• INCLUSION CRITERIA:

For amputee subjects with PLP:

• Male or female subjects, 18 to 75 years of age, active duty military, military healthcare beneficiary, or military retiree
• Written informed consent and written authorization for use or release of health and research study information
• Unilateral limb amputation
• Any level of prosthetic experience
• No prior history of vertebral disk disease/condition, sciatica or radiculopathy.
• No evidence of traumatic brain injury (TBI - permanent or temporary impairments of cognitive, physical and psychosocial functions with an associated diminished or altered state of consciousness)
• No known neurological disease or brain damage
• No neurological condition that would interfere with participation in the study
• Minimum of 3 phantom limb pain episodes each week
• Degree of pain evaluated by VAS scoring of a minimum 3 cm at time of screening for entry into study
• Ability to follow study instructions and likely to complete all required visits.

For healthy control subjects:

• Male or female subjects, 18 to 75 years of age.
• Written informed consent and written authorization for use or release of health and research study information.
• No prior history of vertebral disk disease/condition, sciatica or radiculopathy.
• Normal neurological examination.

Ability to follow study instructions and likely to complete all required visits.

EXCLUSION CRITERIA:

For amputee subjects with PLP:

• Age less than 18 or greater than 75 years.
• Multiple limb amputation.
• Amputation due to diabetes or vascular claudication
• Pending revision surgeries.
• Presence of embedded metallic shrapnel or other metal not compatible with MRI scanning.
• Presence of traumatic brain injury
• Known uncontrolled systemic disease-- known cancer not in remission, known on-going infection, lupus, kidney disease requiring dialysis, any other systemic disease which might affect ability to participate in this study to its conclusion
• Concurrent participation in another investigational drug or device study for phantom limb pain or participation in the 30 days immediately prior to study enrollment.
• Any condition or situation that, in the investigator's opinion, may put the subject at significant risk, confound the study results, or interfere significantly with the subject's participation in the study.
• Current Axis I or II diagnosis determined by a neurologist or psychiatrist in the 6 months prior to entry into the study.
• Subjects with lack of effort as determined by the neurologist or physiatrist. Subjects will be screened for effort using the Test of Memory Malingering (TOMM) first in order to exclude those with blatant exaggeration or malingering.
• Positive pregnancy test at the time of scanning (within 24 hours prior to the scheduled MRI scan, female subjects of child-bearing age will be given a pregnancy test)

For amputee subjects without PLP:

• Age less than 18 or greater than 75 years.
• Multiple limb amputation.
• Amputation due to diabetes or vascular claudication
• Pending revision surgeries.
• Presence of embedded metallic shrapnel or other metal not compatible with MRI scanning.
• Presence of traumatic brain injury
• Known uncontrolled systemic disease- known cancer not in remission, known on-going infection, lupus, kidney disease requiring dialysis, any other systemic disease which might affect ability to participate in this study to its conclusion
• Concurrent participation in another investigational drug or device study for phantom limb pain or participation in the 30 days immediately prior to study enrollment.
• Any condition or situation that, in the investigator's opinion, may put the subject at significant risk, confound the study results, or interfere significantly with the subject's participation in the study.
• Current Axis I or II diagnosis determined by a neurologist or psychiatrist in the 6 months prior to entry into the study.
• Subjects with lack of effort as determined by the neurologist or physiatrist. Subjects will be screened for effort using the Test of Memory Malingering (TOMM) first in order to exclude those with blatant exaggeration or malingering.
• Positive pregnancy test at the time of scanning (within 24 hours prior to the scheduled MRI scan, female subjects of child-bearing age will be given a pregnancy test)

For healthy control subjects:

• Age less than 18 or greater than 75 years
• Presence of an amputation
• Presence of embedded metallic shrapnel or other metal not compatible with MRI scanning.
• Presence of traumatic brain injury
• Known uncontrolled systemic disease-- known cancer not in remission, known on-going infection, lupus, kidney disease requiring dialysis, any other systemic disease which might affect ability to participate in this study to its conclusion
• Any condition or situation that, in the investigator's opinion, may put the subject at significant risk, confound the study results, or interfere significantly with the subject's participation in the study
• Current Axis I or II diagnosis determined by a neurologist or psychiatrist in the 6 months prior to entry into the study
• Positive pregnancy test at the time of scanning (within 24 hours prior to the scheduled MRI scan, female subjects of child-bearing age will be given a pregnancy test)