The purpose of this study is to assess the safety and effectiveness of cortical stimulation delivered concurrent with rehabilitation activities to enhance motor recovery in patients suffering from hemiparesis affecting the upper extremity following a stroke.

Stroke is a leading cause of serious, long-term disability in the United States. According to the American Stroke Association, the prevalence of stroke in the U.S. is approximately 4.8 million with approximately 700,000 additional strokes occurring annually. The 2001 overall death rate for stroke was 58%. Of those who survive, 30 to 50 percent do not regain functional independence, 15 to 30 percent are permanently disabled, and 20% require institutional care at three months after onset.

The most common neurological deficit among these stroke survivors, and thus a substantial contributor to post-stroke disability, is a motor weakness on one (hemiparesis) side of the body. Presently, the only treatment available for patients with motor deficits is rehabilitative therapy. However, many patients are not responsive to standard rehabilitative therapy or achieve a less than satisfactory improvement in function.

The primary objective of this study is to determine the safety and effectiveness of targeted sub-threshold epidural cortical stimulation delivered concurrent with rehabilitation activities to enhance motor recovery in patients suffering from hemiparesis (a motor weakness in one half of the body) affecting the upper extremity (shoulder, arm, wrist, hand) following a stroke. In addition to evaluating changes from baseline level, safety and efficacy measures will be compared to patients who undergo the same rehabilitation activities but without cortical stimulation. The two study groups will be compared to determine the degree to which motor function of the affected limb can be improved beyond rehabilitation alone by epidural stimulation of a targeted cortical region.

Inclusion Criteria:

• Subjects must have an ischemic stroke.
• Moderate to moderately severe upper-extremity hemiparesis.
• Aged 21 years or older.

Exclusion Criteria:

• Primary hemorrhagic stroke.
• Any additional stroke associated with incomplete motor recovery.
• Any neurologic or physical condition impairing function of the target extremity.
• History of seizure disorder.
• History of spinal cord injury, traumatic brain injury, or spontaneous subdural or epidural hematoma that has resulted in a neurologic deficit.
• Contraindication to magnetic resonance (MR) imaging.