SPINAL SUBDURAL ENHANCEMENT AFTER SUBOCCIPITAL CRANIECTOMY

PURPOSE: To characterize transient intraspinal subdural enhancement (p otentially mimicking the subarachnoid spread of tumor) seen on MR imag es in some children after suboccipital craniectomy for posterior fossa tumor resection. METHODS: Radiologic and medical records of 10 consec utive children who had MR imaging for spinal staging after resection o f posterior fossa tumor during a 9-month period were reviewed retrospe ctively. In addition, one case with similar findings of intraspinal en hancement on spinal staging MR images obtained at another institution was included in the review, RESULTS: Intraspinal enhancement thought t o be subdural was seen in four of 10 patients undergoing spinal stagin g MR imaging 6 to 12 days after surgery. In these four patients, MR st udies 5 to 18 days later, without intervening treatment, showed resolu tion of the abnormal enhancement. A fifth patient (from another instit ution) with similar intraspinal enhancement underwent CT myelography 4 days later, which showed no subarachnoid lesions. No metastases have developed in any of these Five patients during the 2.5- to 3.5-year fo llow-up period. CONCLUSION: From analysis of the MR appearance and on the basis of prior myelographic experience, we suggest an extraarachno id, probably subdural, location of this enhancement. Awareness of this phenomenon will reduce the rate of false-positive diagnoses of metast atic disease. Preoperative spinal staging should be considered for pat ients undergoing suboccipital craniectomy.