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[Lumbar meningeal enhancement after surgery in the posterior cranial fossa: a normal finding in children?].

PURPOSE
Spinal meningeal Gd-DTPA enhancement after cranial surgery is a known observation of a not well understood underlying mechanism. This paper demonstrates that this MRI finding is a normal meningeal reaction to subarachnoid hemorrhage, which should not be mistaken for metastatic spread.


MATERIAL AND METHODS
Three pediatric patients were examined by MRI for metastatic spread of malignant infratentorial tumors along the spinal canal two to nine days after the removal of the primary cerebral lesion. The findings were compared with a control group that underwent cranial surgery (cyst resection or fenestration of the posterior cranial fossa) without major bleeding into the subarachnoid space. Unenhanced and enhanced sequences were obtained to prove that the high signal within the CSF is caused by an abnormal Gd-DTPA uptake and not by methemoglobin.


RESULTS
Meningeal enhancement was observed in all patients with intraoperative bleeding resembling subarachnoid masses on enhanced T 1 -weighted images. This was not present in any patient of the control group. This finding lasts for approximately two weeks.


CONCLUSION
The meningeal enhancement renders immediate postoperative studies inconclusive for the detection of metastatic spread. Consequently, the obligatory tumor staging along the spinal canal should ideally be done prior to the resection of a cerebral tumor.