Neurological impairment score in lumbar spinal stenosis

Background and aim

The Oswestry Disability Index (ODI) is an interview-based instrument generally accepted as a measure of disability in patients with lumbar spinal stenosis (LSS). There is, however, no generally accepted measure for neurological impairment in LSS. We therefore developed a scoring system [neurological impairment score in lumbar spinal stenosis (NIS-LSS)] for the assessment of neurological impairment in the lower limbs of patients with LSS, then performed a validation study to facilitate its implementation in the routine clinical evaluation of patients with LSS.

Methods

The NIS-LSS is based on the combined evaluation of tendon reflexes, tactile and vibratory sensation, pareses, and the ability to walk and run; the total score ranges from 0 (inability to walk) to 33 points (no impairment). A group of 117 patients with LSS and a control group of 63 age- and sex-matched healthy volunteers were assessed with the NIS-LSS to evaluate capacity to discriminate between LSS patients and controls. A correlation with the ODI was performed for assessment of construct validity.

Results

The median NIS-LSS was 27 points in LSS patients compared with 33 points in controls. The NIS-LSS discriminated LSS patients from healthy controls to a high degree of significance: the optimum NIS-LSS cut-off value was 32 points with a sensitivity of 85.5 % and a specificity of 81.3 % (p < 0.001). Overall NIS-LSS correlated significantly with the ODI score (p < 0.001). Vibratory sensation (p = 0.04), presence of paresis (p = 0.01) and especially the ability to walk and run (p < 0.001) were the NIS-LSS elements that correlated most closely with the degree of disability assessed by the ODI.

Conclusions

The NIS-LSS is a simple and valid measure of neurological impairment in the lower limbs of patients with LSS (without comorbidity), discriminating them from healthy controls to a high degree of sensitivity and specificity and correlating closely with the degree of disability. It extends our ability to quantify neurological status and to follow changes arising out of the natural course of the disease or the effects of treatment.