Frequency of unexplained meningeal enhancement in the brain after lumbar puncture.

PURPOSE To examine the hypothesis that lumbar puncture alone may cause meningeal enhancement in the brain. METHODS We prospectively reviewed the brain MR examinations of all patients from a 6-month period who were studied within 1 month after lumbar puncture. We also retrospectively reviewed all cases of dural-arachnoidal enhancement in the brain from the preceding 18-month period. RESULTS In the prospective group, only one case out of 97 enhanced brain MR examinations after lumbar puncture did not have a clear cause for dural-arachnoidal enhancement. In the retrospective group, only one case out of 11 with enhancement was not clearly explained. CONCLUSIONS Dural-arachnoidal enhancement in the brain after lumbar puncture is uncommon, if it occurs at all, and lumbar puncture as a cause of enhancement should be considered a rare diagnosis of exclusion.