Early Dural Sac Termination with Lumbar Disc Herniation: A Mimic of Nerve Root Anomalies

The precise location of the dural sac (DS) end is necessary for preventing neural injury during spinal surgery or procedures. There has been no report on problems with spine surgery in patients with early DS termination. A 28-year-old woman presented with low back and leg pain involving the left S1 nerve root. Magnetic resonance imaging (MRI) revealed early DS termination at the lower one-third of the L5 vertebra and lumbar disc herniation at the L5/S1. Microscopic discectomy was performed instead of endoscopic discectomy to avoid unpredictable risks. Due to early DS termination, multiple nerve roots were identified, which look like nerve root congenital anomalies (Neidre and Macnab type II anomalies), and multiple separated nerve roots appeared to exit through a single foramen. After wide exposure by hemilaminectomy, which facilitated adequate visualization and mobilization of the involved nerve roots, the ruptured disc was identified and removed with gentle retraction, avoiding risk of excessive nerve root traction. Unlike other nerve root anomalies, early DS termination could be detected easily with preoperative MRI. Although this condition appears similar to other nerve root anomalies in the surgical field, it is possible to avoid inadvertent neural injury by closely investigating preoperative MRI. If early DS termination is suspected, it is necessary to consider a safer surgical approach.