6 57. Weinstein. J. N. at al. Surgical versus nonsurgical therapy for lumbar spinal stenosis. N. Engl. J. Med. 358.794-810 (2008). 58. Haarmeler. T. & Stolke. D. Spinale Eng& Syndrome. In Theraple unclYeilauf neurcifoglscherEnoankungen (German). 5th edn (Eris Brandt. T.. Dichgans. J. & Diener. H. C) 12