Approximately 30% of patients with epilepsy continue to have seizures despite trying several antiepileptic drugs (AEDs). This 30% of patients is considered to have intractable epilepsy. Some of these patients can have surgery for their seizures- this is where a surgeon removes a piece of brain tissue to remove the seizure focus. This type of surgery can be very helpful—in some cases, > 70% of patients would be expected to be seizure free.
So, what about the patients who do not respond to seizure medications and also are not resective surgery candidates? What do they do? Such patients may be considered for a device to treat their seizures. A device for epilepsy is something that is placed into a patient by a surgeon. The device is programmed to perform a function that stops seizures.
Currently, there are three devices for epilepsy that are commonly discussed. Only one is FDA approved—this is the Vagus Nerve Stimulator. The other two (Deep Brain Stimulator and Neuropace) are not fully FDA approved. At this time, the Vagus Nerve Stimulator can be ordered by your clinicians. Deep Brain Stimulator and Neuropace are not fully FDA approved and are thus not available to the general public.
A brief description of each of these three devices may be of interest:
Vagus Nerve Stimulator (VNS):
- How it works: A battery is placed under the skin on the left side of the chest. A wire goes from this battery to the vagus nerve—this is a large nerve in the neck. Thus, the patient has two areas of surgery- 1) the skin on the left side of the chest and 2) the left side of the neck to attach wires to the vagus nerve. No brain surgery is done. The vagus nerve has connections to the brain—in a widespread manner. The battery produces electrical charge that is transmitted to the vagus nerve. This electrical stimulation is then transmitted to the brain. The device is often programmed to stimulate for 30 seconds and then be off for 5 minutes. This stimulation goes on like clockwork: 30 seconds on/5 minutes off. By stimulating the vagus nerve, which then stimulates the brain, the seizure potential is changed for the better- seizure control can be improved!
Deep Brain Stimulator:
- How it works: Small probes are placed deep in the brain. This requires surgery that involves going through the skull and brain tissue. The probes are programmed to delivery electricity to areas deep in the brain. By stimulating this area, the brain activity changes in a good way- seizure activity can be reduced. Like the Vagus Nerve Stimulator, the Deep Brain Stimulator is programmed to stimulate at a pre-programmed set time. For those who love neuroanatomy, the deep brain area is called the anterior nucleus of the thalamus.
- How it works: Electrodes are placed on the surface of the brain. This involves brain surgery-a piece of skull is opened to place these electrodes. The electrodes are very sophisticated- they are attached to a computer system that allows the detection of seizure activity. Imagine this- the electrodes are placed directly over the part of the brain where seizures are coming from. When a patient has a seizure, the electrodes can detect this activity. The electrodes are then programmed to delivery electricity to the brain. The electricity from the electrodes zaps the brain—and the seizure activity is stopped!
The three devices described in this article can reduce the frequency and intensity of seizure activity, but they are not expected to stop seizures completely. Obviously, this is important for patients to know. For example, the devices are not expected to stop seizures to the point where patients can drive. Placing one of the above devices may help patients reduce seizure medications. This may help with side effects. The devices would not be expected to produce the well known seizure medication side effects, such as feeling sleepy, dizzy, poor coordination (you know—feeling like you are drugged!).
Each device has its own side effects. When a patient has surgery, infection and stroke are always discussed. Fortunately, the procedures do have a very good safety records.
I will plan on going into more detail about these devices in a future article. I will review the risks and benefits in more detail.
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