Phantom Limbs “I feel dead appendages”

What the Research Shows… General Info: Almost all amputees experience some from of phantom limb phenomena (e.g., pain, sensation, etc.) 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 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 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 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 Phantom limb pain more common in adult amputees, less common in child amputees, almost never present in congenital amputees

Suspected Neurological Causes 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 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 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 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 Phantom limb pain and stump pain seem to be linked

Suspected Neurological Causes Reorganization of the Cortex  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  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 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. 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 Current treatments: analgesic, antidepressants, stimulation are minimally effective 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 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)

Mirror Treatment A visual trick, the arm is placed in a box to reverse the image and make it appear like the amputated limb 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 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) Its thought that the pain comes from the brain’s map of the body and what is actually perceived (or no longer perceived)