BION For Stroke Patients

Stroke A stroke is caused when a part of the brain is deprived of oxygen, causing the brain cells in the affected area to die. There are two main types of stroke: those caused by a blockage (ischemic stroke) and those caused by bleeding (hemorrhagic stroke).

Ischemic stroke is the most common type of stroke (accounting for about 83 percent of all cases). The blockage is usually caused by a blood clot. In a cerebral thrombosis, a blood clot forms in a blood vessel of the brain and blocks the flow of blood. In a cerebral embolism, a blood clot forms in another part of the body, breaks loose and travels through the circulatory system, becoming caught in a narrower artery of the brain.

Hemorrhagic strokes are less common than ischemic strokes, but often much more deadly. They are caused when a blood vessel of the brain ruptures. Two types of malformations can cause a hemorrhagic stroke. An aneurysm is a weakened area in the wall of the blood vessel. Pressure from blood as it flows through the vessel can cause the weak spot to bulge. With time and continued pressure, the area can eventually burst, or rupture. An arteriovenous malformation is a cluster of abnormally formed blood vessels. These vessels may be weak and prone to rupture.

Every year, about 700,000 Americans experience a stroke. It's the third leading cause of death in the U.S. Of those who survive, about 50 percent have some degree of one-sided paralysis. Thirty percent require assistance with walking and 26 percent need help with daily activities (like getting dressed or eating).

BION® for Stroke Patients Stroke patients who experience muscle weakness or paralysis are typically given physical therapy in an attempt to regain some strength and usefulness of the affected limbs. However, patients often reach a plateau and may not regain full function. With time, limited or nonuse of the limb causes the muscle to become weaker and more function can be lost.

Researchers are testing a device that can directly stimulate nerves and muscle to elicit contraction (tightening of the muscle) and limb movement. It's called a BION®, or BIOnic Neuron. The BION is a tiny (about the size of two grains of rice) stimulator that's encapsulated in glass. Electrodes are located on each end of the device. The BION is injected into an area where nerve endings meet the affected muscle.

Once the BION is inserted, a special coil is placed around the limb - over the area of BION. The coil sends specific command signals to the implanted BION. Each command generates a single electrical stimulation pulse by the implanted BION, causing a brief twitch of the muscle. The coil can be programmed to send a series of commands or signals, which stimulates muscle contraction. The strength of the signal controls the strength or weakness of the contraction. Researchers can send up to three thousand commands/second.

When implanted into a stroke patient, BION enables weak or paralyzed muscles to involuntary contract providing exercise for the affected limb. Patients use the therapy for 20 to 30 minutes/day, two to three times a day. Once the therapy session is over, the coil is removed. The goal of the treatment is to reverse muscle weakness, strengthen joints and improve range of motion and flexibility.

In the U.S., BION is being tested in three clinical trials for stroke patients at the University of Southern California in Los Angeles. In one trial, researchers are testing the device in stroke patients with shoulder weakness. Another study is looking at patients with hand and finger weakness. A third study is evaluating the effectiveness of BION in stroke patients with wrist and finger contractures (a condition in which the affected joints are "locked" in a closed or tightened position). The BION can only be activated by the coil. So there is no "accidental" stimulation of the muscle and unwanted movement. BION is also being tested for other applications in Canada and Italy.

AUDIENCE INQUIRY For information about BION®: http://ami.usc.edu/projects/ami/projects/bion

For general information about stroke: American Stroke Association, http://www.strokeassociation.orgAmerican Stroke Foundation, http://www.americanstroke.orgNational Institute of Neurological Disorders and Stroke, http://www.ninds.nih.gov