Saturday, April 28, 2007

Seizures, explained from a different angle!

The human brain is composed of about 100 billion neurons, which normally carry on business with a low electrical hum.

These signals can be measured as brain waves that seem to fluctuate slightly in no particular pattern.However, in about 2.5 percent of Americans and 1 percent of the world’s population something unusual happens. The nerves start to fire in lockstep.

The synchronized signals radiate throughout the brain repeatedly for one or two minutes, then abruptly stop.It is more than an internal phenomenon. While the brain cycles through its abnormal sequences, the person possessing the pinkish, three-pound organ loses control and experiences strange feelings and emotions, convulsions, muscle spasms and possibly loss of consciousness.

This is a seizure, and it is an unpleasantly common, unavoidable and unpredictable part of life for people with epilepsy.Many people with epilepsy — actually a grouping of similar disorders — can keep the seizures under control with medication. Drugs help about 80 percent of these patients.

Some, however, cannot tolerate the side effects.That leaves about 1.8 million people in the United States with no way to control their seizures.Now, Yale University and about 23 other centers around the country are testing an implantable miniature computer with sensor electrodes that can detect seizures before they happen and counter them.

The Responsive Neurostimulator, or RNS, is a metal case about 3 inches long, 1½ inches wide, and a third of an inch thick. Made by NeuroPace of Mountain View, Calif., the RNS has been approved by the U.S. Food and Drug Administration as an investigational device.It is curved to match the shape of the cranium, and contains a battery-powered microprocessor designed to detect abnormal electrical activity in the brain and deliver a short series of electrical signals to pull the brain back to normal.

The device fits in a small hole made in the skull and is held in place by screws and other hardware.One lead from the device contains sensors to monitor brain activity. Another line is guided to the point from which the seizures seem to propagate. The small unit is able to record encephalograms and its software can be adjusted.Dr. Robert B. Duckrow, associate professor of neurology and neurosurgery at Yale, who is conducting the tests here, said the idea of brain stimulation is not new.In the past, stimulation has been used to study the function of the brain. In the 1970s, New York neurosurgeon Irving Cooper found that he could cause epilepsy by electrically stimulating a part of the brain called the cerebellum.

Therapeutic use of stimulation is now back in favor, Duckrow said.Pulses were first found to be effective in some patients with Parkinson’s disease, which led researchers to try the same approach on other parts of the brain in hopes of stopping seizures, he said.Dr. Kenneth Vives, director of the stereotactal and functional section of the department of neurosurgery at Yale, said seizures can result from head trauma, stroke, infection or from a genetic predisposition.Often, the seizure-causing part of the brain is anatomically abnormal. There may be a tumor or a vascular irregularity, for example.It is possible sometimes to alleviate seizures by removing the offending section of brain. However, not all seizures are precisely focused.

"You cannot remove all parts of the brain," Duckrow said."We use the device when the seizure area is near an important area. For example, movement or language. The device would be used instead of resection. Surgeons also avoid removing pieces of the brain near the hippocampus, which is important to forming memories."The chief complaint of people with epilepsy is that they don’t know when a seizure is going to happen," he said.Some patients report strange feelings before they have seizures.

Others simply wake up "knowing" that they will have a seizure that day, he said.The RNS is designed to stop seizures by catching the preliminary signals before they can amplify and spread.Before the device is implanted, surgeons use an array of electrodes to pinpoint the origin of the seizures. Then the lead of the RNS is placed accordingly. A set of electrodes monitors brain waves, and goes into action if it detects the signals becoming regular and synchronous.The lead fires in one of several patterns to step the seizure before it starts.

If the first attempt fails, the RNS keeps trying.Eventually, the RNS probably will be equipped with an induction device so that the battery can be replaced with a rechargeable unit. The device is also designed so it can be upgraded or reprogrammed.The safety and efficacy of the RNS unit has been sufficiently demonstrated and the FDA has given permission for a larger study to see how well it works.Yale has so far implanted two of the devices of a total of eight nationwide.

Yale-New Haven Hospital is the only site in Connecticut implanting the devices.Eventually, about 75 people will be recruited.Duckrow said a similar approach might be useful for other problems, such as obsessive compulsive disorder. As more targets are recognized, conditions could be treated with more complicated devices, he said.Meanwhile, stopping seizures is a large enough challenge."Hope is an awesome thing to be able to give to people," Vives said.

Abram Katz can be reached at or 789-5719.


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