Vagus nerve stimulation involves the implantation
of a generator that stimulates the vagus nerve and
thus reduces seizure activity. The vagus nerve is
one of 12 pairs of cranial nerves (i.e., nerves that
originate in the brain). It has motor functions in
the larynx (voice box), diaphragm, stomach, and heart,
and sensory functions in the ears and tongue. It has
both motor and sensory functions in the pharynx (sinuses)
and esophagus. Stimulation of the vagus nerve is thought
to affect some of its connections to areas in the
brain that are prone to seizure activity.
Patients who suffer from complex partial seizures
or generalized seizures where consciousness is lost,
and who do not respond to anticonvulsant medication,
and patients who cannot undergo brain surgery are
considered good candidates for vagus nerve stimulation
therapy. It also may be recommended as a treatment
for photosensitive epilepsy and epilepsy resulting
from head injury.
The procedure is performed under general anesthesia.
A neurosurgeon implants the device, a generator about
the size of a small tape measure, in the upper left
area of the chest. A connecting wire is run under
the skin from the device to the vagus nerve in the
left side of the neck. Three small leads are then
carefully attached to the nerve. Implantation is usually
accomplished within 1 to 2 hours.
For a few days following the procedure, the generator
is programmed to stimulate the vagus nerve at regular
intervals (e.g., for 30 seconds every 5 minutes) at
a frequency determined by the doctor and patient.
The physician adjusts the frequency using a computer.
If a seizure begins between intervals, the patient
activates the stimulator by swiping a magnet over
their chest at the location where the device is implanted.
Risks include possible surgical injury
to the vagus nerve, carotid artery, and internal jugular
Many patients experience 50% reduction in seizure
frequency, and seizures are less severe. Vagus nerve
stimulation eliminates seizures in approximately 15%
of patients, according to some studies, and a small
number experience no improvement.
Complications include coughing, hoarseness,
and swallowing difficulties resulting from injury
to the vagus nerve. Infection, bleeding, and discomfort
at the site can occur. There may be tingling in the
neck, hoarseness, and a slight cough during nerve