Medically Intractable Seizures
What Are Medically Intractable Seizures?
If medications do not successfully control seizures, the seizures are called intractable. A safe and well-tolerated treatment for intractable seizures is neurosurgery. Surgery can help by reducing the number of or completely curing seizures. Eliminating seizures helps:
- Stop the progressive cognitive decline associated with frequent seizures
- Enable patients the freedom to drive again
- Reduce or eliminate the need for anti-seizure medication
If you have intractable seizures, you may be a potential candidate for surgery if:
- Two first-line seizure medicines fail to control seizures
- A two-drug combination of seizure medicines fails to control seizures
- The focal point—the place where your seizures originate—can be identified
- Conditions that often fall into this category include:
- Mesial temporal sclerosis or hippocampal sclerosis (seen in 75 percent of patients undergoing epilepsy surgery)
- Cortical dysplasia (small congenital malformations of the cortex)
- Other congenital anomalies of brain development
- Cavernous angioma (benign vascular tumors)
- Other brain tumors
- Brain trauma
Pre-surgical evaluation involves many tests designed to determine if the seizures are coming from a single location in the brain that may be surgically treated. If all the studies point to a single area as being responsible for the seizures, surgery may drastically reduce, or even eliminate, seizures. Tests include:
- Inpatient video EEG monitoring: Precisely correlates the clinical and electrical features of a seizure
- Electroencephalography (EEG): Records the electrical activity in the brain
- Epilepsy-protocol MRI: Helps identify subtle structural abnormalities in the brain
- Ictal Single-photon emission computed tomography (Ictal SPECT) scan: Identifies areas of greatest blood flow during a seizure
- Positron emission tomography (PET) scan: Shows the brain's use of oxygen or sugar (glucose)
- Neuropsychology testing: Measures your memory, language and cognition
- Intracranial electrodes and invasive EEG monitoring: This is used if all of the presurgical studies do not sufficiently show the origin of your seizures
Epilepsy surgery resection
Epilepsy surgery may be performed on any region of the brain using leading-edge computerized image guidance technology to allow for the safest and most minimally invasive approach available. The procedure typically lasts about four to five hours and is usually performed under general anesthesia with the patient completely asleep. However, if the area to be removed is very close to important brain areas controlling speech or movement, the resection is sometimes performed with the patient awake for a portion of the procedure. This allows for detailed mapping of the sensitive regions while in the operating room to minimize the risk of postoperative disability.
After surgery, patients remain on the same antiepileptic medications they were taking before surgery. If they remain seizure-free for one to two years, they are gradually weaned off the medications.
Multiple studies have shown that the chance of becoming seizure-free after surgery for temporal lobe epilepsy is about 70 percent for the first two years and 50 to 60 percent for life. Please note that some of the patients in these studies who were not considered “seizure-free” had only a single seizure over many years. These studies demonstrate that patients who have good surgical outcomes have better cognitive and memory function than patients who do not have surgery and continue to have seizures.
Outcomes for resection of other areas of the brain are highly variable. These other forms of epilepsy are less common, and the patient population is much smaller. In general, the chance of becoming seizure-free is about 40 to 50 percent, but this may vary depending on each patient’s specific condition.
Vagus Nerve Stimulation (VNS)
Vagus nerve stimulation is a less-invasive procedure recommended for patients who are not good candidates for epilepsy surgery because:
- Seizures are originating from multiple locations in the brain.
- Seizures are originating from both sides of the brain.
- The area the seizures are originating from is too valuable to remove.
The vagus nerve originates in the brain stem and runs down the neck to the chest and abdomen. A vagus nerve stimulator is designed to prevent seizures by sending regular, mild pulses of electrical energy to the brain by way of the vagus nerve. The electrical pulses are supplied by a device similar to a pacemaker.
The neurologist programs the strength and timing of the impulses according to your individual needs. The settings can be programmed and changed by using a programming wand that transmits the information through the skin to the battery. Holding a special magnet near the implanted device causes the device to become active outside of the programmed interval. For people with warnings (auras) before their seizures, activating the stimulator with the magnet when the warning occurs may stop the seizure.
Long-term studies of patients undergoing vagus nerve stimulation show that the reduction in seizure frequency is highly variable. Results can range from no reduction to complete elimination of seizures. Most patients experience a 20 to 60 percent reduction in seizures. The effect of vagus nerve stimulation may take up to two years to be fully realized.