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Vagus Nerve Stimultor (VNS)
In 1997 a Cyberonics, Inc. implantable product (VNS) was
approved for use “as an adjunctive therapy in reducing
the frequency of seizures in adults and adolescents over 12 years of age”. This
“pacemaker to the brain” is surgically implanted in the subcutaneous tissues of
the upper left pectoral region, with a lead (wire) running to the left vagus nerve of the
neck.
Once the incisions are healed the adjustments are made with a control
“wand”, remotely. The typical battery life is 7-10 years with normal use,
although if some patients need increases in the rate or intensity for continued seizure
control, battery life will shorten. VNS Therapy consists of electrical signals that are
applied to the vagus nerve in the neck for transmission to the brain. Vagus means
“wanderer” in Latin. The vagus nerve is appropriately named considering that it
averages 22 inches in length in adults and wanders throughout the upper body. The vagus
nerve is one of the primary communication lines from the major organs of the body to the
brain.
The vagus nerve has proven to be a good way to communicate with the brain because:
There are few if any pain fibers in the vagus nerve.
Electrical stimulation of nerve fibers within the
vagus nerve that travel back to the brain are responsible for the anti epileptic effect.
The surgical procedure to attach the lead to the
vagus nerve does not involve the brain. It is not brain surgery.
The VNS Therapy System delivers VNS Therapy in two ways. First, a doctor programs a
24-hour a day, 7-day a week "dose" of periodic stimulation. One such dose
frequently used by physicians is 30 seconds of stimulation followed by a three-minute
period of no stimulation. The stimulation is automatically delivered (the patient
doesn’t have to "take" anything) until the physician reprograms the
generator or the battery runs out.
The second way VNS Therapy is delivered is when a patient, a family member or caregiver
senses a seizure coming
on and passes the contol magnet over the area in the chest where the generator is
implanted to activate an extra, on-demand stimulation as a seizure begins. The VNS Therapy
magnets are easily carried on the body for fast and effortless accessibility.
VNS Therapy does not typically cause side effects like
depression, dizziness, confusion, weight gain, fatigue, insomnia and low energy. The most
common side effects include hoarseness, a prickling feeling on the skin, shortness of
breath, and increased coughing. And these side effects diminish over time. As with any
surgery, there is a risk of infection.
As of December 2003, over 25,000 patients have already
had VNS implants. As the first non-drug/non-diet therapy, VNS has assumed an increasingly
important role in the treatment of medically refractory seizures. The
long-term safety and effectiveness seen with this treatment has have made VNS a mainstream
treatment option for a broad range of patients- about 30% of the patients currently
implanted were under the age of 18 at time of implant.
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