This technique was developed by the senior author (GWM), and has worked well in the pediatric population The procedure is performed under general endotracheal anesthesia as a same day operation. Usually, peripheral intravenous access is all that is necessary and no Foley catheter is inserted. Appropriate intravenous antibiotics are given before the start of the procedure. The left side of the neck and chest region is prepped and draped. Several cubic centimeters of 0.25% Marcaine with epinephrine is infused in the two-planned incisions , with each described below.
Figure 2 Operative approach for vagus nerve stimulation implantation used at UCLA. (a) Example of marked neck skin incision about halfway between the clavicle and mastoid process, based on the palpated medial edge of the sternocleidomastoid muscle. (b) View of (more ...)
We start with the chest dissection. The skin incision is made parallel to the pectoralis major on the left side . The dissection, best accomplished with curved scissors, should be directly above the fascia of the pectoralis muscle. Once tested, to be sure that the pocket is large enough for the generator and any extra lead wire, especially in younger children, a wet sponge is placed for hemostasis, while work continues on the neck dissection.
The neck incision is transverse, approximately halfway between the clavicle and the mastoid process, based on the medial edge of the sternocleidomastoid muscle . The skin is sharply incised with a #15 or #10 blade (depending on the size of the child), and hemostasis is obtained with bipolar coagulation. Sharp dissection is carried down to the platysma. The platysma and the fascia of the sternocleidomastoid muscle are incised parallel to the skin incision, and a pocket is created between the muscle and the fascia that will be the location of the stress wire loops at the end of the case . Care is taken to expose and preserve the external jugular vein and any superficial cutaneous nerves in the field. Self-retaining retractors are used (either Wheatlander's or Henderson's), with blunt tips.
The medial edge of the sternocleidomastoid muscle and the body of the muscle is dissected and brought laterally to expose the carotid sheath. Releasing a long portion of the muscle helps convert what has been a transverse approach into a longitudinal dissection, parallel to the nerve and carotid artery. The carotid sheath is entered parallel to the major vessels. The medial edge of the internal jugular vein is identified and brought laterally, sometimes sacrificing the facial vein or other large veins crossing the field. It is not uncommon to find several, often large, lymph nodes within the carotid sheath in patients with a long-standing history of taking AEDs. These should be dissected carefully as each has a small draining vein.
The internal jugular vein is retracted laterally and the carotid artery medially. Between these two, the vagus nerve must be identified making sure that it is not confused with the cardiac branch of the vagus nerve, which can cross the field more superficially. After the vagus nerve is dissected a piece of glove cut into a square or rectangle is placed underneath it . The retractors are temporally removed with the piece of glove marking the vagus nerve.
The tunneling tool is passed between the neck and the chest incision. After visual inspection of the leads (to ensure they are intact and the covering is not stripped), they are carefully passed from the neck to the chest. The proximal leads are then attached around the vagus nerve. We prefer to do this using fine DeBakey forceps with the left (non-dominant) hand holding the spiral electrode at its base and the right (dominant) hand manipulating the electrode around the nerve. The nerve itself is not grasped, and this is performed under loupe magnification. It is important to make sure the leads are in adequate contact and are placed in the correct orientation (; positive proximal, negative in the middle, and anchor distal). We prefer to have the hubs of the electrodes pointed toward the surgeon in case the leads need to be eventually removed or replaced. That way the lead system in encountered before the nerve. The distal lead exiting out of the chest incision is attached to the generator with a self-locking system.
At this point the VNS system is ready for the initial programming and testing. The programming paddle and computer are wrapped in a sterile plastic sheet, and the programming is performed through it. The device is first interrogated to confirm the model and serial number and these are recorded for the operative report. The patient's initials and the implant date are programmed into the device. A Systems Diagnostic program is initiated and the impedance is recorded, for the record. The device is then programmed for 30 seconds at 1 milliamp. At this point we assess that the patient is not paralyzed and we watch for bradycardia or abnormal diaphragmatic movement. It is useful to bathe the proximal lead in situ with sterile saline during the programming.
The rubber pledget under the proximal lead and nerve is removed. Two Teflon pledgets are used in the neck to secure the wire loops, which prevents unintended wire breakage or migration . The first pledget typically holds the loop between the carotid sheath and the medial edge of the muscle, and the second loop is between the muscle and fascia. The wound is then copiously irrigated. The platysma is closed with inverted interrupted 3-0 Vicryls. The subcutaneous layer is closed with inverted interrupted 3-0 Vicryls, and the skin is closed with a 4-0 Monocryl subcuticular stitch . Additional Marcaine with epinephrine, Mastisol, and Steri-Strips are used, as well as a local dressing.
The generator is placed into the chest pocket and secured to the fascia of the muscle, using an O silk suture. A second and final systems diagnostic check is performed with the programming paddle on the skin over the generator, to ensure adequate impedance and to check that the system has been turned off. The wound is then copiously irrigated and closed in layers, similar to the neck incision.
The patient is typically extubated in the Operating Room and transferred to the post-anesthesia care unit (PACU). It is our policy to have the patients fully awake, having taken their normal AEDs without vomiting, before release. Patients are given oral antibiotics for 24 hours and a few pain medications. Children and parents are instructed to keep the local dressing on for five days, and can get it wet thereafter. For children with very frequent seizures, the device may be first programed in the PACU once, fully away and able to protect their airway. Children typically return to school within a few days post surgery and are seen at a one-month visit to check the wound sites.