Surgical Implantation

Surgical implantation of the Vagus Nerve Stimulator is an outpatient procedure and is relatively simple from a surgical perspective. First, the surgical team makes two incisions, one in the left upper chest and the second on the left neck (cervical) above the vagus nerve. Next, a device known as a tunneler is passed through the chest incision up to the cervical opening; this will allow the wires from the electrode to the pulse generator to go neatly inside the body. With the wire put in place, the electrode with adjustable strings is then placed around the vagus nerve and is connected to the wires. Touching the electrode may damage it; therefore, the strings are used for manipulation and proper placement. A strain-relief bend is created, and the electrode is secured to the fascia. The pulse generator is then connected to the wires and placed in a deep subcutaneous tissue in the left upper chest. The incisions are closed, and the operation is complete. The patient can usually leave the hospital on the same day after the operation (Shafique, Dalsing 324).

Figure 4
Photo by Arcadian

The pulse generator is initially set at zero amps for two weeks following surgery; afterwards, the doctor or neurologist sets the pulse generator to desired levels for adequate therapy (Shafique, Dalsing 324).

Analysis

Advantages

The major advantages of the VNS device are the safety of the medical procedure and the durability of the device itself. Implantation of the device is a low-risk operation due to the simplicity of the surgery, usually an outpatient procedure. The device is also FDA approved for both depression and epilepsy treatment. The biggest advantages of the VNS system are the positive results it shows for patients, who are unable to cope with the side effects of drugs, or who suffer from an otherwise intractable disease that is resistant to drug treatments. Although there are very few formal studies for the VNS treatment of depression, preliminary results look promising. Finally, the VNS procedure can be ideal for patients suffering from both epilepsy and depression, which often coincide.

Disadvantages

A major disadvantage of the VNS therapy is its cost: $24,000 for the newest units (Guberman 172). The required surgery and the presence of a foreign device in the body are other disadvantages. The device must be replaced every 10 years, which requires further surgery. Another major disadvantage is that the mechanism by which the VNS elicits symptomatic relief is largely unknown. As a result, it is difficult to optimize the technology to minimize side effects, which include vagus nerve injury (i.e. during surgery) or parasympathetic over-stimulation. These are presented in Tables 1 and 2.

Conclusion

As a whole, the VNS therapy provides an alternative treatment for both epilepsy and depression. It is especially useful in providing treatment for drug-resistant forms of both diseases. Since VNS is a relatively new form of therapy, extensive data recording the long-term effectiveness is not yet available. However, initial studies on epileptic patients with the VNS implantation noted a 50% seizure reduction post-implantation, which occurred in 36.8% of patients in one year, 44.3% in two years, and 42.7% in three years. Additionally, major side effects subsided during the three year follow-up period (Shafique, Dalsing 326). In studies involving the VNS therapy for treatment of drug-resistant depression, most antidepressant reaction was seen in the initial phase of the treatment. The response rate in 12 months was 44.1%, while 39% of non-responders displayed improvement by 24 months.

It is remarkable that the VNS treatment is so effective with so little knowledge on its mechanism of action. The VNS system is bound to shed light on additional neural processes, opening the door for new stimulation techniques and treatments. It is expected to serve as a bench-mark for these future stimulation techniques.