Vagal Nerve Stimulation (VNS)
Vagal Nerve Stimulation for Epilepsy and Depression
Vagal nerve stimulation (VNS) is a treatment option that is currently approved in the US and limited to the treatment of intractable epilepsy and treatment-resistant depression.
What is Vagal Nerve Stimulation?
Vagal nerve stimulation or VNS refers to the application of a small electrical current to the vagus nerve as it courses through the neck. This large nerve originates from the brainstem and travels in the neck area to terminate in several organs including the heart, the lungs and the gastrointestinal system. It participates in several critical functions including heart rate control, peristalsis and the size of the airways opening. Stimulating the vagal nerve appears to stabilize abnormal electrical activity in the brain by sending regular, mild pulses of electrical energy to the brain through the vagus nerve, with the help of a pulse-generator device similar to a pacemaker.
While the effect of VNS is on the brain, the procedure does not include brain surgery. Once the pulse generator is programed after surgery, patients do not generally feel the pulses.
Indications
Epilepsy and depression are debilitating conditions caused by irregular brain activity affecting the entire lifespan of a patient as well as their caregivers. Fortunately, neuromodulation with the use of VNS may offer hope for those suffering from these conditions.
VNS for Epilepsy
Patients suffering from epilepsy can be considered for VNS if they have failed a proper trial of at least two (2) anti-epileptic medications. VNS does not replace medications and the therapy is added on the regime that works the best for the patient. Although not curative, VNS can improve seizure control in those patients and the therapeutic effect tends to increase over time. On average, patients experience approximately a 25% reduction in seizure frequency after three months of therapy, and the benefits increase over time. Approximately 50%-60% of patients will experience a 50% reduction in seizure frequency after two years of therapy. This improvement in efficacy over time is likely the result of progressive device programming and broad neuromodulatory changes in the epilepsy network. Despite being used in the clinical setting for several years, the mechanism of action of VNS is not fully understood. It is thought that the stimulation leads to modulation in the local brainstem circuitry; in turn, these local circuits engage more widespread pathways leading to desynchronization in the epileptogenic zones.
The broad effects of VNS make this therapy beneficial for patients with multifocal or generalized epilepsy where a specific seizure focus cannot be identified and treated surgically. As VNS does not require the identification of a focus, it still results in reduced seizure frequency.
VNS for Depression
Initial clinical experience suggested that VNS may improve depression. Epilepsy patients undergoing treatment with VNS reported enhanced mood, even in cases where the seizure frequency was not reduced. Subsequent dedicated clinical trials demonstrated that VNS can reduce the severity of major depression by about 30%. Patients with depression of moderate severity and who have experienced some improvement with medication are more likely to benefit from VNS therapy.
VNS is not curative for depression but it can add another dimension to the overall treatment plan. Patients who undergo this therapy should continue to closely follow the recommendations of their mental health providers. In particular, patients should continue to take their medications and attend their therapy sessions.
VNS Surgical Procedure
VNS surgery involves the insertion of two main components: the lead and the generator. The lead is inserted through a small incision in the anterior mid-neck area. Through this incision, the vagus nerve is identified and isolated and the dedicated lead is gently secured to it. The preferred method is to implant the device on the left side of the body.
The generator is inserted in the upper chest area. Through technological advancements, the size of the pulse generator has reduced over time. Therefore, the insertion requires only a small incision typically located about 1 inch under the clavicle. It is secured in place to the subcutaneous tissue. Finally, the lead is tunneled under the skin from the neck to the chest; all of the components are discretely implanted under the skin.
There are a few options available for the implanted generator. For example, one generator senses the heart beat and can trigger an additional electrical pulse when the heart rate exceeds a predetermined level. This type of system can be beneficial for patients who tend to experience a higher heart rhythm at the onset of a seizure. Another generator is designed to hold a longer battery life which can be advantageous for patients requiring stronger electrical stimulation. Finally, another model possesses a discreet profile.
VNS Post-operative Care
After VNS surgery, patients generally remain in the hospital for one day. We recommend keeping the wounds dry for a few days and to avoid irritating the surgical sites to help prevent infection.
The patient should plan to meet with their neurologist, in the case of epilepsy, or their psychiatrist, in the case of depression within a month of the surgery.
VNS Programming
The electrical impulse produced by the device is adjusted by the physician’s programmer. The programmer communicates non-invasively with the implanted device. Typically, the generator is adjusted gradually over time to make sure that the stimulation is well-tolerated. Possible side-effects include hoarseness of the voice and shortness of breath.
VNS is administered in cycles. The pulse is sent for a few seconds every few minutes. The providers can adjust the intensity and the frequency of the pulse as well as the duration of the on/off cycles. The patient may elect to administer additional impulses using a magnet provided with the device. This feature is especially useful in patients who can feel an aura or sensation before a seizure.
VNS Specialists
Clinic Location
1301 20th St, #150, Santa Monica, CA 90404
310-582-7641