A sensor system 2 for sensing activity in a target recurrent laryngeal nerve (RLN) comprises an elongate endotracheal tube 10 for insertion through a nasal passageway. The tube has a maximum transverse dimension of 5 mm. A maximum internal transverse dimension may be 3 mm. A sensor arrangement 6 is disposed on an external surface of the tube. The sensor arrangement comprises sensors 18 extending longitudinally along the tube for sensing electrical activity in the RLN. Each of the sensors 18 is at least partially unsecured relative to the tube to enable lateral sensor movement. This allows the sensors to conform to the anatomical geometry of the trachea. The tube may comprise a portion, e.g. a bend 14 in the tube, to limit insertion into the nose. The sensors may be secured to the tube at a spaced apart first zone 20 and second zone 22.
