Depicting of forward shifting of posterior dural sac alone on flexion position cannot reliably diagnose Hirayama disease, which should be established only if there is forward shifting of posterior dural sac, plus increased ratio of x/y and decreased ratio of a/b on flexion position from associated mass effect on the spinal cord.
Department of Radiology, Tuen Mun Hospital, Tuen Mun, Hong Kong. vincentlai [at] hkcr.org
Eur J Radiol. 2011 Dec;80(3):724-8
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