The natural clinical course of lumbar spinal stenosis: a longitudinal cohort study over a minimum of 10 years

Little is known about the short- and long-term prognoses of conservative treatment of lumbar spinal stenosis (LSS). Furthermore, there are no reports in the literature that investigate the relationship between longitudinal imaging changes and clinical symptoms in patients with LSS. This longitudinal cohort study aimed to clarify the morphologic changes and role of conservative treatment in LSS. This study included 34 patients with leg or low back pain who had received a diagnosis of LSS by magnetic resonance imaging (MRI). The patients' average age was 58 years at the initial examination. All participants received conservative treatment with or without medication for over 10 years. The clinical course was assessed by using the Japanese Orthopaedic Association scoring system, a visual analog scale for back or leg pain, and symptomatic Johnsson's classification. Additionally, patients' dural sac cross-sectional area was measured on axial MRI. One patient could not be contacted and four others died during this investigation. After an average follow-up of 11.1 years, symptoms improved in approximately 30 % of patients, remained unchanged in 30 %, and worsened in 30 %. The dural sac cross-sectional areas in both the worsened and unchanged groups were significantly smaller than that of the improved group (P < 0.05). In the worsened group, the average area at the initial examination was < 50 mm(2). Some patients underwent surgery during this observation, and had severe narrowing (< 40 mm(2)) of the area at the initial examination. This study showed that clinical symptoms of LSS did not develop in more than 60 % of patients who received conservative treatment, which was dependent on the severity of LSS. In patients with severe LSS and a dural sac cross-sectional area < 50 mm(2), the clinical course may deteriorate with conservative treatment, and surgery should be considered at an early stage.