Transcript Phantom Limbs

Phantom Limbs
“I feel dead appendages”
What the Research Shows…
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General Info:
Almost all amputees experience some from of phantom
limb phenomena (e.g., pain, sensation, etc.)
In one study, over 75% of participants experienced
phantom limb pain
If phantom limb pain is not present immediately following
the amputation, usually does not occur
Phantom limb pain seems to be more severe in more distal
parts of phantom limb; described as “stabbing, throbbing,
burning, or cramping”
Phantom limb pain more common in adult amputees, less
common in child amputees, almost never present in
congenital amputees
Suspected Neurological Causes
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Pain-Memory Hypothesis:
Idea that chronic pain present in the limb prior to
amputation results in continued sensation of pain after
removal of limb. Value of this hypothesis is empirically
uncertain
Peripheral Nervous System Changes:
Neuromas: small bulbs that form on end of damaged
neurons (e.g,. amputated limbs), created sporadic neuronal
activity
Reorganization: Neurons that once innvervated the
amputated limb may make new connections to muscles,
fibers in stump
Phantom limb pain and stump pain seem to be linked
Suspected Neurological Causes
Reorganization of the Cortex
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Primary Somatosensory Cortex
 Area of cortex that was mapped to limb prior
to amputation is invaded by inputs from
adjacent areas of somatosensory cortex (e.g.,
face and rest of fingers)
 Intensity of PLP seems to be related to the
degree of cortical reorganization
 PLP could be a result of the incongruence of
somatosensory input and motor intention
Suspected Neurological Causes
Reorganization of the Cortex
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Primary Motor Cortex
 Can create sensations of phantom movement by
stimulating area of motor cortex mapped to amputated
limb
 Stimulation of motor cortex mapped to amputated
limb frequently (86% of trials) results in
corresponding muscle contractions in stump
 The activation of the hand area of the motor cortex
continues to be associated with a hand movement
despite the fact that the descending motor commands
generated by this activation now result in stump
muscle contractions.
Suspected Neurological Causes
Spinal Cord
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PLP could be related to disinhibition of
components of the spinal cord – including
downregulation of opioid receptors, damage
to inhibitory GABA interneurons, and
spinal remapping of the lost limb.
Treatment
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Current treatments: analgesic, antidepressants, stimulation are
minimally effective
visual, sensory, and motor feedback to the cortex might be an
important determinant of phantom limb phenomena and pain
 Prosthesis: using a motor-driven prosthesis that reads
electrical signals in stump muscles and effects movement of
prosthesis seems to decrease PLP possibly due to reversal of
cortical reorganization
 Discrimination training of stimuli by regimen of stimulation
of stump = less pain and reversal of cortical reorganization
 Pharmacological: NMDA receptor agonists, GABA agonists
 Stimulation of cortical areas by TMS or direct current may
be viable options
 Imagined movements of phantom also helped – including
mirror treatment (no controlled studies as of yet on mirror
treatment) http://youtube.com/watch?v=kzLUQR_hMqY
Mirror Treatment
A visual trick, the arm is placed in a box to
reverse the image and make it appear like
the amputated limb
 Shifts the emphasis from the site of the pain
back to the brain
 Its thought that the pain comes from the
brain’s map of the body and what is actually
perceived (or no longer perceived)
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