The sensation loss over the top of the foot indicates which nerve root?

The loss of sensation over the top of the foot primarily corresponds to the distribution of the L5 nerve root. The L5 nerve root innervates the skin on the dorsum of the foot, particularly around the first to third toes. This is due to its role in the sensory supply of the foot and its connections to dermatomes that encompass these areas.

When assessing a patient with sensory deficits, particularly those involving numbness or loss of feeling, the distribution of these sensations can help localize the specific nerve root affected. L4 generally affects the medial aspect of the foot and the lower leg, S1 is associated with the lateral aspect and the heel, while C6 primarily corresponds to the sensory distribution in the thumb and forearm area. Therefore, the correct identification of L5 is crucial when considering sensory deficits on the top of the foot.