Vignette
Inside your inner ear, a network of structures called the
vestibular system tracks your head's movement and alerts your
brain to its orientation. When the system is damaged —
by trauma, infection, chemotherapy, or certain antibiotics
— the result is lost balance and wobbly vision. "People
can't keep their eyes on a target, and they feel like they're
watching the world through a video camera," Charles C. Della
Santina, director of the Johns Hopkins Vestibular
Neuroengineering Laboratory, says of the roughly 30,000
Americans who suffer from this damage. "Every time their heel
hits the ground, the world bounces."
Della Santina has invented a matchbox-sized, multi-channel
pros-thesis, pictured here, to help restore balance. The box,
which contains gyroscopes that measure the head's movement
and transmit electronic pulses to the brain, is the first
implant that tracks movement in three dimensions, just like
an inner ear.
Though it hasn't been tested on people yet, it has been tried
on some dizzy chinchillas. The animals were given the
antibiotic gentamicin, which impaired their inner ears, and
then were rigged up to a prosthesis. When the device was
activated, the chinchillas regained some of their
vision-stabilizing reflexes.
Testing on human volunteers is at least a few years away, and
there are still refinements to be made: lowering the power
requirements, reducing electrical interference with other
nerve branches, improving the timing patterns of the
electrical stimulation, and shrinking it to fit beneath the
scalp behind the human ear. Although Della Santina doesn't
expect the demand for such a device to be as great as for a
cochlear implant, which helps restore hearing, he notes that
people who need it are often severely affected. "Some people
are really desperate for anything that will help," he says.
—Kristi Birch