The rerouting phenomenon is believed to
occur in patients with "incomplete" spinal cord injuries, in which the
cord remains connected to the brain. It works like emergency circuitry
patching - the brain automatically switches movement control to a new
location when the legs are stimulated.
By studying patients with incomplete
injuries, the researchers hope to be able to identify in each patient
where the movement control center has shifted to, and then target the
new location with interventions that stimulate muscle function.
Early results from four patients are so
encouraging, the scientists foresee a potential breakthrough in the
care and recovery of spine-injured patients.
What normally happens is that the brain
transmits a signal down the spinal cord telling the leg muscles to
move. But to determine what changes have occurred in the brain
following spinal injury, UC researchers working at the Drake Center are
essentially reversing the physiological process.
They stimulate patients' leg muscles
using an external electrical source, a StimMaster stationary "bicycle"
designed by nationally known electrical stimulation expert Steven
The StimMaster delivers a series of small
electrical charges to the patient's legs, triggering them to pedal. The
leg movements in turn send a signal up the still-intact spinal cord
pathways to the brain, the reverse of the normal process. This
activates the leg-control center - much like pushing a car while it's
in gear turns over the engine and fires the spark plugs.
Then, thanks to some highly sophisticated
technology in UC's Center for Imaging Research, a 4-Tesla FMRI
(functional magnetic resonance imaging) scanner, the researchers can
track the neurological signals in the brain to pinpoint the location of
the movement control center.
A Tesla is a unit of magnetic field
strength, and MRI scanners usually run at 1.5 Teslas. The stronger the
magnet, however, the better the images obtained of the structure,
chemical processes and function of a patient's brain. UC's 4-Tesla MRI
is one of the most powerful in Ohio, and one of only about a dozen in
"When we're working with someone who
might not have walked for three or four years," says principal
investigator Jonathan Strayer, MD, of the Department of Physical
Medicine and Rehabilitation, "we're able to take a picture of the
leg-control 'biomarker' in the brain that shows it expanding. That
gives us an idea of what's going on, and where it's happening, that
allows us to target the brain with other interventions."
This approach is not yet seen as a cure,
says Dr. Strayer, who himself has an incomplete spinal injury. But it
could lead to a breakthrough in care and recovery by significantly
increasing the patient's quality of life.
Spinal cord-injured patients, for
example, often become obese from lack of exercise. But the combination
of muscle stimulation and exercise can help control weight gain, while
at the same time reducing blood pressure, pulse rate and other medical
complications and increasing the patient's range of motion.
"And even if we can't get these patients
to walk yet," adds Dr. Strayer, "we can give them a better quality of
life. One of our patients, for example, although not able to walk, has
regained a degree of independence by being able to drive again."
The StimMaster is not only yielding
important information about the mechanism of the body's automatic
rhythmic movements, and identifying what's going on when it fails, says
Dr. Strayer. It's also proving cheaper and more efficient than the
standard treadmill for exercise therapy.
A "deconditioned" patient on a treadmill,
for example, must be supported in a harness and requires help from
several therapists. The equipment is expensive, the therapy exhausting.
Using the StimMaster cycle, however, the
patient sits comfortably in a cushioned seat, without requiring
mechanical or human physical support.
Another benefit of the cycling might be
stimulation of what scientists call the central pattern generator
(CPG). This nerve mechanism, thought to be located in the spinal cord,
controls rhythmic movements such as walking without brain input.
"Unfortunately," says Stephen Page, PhD,
co-principal investigator and research director in physical medicine
and rehabilitation, "you can't take the spinal cord apart. And it has
no blood flow to take up a contrast medium and generate a visual image,
which makes it very tough to figure out."
An important next step, therefore, just as it's done in the brain, is to find a way of generating an image of the spinal cord.
"Science is deliberate," observes Dr.
Page. "We can't start on the spine until we understand the effect of
spinal injury on the brain. First we need a good marker of what's going
on there."So we have to start on things we know, or study people who
are less impaired, like our incomplete spinal cord injury patients.
When we have this pilot data, it will be reasonable then to move down
the spinal cord to see what's going on there."