FIG 2.

Unsubtracted (A) and subtracted (B) left LDDSM images on day 1 demonstrate subdural contrast injection at the thoracolumbar junction that appears as a nondependent thick contrast column overlying the middle of the osseous spinal canal (solid arrows in A and B). Given the predominantly intrathecal injection, compare the subdural contrast appearance with the dependently layering menisci of intrathecal contrast filling the nerve root sheaths (arrowheads in A and B). On the same-day left lateral decubitus CTM (C), subdural contrast appears as nondependent collections (solid arrows in C), more hyperattenuating than the intrathecal contrast (dashed arrow in C). The next-day CTM (immediately following the contralateral right LDDSM) shows no residual subdural contrast at the T12/L1 level (solid arrows in D). The time interval between images A/B/C and image D is approximately 22.5 hours.