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Introduction: Surgery for lumbar spinal stenosis (LSS) is one of the most common indications for elective spine surgery in developed countries and postoperative cerebrovascular complications must be taken into consideration. The main objective of this study was to determine and investigate the risk of stroke during the first year after surgery for LSS.

Materials and Methods: This retrospective register study included 64,179 patients from the Swedish spine register (Swespine) operated from 2001 through 2020 for central or lateral LSS. Outcomes were collected from the Swedish stroke register (Riksstroke). The primary outcome was the diagnosis of peri- or postoperative ischemic/hemorrhagic stroke within the first year after LSS surgery. The registers included background data like sex, age, smoking, and previous spine surgery, in addition to surgical/stroke care data like levels of decompression, surgery with instrumentation, type of stroke and length of hospitalisation. Initial analysis with histograms and a life table was used to present the hazard of stroke during the first year after surgery. An adjusted cox regression model was used to analyse the risk for stroke. The model was adjusted for age (<64, 65-74, ≥75), sex, smoking and whether implants were used or not.

Results: During the first year after surgery 426 patients (0,66%) developed a stroke. Out of these 37 (0,06%) were classified as hemorrhagic, 379 (0,59%) as ischemic and 10 (0,02%) as unclassified. The risk for stroke was highest during the first 30 days (n=72, (0,11%)). Smoking (HR, 1,82; 95% CI, 1,31-2,52; p<0,001), age 65-74 years (HR, 2,65; 95% CI, 1,91-3,67; p<0,001) and age ≥75 years (HR, 6,04; 95% CI, 4,42-8,25; p<0,001) were associated as risk factors for postoperative stroke. Surgery with implants was not associated with an increased risk (HR, 1,01; 95% CI, 0,73-1,40; p=0,967).

Conclusion: The peri- and postoperative risk for stroke during the first year after LSS surgery was 0,66% and increased age and smoking were identified as risk factors. The highest number of strokes occurred during the first 30 days and more specific, the first days after surgery. This study gives the basis for further research of cerebrovascular complications after LSS surgery.