MAGNETIC-RESONANCE-IMAGING OF EXTRADURAL BLOOD PATCHES - APPEARANCES FROM 30 MIN TO 18-H

We have used magnetic resonance imaging to examine five patients treat ed with extradural blood patches for persistent post lumbar puncture h eadache. Images were obtained between 30 min and 18 h after patching. Extradural blood patch injection produced a focal haematoma mass aroun d the injection site which initially compressed the thecal sac and ner ve roots. The main bulk of the extradural clot extended only three to five spinal segments from the injection site, although small amounts o f blood spread more distally. Spread from the injection site was princ ipally cephalad. Mass effect was present at 30 min and 3 h, but clot r esolution had occurred by 7 h, leaving a thick layer of mature clot ov er the dorsal part of the thecal sac. Eighteen hours after injection o nly small widely distributed clots, adherent to the thecal sac, were d emonstrated. Extensive leakage of blood from the injection site into t he subcutaneous tissues was present in all patients.