segunda-feira, 30 de janeiro de 2012

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Research cracking Parkinson’s

MONDAY, JANUARY 30, 2012 | Progress in the fight against Parkinson’s disease has been made in a recent study authored by two University of Cincinnati professors.

This study is the first examining the effectiveness of constant-current stimulation of the brain as a treatment for Parkinson’s symptoms.

The study was co-authored by Dr. Fredy J. Revilla, an associate professor of neurology and UC Health neurologist, and Dr. George Mandybur, an associate professor of neurosurgery, and was published Jan. 11 in the medical journal The Lancet Neurology.

Deep brain stimulation, or DBS, has been proven to reduce the symptoms of Parkinson’s disease and side effects of some medications, such as motor fluctuations and dyskinesia. DBS devices apply voltage to brain tissue, which stimulates the subthalamic nucleus — a lens shaped compact cluster of neurons — found deep in the brain tissue.

 “The purpose of the study was to find a new way of applying stimulation to the brain through these devices,” Revilla said.  “Traditionally the stimulation was done by delivering constant voltage, and this study looked at delivering constant current.”

Constant voltage stimulates brain tissue with a steady voltage, but the current, or rate of application, is not always the same.  On the other hand, constant current applies stimulation at a constant rate, but the voltage may vary.

The Libra and LibraXP, DBS devices manufactured by St. Jude Medical, were examined in the Lancet Neurology study and provide constant-current stimulation.

These devices are not yet available in the U.S., but St. Jude Medical has applied for U.S. Food and Drug Administration approval.  Medtronic — the only company that currently makes DBS devices in the U.S.— has recently added a constant-current feature to compete in the medical innovation market.

“At this point, we know that the constant-current stimulation is at least as effective as the traditional constant-voltage stimulation,” Revilla said. “What is not known yet is if constant-current stimulation is better than constant-voltage.”

Medication for Parkinson’s disease helps reduce the symptoms for a period of time, giving the patient a period of “on time” where symptoms are minimal.  When the medication wears off, the symptoms return and the patient experiences “off time.”

“What the study did was measure the number of hours the patient had in the ‘on’ state, and then after deep brain stimulation with a constant-current device the same number was measured,” said Dr. Revilla.  “What was found is an increase in the number of hours in the ‘on’ state, and as a consequence the patient has a longer period of time every day where they can function closer to normal.” Fonte: News Record.

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