An electrosurgical apparatus for treating tissue, comprising: an elongated shaft including a proximal region, a distal region having 2. an electrically conductive region (112, 312), and one or more lumens (60, 702) therethrough; and a stylet (62, 402) located within one of said one or more lumens (60, 702) for obturating at least a portion of an opening defined by a distal end of said elongated shaft to define an obturated portion; the stylet (62, 402) comprising: an elongated member having a distal end, a thermocouple (52, 602) having a thermocouple distal end, the thermocouple distal end occluding at least part of the obturated portion, wherein said thermocouple (52, 602) comprises said elongated member, said elongated member having a thermocouple junction (54, 604, 608) formed at the distal end of said elongated member, characterized in that the stylet further comprises an occluding component attached to the elongated member, the occluding component having a distal face; wherein said occluding component surrounds and is affixed to a distal portion of said thermocouple (52, 602), wherein the obturated portion is at least partially occluded by the occluding component, to prevent the passage of tissue into the elongated shaft, while allowing fluid to exit through said distal opening. an elongated shaft including a proximal region, a distal region having 2. an electrically conductive region (112, 312), and one or more lumens (60, 702) therethrough; and a stylet (62, 402) located within one of said one or more lumens (60, 702) for obturating at least a portion of an opening defined by a distal end of said elongated shaft to define an obturated portion; the stylet (62, 402) comprising: an elongated member having a distal end, a thermocouple (52, 602) having a thermocouple distal end, the thermocouple distal end occluding at least part of the obturated portion, wherein said thermocouple (52, 602) comprises said elongated member, said elongated member having a thermocouple junction (54, 604, 608) formed at the distal end of said elongated member, an elongated member having a distal end, a thermocouple (52, 602) having a thermocouple distal end, the thermocouple distal end occluding at least part of the obturated portion, wherein said thermocouple (52, 602) comprises said elongated member, said elongated member having a thermocouple junction (54, 604, 608) formed at the distal end of said elongated member, characterized in that the stylet further comprises an occluding component attached to the elongated member, the occluding component having a distal face; wherein said occluding component surrounds and is affixed to a distal portion of said thermocouple (52, 602), wherein the obturated portion is at least partially occluded by the occluding component, to prevent the passage of tissue into the elongated shaft, while allowing fluid to exit through said distal opening. an occluding component attached to the elongated member, the occluding component having a distal face; wherein said occluding component surrounds and is affixed to a distal portion of said thermocouple (52, 602), wherein the obturated portion is at least partially occluded by the occluding component, to prevent the passage of tissue into the elongated shaft, while allowing fluid to exit through said distal opening.