The vagus nerve is 1 of the 12 pairs of cranial nerves that originate from the brain. It is a portion of the autonomic nervous system, controlling involuntary body functions. The nerve passes through one’s neck, traveling between the chest, abdomen, and lower part of the brain. It is connected to motor functions in the voice box, diaphragm, and stomach, along with heart and sensory functions in the ears and tongue. It is linked to motor and sensory functions in the sinuses and esophagus.
Vagus nerve stimulation (vagus nerve stimulation) sends mild, regular pulses of electrical energy to the brain via the vagus nerve, using a device similar to a pacemaker. No physical involvement of the brain is in this surgery. Patients cannot typically feel the pulses. It is important to keep in mind that vagus nerve stimulation is a treatment option limited to select individuals with epilepsy or treatment-resistant depression.
Individuals with any of the following criteria can potentially be unsuitable candidates for vagus nerve stimulation:
- One vagus nerve
- Receiving other concurrent brain stimulation forms
- Heart arrhythmias/other heart abnormalities
- Dysautonomias (abnormal functioning of the autonomic nervous system)
- Lung diseases or disorders (shortness of breath, asthma, etc.)
- Ulcers (gastric, duodenal, etc.)
- Vasovagal syncope (fainting)
- Pre-existing hoarseness
VAGUS NERVE STIMULATION IMPLANTATION
This procedure, performed by a neurosurgeon, typically takes about 45-90 minutes with the patient most commonly under general anesthesia. It is typically performed on an outpatient basis. As with all surgeries, there is a small risk of infection. Other surgical risks of vagus nerve stimulation include inflammation or pain at the incision site, damage to nearby nerves and nerve constriction.
The procedure requires two small incisions. The first incision is made on the upper left side of the chest where the pulse generator is implanted. A second one 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 10-13 mm thick, depending on the model used. Newer models can be smaller. The stimulator contains a battery, which can last from one to 15 years. When the battery is low, the stimulator is replaced with a less invasive procedure which requires only opening the chest wall incision.
The stimulator is most commonly activated two to four weeks after implantation, although in Certain cases it can be activated in the operating room at the time of implantation. The treating neurologist programs the stimulator in his or her office with a small hand-held computer, programming software and a programming wand. The strength and duration of the electrical impulses are programmed. The amount of stimulation varies by case but is typically initiated at a low level and slowly increased to a suitable level for the individual. The device runs continuously and is programmed to turn on and shut off for specific periods of time (e.g. 30 seconds on and 5 minutes off).
Patients are provided with a handheld magnet to control the stimulator at home (which must be activated by the physician to magnet mode). When the magnet is swept over the pulse generator site, extra stimulation is delivered regardless of the treatment schedule. Holding the magnet over the pulse generator will turn the stimulation off while the magnet is in position. Removing it will resume the stimulation cycle. All maneuvers performed with the magnet can be done by the patient, family members, friends or caregivers.
Side effects are most commonly related to stimulation and typically improve over time. These can include any of the following:
- Increased coughing
- Changes in voice/speech
- General pain
- Throat or neck pain
- Throat or larynx spasms
- Muscle movements or twitching related to the stimulation
- Nausea or vomiting
- Impaired sense of touch
- Prickling or tingling of the skin
Of these, hoarseness, coughing, throat tickling and shortness of breath are the most common and are typically temporary.
If you have received vagus nerve stimulation, you should monitor your condition and overall health closely. If any of the following occur, call your doctor right away:
- Constantly hoarse voice
- Stimulation which becomes painful or irregular
- Stimulation which causes choking, breathing or swallowing difficulties or a change in heart rate
- Changes in your level of consciousness, such as increased drowsiness
- Signs that the pulse generator can not be stimulating properly or that the battery is depleted (the device stops working)
- Any new or unusual changes related specifically to the stimulation
In addition, you should call your physician before you undergo any medical tests that might affect, or be affected by vagus nerve stimulation, such as magnetic resonance imaging (MRI), or before you have any other medical devices implanted.
The FDA approved vagus nerve stimulation as a seizure treatment in 1997. vagus nerve stimulation can be considered as a treatment option in patients who have tried two or more anti-epileptic drugs (anti-epileptic drugs) without adequate control of their seizures or in patients who have not responded to anti-epileptic drugs and cannot undergo brain surgery. It is important to keep in mind that vagus nerve stimulation is used in conjunction with anti-epileptic drugs, not instead of them. In addition, vagus nerve stimulation is considered a palliative procedure which can effectively improve seizure control but does not generally produce complete seizure-freedom. vagus nerve stimulation can take up to two years to have an effect on a patient’s seizures. If vagus nerve stimulation proves effective, it can enable a patient to decrease doses of anti-epileptic drugs over time.
The goal of vagus nerve stimulation is to reduce the number, length and severity of seizures. vagus nerve stimulation can also reduce the time it takes to recover after a seizure. Nevertheless, vagus nerve stimulation is not successful in all patients. The success of this treatment differs. Certain patients report less frequent seizures, others report a slight reduction, while certain 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
For people with warnings (auras) before their seizures, activating the stimulator with the magnet when the warning occurs can help shorten or even stop the seizures.
Soon after vagus nerve stimulation was approved by the FDA as a seizure treatment, reports indicated a possible decrease in depression symptoms in patients who had the device implanted for seizure control. Like electroconvulsive therapy, vagus nerve stimulation is believed to work by using electricity to influence the production of brain chemicals called neurotransmitters. Depression has been tied to an imbalance in those chemicals.
In studies involving more than 200 patients leading to the 2005 FDA approval of vagus nerve stimulation for treatment-resistant depression (TRD), the device showed no benefit during the first two or three months. After one year Nevertheless, 20-30 percent of patients reported significant improvements, and half of these patients reported that their symptoms had nearly resolved completely. Nevertheless, other patients did not improve or their symptoms worsened. vagus nerve stimulation has been FDA-approved for people with chronic or recurrent TRD who have failed to respond to four or more adequate treatments.
Vagus nerve stimulation should not be considered in patients presenting with any of the following:
- Acute suicidal thoughts or behavior
- History of schizophrenia, schizoaffective disorder or delusional disorders
- History of rapid cycling bipolar disorder
Much controversy on the efficacy of vagus nerve stimulation as a treatment for TRD exists. At this stage, more outcomes data is in the works. Currently, vagus nerve stimulation is not a covered benefit of most insurers for TRD. Nevertheless, depending on the results of pending studies it can once again reach the point of insurance coverage.