What are the next steps to diagnose a patient with suspected neuropathy and degenerative disc disease?

Diagnostic Approach for Suspected Neuropathy and Degenerative Disc Disease

The next steps in diagnosing a patient with suspected neuropathy and degenerative disc disease should include MRI of the spine without contrast as the primary imaging modality, followed by targeted neurological testing including electromyography (EMG) and nerve conduction studies if radiculopathy is suspected. 1

Initial Imaging

1. MRI of the spine without IV contrast

   • Gold standard for evaluating soft tissue abnormalities including disc herniation, nerve root compression, and spinal cord pathology 1
   • Particularly useful for detecting inflammatory changes in paraspinal and epidural soft tissues 1
   • Should focus on T2-weighted/STIR sequences to enhance detection of inflammation 1
   • Should be interpreted by an experienced radiologist 1

2. Plain radiographs of the spine

   • Useful for initial assessment of spondylosis, degenerative disc disease, and spinal alignment 1
   • Can help rule out bony abnormalities but has limited utility for soft tissue evaluation 2
   • Consider flexion-extension views to assess for instability 1

Neurological Assessment

1. Comprehensive neurological testing

   • Assess for specific nerve root involvement:
     • L4 nerve root: Knee strength and reflexes
     • L5 nerve root: Dorsiflexion strength of foot and big toe
     • S1 nerve root: Plantar flexion strength and Achilles reflexes 2
   • Perform Lasègue test (straight leg raise) which has 91% sensitivity for disc herniation 2
   • Crossed Lasègue test has higher specificity (88%) but lower sensitivity (29%) 2

2. Electrophysiological studies

   • EMG and nerve conduction studies to differentiate between:
     • Radiculopathy (nerve root compression from disc disease)
     • Peripheral neuropathy (such as diabetic neuropathy)
     • Combined pathology 1
   • Particularly important when diagnosis is uncertain 1
   • Can help identify the location and severity of nerve damage 1

Laboratory Testing

1. Inflammatory markers

   • ESR and CRP to assess for inflammatory processes 1
   • Particularly important if infection is suspected 1

2. Metabolic screening

   • HbA1c and glucose testing to evaluate for diabetes 1
   • Consider testing for vitamin B12 deficiency, thyroid dysfunction 1

3. Additional testing for neuropathy

   • If peripheral neuropathy is suspected:
     • Temperature sensation
     • Pinprick sensation
     • Vibration perception (using 128-Hz tuning fork)
     • Pressure sensation (using 10-g monofilament)
     • Ankle reflexes 1

Special Considerations

1. Red flags requiring urgent evaluation

   • Progressive neurological deficits
   • Bladder or bowel dysfunction
   • Fever or signs of infection
   • History of cancer
   • Unexplained weight loss 2

2. When to consider advanced imaging

   • MRI with contrast if infection or malignancy is suspected 1
   • CT scan if MRI is contraindicated or for better visualization of bony structures 1
   • Consider CT myelography if MRI is contraindicated and detailed neural assessment is needed 1

3. When to consider biopsy

   • If infection is suspected and blood cultures are negative
   • Image-guided biopsy for suspected infection or malignancy 1
   • Consider second biopsy if first is non-diagnostic 1

Diagnostic Pitfalls to Avoid

1. Overreliance on imaging findings

   • High rate of abnormal findings in asymptomatic individuals 1
   • MRI findings must be correlated with clinical presentation 1

2. Missing combined pathologies

   • Patients may have both degenerative disc disease and peripheral neuropathy concurrently 3, 4
   • Diabetic lumbosacral radiculoplexus neuropathy can mimic radiculopathy from disc disease 4

3. Delayed diagnosis of serious conditions

   • Ensure timely evaluation of red flags to prevent missed diagnoses of cauda equina syndrome, infection, or malignancy 2

By following this systematic approach, clinicians can effectively diagnose the underlying cause of symptoms in patients with suspected neuropathy and degenerative disc disease, leading to appropriate treatment planning and improved outcomes.