A simple treatment for imagined pain in an amputated limb
EVEN the master organ - the brain -
can at times get fooled. Sometimes a
person feels that a limb that had been
amputated is still there but is paralysed.
The patient can actually feel all the parts
of the phantom limb but cannot move it
and this causes extreme discomfort and
a persistent pain. Now, Vilayanus S
Ramachandran, professor of neuroscience at the University of California,
San Diego, has devised a treatment to
rid patients of phantom limb pain.
But why does the brain generate a
phantom limb in the first place? It seems
that when a limb is lost or amputated,
the brain modifies its sensory maps.
Though the brain no longer gets any
responses from the lost linab, it continues to get stimuli from adjacent body
parts. These stimuli fool the brain into
believing that the missing limb is still there.
For instance, when 28-year-old
Derek Steen met with an accident 10
years ago, the nerves in his left hand
were damaged and it had to be amputated. No sooner was this done that he
started complaining about severe pain
where his left hand had been. To treat
Steen, Ramachandran came up with an
ingenious idea - he constructed a simple box, with a vertical mirror in the
middle, having no lid or front and costing a mere us $5 - which he hoped
would work.
Steen was asked to place his right
hand in the box and move his hand as if
he were conducting an orchestra. Seeing
is believing. So when Steen waved his
right arm, the mirror fooled his brain
into perceiving the mirror image as his
reconstructed left arm. As he watched
his image he got instant relief, but, if he
closed his eyes he felt the paralysis return.
But the whole exercise created a
conflict in Steen's mind. Explains
Ram;chandran, "Steen's vision was
telling him that his arm had come back
and was obeying his commands. But he
was not getting any feedback from the
muscles in his arm." This conflict probably told the brain that there was something wrong. But the human brain,
especially that of an adult, is rather
stubbornly slow in accepting new
experiences. So Steen had to repeat the
exercise over a period of 3 weeks before
his brain saw through the absurdity of
the whole thing and decided that it
would have nothing to do with it. As a
result, for Steen, the phantom limb vanished.
Ramachandran is now using the
same technique to treat other kinds of
phantom limb pain, including a clenching spasm of phantom hands.
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