at baseline and 6 months postintervention were 56 ± 6.9 and 18 ± 4.2, respectively (P < .0001). There was agreement on the number of levels between MRI and CTM in 10 patients (50%). MRI overestimated the number of involved levels in 9 patients (45%), whereas in the remaining 1 patient (5%), MRI underestimated the number of involved levels. The weighted κ value for agreement between MRI and CTM on the number of levels involved necessitating decompression was 0.4 (95% CI, 0.18-0.77; P = .0009).

CONCLUSIONS

CTM has a role as an adjunct imaging modality to formulate an effective management plan in patients presenting with symptomatic lumbar DDD in cases where MRI findings are inconclusive and ambiguous.

LEVEL OF EVIDENCE

4.

Myelography in the Assessment of Degenerative Lumbar Scoliosis and Its Influence on Surgical Management

Objective

Myelography has been shown to highlight foraminal and lateral recess stenosis more readily than computed tomography (CT) or magnetic resonance imaging (MRI). It also has the advantage of providing dynamic assessment of stenosis in the loaded spine. The advent of weight-bearing MRI may go some way towards improving assessment of the loaded spine and is less invasive, however availability remains limited. This study evaluates the potential role of myelography and its impact upon surgical decision making.

Methods

Of 270 patients undergoing myelography during 2006–2009, a period representing peak utilisation of this imaging modality in our unit, we identified 21 patients with degenerative scoliosis who fulfilled our inclusion criteria. An operative plan was formulated by our senior author based initially on interpretation of an MRI scan. Subsequent myelogram and CT myelogram investigations were scrutinised, with any additional abnormalities noted and whether these impacted upon the operative plan.

Results

From our 21 patients, 18 (85.7%) had myelographic findings not identified on MRI. Of note, in 4 patients, supine CT myelography yielded additional information when compared to supine MRI in the same patients. The management of 7 patients (33%) changed as a result of myelographic investigation. There were no complications of myelography of the total 270 analysed.

Conclusion

MRI scan alone understates the degree of central and lateral recess stenosis. In addition to the additional stenosis displayed by dynamic myelography in the loaded spine, we have also shown that static myelography and CT myelography are also invaluable tools with regards to surgical planning in these patients.