Diagnostic Testing and Imaging of Pain

Charan Singh

Edward Gillis

Introduction

In the United States, chronic pain affects more than 100 million adults and accounts for approximately $600 billion annually in medical costs and lost productivity (Martucci & Mackey, 2017). Lower back pain is extremely prevalent, with a mean prevalence of 31% for individuals worldwide and a lifetime prevalence between 11% and 84% (Hoy et al., 2012).

In the United States, approximately 80% will be affected at some point in their lives with chronic lower back pain, accounting for 12% to 15% of healthcare visits (Hoy et al., 2012). Imaging has allowed for increased understanding and management of chronic pain, particularly lower back pain. Diagnostic imaging is used to identify the source of pain and/or pathology that could compromise neurologic functioning.

Common imaging studies include:

Plain radiographs
CT/CT myelogram
CT/MR diskography
Bone scan/positron emission tomography (PET)
MRI

Common indications of imaging studies in chronic pain:

Low back and joint pain
Osteoarthritis
Malignancy
Sequela of trauma
Neuropathy/myelopathy
Image-guided interventions such as epidural steroid injections, vertebroplasty/kyphoplasty.

Chronic spine pain is generally secondary to degenerative changes, with osteophyte formation, disk and facet degeneration resulting in narrowing of the central canal and impingement on exiting nerve roots.

Plain Radiographs/CT

The imaging of uncomplicated chronic pain generally begins with radiographs (Figure 4-1). Presence of osteophytes, spondylolisthesis, dynamic instability, and disk space reduction usually correlates with underlying spinal/neural foramina stenosis. The oblique “Scottie dog” views (Figure 4-2) help determine spondylolysis (pars defects), facet arthropathy, and neural foramina compromise. If there is concern for fracture, superior bony anatomy can be achieved with a noncontrast CT examination.

Magnetic Resonance Imaging

MRI is widely used as a standard method for evaluating spine abnormalities and disease. MRI is ordered with contrast (gadolinium) to improve the clarity of soft tissue images, particularly inflammation, tumors, blood vessels, and, for some organs, blood supply. In general, the decision to include contrast is based on the differential diagnosis and medical condition of the patient, with recommendations provided in Table 4-1.

Figure 4-1. Lateral views of (A) the cervical and (B) lumbar spine in neutral position. Cervical spine with severe degenerative spondylosis. Lumbar spine with severe degenerative spondylosis, which results in 2 mm retrolisthesis of L2 on L3. Note the chronic compression fracture of L1.

Figure 4-2. Right lateral oblique view of the lumbar spine shows the normal appearance of the “Scottie dog.” The transverse process of L3 represents the nose. The pedicle of L3 forms the eye. The inferior L3 articular facet forms the front leg. The superior articular facet of L3 forms the ear. The pars interarticularis, the lamina between the facets, is the neck. Any abnormality at the neck could represent a pars fracture. The circle represents the approximate location of the neural foramen.

Table 4-1. MRI Contrast versus No Contrast

Body Region	Reason for Imaging	MRI with or without Contrast
Brain	Headache/migraine Mental status change/memory loss Seizures, stroke, transient ischemic attack, trauma	MRI brain without contrast
Brain	Cranial nerve lesion Infection Metastatic disease Multiple sclerosis Neurofibromatosis Pituitary involvement	MRI brain with and without contrast
Spine—cervical, thoracic, and/or lumbar	Neck/back pain Disk herniation/radiculopathy Extremity pain/weakness Compression fracture Stenosis Trauma	MRI spine (region) without contrast
Spine—cervical, thoracic, and/or lumbar	Diskitis Mass/lesion Osteomyelitis Postsurgery	MRI spine (region) with and without contrast
Extremity—nonjoint	Fracture/stress fracture Muscle/tendon tear	MRI (extremity) without contrast
Extremity—nonjoint	Abscess Cellulitis Morton’s neuroma Osteomyelitis Soft tissue tumor/mass/ulcer	MRI (extremity) with and without contrast
Extremity—joint	Arthritis Cartilage tear Fracture/stress fracture Internal derangement Joint pain Ligament/meniscal/muscle or tendon tear	MRI (joint) without contrast
Extremity—joint	Abscess Cellulitis Osteomyelitis Tumor/mass/ulcer	MRI (joint) with and without contrast
Pelvis	Pelvic pain Muscle/tendon tear Sacroiliac joints Pelvic pain Adenomyosis/endometriomas Uterine anomalies	MRI pelvis without contrast
Pelvis	Abscess/ulcer Osteomyelitis Adnexal mass Endometrial/ovarian cancer Known fibroids/ovarian cysts	MRI pelvis with and without contrast
Abdomen	Pancreas, gallbladder, liver, ducts	Magnetic resonance cholangiopancreatography without contrast
Abdomen	Kidneys, liver Mass/infection	MRI abdomen with and without contrast
Brachial plexus	Brachial plexus neuropathy	MRI chest without contrast

For the patient with spinal pain, MRI without contrast is indicated in presurgical planning if the patient fails conservative management. If there is a contraindication to MRI, a CT myelogram (Table 4-2) may be obtained. MRI with contrast is indicated in postsurgical patients with ongoing pain/radiculopathy to differentiate residual disk pathology versus scarring.

Table 4-2. Commonly Affected Nerve Roots and Associated Sensorimotor Deficits

Nerve Root	Pain/Numbness	Motor Weakness
C5	Lateral upper arm	Elbow flexion
C6	Lateral forearm and 1st-2nd fingers	Wrist extension
C7	Palm and 3rd finger	Elbow extension
C8	Medial forearm and 4th-5th fingers	Finger flexion
L2	Anterior and medial thigh	Hip flexion and adduction
L3	Anterior thigh and knee	Knee extension and hip flexion and adduction
L4	Anterior and medial calf	Hip extension, flexion, adduction
L5	Lateral leg and medial foot (arch)	Foot dorsiflexion and toe flexion and extension
S1	Posterior thigh and calf, heel and lateral foot	Foot plantarflexion and toe and knee flexion