What is the general pattern of motor and sensory loss in a complete lumbar plexus injury?

What is the general pattern of motor and sensory loss in a complete lumbar plexus injury?

• A. Deficits across multiple thigh groups (femoral and obturator) with sensory loss in corresponding thigh regions and possible lateral thigh involvement.
• B. Isolated single nerve distribution impairment
• C. Only sensory loss in distal leg
• D. Only motor weakness without sensory loss

Answer: (A)

A complete lumbar plexus injury produces combined motor and sensory loss across several thigh nerve territories because the plexus gives rise to multiple branches that innervate both thigh muscles and skin. When the femoral and obturator nerves are affected, you see weakness of multiple thigh muscle groups—knee extension from the quadriceps and hip flexion/adduction from nearby muscles, plus reduced thigh movements overall. Sensory loss follows the same pattern: the anterior thigh (femoral nerve) and the medial thigh (obturator nerve) are affected, and there may also be sensory loss on the lateral thigh if the lateral femoral cutaneous nerve is involved. This combination—deficits across several thigh muscle groups with corresponding sensory loss, and the potential additional lateral thigh involvement—best describes the pattern of a complete lumbar plexus injury.

A complete lumbar plexus injury produces combined motor and sensory loss across several thigh nerve territories because the plexus gives rise to multiple branches that innervate both thigh muscles and skin. When the femoral and obturator nerves are affected, you see weakness of multiple thigh muscle groups—knee extension from the quadriceps and hip flexion/adduction from nearby muscles, plus reduced thigh movements overall. Sensory loss follows the same pattern: the anterior thigh (femoral nerve) and the medial thigh (obturator nerve) are affected, and there may also be sensory loss on the lateral thigh if the lateral femoral cutaneous nerve is involved. This combination—deficits across several thigh muscle groups with corresponding sensory loss, and the potential additional lateral thigh involvement—best describes the pattern of a complete lumbar plexus injury.