In S1 radiculopathy, which area of sensation is affected?

In S1 radiculopathy, which area of sensation is affected?

• A. Dorsum of foot
• B. Big toe
• C. Lateral foot
• D. Medial malleolus

Answer: (C)

S1 radiculopathy causes sensory changes in the S1 dermatome, which spans the posterolateral leg and the lateral aspect of the foot, including the lateral malleolus. The areas on the dorsum of the foot and the big toe are primarily L5, while the medial malleolus corresponds to L4. Therefore, the area most consistent with S1 involvement is the lateral foot. Additionally, S1 often affects ankle plantar flexion and the Achilles reflex, reinforcing the posterior/lateral involvement pattern.

S1 radiculopathy causes sensory changes in the S1 dermatome, which spans the posterolateral leg and the lateral aspect of the foot, including the lateral malleolus. The areas on the dorsum of the foot and the big toe are primarily L5, while the medial malleolus corresponds to L4. Therefore, the area most consistent with S1 involvement is the lateral foot. Additionally, S1 often affects ankle plantar flexion and the Achilles reflex, reinforcing the posterior/lateral involvement pattern.