National Physical Therapy Examination (NPTE) Practice Exam

If diagnosed with L3-4 disc herniation, which nerve root is most likely affected?

1. L3

2. S1

3. L5

4. L4

The correct answer is: L4

In the case of an L3-4 disc herniation, the nerve root that is most likely affected is the L4 nerve root. This is due to the anatomical arrangement of the lumbar spine and the way in which herniated discs typically impact nerve roots. The lumbar vertebrae and their associated nerve roots are organized in such a way that herniation at one level primarily affects the nerve root that exits at that level or the nerve root directly below it. Since the L3-4 intervertebral disc herniation occurs between the third and fourth lumbar vertebrae, it exerts pressure on the L4 nerve root, which exits the spinal canal at the L4-5 foramen. This understanding is crucial for determining the precise location of symptoms and for planning appropriate treatment strategies. Symptoms associated with L4 nerve root compression may include pain, numbness, or weakness in the anterior thigh and may also affect the ability to extend the knee, as this root contributes to the innervation of the quadriceps muscle. The other choices, such as the L3, S1, and L5 nerve roots, may not be primarily impacted by an L3-4 disc herniation, as they correspond to different levels