Vagus Nerve Stimulation
The vagus nerve is one of 12 pairs of cranial nerves that originate in the brain and is part of the autonomic nervous system, which controls involuntary body functions. The nerve passes through the neck as it travels between the chest and abdomen and the lower part of the brain. It is connected to motor functions in the voice box, diaphragm, stomach and heart, and sensory functions in the ears and tongue. It is connected to both motor and sensory functions in the sinuses and esophagus.
Vagus nerve stimulation (VNS) sends regular, mild pulses of electrical energy to the brain via the vagus nerve, through a device that is similar to a pacemaker. There is no physical involvement of the brain in this surgery and patients cannot generally feel the pulses. It is important to keep in mind that VNS is a treatment option limited to select individuals with epilepsy or treatment-resistant depression
The Food and Drug Administration (FDA) approved VNS as a seizure treatment in 1997. VNS may be considered as a treatment option in patients who have tried two or more anti-epileptic drugs (AEDs) without adequate control of their seizures, or in patients who have not responded to AEDs and cannot undergo brain surgery. It is important to keep in mind that VNS is used in conjunction with AEDs, not instead of them. VNS can take up to two years to have an effect on a patient’s seizures. If VNS proves effective, it may enable a patient to decreases dosages of AEDs over time.
The goal of VNS is to reduce the number, length and severity of seizures. VNS may also reduce the time it takes to recover after a seizure. However, VNS is not successful in all patients. The success of this treatment differs – some patients report less frequent seizures, others report a slight reduction, while some patients do not respond at all. The following results have been noted in select patients with epilepsy:
- Less severe or shorter seizures
- Better recovery after seizures (postictal period)
- Improved sense of well-being
- Improved mood
- Improved alertness, memory, and cognitive skills
- Fewer emergency room visits
Surgery – VNS
- The procedure usually takes about 50 to 90 minutes with the patient under general anesthesia and in such cases, a hospital stay of one night may be required. However, some physicians perform the procedure using local anesthesia on an outpatient basis. As with all surgeries, there is a small risk of infection. Other surgical risks of VNS include inflammation or pain at the incision site, damage to nearby nerves, and nerve constriction.
- The procedure requires two small incisions. The first one is made on the upper left side of the chest where the pulse generator is implanted. A second incision is made horizontally on the left side of the lower neck, along a crease of skin. This is where the thin, flexible wires that connect the pulse generator to the vagus nerve are inserted.
- The device or implant is a flat, round piece of metal that measures about an inch and a half (4 cm) across and 10 to 13 millimeters thick, depending on the model used. Newer models may be somewhat smaller. The stimulator contains a battery, which can last from one to 15 years. When the battery is low the stimulator needs to be replaced via a surgical procedure that is similar to, but less involved than the original implantation.