What type of head and neck computed tomography (CT) scan is best to evaluate for nerve compression, tumor, or epidural space mass causing new progressive right arm weakness in a patient who cannot tolerate Magnetic Resonance Imaging (MRI)?

CT Imaging for Nerve Compression Evaluation in MRI-Intolerant Patients

For patients who cannot tolerate MRI, a CT neck with intravenous (IV) contrast extending from the skull base to mid-thorax is the most appropriate imaging study to evaluate nerve compression, tumors, or epidural masses causing progressive right arm weakness.

Optimal CT Protocol

• CT neck with IV contrast is the preferred alternative when MRI cannot be performed, providing excellent visualization of the lower course of nerves and potential compressive lesions 1
• The scan should extend from the skull base to the mid-thorax to evaluate the full extent of potentially affected nerves, particularly important for detecting thoracic causes of nerve compression 1
• Thin-section high-resolution technique should be employed, with particular attention to the posterior skull base and neural foramina 1
• Non-contrast CT may be sufficient in patients with contraindications to contrast agents, though it provides less optimal soft tissue evaluation 1

Anatomical Considerations

• Progressive right arm weakness suggests possible compression of cervical nerve roots, brachial plexus, or spinal cord 1
• The imaging protocol must visualize the full extent of potentially affected nerves from the skull base through the neck and into the thorax 1
• CT can effectively evaluate:
  • Bony abnormalities causing foraminal stenosis 2
  • Space-occupying lesions in the neck or thorax 1
  • Metastases, schwannomas, paragangliomas, and meningiomas that may affect cranial or cervical nerves 1

Advantages of CT in This Clinical Scenario

• Rapid scanning time and widespread availability make CT an excellent alternative when MRI is contraindicated 1
• Superior visualization of bony structures compared to other modalities 2, 3
• Ability to detect thoracic causes of nerve compression that may be missed with limited imaging 1
• Can differentiate between vascular structures and solid masses with IV contrast enhancement 1

Limitations and Considerations

• CT provides less soft tissue contrast than MRI, which may limit evaluation of subtle nerve pathology 4, 5
• Radiation exposure is a consideration, though modern protocols aim to minimize dose 1
• Some small demyelinating lesions or subtle nerve inflammation may be missed 6
• Consider extending to include CT head without contrast if there is concern for intracranial pathology 1

Clinical Applications

• CT neck with IV contrast can identify:
  • Tumors or lymphadenopathy causing nerve compression 1
  • Bony lesions affecting neural foramina 1, 2
  • Vascular abnormalities potentially compressing nerves 1
  • Metastatic disease affecting the cervical spine or surrounding structures 1

Alternative Considerations

• If contrast is contraindicated, non-contrast CT may still provide valuable information, particularly for bony abnormalities 1
• In some cases, CT myelography might be considered as a second-line approach if initial CT findings are inconclusive 7, 2
• For patients with suspected vascular pathology, CT angiography (CTA) of the neck might provide additional information 1

By following this approach with CT neck with IV contrast from skull base to mid-thorax, clinicians can obtain the most comprehensive evaluation possible for nerve compression in patients who cannot undergo MRI.