Cannula and electrode assembly (32) which includes: a cannula (42), which includes a cannula body (50) having: opposite proximal and distal ends； a distal section (56) that is electrically conductive, in which the distal section defines the distal end of the cannula body； a lumen (52) extending distally and longitudinally from the proximal end of the cannula body, the lumen is sized to receive the body (74) of an electrode (66)； and a lateral opening (58) that is proximally separated from the distal end of the cannula body, in which the lateral opening opens to the lumen of the cannula body, in which the cannula body (50) is formed further so that: a curve (54) is located in the body (50) proximal to the distal section (56) of the cannula； the lumen (52) of the body extends to and through the curve (54) and the distal section (56) of the body； the lateral opening (58) is formed so that it extends through a part of the cannula body that defines an outer part of said curve (54), and in which the cannula and electrode assembly (32) includes In addition: an electrode (66) adapted for connection to a cable (92) that connects the electrode to a control console (36), in which the electrode has an electrode body (74) sized to settle in the lumen (52) of the body (50) of the cannula, in which the electrode body has: a distal section (82) formed from electrically conductive material that is electrically connected to a conductor internal to the cable (92) and a section (80) proximal to the distal section formed from elastic material, characterized in that the body (74) of the electrode is formed such that a section (80) formed from elastic material is positioned such that, when the body of the electrode is inserted into the lumen (52) of the cannula, the section (80) is inside the lumen section defined by the curve (54) and the section (80) of the electrode body is shaped to define a curve so that, depending on the rotation orientation of the body (74) of the electrode relativ
