Professional and Linguistic Assessments Board (PLAB) Practice Exam

The function of the big toe is associated with which spinal level?

1. L4

2. L5

3. L3

4. L2

The correct answer is: L5

The function of the big toe is primarily associated with the L5 spinal level due to its involvement in the sensory and motor innervation provided by the lumbosacral plexus. The L5 nerve root contributes to the innervation of the muscles that control the movements of the big toe, notably the extensor hallucis longus, which extends the big toe. Additionally, sensory innervation to the region of the big toe is also supplied by the L5 nerve root. In contrast, the other spinal levels (L4, L3, and L2) contribute to the innervation of different muscle groups and areas. For example, L4 is more involved with the innervation of the quadriceps and the knee extension function, while L3 is related to hip flexors and adductor functions. L2, being higher in the spinal column, primarily influences movements at the hip and upper thigh. Thus, for big toe function specifically, L5 is the most relevant spinal level.