What is the next step in evaluating an 84-year-old patient with a history of falls, chronic low back pain, decreased sensation to monofilament (monofilament test) bilaterally, and decreased proprioception?

Evaluation of an 84-Year-Old Patient with Falls, Chronic Low Back Pain, and Sensory Deficits

The next diagnostic test for this 84-year-old patient with falls, chronic low back pain, decreased sensation to monofilament bilaterally, and decreased proprioception should be an MRI of the cervical and thoracic spine without IV contrast.

Rationale for Spine MRI

The patient's clinical presentation strongly suggests sensory ataxia with the following key findings:

• Decreased sensation to monofilament testing bilaterally
• Decreased proprioception
• History of falls
• Chronic low back pain

These findings point to a potential dorsal column pathology in the spinal cord, which is best evaluated with MRI imaging 1. In patients with chronic disequilibrium due to sensory ataxia and loss of proprioception that is out of proportion to other sensory modalities, spine MRI is particularly useful to evaluate the dorsal columns of the spinal cord 1.

Specific Conditions to Evaluate

MRI of the cervical and thoracic spine without IV contrast can help identify several potential causes of the patient's symptoms:

1. Compressive myelopathy - Common in elderly patients and can cause progressive sensory deficits
2. Vitamin B12 or copper deficiency - Can affect the dorsal columns
3. Tabes dorsalis (neurosyphilis) - Less common but should be considered
4. Spinal cord atrophy - Reported in several forms of degenerative ataxia 1

Diagnostic Algorithm

1. Initial assessment: The patient has already had monofilament testing and proprioception assessment showing bilateral deficits
2. Next step: MRI cervical and thoracic spine without IV contrast
3. If MRI is negative or inconclusive: Consider:
   • Laboratory testing for vitamin B12, copper levels
   • Nerve conduction studies/EMG if peripheral neuropathy is suspected
   • MRI with contrast if inflammatory or infectious causes are suspected

Why Not Other Tests First?

• CT imaging: Less sensitive than MRI for evaluating spinal cord pathology and soft tissues 1
• Blood tests alone: While important, the neuroimaging should be prioritized given the significant neurological deficits and fall history
• Nerve conduction studies: May be helpful after MRI if peripheral neuropathy is suspected rather than dorsal column pathology

Important Clinical Considerations

• The patient's age (84 years) increases risk for both degenerative spine disease and falls
• The combination of decreased proprioception and monofilament sensation suggests involvement of both large fiber (position sense) and small fiber (light touch) sensory pathways
• The International Working Group on the Diabetic Foot risk stratification system would classify this patient as high risk (Category 3) due to LOPS and history of falls 1

Pitfalls to Avoid

• Delay in diagnosis: Falls in elderly patients significantly increase morbidity and mortality
• Focusing only on peripheral neuropathy: The proprioception deficits suggest possible central nervous system involvement
• Attributing symptoms solely to age: The specific pattern of deficits warrants thorough investigation
• Missing vitamin deficiencies: If MRI is negative, vitamin B12 deficiency should be ruled out as it is a treatable cause of sensory ataxia

By obtaining an MRI of the cervical and thoracic spine without IV contrast, you can efficiently evaluate for the most likely causes of the patient's sensory deficits and falls, allowing for targeted treatment to prevent further functional decline and injury.