Vagus Nerve Stimulation Treats Epilepsy

Vagus nerve stimulation (VNS) increases blood flow in the thalamic areas of the brain, improving seizure control in patients with epilepsy, according to a study presented at the annual meeting of the American Epilepsy Society/American Clinical Neurophysiology Society in Philadelphia (PA, USA).

VNS causes activation of synaptic activities at multiple sites in the brainstem and both cerebral hemispheres. The results of the study confirm earlier evidence that altered thalamic processing contributes to the anti-seizure effects of VNS. The study involved 11 patients with partial epilepsy who were uncontrolled with anti-epileptic drugs and who had complex partial and general tonic clonic seizures.

During one year of VNS, seizure control improved in most patients by up to 91%. After three months of therapy, each patient had brain-flow imaging with positron emission tomography (PET). Images comparing VNS-on versus VNS-off states showed numerous sites of brain activity with VNS on. Among those sites, only the right and left thalami were significantly associated with greater seizure control. VNS has not been reported to cause the type of side effects associated with anti-epileptic drugs (cognitive dysfunction, liver damage, and blood disorders).

The VNS used in the study was the Neurocybernetic Prosthesis (NCP) System, a stopwatch-sized generator that is implanted just under the skin in the left chest area to deliver pre-programmed, mild intermittent electrical pulses to the left vagus nerve 24 hours a day. The NCP system is the product of Cyberonics (Houston, TX, USA).

"The study results are significant because they show that if patients respond to VNS therapy in the short term they will continue to respond favorably over the long term,” said Thomas R. Henry, M.D., neurologist at Emory University (Atlanta, GA, USA) and the investigator in the study. This will enable doctors to accurately predict long-term seizure control, "something that has not been possible up until now.”




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