Pathoanatomy of clinical findings in patients with sciatica: a magnetic resonance imaging study

Object. Anatomical details of nerve root compression may explain the produc tion of the signs and symptoms of sciatica. The authors of anatomical studi es have offered many theories without clearly demonstrating the clinical re levance of the observations. Clinicoanatomical series are scarce and are af fected to a great extent by selection bias. Methods. The authors created a schematic drawing of the lumbar anatomy base d on both the literature and in vitro anatomical observations. A diagnosis was then made with the aid of detailed and standardized clinical and magnet ic resonance (MR) imaging studies in primary-care patients who presented wi th pain that radiated into the leg. Clinical and MR imaging findings were c orrelated. Finally, the anatomical drawing was compared with the clinical d ata. The higher the vertebral level of symptomatic disc herniations, the more li kely the compression will be more laterally situated. Classic symptoms of s ciatica (typically, dermatomal pain; increase in pain when coughing, sneezi ng, or straining; and testing positive for pain during straight leg raising ) were most likely to occur with compression of the nerve root in the axill a and with mediolateral disc herniations. Conclusions. The L-3, L-4, L-5, and S-1 nerve roots each tend to be compres sed at different sites along the rostrocaudal course of the nerve root. Dis c herniations become symptomatic at different sites for each disc level. Th e schematic drawing produced a priori could well be used to explain these f indings. Expectations of particular clinical findings can be predicted by s pecific pathoanatomical findings.