03 October 2007

Re-Myelinating Neurons and Innervating Prostheses

In multiple sclerosis, a person's own immune system attacks the protective myelin sheath around axons. A new drug may allow brain cells to regrow myelin around neural pathways.
Biogen has published the latest preclinical data on its anti-Lingo-1 antibody in this month's issue of Nature Medicine, which suggest the drug can promote myelin production and placement around damaged nerves, at least in animals.

Normally myelin acts a protective cellular sheath around nerve fibres but if it is destroyed, as is the case in MS patients, the cells lose their ability to send signals to the body and can eventually die. This contributes to the disability seen in MS sufferers.

...Lingo-1 itself appears to be a molecular switch which blocks the ability of cells in the central nervous system to produce myelin. A Lingo-1 antibody effectively 'blocks the blocker' and the end result is that myelin production is restarted.

"While preliminary, these findings are encouraging and suggest that the anti-Lingo-1 antibody has the potential to repair some of the damage caused to the CNS. This may be an entirely new approach to treating MS," said Dr Alfred Sandrock, Senior Vice President of Neurology Research and Development at Biogen.

Persons who are paralyzed, or lose limbs due to trauma or disease are in need of a means to transmit nerve impulses beyond the point of paralysis or amputation. These relayed signals can stimulate either denervated muscles or prosthetic actuators to restore lost movement.
Trauma and disease can lead to paralysis or amputation, reducing the ability to move or talk despite the capacity to think and form intentions. In spinal cord injuries, strokes, and diseases such as amyotrophic lateral sclerosis (Lou Gehrig's disease), the neurons that carry commands from the brain to muscle can be injured. In amputation, both nerves and muscle are lost.

Neural prosthetic devices represent an engineer's approach to treating paralysis and amputation. Here, electronics are used to monitor the neural signals that reflect an individual's intentions for the prosthesis or computer they are trying to use. Algorithms form the link between neural signals that are recorded and the user's intentions that are decoded to drive the prosthetic device.

...Through a better quantitative understanding of how the brain normally controls movement and the mechanisms of disease, he [Ram Srinivasan] hopes these devices could one day allow for a level of dexterity depicted in movies, such as actor Will Smith's mechanical arm in the movie, "I, Robot."

The gap between existing prototypes and that final goal is wide.

Robotics and nerve-machine interfaces appear to be progressing along parallel paths. Quadraplegics may use robotic assistants they control via brainwaves, before the means to heal or bypass their spinal cord injuries are perfected. Such robot assistants may take many forms, including exoskeletons enclosing the person, robotics enhanced powered wheel chairs, or robots that are separate from the person, and free to perform household and patient care tasks when ordered to do so by the quadraplegic's brain signals.

Eventually, disrupted spinal cords will be re-connected, and an otherwise very lengthy physical rehabilitation will be shortened by neuro-electronic prosthetic devices.

The promising approach above to treating MS by blocking Lingo-1, suggests that similar approaches my be effective in treating Parkinson's, Alzheimer's, and other neurodegenerative disorders that currently cause significant morbidity and mortality.

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