Pictured here are two different leads, or wire-like structures that are connected to the generator. At the opposite end of the lead are electrodes; this is the end that is placed in the epidural space, near the spinal cord. The electrodes deliver the electrical signals to the spinal cord.
There are two main types of leads: percutaneous and surgical. Percutaneous means "under the skin," so a percutaneous lead will be inserted in the soft tissue by means of an incision. Placement of the other type of lead is often left to spine surgeons who have more skill and practice in traditional back surgery.
Some manufacturers make different types of percutaneous leads, claiming that this will improve the pain management provided by the system. For example, on the model on the right shown here, according to the manufacturer, the leads can programmed individually by the doctor. But the degree to which this feature is helpful in relieving back pain is debatable, according to some physicians.