What condition is characterized by paralysis below the neck, affecting both arms and legs?

Quadriplegia is a condition where there is paralysis affecting all four limbs—both arms and legs—due to an injury or disease that impacts the spinal cord, particularly in the cervical region of the spine. This paralysis occurs because the signals from the brain cannot effectively communicate with the muscles below the level of the injury.

In this specific context, since the paralysis affects both the arms and legs, quadriplegia is the only correct answer. Paraplegia refers to paralysis of the lower half of the body, specifically the legs, usually resulting from spinal injuries to the thoracic or lumbar regions. Hemiplegia indicates paralysis on one side of the body, impacting either an arm and a leg on the left or right side, often due to a stroke. Monoplegia entails paralysis of a single limb, which does not encompass the paralysis experienced in quadriplegia. Thus, the definition and characteristics of quadriplegia align precisely with the condition described in the question.