Size of the subarachnoid space in stenosis of the lumbar canal.

Measurements of the subarachnoid space at myelography were carried out in three groups of patients, one group with stenosis of the lumbar spinal canal, one group without stenosis, and one intermediate group. Although spinal canal stenosis is most prominent at disc levels, the results demonstrate decreased sagittal diameter at mid-vertebral body level as well. The mean transverse diameters did not differ in three groups. This points towards congenital or developmental factors as the basic abnormality in the majority of patients with stenosis of the lumbar spinal canal.