Evaluation of the post-operative lumbar spine with MR imaging. The role of contrast enhancement and thickening in nerve roots.
OBJECTIVE
Two new signs of lumbar nerve-root affection have been reported in recent years on the basis of MR examinations, namely: thickening in nerve roots; and contrast enhancement in nerve roots. The aim of this study was to assess contrast enhancement in nerve roots in a standardised way, and to evaluate the clinical significance of contrast enhancement and of nerve-root thickening in the symptomatic post-operative lumbar spine.


METHODS
A total of 121 patients (who had previously been operated on for lumbar disc herniation) underwent 152 MR examinations, mainly on a 1.5 T system. Focal nerve-root enhancement was identified by visual assessment. Intradural enhancement was also quantified by pixel measurements that compared the affected nerve roots before and after contrast administration. Non-affected nerve roots were used as reference.


RESULTS
Enhanced nerve roots in the dural sac increased at least 40-50% in signal intensity after contrast administration compared to pre-contrast images and also compared to non-affected nerve roots. Intradural nerve-root enhancement was seen in 10% of the patients and focal enhancement in the root sleeve was seen in a further 26%. Nerve-root thickening was seen in 30%. Good correlation with clinical symptoms was found in 59% of the patients with intradural enhancement, in 84% with focal enhancement, and in 86% with nerve-root thickening. The combination of thickening and enhancement in the nerve root correlated with symptoms in 86% of the patients.


CONCLUSIONS
Nerve-root enhancement (whether focal or intradural) and thickening in the nerve root are significant MR findings in the post-operative lumbar spine. In combination with disc herniation or nerve-root displacement, these two signs may strengthen the indication for repeat surgery. However, root enhancement within 6 months of previous surgery may be a normal post-operative finding.
Grane
P
P
Department of Neuroradiology, Karolinska Hospital, Stockholm, Sweden.
Lindqvist
M
M
D000328:Adult; D000368:Aged; D001100:Arachnoiditis / Q000175:diagnosis / Q000473:pathology; D002921:Cicatrix / Q000175:diagnosis / Q000473:pathology; D003287:Contrast Media; D004388:Dura Mater / Q000473:pathology; D005069:Evaluation Studies as Topic; D005260:Female; D005500:Follow-Up Studies; D019786:Gadolinium DTPA; D006801:Humans; D007089:Image Enhancement; D007405:Intervertebral Disc Displacement / Q000175:diagnosis / Q000601:surgery; D008159:Lumbar Vertebrae / Q000473:pathology / Q000601:surgery*; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009408:Nerve Compression Syndromes / Q000175:diagnosis / Q000473:pathology; D010523:Peripheral Nervous System Diseases / Q000175:diagnosis / Q000473:pathology; D012008:Recurrence; D012086:Reoperation; D013126:Spinal Nerve Roots / Q000473:pathology*; D013130:Spinal Stenosis / Q000175:diagnosis / Q000473:pathology
D003287:Contrast Media; D019786:Gadolinium DTPA