Inclusion criteria for pain subjects:
- Subject is 18-75 years old.
- Subject is able to give written informed consent.
- Subject is currently diagnosed with lower extremity radicular pain regardless of specific or suspected etiologies.
- Subject has a clear dermatomal distribution of the painful area extending to the distal lower extremities.
- Subject reports ongoing pain intensity of 4 or greater using the visual analogue scale (VAS) during the week prior to enrollment.
Inclusion criteria for healthy subjects:
- Subject is 18-75 years old.
- Subject is able to give written informed consent.
- Subject has no history of chronic back/spine pain.
Exclusion criteria for all groups:
- Subject recently received a lumbar ESI (within 8 weeks).
- Subject starts new NSAID medication for pain during the study.
- Subject has predominantly axial low back pain.
- Subject has known pain condition secondary to hip joint arthritis.
- Subject is pregnant or breastfeeding.
- Subject has allergy to lidocaine.
- Subject is treated with chronic corticosteroid therapy.
- Subject is on anticoagulation therapy (i.e. Coumadin, Plavix, or Lovenox).
- Subject has a known bleeding disorder (i.e. hemophilia).
- Subject has uncontrolled high blood pressure [>170/100].
- Subject has a known heart condition.
- Subject has known inflammatory disease (i.e. inflammatory bowel disease; ankylosing spondylitis; etc.).
- Subject has known liver dysfunction or renal insufficiency or impaired elimination (Renal dysfunction is defined as eGFR < 60. Hepatic dysfunction is defined as LFTs ≥ 3x ULN).
- Subject has been hospitalized recently (within one month) for a major psychiatric disorder (i.e. major depression, bipolar disorder, schizophrenia, anxiety disorder, or psychosis).
- Subject has contraindications to MRI and PET scanning (i.e. presence of a cardiac pacemaker or pacemaker wires, metallic particles in the body, vascular clips in the head or previous neurosurgery, prosthetic heart valves, or claustrophobia).
- Subject had research-related radiation exposure in the last 12 months.
- Subject tests positive for use of illicit drugs, marijuana, or non-prescribed drugs.