Mid- to long-term natural history of degenerative lumbar spinal stenosis and predictors for clinical deterioration.

Objective: Mid- to long-term data on the natural history of degenerative lumbar spinal stenosis (LSS) remain limited as surgery is increasingly favored. The aim of this study was to characterize the prevalence of clinical deterioration over long-term follow-up and to identify risk and protective factors.

Methods: In this retrospective cohort study, adult patients with symptomatic LSS and a follow-up period ≥ 5 years were analyzed. Clinical deterioration was defined by at least one of the following factors: myotomal lower limb weakness, sphincter disturbance, or a decrease in walking tolerance to ≤ 10 minutes due to neurogenic claudication. Radiological assessment included standing lumbar radiographs and lumbosacral MR images obtained after symptom onset. A univariate analysis was performed, with variables demonstrating significance levels of p < 0.1 included in the subsequent multivariable logistic regression analysis. Receiver operating characteristic (ROC) curves and Kaplan-Meier survival curves were plotted for statistically significant risk factors.

Results: A total of 202 patients with symptomatic LSS and adequate follow-up were included. The mean age was 65.2 ± 4.2 years at the onset of neurological symptoms and the mean follow-up duration was 121 ± 40 months. Clinical deterioration occurred in 39 patients (19.3%). Among those with deterioration, 36 (92.3%) reported reduced walking tolerance due to neurogenic claudication, 8 (20.5%) had myotomal weakness, and 2 (5.1%) experienced sphincter disturbance. Upon multivariate analysis, the presence of lumbar developmental spinal stenosis was a risk factor for deterioration (p = 0.031), while an increased dural sac area was protective (p = 0.045); adjusted hazard ratios were 10.11 and 0.98, respectively. A dural sac area < 55 mm2 had an area under the ROC curve of 0.781 for predicting clinical deterioration within 5 years of symptom onset.

Conclusions: Patients with lumbar stenosis and neurogenic claudication mostly remained ambulatory without developing motor deficits or sphincter dysfunction. Conservative management is an option for patients with tolerable symptomatology and low functional expectations, especially in the absence of the identified risk factors of developmental narrowing of lumbar canal dimensions and critically reduced dural sac area over the most stenotic level.