Surgery for Medically Intractable Epiepsy
For about 70 percent of people with epilepsy, seizures
can be controlled with anti-epileptic drugs (AEDs).
When seizures are not well managed by medication (as
indicated by the severity or frequency of seizures),
the condition is referred to as medically intractable
Surgery generally is reserved for these most severe
cases of epilepsy. Candidates for surgery at the University
Comprehensive Epilepsy Center are evaluated carefully
by a multidisciplinary team spanning the disciplines
of neurology/epileptology, neurosurgery, neuropsychology,
neuroradiology, neurophysiology, advanced practice nursing,
social work, nutrition, and rehabilitation therapy.
This team actively involves patients and their families
in the patients treatment plan.
The surgical team gathers as much information as possible
about the patients condition and, significantly,
the unique structure of his or her brain prior to the
operation. Of particular concern is pinpointing the
precise location of the epileptic focus, the area in
the brain where seizures originate. Continuous video
EEG monitoring, the Wada test, functional MRI studies,
and other tests described in Diagnostic
Tests for Epilepsy are valuable tools prior to surgery.
Intraoperative EEG Monitoring and Intraopertive
During epilepsy operations, intraoperative EEG monitoring
may be performed to provide objective information about
the anesthetized patient. This gives the surgeons immediate
feedback on signs of impending risk and enables them
to feel comfortable with a greater degree of surgical
intervention than they would have without intraoperative
Normally, a patient undergoes a variety of scans and
tests prior to surgery. Surgeons use the data they obtain
from the tests to pinpoint the areas of the brain requiring
surgery. While many of these tests are extremely accurate,
a higher degree of accuracy is obtained when the tests
are actually done during the surgery. The accuracy is
increased because in addition to being more up-to-date
and recent, the tests are done on the patient while
the patient is in the exact position for surgery. In
addition, many of these tests provide on-going feedback
throughout the operation, giving the surgeon information
that enables more informed decisions to be made regarding
the patient's care.
Another technique uses MRI technology to obtain images
of the brain during surgery. In intraoperative MRI,
real-time visualization allows surgeons to confirm the
location of lesions, plan and reconfirm the optimal
surgical approach, and verify complete lesion removal
prior to closure.
Conventional surgical navigation systems rely on images
obtained prior to surgery and cannot account for movement
of the brain during the surgery that could result simply
from exposure or from tissue removal. With the use of
MRI images obtained during various points in the surgery,
the navigation system continuously adjusts to account
for any brain shift, thereby minimizing harm to healthy
and/or eloquent areas of the brain.
University Hospital is one of two hospitals in the world
currently to utilize a compact OR-based MRI system (PoleStar
N-10) that successfully addresses the problems associated
with early versions of intraoperative MRI systems, including
cumbersome design, limited application, and high cost.
The type of epilepsy a patient has, in conjunction
with pre-operative testing, determines which type of
surgery will be performed. Because precise location
of the epileptic focus is so important to an operations
success, the Center has developed expertise in Functional
Image Guided Surgery (FIGS). FIGS combines Functional
MRI with frameless stereotactic surgery to create a
precise, detailed "road map" for the surgeon
to follow. At every second of the procedure, the surgeon
knows the proximity of healthy brain tissue and therefore
can avoid removing or damaging it.
Surgical procedures offered at the Center include:
- Temporal and extratemporal
cortical resections for adults and children.
Some seizures originate from a specific point in the
brain, an area referred to as the seizure focus. This
area varies from person to person. The technology
available todaycontinuous video EEG monitoring,
MRI, and SPECToften enables epileptologists
to pinpoint the seizure focus. When surgery is indicated,
a neurosurgeon operates to remove the affected brain
tissue. The most common resection is for people with
epilepsy located at the temporal lobe, at the brains
outer lower region. The surgery results in reduction
or elimination of seizure activity between 70 and
90 percent of the time.
- Corpus callosotomy.
When seizures originate in one half of the brain and
spread to the other, a corpus callosotomy can be performed
to sever the neural connections between the brains
two hemispheres. This surgery usually is performed
This "disconnection" is not a cure, but
it can reduce the severity of generalized seizures.
Corpus callosotomy can also keep seizures from spreading
to other areas of the brain. However, partial seizures
may increase after surgery.
As the name suggests, this surgery involves removal
of about half of the brain, or a hemisphere. Hemispherectomy
usually is reserved for children with severe, frequent,
and often life-threatening epilepsy that cannot be
controlled by medication. The seizures originate from
one side of the brain, and typically, the child has
some degree of paralysis on the opposite side of the
Removing half of someones brain is, indeed,
a radical concept, and there may be some very serious
complications, including fluid build-up in the brain,
infection, and coma. There is permanent loss of hand
mobility on the side opposite of the removed hemisphere,
and vision also may be affected. But doctors have
found that for many of these children, hemispherectomy
significantly or completely controls seizures and
enables the youngsters to function well with improved
behavior and intelligence. Especially in younger children,
the remaining half of the brain compensates for the
- Vagal Nerve Stimulation.
Unlike the surgeries described above, this operation
is not performed on the brain. The body has two vagus
nerves, one that travels up the left side of the neck
and one on the right. One of the left nerves
jobs is to relay information to areas of the brain
that are believed to produce seizures. When this nerve
is stimulated by a low level of electrical current,
some people find that their seizures are less frequent
or less severe. Vagal nerve stimulation has most commonly
been used for patients with partial seizures.
A small, battery-operated device called a vagal nerve
stimulator can be placed in a persons body.
It can be programmed to deliver stimulation at regular
intervals, or it can be activated with a magnet when
a patient experiences an aura. The surgery involves
implanting the devices generator under the skin
in the patients upper left chest. A connecting
wire is guided under the skin and attached to the
vagus nerve, which is located on the left side of
the neck. The operation lasts about two hours, and
a common temporary side effect of the surgery is hoarseness,
as the vagus nerve is located near the voice box.
Sometimes people experience coughing or a tingling
in their throat when the stimulator is activated;
adjusting the amount of current can remedy this side
The vagal nerve stimulators effectiveness varies.
Most patients can expect a 50 percent reduction in
seizures, while others experience better or worse
results. The device is not considered to be a cure,
so patients generally continue taking anti-epileptic
medication. In cases where the stimulator has proven
highly effective, the doctor may decide that a patients
medications can be reduced.
- An incision is made
in the lower neck to place an electrode around
the vagus nerve.
- The stimulator is implanted
under the skin in the chest wall through a second
- Similar to a heart pacemaker,
the stimulator emits an electrical impulse every
five minutes that stimulates the vagus nerve.