FDA approves novel rehabilitation system for stroke victims

New MicroTransponder Vivistim Paired VNS System (Vivistim System) works using vagus nerve stimulation (VNS).The Vivistim System is intended to be used, along with post-stroke rehabilitation therapy, in patients who have had ischemic stroke, to electrically stimulate the vagus nerve to reduce deficiencies in upper limb and extremity motor function and to improve patients' ability to move their arms and hands.

The MicroTransponder Vivistim Paired VNS System is manufactured by MicroTransponder Inc.

"People who have lost mobility in their hands and arms due to ischemic stroke are often limited in their treatment options for regaining motor function" said Christopher M. Loftus, M.D., acting director of the FDA's Center for Devices and Radiological Health's Office of Neurological and Physical Medicine Devices. "Today's approval of the Vivistim Paired VNS System offers the first stroke rehabilitation option using vagus nerve stimulation. Used alongside rehabilitative exercise, this device may offer benefit to those who have lost function in their upper limbs due to ischemic stroke."

Most common type of stroke is ischemic stroke, meaning the blood vessels to the brain become clogged, which blocks blood flow from reaching the brain. Depending on how long the brain is deprived of blood and where in the brain the stroke occurs, stroke can lead to brain damage, temporary or permanent disabilities, and in some cases, death. Disabilities resulting from stroke may include, but are not limited to, total or partial paralysis or difficulty with muscle movement.

To use the Vivistim System, an implantable pulse generator (IPG)—which generates a mild electrical pulse—is implanted just under the skin in the chest of the patient. Attached to the IPG is a lead wire that is implanted under the skin and leads up to electrodes that are placed on the left side of the neck where the vagus nerve is.

Accompanying the implantable components are clinician software preloaded onto a laptop and a wireless transmitter to be used only by a health care provider. The software allows a health care provider managing a patient's rehabilitation to input the appropriate settings on the IPG, including amplitude, frequency, and pulse width for the stimulation, and also records stimulation history, movements performed, and information about the IPG. The wireless transmitter communicates adjustments to the IPG settings made using the software.

The Vivistim System, a prescription device, may be used in both clinical and at-home settings to provide VNS. If it is to be used during home rehabilitation exercises, the software and the wireless transmitter are not used by the patient. However, the patient is supplied with a magnet that can be passed over the IPG implant site to activate the IPG to begin a 30-minute stimulation session during rehabilitative exercise. When directed by a physician and with appropriate programming to the IPG, patients are trained on how to use the Vivistim System at home, as well as its safety features, to avoid any unwanted electrical stimulation.

The Food and drug administration evaluated the safety and effectiveness of the Vivistim System in a clinical study of 108 patients at 19 clinical sites in the U.S. and the U.K. who received the Vivistim System. Patients were split into a study group (53 patients) and a control group (55 patients), whereby both groups were asked to complete 300-400 physical therapy exercises for 90 minutes a day, three times a week for six weeks. The control group received only a very low level of VNS for the first five exercises of the 300-400-movement series and had no stimulation whatsoever for the rest of each session. The treatment group received the appropriate amount of VNS throughout all 90-minute rehabilitation sessions. Both groups received physical therapy sessions that were equivalent in quantity and quality. Following the initial six-week study, all patients received follow-up assessments at 1, 30, and 90 days following the study.

Effectiveness for the Vivistim System was measured using the Upper Extremity Fugl-Meyer Assessment (FMA-UE), a stroke specific measure of motor impairment. Progress was measured as an increase in motor function from baseline after six weeks of therapy. Patients in the treatment group had an average score increase of 5 points, whereas patients in the control group had an average score increase of 2.4 points. Additionally, 47.2% of those in the treatment group saw an improvement of 6 or more points in the FMA-UE score 90 days post-therapy as compared with 23.6% in the control group.

Adverse events included but were not limited to dysphonia (difficulty speaking), bruising, falling, general hoarseness, general pain, hoarseness after surgery, low mood, muscle pain, fracture, headache, rash, dizziness, throat irritation, urinary tract infection and fatigue.

The Vivistim System is not approved for use outside of its intended use to stimulate the vagus nerve during chronic ischemic stroke rehabilitation therapy for moderate to severe loss of upper extremity function. It should not be used in patients with vagotomy, which is surgical removal of part of the vagus nerve.

Patients should discuss with their providers any prior medical history of: other concurrent forms of brain stimulation; current diathermy treatment, which uses electrical current stimulation to produce "deep heating" beneath the skin in subcutaneous tissues, deep muscles and joints; depression or suicidality; schizophrenia, schizoaffective disorder, or delusional disorders; rapid cycling bipolar disorder; previous brain surgery or central nervous system injury; progressive neurological diseases other than stroke; cardiac abnormalities, including arrhythmia; dysautonomias, or medical conditions caused by problems with the autonomic nervous system; respiratory diseases or disorders, including dyspnea and asthma; ulcers; vasovagal syncope; and pre-existing hoarseness.

The Vivistim System was granted Breakthrough Device designation. To qualify for such designation, a device must be intended to treat or diagnose a life-threatening or irreversibly debilitating disease or condition and meet one of the following criteria: the device must represent a breakthrough technology; there must be no approved or cleared alternatives; the device must offer significant advantages over existing approved or cleared alternatives; or the availability of the device is in the best interest of patients.

The FDA reviewed the MicroTransponder Vivistim Paired VNS System under the Premarket Approval (PMA) pathway. PMA is the most stringent type of device marketing application required by the Food and drug administration and is based on a determination by the Food and drug administration that the PMA application contains sufficient valid scientific evidence to provide reasonable assurance that the device is safe and effective for its intended use.