Comprehensive Osteopathic Medical Licensing Examination (COMLEX USA) Practice

Which dermatome is responsible for sensation in the lateral lower leg?

1. Dermatome S1

2. Dermatome L4

3. Dermatome T12

4. Dermatome L2

The correct answer is: Dermatome S1

The correct response indicates that the S1 dermatome is associated with sensation in the lateral lower leg. This is essential to understand, as dermatomes are areas of skin that are mainly supplied by a single spinal nerve root. Specifically, the S1 nerve root contributes to the lateral aspect of the lower leg and the heel. It innervates structures in the lower leg, particularly involving the sural nerve, which provides sensation to the lateral side of the lower leg and foot. This dermatome is critical when considering conditions like sciatica or other nerve root compromises, where patients may report sensory loss or altered sensation in this region. Examining the incorrect options, the L4 dermatome primarily covers the medial aspect of the lower leg and the foot. T12 is more related to the abdominal region and does not reach the lower limbs, while L2 primarily affects the upper thigh region. Hence, their corresponding sensory distributions do not include the lateral lower leg. Understanding these details helps clarify why S1 is the correct answer for this question regarding sensory innervation in the lateral lower leg.