UCSF

Purpose

Both laboratory markers and radiographic findings in the setting of spinal infections can be nonspecific in determining the presence or absence of active infection, and can lag behind both clinical symptoms and antibiotic response. Magnetic resonance imaging (MRI) with diffusion-weighted imaging (DWI) has been shown to be helpful in evaluating brain abscesses but has not been commonly used in evaluating spinal infections. We aimed to correlate findings on DWI of the spine to results of microbiological sampling in patients with suspected spinal infections.

Methods

Patients who underwent MRI with DWI for suspicion of spinal infections and microbiological sampling from 2002 to 2010 were identified and reviewed retrospectively in this institutional review board approved study. In addition to DWI, scans included sagittal and axial T1, fast-spin echo (FSE) T2, and post-gadolinium T1 with fat saturation. Regions of interest were drawn on apparent diffusion coefficient (ADC) maps in the area of suspected infections, and ADC values were correlated with microbiological sampling.

Results

Of 38 patients with suspected spinal infections, 29 (76%) had positive microbiological sampling, and 9 (24%) had negative results. The median ADC value was 740 × 10^-6 mm²/s for patients with positive microbiological sampling and 1980 × 10^-6 mm²/s for patients with negative microbiological sampling (p < 0.001). Using an ADC value of 1250 × 10^-6 mm²/s or less as the cut-off value for a positive result for spinal infection, sensitivity was 66%, specificity was 88%, positive predictive value was 95%, negative predictive value was 41% and accuracy was 70%.

Conclusion

In patients with suspected spine infection, ADC values on DWI are significantly reduced in those patients with positive microbiological sampling compared to patients with negative microbiological sampling. The DWI of the spine correlates well with the presence or absence of spinal infection and may complement conventional magnetic resonance imaging (MRI).