This video will describe peripheral nerve evaluation, which is one element of the treatment process known as sacral neuromodulation. The objectives of this video are to describe peripheral nerve evaluation, or P&E, including the background behind this therapy, its purpose, the equipment needed, and the actual procedure. Interstim sacral neuromodulation was first introduced in the U.S. in 1997. Indications for treatment include symptoms of overactive bladder and urgent continence refractory to medical and behavioral treatment, as well as non-obstructive urinary retention. Sacral neuromodulation utilizes stimulation of the sacral nerve plexus to modulate the reflexes that control bladder function. The system consists of a lead wire and a generator that send an electrical pulse to the sacral plexus in order to improve voiding function. This treatment protocol is a two-step process. First, there is a test phase, which P&E accomplishes, followed by an implantation phase if the test phase is successful. P&E is designed as a screening tool to locate and verify the integrity of the sacral nerves in order to assess patient response to sacral neuromodulation. This allows the patient and caregiver to make an informed decision regarding the permanent implant. The equipment needed for P&E include lead wires, a frame and needle, patient cable with J-hook, anesthetic and marking pen, adhesive tapes and dressings, patient cables with plugs, and grounding pads. Important elements of P&E include patient positioning, frame and needle placement, the test stimulation, lead wire placement, and applications of dressings that will secure the lead wires in place during the test phase. P&E is an office-based procedure. The patient lies prone with a pillow under the hips in order to place the sacrum in a horizontal plane. The patient is prepped and draped to allow visualization of the lower lumbar and sacral area. Footwear should also be removed for placement of a grounding pad. This grounding pad is connected to the patient cable with plug, which is in turn connected to the stimulator box in order to produce the test stimulation. Our goal is to place the frame and needle through the S3 foramen. This area is identified with the help of bony landmarks. The S3 foramen is located nine centimeters cephalad to the tip of the coccyx and two centimeters lateral on each side. The frame and needle is nine centimeters long and can be used to obtain this measurement. Local anesthetic is then placed subcutaneously, both superficially and down to the level of the bony plate of the sacrum. Care should be taken to avoid infiltrating the sacral nerves, which would prevent accurate test stimulation. The sacral nerves are located on the posterior medial surface of the sacrum in a medial-to-lateral orientation. The sacral nerves are located on the posterior medial surface of the sacrum in a medial-to-lateral orientation. The foramen needle should be placed parallel to the S3 nerve. The needle is inserted one and a half centimeters cephalad to S3 at a 60 degree angle. Due to anatomic variation, this angle may vary. For most patients, the three and a half inch needle is adequate, but a five inch needle is also available. Once the foramen needle is correctly placed, the J-hook is connected to the uninsulated portion of the foramen needle. The other end is connected to the test stimulation cable, which is in turn plugged into the stimulator box. Nerve responses are then tested, and the patient is instructed as to what she will feel. So now we're going to do the stimulation, and like I said, you'll feel somewhere ideally between the vagina and rectum, but you just tell us what you feel, if you feel anything, okay? Okay. I'm going to start, I'm going to go real, real slow, okay? Okay. As soon as you feel a pressure or a tapping inside, you let me know, okay? Okay. All right, here I go. Pressure. Okay, where do you feel that pressure? Um, in between my vagina and my rectum. The process is repeated on the other side with needle placement and sensory testing. Once proper sensation is achieved on both sides, the lead wire is guided into place through the foramen needle, and the needle is removed. The lead wire is a temporary wire that is coiled, insulated, and multi-stranded. There is an indicator on the lead wire to assist with depth adjustment. The lead wire contains a stylet, which is removed after needle removal. The lead wire cannot be positioned once the foramen needle has been removed. Final sensory testing can be performed once lead wire placement is completed. Once lead wire placement is finalized, the skin is cleaned, and the lead wires are fixed in place. It is important that the lead wires are fixed securely, because accidental dislodging or removal of the lead wires can affect the success of the test. Grounding pads are also fixed to the skin. These are the same pads used previously during the test phase. The wires are coiled and affixed to the skin with adhesive, sterile tape, and a transparent occlusive dressing. The lead wire is attached to the patient cable with a plug. The other end of the plug will ultimately be attached to the test stimulator box. All elements of the setup are again secured in place carefully in order to prevent migration or dislodging of the wires. Only one lead wire can be plugged into the test stimulator box at a time. The side that produced the better sensory response is hooked up first. The other wire is coiled up and placed in a bag for later use. The final phase of P&E is patient instruction. Understanding use of the stimulator box, how to complete the voiding diary, and the important activity limitations are vital to the success of this treatment. The wire plugs into the test stimulator box as shown. It can easily be unplugged as needed for clothing changes. Otherwise, the wire should be plugged in at all times during the test phase to achieve constant stimulation. The physician controls for the stimulator box are located under a removable cover. These controls allow for limit setting of the pulse width and amplitude of the electrical signal, as well as adjustment of lead electrode polarities. The patient and family member are then instructed in use of both the lead wire and the test stimulator box. The lead wire can only be plugged into the stimulator box in one direction. The amplitude or strength of the stimulation is adjusted with the dial on the test stimulator box. Only very minor adjustments are needed. When the stimulator box is turned on, a green light should blink. The box should always be turned off prior to unplugging and re-plugging the wire. A family member is shown how to switch lead wires, including unplugging the wire and re-plugging the wire. A family member is shown how to switch lead wires, including unplugging the first wire and removing the second wire from the storage bag on the patient's lower back. Equally important are activity limitations in order to prevent accidental dislodging or removal of the lead wires during the test phase. These include no bathing, no significant bending or twisting, and careful maintenance of the patient cable to avoid snagging it on objects or clothing. Turn it up as much as you can tolerate it without it being painful. That's probably good right there. That's about one and a half. That's excellent. For the next week, the patient will complete the test phase of sacro-neuromodulation. She will then return to the office for wire removal and review of the voiding diary. P&E provides a screening tool to test the benefits of sacro-neuromodulation in the individual patient. It is an office-based procedure which involves placement of temporary lead wires. Testing takes place over a one-week period. Patient education is vital to the success of this treatment. Assessments for improvement in voiding function allow both the patient and care provider to make an informed decision regarding placement of a permanent neuromodulation implant.

peripheral nerve evaluation

sacral neuromodulation treatment

bladder function

test phase

patient education