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Experimental brain implant curbs epileptic seizures

David Bonanno was devastated when he lost his driver's license at the age of 24. The inability to drive hampered his freedom and made him dependent on others to get around. But being stripped of his license was just another piece of independence that epilepsy was slowly taking from him.

Ten years earlier when his seizures first began, they were mild. He would experience moments of forgetfulness or would fidget with his hands. But as time went on, the seizures became more frequent and debilitating. In 1994, an MRI showed a small growth in the temporal lobe of his brain that looked like a cyst. In the hopes that taking it out might eliminate the seizures, he went to see Mayo Clinic neurosurgeon Dr. Robert Wharen, who removed what turned out to be a small, non-cancerous tumor.

For seven months, the seizures stopped. Then they came back with a vengeance. Some days Bonanno had several; most days he suffered from terrible dizziness, nausea and fatigue. He became depressed and was unable to keep a job. Medications were tried, but none calmed the electrical storm. Neurologists pinpointed the area of the brain that triggered the seizures, but because it controlled speech, removing the problem tissue was not an option.

Bonanno had resigned himself to never getting better. He was one of the 10 to 15 percent of epilepsy sufferers who aren't helped by multiple medication therapy and aren't candidates for surgery. But in late 2004, his phone rang. Mayo Clinic was calling to tell him about a clinical trial aimed at determining if a new neurotransmitter surgically implanted in the brain could safely suppress epileptic seizures. The trial was enrolling patients like him. Was he interested?

Dr. Robert Wharen checks David Bonanno's brainwave activity at a follow-up visit.

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"It didn't take me but a second to say yes," says Bonanno. "I was ready to try anything."

Bonanno signed on to try the Responsive Neurostimulator (RNS) system developed by Neuropace. The device constantly monitors the brain's electrical activity for seizure onset. If it detects something, it delivers mild electrical stimulations through electrodes placed in seizure hot spots. The idea is to stop seizures before the patient experiences symptoms. The device records all brainwave activity. At regular intervals, patients upload the data over a phone line to a central system by holding a special computer-attached device over their implant. Patients in the study stay on all medications they were previously taking, keep a seizure diary and go in for monthly follow-ups.

Bonanno says the date of his surgery — March 8, 2005 — was the start of a new life. During the two-hour procedure, Wharen implanted the watch-sized device under the skull on the left side of Bonanno's head and connected the device to electrodes placed over previously identified trigger areas of his brain. Bonanno says recovery was quick and the results, immediate.

"The first month, I felt a little tingle above my left ear, like my brain was being tickled," he says. "I could feel when a seizure was coming on, but now I don't feel anything. The only way to tell is when they scan the implant."

According to the data obtained from Bonanno's neurostimulator, it aborted more than 240 potential seizures in a two-month period alone.

"This implant has worked remarkably well for him," says Dr. David Chabolla, a Mayo Clinic neurologist who specializes in epilepsy. "We're trying to learn how best to use this device, and the way we implanted the electrodes around his seizure focus points may help us understand how to make it more effective for other patients."

Bonanno has had the best results of the four patients enrolled in the study at Mayo Clinic in Jacksonville, Chabolla says. But all participants have experienced some improvement without significant complications. These patients and 70 others enrolled at 12 other sites will have their progress monitored for two years.

There are big differences between the RNS stimulator and another implant currently available for epilepsy, the Vagal Nerve Stimulator (VNS). While the RNS device is placed on the brain with wires leading directly to the source of the seizures, the VNS device is implanted in the chest under the collarbone and works by stimulating the vagus nerve in the neck, which connects the lower part of the brain to the heart, lungs and GI tract. The VNS device turns on and off at predetermined intervals, but the new RNS implant only goes on when it detects the onset of a seizure. It also records the brainwave activity used for ongoing monitoring.

"It's a huge benefit because you are getting the stimulation to the brain when you need it and not getting it when you don't," says Wharen. "It improves effectiveness and minimizes side effects, and the battery lasts longer."

The second phase of the trial will begin enrolling new patients in early 2006 to further explore the effectiveness of the implant. Chabolla hopes there will be more successes like Bonanno. At an appointment in November, the neurologist informed his patient that after years of sitting in the passenger seat, Bonanno was finally seizure-free and eligible to re-apply for a driver's license.

"My life is getting back on track," says Bonanno. "It's finally starting over."

Info:
Epilepsy Program
(904) 953-2498

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Learn more about the treatment of epilepsy at Mayo Clinic in Jacksonville.