Brain pacemaker alleviates seizures

DUKE UNIVERSITY Medical Center researchers have discovered a promising new way to alleviate epileptic seizures by stimulating a facial nerve that extends into the brain, disrupting the cycle of seizure activity. Their experiments in rats also involved testing the concept of a "brain pacemaker," which could be reduced to a small device that could detect potential seizure activity and stimulate the nerve to prevent seizures in humans.

Their findings, reported in the Journal of Neuroscience, offer hope of greatly improved seizure control for the 10-50 per cent of epileptic sufferers whose disorder is resistant to antiepileptic medication or surgery.

In the paper, Associate Professor of Neurobiology Miguel Nicolelis and colleagues report that stimulating one of the two trigeminal nerves in rats given a seizure-producing drug could reduce those seizures up to 78 per cent. Stimulation of both trigeminal nerves, which carry sensory information from either side of the jaw into the brain, proved even more effective. According to Nicolelis, the powerful effects of vagus nerve stimulation also meant that only one vagus nerve, the one that does not affect the heart, could be stimulated in attempts to reduce seizures.

Thus, Nicolelis and his colleagues reasoned that the trigeminal cranial nerve which seemed more benign because it innervates only the face might prove a more effective route to preventing seizures. The scientists tested their theory by treating rats with a seizure-producing drug and attempting to reduce or eliminate those seizures through trigeminal nerve stimulation.

The scientists' finding lends support to the theory that nerve stimulation reduces seizures by activating a non-specific "arousal" mechanism in the brain. Such non-specificity implies that any nerve reaching into the appropriate brain regions can be stimulated to disrupt synchrony.

They Also found that they could stimulate both trigeminal nerves using a lower current and yet achieving even greater seizure reduction. The ability to use lower voltages reduces the chance of nerve damage or pain from nerve stimulation. The neurobiologists, working with Duke biomedical engineers, developed and tested a system in the rats that would monitor their brain wave patterns via brain electrodes and automatically activate the trigeminal nerve stimulation only when the tell-tale patterns marking a seizure appeared.

The seizure-related system proved almost 40 times more effective at seizure reduction per second of stimulation than was periodic stimulation not related to seizure activity, the scientists said. Microchip technology could allow the EEG detection and pattern- analysis circuitry to be reduced to a tiny size, said Nicolelis, and he and his biomedical engineering colleagues are now developing such microcircuitry.

Also, he said, such pattern analysis could be highly sophisticated, using multiple methods, or algorithms, for recognizing pre- seizure brain wave patterns and "voting" on whether a seizure was imminent. Using such multiple methods could increase the accuracy of detection of pre-seizure activity, Nicolelis said.

Besides developing the "neurochips" for such a brain pacemaker, Nicolelis and his colleagues will also explore the ability of trigeminal nerve stimulation to reduce or prevent a wide variety of seizures.

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Section  : Science & Tech
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