For our readers worldwide, especially in the United States, Jan Lexell, our issue editor, has brought together a series of international papers that make for an absorbing portrait of traumatic brain injury (TBI) rehabilitation in Europe and Canada. It is striking to what degree public policy has become involved in the development of recent TBI programs in nations such as Denmark, Sweden, and the Netherlands. To be sure, public policy is stimulated by consumers and their problems, and it is a reasonable expectation that local, regional, and national governments respond to the needs of their citizens. However, the degree of support for the continuum of TBI programs spanning acute stages through long-term community involvement is encouraging. It is good to see public policy perspectives driving the emergence of specialized TBI rehabilitation services, building in research and education components as well, for a condition that has been characterized for many years as a "silent epidemic." Our readers will find much to think about and discuss as they read this issue.

When the articles in this issue were under development, a newsworthy event, linked to the universe of disability and, in a real sense, happening beyond international boundaries, created a quick splash of news that is worth retelling to our readership. The event was most important to a specific person with very severe disability but is likely to have profound implications for large numbers of people with disabilities in the future. On April 26, 2007, astrophysicist Stephen Hawking, wheelchair bound for 4 decades, took a ride in a zero-gravity jet plane and experienced weightlessness. Hawking, a mathematics professor at the University of Cambridge, who has done groundbreaking work on the origins of the universe and the gravitational effects of black holes, has the disease amyotrophic lateral sclerosis, also known as Lou Gehrig's disease. Aboard the zero-gravity jet, he fulfilled a lifelong dream to contribute to first steps that, he hopes, will lead the human family, and perhaps, especially, its disabled branch, into space and what it has to offer. The special jet, taking off from Cape Canaveral, climbing to around 32,000 feet and making a parabolic dive back to 24,000 feet, allowed Professor Hawking to experience weightlessness for about 25 seconds. Symbolically and actually, Hawking became free of his wheelchair, tethered only to precautionary medical monitoring devices. In fact, one important aspect of this flight was to see how well his body could tolerate the gravitational forces that resulted when he left the earth's atmosphere. Both before and after weightlessness on a zero-gravity jet, passengers experience about 1.8g, causing their bodies to weigh almost twice what they do on earth (1g) as the aircraft climbs and then dives. Despite his frailty, Professor Hawking, a longtime space advocate, embraced the opportunity to experience the "ups and downs" of such a trip.

Orbital treatment centers for disabled individuals with Lou Gehrig's disease, spinal cord injury, TBI, and other neurological and orthopedic conditions will likely be an integral part of future space development. On earth, many such persons require assistance of others for transfers, ambulation, activities of daily living, toileting, and the use of instrumental devices of daily living. All of these functions as well as many others could be handled more easily and, perhaps, with greater dignity for everyone if gravity were not a factor. The prospect of recovery of function after severe TBI in an environment that may be less physically challenging may excite us but may also give us a pause. Many challenges have confronted the normal physiologies of our astronauts when they have traveled in space. Much research will have to be done on the adaptive capabilities of individuals with disability before we can materialize the concept of orbital treatment centers. It is hoped, like today's emerging programs and perspectives described in this international issue, outer space, Ray Bradbury's "final frontier" may offer, in the world of tomorrow, new transnational opportunities for delivering services to the community of persons with disability including persons with TBI.

Nathaniel H. Mayer, MD

Editor