Pathoanatomical characteristics of clinical lumbar spinal stenosis

BACKGROUND: There is no clear picture of pathoanatomy in clinically diagnosed LSS. Findings in the literature regarding imaging in LSS are heterogeneous. OBJECTIVE: Characterize the pathoanatomy of LSS, as reported in the radiology reports, for a large community-based sample of patients with the clinical diagnosis of LSS. METHODS: Retrospective review of clinical radiology reports. The sample comprised patients 40 years of age or older, with clinically diagnosed LSS. Radiology reports for lumbar MRI were obtained and data were extracted pertaining to the type and location of LSS. RESULTS: 173 subjects with a mean age of 66.2 ± 11.7 years were included (61% women). 68.2% had mixed stenosis, 19.1% had central stenosis only, and 12.7% had lateral stenosis only. By level, the most prevalent findings were at L4/5 (93%), L3/4 (66%) and L5/S1 (49%). This pattern was different in those with lateral stenosis only, where the proportion of findings at L5/S1 was higher than at L3/4. 156 subjects (90.2%) had findings of at least moderate severity. Considering moderate-severe findings only, 31% had mixed stenosis and 40.0% had multi-level findings (90.5% at adjacent segments). When mild findings were included for subjects with at least one moderate-severe finding the rate of mixed stenosis increased to 59%, and multi-level stenosis to 68.6%. The most common multi-level combinations were L3/4 and L4/5 for two-level stenosis and L2/3 through L4/5 for three-level. CONCLUSION: Results of this study confirm a number of pathoanatomical patterns in people diagnosed with LSS, including a high proportion of stenosis at L4/5, followed by L3/4 and L5/S1. Results also suggest a high prevalence of multi-level stenosis at adjacent segments. The prevalence of mixed stenosis varied from 31% to 68.2%; inclusion of mild findings resulted in a higher rate of both mixed and multi-level stenosis, compared to analysis of moderate-severe findings only. These results may guide future studies on LSS pathophysiology, by focusing attention toward the most prevalent radiological findings.