Neuroprosthetics: Technology strikes a nerve

29. October 2013
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Man and machine in intimate harmony: Thanks to neuroprosthetic innovations, medical devices are increasingly taking over tasks no longer ably performed by the nerve cells, for instance in cases of paraplegia or retinitis pigmentosa. From the research laboratories: more innovations.

Neuroprosthetic tools such as pacemakers, brain pacemakers or cochlear implants have long conquered a place in the clinic. Inspired by successful outcomes, doctors and engineers are trying together to develop solutions to prevent further suffering – with success.

Thoughts control devices

In severe conditions of the central nervous system, such as paraplegia, brainstem-based infarction and amyotrophic lateral sclerosis, researchers hold great hopes for brain-computer interfaces (BCI), ie the area of intersecting contact between the PC and the patient’s brain, in managing the control of external devices. There is a distinction made here between invasive and non-invasive methods. Scientists at the University of Bremen succeeded through controversial experiments using macaques in developing a fast BCI. When they placed electrodes in the motor cortex, they achieved more precise measurements. Their conclusion: it is generally possible to transform signals of visual alertness into computer signals. Based on these results they now want to clarify how signals could be used for instance to control a wheelchair. Professor Gabriel Curio, Berlin, restricts his work to non-invasive options. He investigates ultra high-frequency EEG oscillations, which are related to cortical action potentials, in the somato-sensory system. Already a few years ago Curio presented a “mental typewriter”, with which the patient controls a computer via a surface EEG. For paraplegics there are also other options.

Technology makes mobile

Professor Yoshiyuki Sankai at Cyberdyne, Japan, has developed an intelligent exoskeleton, known as Hybrid Assistive Limb® (HAL®), for these patients. When nerve signals from the brain get to the muscles, electrical impulses can be detected on the skin surface. A microcomputer recognises the message given to move and transforms it via electric motors into a walking gait. Using the system, those with paraplegia will manage to take steps which have no longer been possible due to weak nerve impulses. At the University Hospital Bergmannsheil a group of colleagues working under Professor Dr. Thomas A. Schildhauer are now studying whether the symptoms associated with paraplegia improve if patients regularly exercise using the exoskeleton on a treadmill. “Through the training in the suit we have observed significantly increased mobility of the paralysed patients, an intensified formation of muscle, more muscle power and a higher level of activity”, says Schildhauer. Engineers at Fraunhofer IBMT have set themselves a different focus. They are working on “Myoplant“, implantable systems for controlling prosthetic hands. Their challenge: that the prosthesis not only carry out motor actions, but also provide the user with sensory feedback, for e.g. on temperature or texture of materials. At the German Primate Centre the Myoplant-complete-system has already survived its baptism of fire; before it reaches series production there is a lot of work yet awaiting the researchers.

Help the brain to make the leap

By contrast, deep brain stimulation procedures made their way into the clinic long ago – so far 75,000 people worldwide have received the respective devices as implants. Early in 2013 a group of colleagues from Magdeburg for the first time implanted a brain pacemaker in a case of neuroacanthocytosis, a rare movement disorder of variable genesis. Encouraged by success, researchers are at work on components involved in electrophysiological and neurochemical monitoring in long-term therapy-resistant epilepsy. Here, invasive insertion of implanted electrodes is required, something which can lead to infections or bleeding. With the new INCRIMP system, in future in addition to long-term measurements targeted micro-stimulation of cerebral structures should also be possible. With this aim in mind, material researchers have specifically developed electrodes based on carbon nanotubes. The implants communicate wirelessly with external components involved in system management or in collecting data. In addition, cluster headache is a topic shifting more and more into the range of interests of neurologists. They have implanted neurostimulatory systems in the jaw. Once cluster attacks occur, patients activate the device via an external console and electrical stimuli strike the pterygopalatine ganglion. One multicenter, randomised, placebo-controlled study has now shown that in 67.1 percent of all attacks after 15 minutes the device relieves the pain – compared to 7.4 percent for the placebo. The authors judge their system as used on cluster headache to be an “effective new therapy with double benefits, namely acute pain relief and preventive effects”.

Chips at eye level

Ophthalmology benefits from neuroprothetic innovations as well. “For 15 years, a network of clinics and institutes has been working on the development of electronic retinal implants”, says Dr. Walter-G. Wrobel from the firm Retina Implant AG. “The Natural and Medical Sciences Institute at the University of Tübingen has been with us from the beginning and its expertise in nerve-chip coupling has contributed decisively to our success”. Patients with retinitis pigmentosa (RP) or age-related macular degeneration (AMD) can benefit from this. In order to compensate for the loss of photoreceptor cells in the retina, the doctors implant the Argus II System onto the retinal surface. A special pair of glasses transmits images wirelessly to electronic components. “This new, surgically implantable aid is an option for patients who have lost their eyesight due to RP and for whom no FDA-approved treatments exist”, says Jeffrey Shuren, Director of the FDA Center for Devices and Radiological Health. “The device can make adults with RP, who no longer perceive form and movement, more mobile and help them to perform their daily activities”. There remains the option of placing light-sensitive microchips directly beneath the retina, without an external camera being necessary. As part of projects at FutureRet, engineers and doctors are seeking to improve the optical resolution and the corrosion resistance of their implants. Integrated circuits contribute in reducing energy consumption.

Many perspectives – many challenges

Through advances in computer systems and in the increasing miniaturisation of electronic components, working groups have made impressive achievements in aiming to provide patients with a better quality of life. Numerous ideas long ago made the leap from basic research to application, in other projects there are promising results coming from animal experiments. Things are now exciting, and will remain so over the coming years.

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Dr. Kavirayani Krishna Murthy
Dr. Kavirayani Krishna Murthy

very interesting and informative on line medical magazine with latest technological advances

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