Observer variability in the evaluation of multiple lumbar stenosis by routine MR--myelography and MRI

Retrospective study.

To determine whether magnetic resonance myelography (MRM) improves the evaluation of the severity of stenosis in patients with multilevel lumbar stenosis.

MRM shows a similar image as myelography in a noninvasive manner.

One hundred patients over 50 years of age with multiple lumbar stenosis who were prospectively referred for MR imaging (MRI) with MRM were enrolled in the study. The most severe stenotic segment and the degree of stenosis of that segment, as assessed by the extent of remaining subarachnoidal space (1: normal to 50%; 2: over 50% but not a total blockage; 3: total blockage) were evaluated in a blinded manner by 2 observers. Conventional MRI (class A), MRM (class B), and MRI combined with MRM (class C) were evaluated independently and interobserver and intraobserver reliability were assessed.

In the selection of the most severe segment and degree of stenosis, for both observers, the consensus between class (B) and class (C), was higher than that of class (A) and class (C). The average kappa values for interobserver agreement in the selection of the most severe segment/assessing the degree of stenosis for classes (A), (B), and (C) were 0.649/0.727, 0.782/0.771, and 0.832/0.784, respectively. Intraobserver kappa values were also highest for class (B), followed by class (C), and then class (A). Observations were within the range of "almost perfect" (0.81< or =kappa< or =1), with the exception of the selection of the most severe segment in class (A) by one of the observers.

When employed in routine practice, MRM could be of value for improving observer reliability in the assessment of severity of stenosis in multiple lumbar stenosis.