Anatomic issues related to cervical and lumbosacral radiculopathy.

The anatomy of cervical and lumbar spinal nerves is well established. Knowledge of the normal and pathoanatomy of impingement of these roots is helpful in the diagnosis of radiculopathy in many cases. Frequently, symptoms and signs do not correlate with expected anatomical patterns. Variations of nerve roots, spinal nerves, and plexuses occur commonly. Neuroanatomical anomalies and musculoskeletal abnormalities account for many of the variations seen with unexpected radicular patterns. Unfortunately, the delineation of segmental innervation has been achieved by several different methods and definitive studies are lacking. Although there is a regular and orderly progression of innervation within each individual, it is likely that innervation patterns differ considerably between individuals.