Spinal Dural Sac, Nerve Root Cuffs, Rootlets, and Nerve Roots

Nerve rootlets leave the spinal cord at the anterolateral and posterolateral sulci. Anterior rootlets contain predominantly efferent fibers from the anterior horn and carry motor signals to voluntary muscles. At thoracic and upper lumbar regions, they also carry preganglionic sympathetic fibers from the lateral horns. Posterior rootlets are prolongations of pseudounipolar nerve cells located at dorsal root ganglions (DRGs). Rootlets join to form the anterior roots (from 6 to 8 anterior rootlets) and posterior roots (from 8 to 10 posterior rootlets).