Just like in electronics, the larger the diameter of a wire and the better insulated it is, the faster the transmission of electricity. So it is with nerves. The nerves that make you feel and move require extremely fast conduction and therefore are very large in diameter and are covered with a fatty insulation called myelin. The pain nerves, in contrast, are not myelinated and are very small. When we get cut with a razor, for instance, we feel the blade cross our skin and we even withdraw reflexively, but the pain may follow a few minutes later.
Researchers in Holland found that these different nerve types are destroyed at different degrees of heat. The pain nerves are the most vulnerable because they are so small and uninsulated. By heating the spinal ganglion to 52° Centigrade (~125° Fahrenheit), these small pain nerves were destroyed but only partially injuring some of the other nerves. They did this by sending electricity down the needle at the speed of radio waves (60,000 cycles/second). At this speed, by varying the voltage, the temperature of the tissues surrounding just the tip of the needle could be accurately and consistently kept at the target 52°Centigrade. However, in spite of this precision, some patients were left with numb or weak limbs.
One of the founding fathers of this radio-frequency technique, Dr Menno Sluijter from Amsterdam felt that the temperature and therefore the nerve destruction, had little to do with the pain relief. He felt that the electricity was sufficient to modulate the neural chemistry of the spinal cord such that new pain killing receptors were manufactured by the body. To prove this, he made the radiofrequency machine turn on for 0.2 seconds and then turn off for 0.8 seconds making sure that the nerve never got hotter than normal. By doing this, he gave the same dose of electricity but the spinal ganglion was NEVER injured – yet the patient received the same relief as if the gangion was destroyed! He referred to this adaptation as pulsed radiofrequency technique. As no tissue is destroyed, he felt it was a much safer technique.