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

Anatomical details of nerve root compression may explain the production of the signs and symptoms of sciatica. The authors of anatomical studies have offered many theories without clearly demonstrating the clinical relevance of the observations. Clinicoanatomical series are scarce and are affected to a great extent by selection bias.

The authors created a schematic drawing of the lumbar anatomy based on both the literature and in vitro anatomical observations. A diagnosis was then made with the aid of detailed and standardized clinical and magnetic resonance (MR) imaging studies in primary-care patients who presented with pain that radiated into the leg. Clinical and MR imaging findings were correlated. Finally, the anatomical drawing was compared with the clinical data. The higher the vertebral level of symptomatic disc herniations, the more likely the compression will be more laterally situated. Classic symptoms of sciatica (typically, dermatomal pain; increase in pain when coughing, sneezing, or straining; and testing positive for pain during straight leg raising) were most likely to occur with compression of the nerve root in the axilla and with mediolateral disc herniations.

The L-3, L-4, L-5, and S-1 nerve roots each tend to be compressed at different sites along the rostrocaudal course of the nerve root. Disc herniations become symptomatic at different sites for each disc level. The schematic drawing produced a priori could well be used to explain these findings. Expectations of particular clinical findings can be predicted by specific pathoanatomical findings.