Apparatus, including a guidewire, having a distal end dimensioned to penetrate into a nasal sinus and a balloon, which is fitted over the guidewire in proximity to the distal end. There is an inflation channel, which runs along the guidewire and is coupled to convey a pressurized fluid into the balloon so as to inflate the balloon. The apparatus also includes a first electrode, fixedly attached to a distal tip of the guidewire, and a second electrode, fixedly attached to the guidewire at a location proximal to the distal tip. There are conductive leads running along the guidewire and coupled to apply an electrical potential between the first and second electrodes.