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Epidural block: myelographic evaluation with a single-puncture technique using metrizamide.

A simplified technique using metrizamide for myelographic delineation of extrinsic spinal cord blocks is described. This method was successfully used in eight consecutive examinations without adverse effects. A single lumbar puncture is followed by instillation of metrizamide into the subarachnoid space. With the needle left in place and the patient in the Trendelenburg position, the contrast agent is sequentially displaced above any encountered extradural blocks by further injection of diluent or sterile saline into the caudal thecal sac. Thus, multiple levels of blockage may be defined at their upper and lower margins. This method offers an expedient and safe alternative to combined lumbar and C1-2 lateral cervical puncture, leaves a minimum amount of metrizamide "trapped" below a block, and has several advantages over use of iophendylate. Additionally, the examination may be supplemented with CT scanning when desirable.