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Lumbar spondylolysis: reactive marrow changes seen in adjacent pedicles on MR images
J L Ulmer1, A D Elster, V P Mathews
1Department of Radiology, Bowman Gray School of Medicine, Wake Forest University, Winston-Salem, NC 27157-1022.
Objective:
In a search for ancillary MR findings for the diagnosis of spondylolysis, we performed a retrospective study to characterize changes in MR signal intensity of marrow within lumbar pedicles at the level of a spondylolytic defect. These reactive marrow changes were classified according to the anatomic-pathologic scheme developed for degenerative disk disease by Modic et al.
Materials And Methods:
Two neuroradiologists retrospectively reviewed MR images of 60 patients with lumbar spondylolysis confirmed by conventional radiography or CT. The MR signal of each pedicle at the level of a pars defect was compared on T1- and T2-weighted sagittal images to that at the next higher level. When both observers concurred that the signal of the involved pedicle differed significantly from that of its neighbor, this signal change was classified into one of three types (type I: hypointense on T1-weighted images, hyperintense on T2-weighted images; type II: hyperintense on T1-weighted images, isointense or hyperintense on T2-weighted images; type III: hypointense on both T1- and T2-weighted images).
Results:
Changes in MR signal intensity of pedicles adjacent to spondylolytic defects were observed in 24 (40%) of the 60 patients. Type I changes were seen in three patients, all less than 24 years old. Type II changes were seen in 17 patients with a median age of 35 years. Type III changes were seen in four patients with a median age of 51 years. The distribution of changes in signal intensity in the pedicle as a function of age was significant (p = .001).
Conclusion:
Categories of changes in MR signal intensity, similar to those described adjacent to degenerating disks, can be seen in lumbar pedicles adjacent to a spondylolytic defect of the pars interarticularis and are distributed as a function of age. Awareness of this finding may aid in establishing the correct diagnosis of spondylolysis on MR imaging and prevent erroneous interpretation of abnormal signal intensity in the pedicles in these patients.
Insights
Magnetic resonance imaging (MRI) can reveal reactive marrow changes in lumbar pedicles adjacent to spondylolysis. These changes, classified by signal intensity, correlate with patient age and aid in diagnosis.
Area of Science:
- Radiology
- Orthopedic Imaging
- Spine Diagnostics
Background:
- Spondylolysis, a defect in the pars interarticularis, can be challenging to diagnose solely with conventional imaging.
- Ancillary magnetic resonance imaging (MR) findings may improve diagnostic accuracy.
- Reactive marrow changes in lumbar pedicles adjacent to spondylolytic defects have not been fully characterized.
Purpose of the Study:
- To characterize MR signal intensity changes in lumbar pedicle marrow at the level of a spondylolytic defect.
- To classify these reactive marrow changes using a scheme similar to that for degenerative disk disease.
- To determine if these changes correlate with patient age.
Main Methods:
- Retrospective review of MR images from 60 patients with confirmed lumbar spondylolysis.
- Comparison of MR signal intensity in pedicles at the defect level versus the next higher level on T1- and T2-weighted sagittal images.
- Classification of signal changes into three types (I, II, III) based on T1 and T2 signal intensity.
Main Results:
- MR signal intensity changes were observed in 24% of patients (24/60).
- Type I changes (hypointense T1, hyperintense T2) were seen in younger patients (<24 years).
- Type II changes (hyperintense T1, iso/hyperintense T2) were seen in middle-aged patients (median 35 years).
- Type III changes (hypointense T1/T2) were seen in older patients (median 51 years).
- The age distribution of these signal intensity changes was statistically significant (p = .001).
Conclusions:
- Lumbar pedicles adjacent to spondylolytic defects exhibit MR signal intensity changes analogous to those seen with degenerative disk disease.
- These pedicular marrow changes are age-dependent.
- Recognizing these MR findings can assist in diagnosing spondylolysis and prevent misinterpretation of abnormal signals.