The University of Southampton, UK is taking the initiative in partnership with the Alfred Mann Foundation (AMF), a non-profit medical research organisation in the US. The study is aimed at exploring the feasibility of using radio frequency microstimulator (AMF RF microstimulator) electrical stimulation devices to improve motor recovery and re-learning of arm and hand function following stroke.
The research is based on the AMF RF micro stimulators that are implanted into a patient''s arm and act like ''bionic neurons'' mimicking the messages from the brain to hopefully recreate useful function in paralyzed or weak arms. The pioneering system is designed to provide electrical stimulation to both control and re-educate weak or paralyzed muscles to produce functional arm and hand movements in patients who have suffered damage to the central nervous system following a stroke. The devices are exclusively for clinical investigations.
At the end of April, five AMF RF micro stimulators were implanted close to the nerves supplying muscles in a female patient''s arm under local anesthetic at Southampton General Hospital. On 13 May, she will be fitted with a cuff which will send signals to the AMF RF micro stimulators and the system will be programmed to produce functional patterns of movement.
The cylindrical micro stimulators measure 1.7 centimeters long and 2.4 millimeters in diameter. They can be injected into the body through a small incision which should reduce the expense and risks of a surgical procedure. They are implanted next to a nerve or adjacent to a muscle at the motor point near to where the nerve attaches. Once implanted, the micro stimulators receive power and stimulation commands via a link from a radio frequency coil fitted to the arm, which is in turn connected to a control unit.
Both deep and superficial muscles can be individually activated allowing more selective control of movement, which is particularly useful in the forearm and hand. The patient should be able to extend her elbow and wrist and open her hand. By switching off the micro stimulators implanted in the finger and thumb,she will be able to use her own remaining control of finger and thumb flexion to grasp an object, while continuing stimulation to the wrist extensors will maintain a functional hand position for grasping.
The University of Southampton project is led by Dr Jane Burridge, Senior Lecturer in Neurorehabilitation in the University''s School of Health Professions and Rehabilitation Sciences. The University is becoming a centre of excellence in the study of movement disorders, with a multidisciplinary team of therapists,doctors, neuroscientists and engineers involved in this project.
Dr Burridge explains: ''Following a stroke, between 30 per cent and almost 66 per cent of patients have problems regaining upper limb function. Many therapeutic approaches to recovery are available, though controversy exists about their effectiveness. However, until now electronic stimulation devices have not been well accepted, mainly because with surface systems people have difficulty putting the electrodes in the correct place to achieve a useful movement and implanted systems have involved major surgery.
''This study aims to address both these issues. Because the system is implanted, electrodes do not need to be placed on the skin and because individual muscles are activated, a more functional, natural movement is possible. The implantable microstimulator can remain implanted even if no longer needed and the system is designed to facilitate recovery by supporting voluntary movement rather than replacing it. It is also less invasive than previous generations of neural implants and because the electrodes are so small they can be implanted into many different muscles, providing the potential to create the fine, graded movement essential for hand and arm function.''
The next phase of the study will involve the patient varying the amount of time the muscles are stimulated and using the system at home. Research into the development of the system will continue with the patient over the next few months. This will involve extensive measurements of movements, forces generated by stimulation, the effect of the activity on the muscles and the ability to control movement. Researchers will also be looking at whether using the system improves everyday hand and arm skills.
At the end of this study, if the system works and there is sufficient evidence for its effectiveness in improving arm and hand function, a clinicaltrial will be designed and carried out.
