RADIOLOGICAL SOCIETY OF NORTH
AMERICA 2003 (RSNA): Scientific Papers
Neuroradiology/Head and Neck (My Aching Back)
POSTURAL VARIATION IN DURAL SAC CROSS SECTIONAL
AREA MEASURED IN NORMAL INDIVIDUALS SUPINE, STANDING, AND SITTING,
DATE: Thursday: December 04, 2004
START TIME: 11:40 AM
END TIME: 11:47 AM
LOCATION: ROOM N228
Francis W. Smith, MD
University of Aberbeen, Scotland, U.K.
Yoichiro Hirasawa MD
Waseem Bashir MBBS
Malcolm Pope PhD
Keywords: Spinal canal
Clinical symptoms in lumbar spinal stenosis are posture-related.
Pain and numbness in the buttock and leg are often provoked either
by walking or by prolonged standing. Symptomatic relief may be obtained
by lying and sitting. It is well known that the available space
within the lumbar spinal canal decreases with extension, axial loading,
and increases in flexion. The unique design of Position MRI allows
patients to be scanned whilst standing, sitting or lyijng down.
This facilitates imaging in postures where patients report discomfort.
Before this new capability is applied to diagnosis, the relationship
between dural sac cross sectional area and lumbar posture in normal
individuals must be ascertained.
METHODS AND MATERIALS
29 male volunteers, with no symptoms of low back pain or sciatica,
were recruited for this study. The mean age was 32.9 years (21-61).
Prior to imaging each individual lay for 20 minutes in the supine
position before studied with pMRI using a 0.6T FONAR Indominitable
Stand-up MRI scanner. Data was collected in the supine, standing,
simple sitting, sitting flexion and sitting extension positions.
Cross sectional area of the dural sac and diameter of the dural
sac, in both sagittal and axial images were measured at the level
of the disks at L3/4, L4/5 and L5/S1 on pMRI images, by two trained
Statistically significant positional dependence of the dural sac
diameter was found at the L3/4, L4/5 and L5/S1 levels. The smallest
dural sac dimensions were found in the supine position. The greatest
area was found in the sitting flexed position. In the erect posture
the area was less than sitting in neutral or flexion. Sitting in
extension was found to have a smaller area than sitting in flexion.
The difference in the cross-sectional area was also statistically
significant in each posture at all levels studied. The supine posture
gave the smallest cross-sectional area compared to sitting in flexion
and in extension.
Alterations in the dimensions of the dural sac can be observered
and accurately measured in different postures, using pMRI. This
information will be useful for the examination and management of
patients sufferijng from lumbar spinal canal stenosis.