MRI Thoracic Spine Without IV Contrast
For a patient with a palpable soft lump over the thoracic central spine causing wrist numbness when pressure is applied, MRI of the thoracic spine without IV contrast is the best initial imaging modality. This presentation suggests a soft tissue mass with potential neural compression that requires detailed soft tissue characterization, which MRI provides superior to all other modalities 1, 2.
Clinical Reasoning
This clinical scenario raises concern for a soft tissue mass causing mechanical nerve compression when pressure is applied. The key features are:
- Palpable soft lump = likely soft tissue pathology (lipoma, ganglion, neurofibroma, or other mass) 1
- Positional wrist numbness = suggests nerve compression (likely thoracic nerve root or sympathetic chain involvement causing referred symptoms) 3
- Reproducible with pressure = mechanical compression rather than intrinsic cord pathology 1
Why MRI Without Contrast is Optimal
MRI without IV contrast is the single best modality because it:
- Provides superior soft tissue resolution to characterize the mass (lipoma, cyst, neurofibroma, schwannoma, ganglion) 1, 2
- Evaluates for nerve root compression and relationship of the mass to neural structures 1
- Assesses the spinal cord for any compression or signal abnormality 1, 2
- Identifies marrow pathology if there is any osseous involvement 2, 4
- Allows complete preoperative surgical planning if intervention is needed 5
When to Add Contrast
MRI without AND with IV contrast should be obtained instead if:
- There is clinical suspicion for infection (fever, recent infection, immunosuppression, IV drug use) 1, 2
- There is concern for neoplasm (history of cancer, unexplained weight loss, constant pain, age >65) 1, 2, 3
- The initial non-contrast MRI shows findings suspicious for tumor or infection requiring further characterization 1
Role of Other Modalities
CT without contrast is complementary but not primary, as it:
- Depicts osseous detail well but misses soft tissue pathology 2, 4
- Is appropriate only when MRI is contraindicated or for presurgical bony anatomy assessment 2
Plain radiographs have no role here, as they cannot characterize soft tissue masses and would miss the pathology entirely 1
Critical Pitfalls to Avoid
- Do not delay MRI if myelopathy signs develop (spasticity, hyperreflexia, gait disturbance, bladder dysfunction), as this requires immediate evaluation 2, 3
- Do not order CT with IV contrast alone, as there is no literature supporting this for soft tissue mass evaluation 2
- Do not assume the mass is benign without imaging—lipomas are common but neurogenic tumors (schwannoma, neurofibroma) can present identically and require different management 5, 4
- Assess for red flags including progressive neurologic deficits, which would escalate urgency 1, 3