The reasoning: one crossing for the body, bilateral control for most cranial nuclei
Corticospinal tract: origins — M1 (~30%), premotor/SMA (~30%), parietal S1/areas 5, 7 (~40%; modulate sensory relay). ~1 million fibres per pyramid. Course: corona radiata → posterior limb of internal capsule → middle three‑fifths of cerebral peduncle → basis pontis (dispersed) → medullary pyramid → decussation (~85–90%) → lateral CST (distal limbs; somatotopy — cervical medial, sacral lateral) / anterior CST (~10%, axial, crosses segmentally). Direct cortico‑motoneuronal synapses (primates) enable independent finger movement.