A steerable medical apparatus includes a shaft (14), a steering mechanism (38), and an actuation mechanism (48). The shaft has a proximal portion (16), a distal portion (18), a first pull wire (20), and a second pull wire (22). The distal ends of the first (20b) and second (22b) pull wires are coupled to the distal portion of the shaft. The steering mechanism has a first wheel (40) and a second wheel (42) coupled by a differential mechanism (44). The proximal ends of the first (20a) and second (22a) pull wires are respectively coupled to the first and second wheels. The actuation mechanism is coupled to the steering mechanism. Actuating the actuation mechanism in a first operational mode causes the distal portion of the shaft to curve in a first plane. Actuating the actuation mechanism in a second operational mode causes the distal portion of the shaft to curve away from the first plane.
