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Association between annular tears and signal intensity of the intervertebral discs. 2008

General Spine

Aseem Sharma, MD
Franz J Wippold, MD, ASSR Member

Scientific Paper

Purpose

To study if the presence of annular tears is associated with the loss of normal hyperintensity of the central portion of intervertebral discs on T2-weighted MR images.

Methods & Materials

Using the hospital radiology database, thirty-four patients were identified, on whom MR imaging of the lumbar spine had been performed on more than one occasion from 2001 until 2007. Studies were interpreted by consensus in a random, blinded fashion by two experienced neuroradiologists. For each patient, 6 intervertebral discs between T12 through S1 vertebral levels were evaluated for presence, conspicuity, and extent of annular tears. Signal intensity of the discs was graded on a scale ranging from 1 through 6, with grade 1 representing normal, uniformly hyperintense disc (with the exception of intranuclear cleft), and grade 6 representing complete absence of any hyperintense signal within the disc.

Distributions of signal intensity grades by presence of annular tears were analyzed by contingency tables and differences were tested for statistical significance with chi-square tests. Mean signal intensities, and changes in signal intensities, were compared for the patients with and without annular tears and differences were tested for statistical significance with the Wilcoxon test.

Results

The study group included 10 males and 24 females, with ages ranging from 20 years to 88 years. The duration between the studies varied from 4 months to 69 months, with 29 patients having an interval of more than 1 year between the studies. Annular tears were identified in 152 of 204 discs (74.5%). Discs with annular tears demonstrated loss of normal hyperintense signal more often than discs without annular tears. Only 13 of 152 discs (8.5%) with annular tears demonstrated a grade 1 signal, while 30 of 52 discs (58%) without annular tear had grade 1 signal (p<0.0001). 95 of 98 discs (97%) with a signal intensity grade of 3 or more demonstrated annular tears (p<0.0001). Mean signal intensity grade of discs with annular tears was 3.1 + 1.2, compared to that of 1.5+ 0.67 for discs without annular tears (p <0.0001). The discs with annular tears demonstrated a mean change in the signal intensity of 0.40 + 0.87 on the follow up study, compared to a mean change of 0.15 + 0.6 for discs without annular tears(p= 0.04). The difference was greater for discs with grade1 signal intensity at the time of initial study. These discs had a mean change in their signal intensity grade of 0.9 + 0.49 on follow up study when an annular tear was present, compared to 0.3 + 0.53 in the absence of annular tear (p=0.0007).

Conclusion

Annular tears show strong association with loss of intervertebral disc signal intensity on T2-weighted MR images, with 91.5% of discs with annular tears demonstrating some loss of signal. The discs demonstrating normal signal intensity (grade 1) with annular tears are more likely to lose signal intensity on the follow up examination, when compared to those without annular tears.

References

None