Signal Intensity Of Cerebrospinal Fluid On MR Images Indicates The Severity Of Degenerative Lumbar Spinal Canal Stenosis

Abstract

Conservative management is unlikely to be effective in patients with degenerative lumbar spinal canal stenosis (LSCS), when stenosis is severe. In this study, we investigated the significance of the signal intensity of cerebrospinal fluid (CSF) on MRI with respect to the severity of stenosis. Twenty LSCS patients were reviewed. They all showed single level stenosis, and patients showing multiple stenosis were excluded. The severity of stenosis was evaluated by myelograms, and they were divided into two groups based on the severity on the myelograms. Ten were in complete block (CB) and 10 in incomplete block (IB). On MR T2-weighted images, we measured the signal intensity of CSF at both the cranial and caudal side from the stenotic level; then the signal intensity ratio (SIR) was calculated as the relative value of cranial CSF compared to caudal side. In results, SIR was 1.26 +/0.16 in CB group, and 0.96 +/0.14 in IB group. There was a significant difference between the two groups (p<0.05; unpaired t-test). In this analysis using NIH image software, high number indicated low signal intensity on MRI. This result indicated the CSF in the IB group showed similar signal intensities at both the cranial and caudal side; whereas, in the CB group, the CSF showed higher signal intensity (brighter) on MRI at the caudal side compared to that at the cranial side. In other words, when CSF at the caudal side shows higher signal intensity on T2-MR images compared to the cranial side, the spinal canal stenosis is severe and shows complete block on myelograms.