NCS Advantage Practice Exam

Discs in the lumbar region sit right where several nerve roots travel to their targets, so a herniation can impinge more than one root depending on its size and exact location. At the L4-5 level, the disc lies where the traversing nerves pass by on their way to the lower foramen, and the roots contributing to the leg’s movement and sensation are all nearby. A typical, smaller lateral herniation may press the exiting or traversing L5 root, but a larger or more central herniation can affect adjacent roots as well, and in the core region can even impinge the cauda equina. That means you can see involvement of the L4 distribution (knee extension, patellar reflex), the L5 distribution (great toe dorsiflexion, dorsum of the foot sensation), and the S1 distribution (plantar flexion, lateral foot/sensation) from the same herniation. So, depending on the extent and location, all of these nerve distributions can be affected.