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, USING pMRI
DATE: Thursday: December
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.
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 observers.
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.