Follow-up MR imaging in patients with pyogenic spine infections: lack of correlation with clinical features.

BACKGROUND AND PURPOSE Follow-up MR imaging examinations are increasingly used to monitor response to treatment in patients with spine infection. We aim to describe follow-up MR imaging examination findings 4-8 weeks after diagnosis and initiation of treatment of spine infections and to compare with clinical findings. MATERIALS AND METHODS Thirty-three patients with spinal infection and available baseline and 4-8-week follow-up MRIs were included in this retrospective cohort study. Baseline and follow-up MR imaging were graded by 2 neuroradiologists blinded to clinical characteristics and outcome. Clinical findings and outcomes were independently obtained by retrospective review of the medical record. RESULTS Compared with baseline MR imaging examinations, follow-up MR imaging more frequently demonstrated vertebral body loss of height (26/33 [79%] versus 14/33 [47%]; P < .001) and less frequently demonstrated epidural enhancement (19/32 [59%] versus 29/33 [88%]; P = .008), epidural canal abscess (3/32 [9%] versus 15/33 [45%]; P = .001), and epidural canal compromise (10/32 [31%] versus 19/33 [58%]; P = .008). Most follow-up MR imaging examinations demonstrated less paraspinal inflammation and less epidural enhancement compared with baseline. However, vertebral body enhancement, disk space enhancement, and bone marrow edema more often were equivocal or appeared worse compared with baseline. Twenty-one of 32 (66%) follow-up MR imaging examination overall grades were considered improved, 5 (16%) were equivocal, and 6 (19%) were worse. No single MR imaging finding was associated with clinical status. CONCLUSION Soft tissue findings, not bony findings, should be the focus of clinicians interpreting follow-up MR imaging results. No single MR imaging parameter was associated with the patients' clinical status.