What diagnostic tests are needed for a postmenopausal female with severe low back pain, difficulty in ambulation, and electric-like sensations in the legs, with a history of Rheumatoid Arthritis (RA), breast cancer, and diabetes mellitus, currently on Anastrozole, pioglitazone (thiazolidinedione), and sitagliptin (dipeptidyl peptidase-4 inhibitor)?

Diagnostic Tests for a 64-Year-Old Female with Severe Low Back Pain and Neurological Symptoms

For this 64-year-old female with severe low back pain, difficulty in ambulation, and electric-like sensations in the legs, with multiple risk factors for serious pathology, an urgent MRI of the lumbar spine is the most appropriate initial diagnostic test. 1

Initial Assessment Considerations

This patient presents with several concerning features that warrant prompt diagnostic evaluation:

• Severe neurological symptoms (electric-like sensations in legs and difficulty ambulating) suggesting possible radiculopathy or spinal stenosis 1
• Multiple risk factors for vertebral metastasis (history of breast cancer stage 3A with prior radiation and chemotherapy) 1
• Risk factors for osteoporosis (postmenopausal status, history of TAHBSO at age 30, kyphosis, frail appearance, and current Anastrozole therapy) 1
• Sudden onset of symptoms without trauma, concerning for possible pathological fracture 1

Recommended Diagnostic Tests

Primary Diagnostic Test

• MRI of the lumbar spine (preferred over CT) 1
  • Provides superior visualization of soft tissue, vertebral marrow, and spinal canal
  • Can identify serious underlying conditions including metastatic disease, spinal cord compression, disc herniation, and spinal stenosis
  • Particularly indicated given the history of cancer, which is the strongest predictor of vertebral cancer 1
  • Should be performed urgently due to the presence of severe neurological symptoms 1

Additional Tests to Consider

• Erythrocyte sedimentation rate (ESR) 1

  • An ESR ≥20 mm/h has 78% sensitivity and 67% specificity for cancer
  • Useful as a screening test in conjunction with imaging 1

• Plain radiography of the lumbar spine 1

  • May be used as an initial evaluation for possible vertebral compression fracture given the patient's risk factors for osteoporosis
  • However, MRI would still be required given the neurological symptoms and cancer history 1

• Bone mineral density testing 1

  • Indicated due to multiple risk factors for osteoporosis (postmenopausal status, Anastrozole therapy, smoking, kyphosis) 1

Diagnostic Algorithm

1. Immediate MRI due to:

   • Severe progressive neurological symptoms (difficulty ambulating, electric-like sensations) 1
   • History of cancer (breast cancer stage 3A) 1
   • Risk of spinal cord compression requiring urgent intervention 1

2. Laboratory studies to be obtained concurrently:

   • ESR and C-reactive protein to screen for inflammatory/malignant processes 1
   • Complete blood count to evaluate for infection or malignancy 2
   • Calcium, phosphorus, alkaline phosphatase to assess for bone metabolism abnormalities 2

3. If MRI is contraindicated or unavailable:

   • CT scan would be the next best option, though it provides less detailed soft tissue visualization 1

Important Clinical Considerations

• Avoid delaying imaging in this patient despite general recommendations against routine imaging for nonspecific low back pain 3

  • The presence of multiple red flags (cancer history, neurological deficits, age >50) justifies immediate advanced imaging 1, 4

• Electrophysiologic testing (EMG/NCS) is generally not recommended as an initial test but may be considered later if peripheral nerve involvement needs to be distinguished from radiculopathy 1, 5

• Discography and other invasive diagnostic procedures should be avoided initially and only considered if surgical intervention is being planned 2

• Beware of incidental findings on MRI that may not correlate with the patient's symptoms - clinical correlation is essential 1, 2

• Consider the impact of Anastrozole (aromatase inhibitor) which increases risk of bone loss and fractures in postmenopausal women with breast cancer 1