Quantitative assessment of dural ectasia as a marker for Marfan syndrome

PURPOSE: To establish normal values for lumbosacral dural sac dimensions wi th magnetic resonance (MR) imaging and to use these values to assess the se nsitivity and specificity of dural ectasia as a marker for Marfan syndrome. MATERIALS AND METHODS: MR imaging was performed to measure dural sac diamet er (DSD) from L1 through S1 in 44 adult patients with Marfan syndrome and i n 44 matched control subjects. DSD values were corrected for vertebral body size, yielding dural sac ratios (DSRs). The control subjects served to est ablish the upper limit of normal DSR values at the L1 through S1 levels. RESULTS: Cutoff values for normal DSRs for L1 through S1 were 0.64, 0.55, 0 .47, 0.48, 0.48, and 0.57. Significant DSR differences were shown at all le vels between patients with Marfan syndrome and control subjects (P < .001 a t all levels). At L1 through S1, the sensitivity of dural ectasia as a mark er for Marfan syndrome was 45%-77%, and the specificity was 95% or greater. By combining levels L3 and S1, dural ectasia as a marker for Marfan syndro me yielded a sensitivity of 95% (42 of 44 patients) and a specificity of 98 % (43 of 44). The presence of dural ectasia excelled, compared with the pre sence of other Marfan syndrome manifestations in the patient population. CONCLUSION: Abnormal DSR values at L3 or S1 can be used to identify Marfan syndrome with 95% sensitivity and 98% specificity.