A medical device for directionally focusing energy to a treatment site, the medical device including a shaft having an elongated body defining a proximal portion and a distal portion opposite the proximal portion, the distal portion including at least one electrode having a contact portion and a permeable sheath at least partially surrounding the at least one electrode, the permeable sheath and the at least one electrode defining an insulation cavity, the permeable sheath being impermeable to an insulation material introduced to the insulation cavity from a fluid source configured to be coupled to the shaft.
