What imaging modality is recommended for a female patient with sudden onset painless bilateral leg weakness?

From the Guidelines

For a female patient with sudden onset painless bilateral leg weakness, MRI of the spine is the recommended initial imaging modality. This presentation suggests a possible spinal cord pathology, and MRI provides excellent visualization of the spinal cord, nerve roots, and surrounding structures. The MRI should include the entire spine with particular focus on the thoracic region, as this could represent a spinal cord compression, transverse myelitis, or other acute myelopathy. Contrast enhancement with gadolinium is typically included to help identify inflammatory or neoplastic processes. The study should be performed urgently, as delayed diagnosis of spinal cord compression can lead to permanent neurological deficits. While CT may be considered if MRI is contraindicated (such as in patients with certain implanted devices), it provides less detailed information about the spinal cord itself. The painless nature of the weakness is particularly concerning for a vascular or demyelinating etiology rather than a mechanical compression, making MRI even more valuable for its superior soft tissue contrast and ability to detect subtle signal changes within the cord. According to the most recent guidelines, IV contrast or MRI spine area of interest without IV contrast is usually appropriate for the initial imaging of patients with acute onset myelopathy 1.

Some key points to consider in this patient's evaluation include:

• The clinical presentation of sudden onset painless bilateral leg weakness is suggestive of a spinal cord pathology, such as spinal cord compression or transverse myelitis.
• MRI is the preferred imaging modality for evaluating spinal cord pathology due to its excellent visualization of the spinal cord, nerve roots, and surrounding structures.
• The use of contrast enhancement with gadolinium can help identify inflammatory or neoplastic processes.
• Urgent evaluation is necessary to prevent permanent neurological deficits.
• Guillain-Barré syndrome is also a possible diagnosis, characterized by rapidly progressive bilateral weakness of the legs and/or arms, but MRI of the spine is still the recommended initial imaging modality to rule out other causes of weakness 1.

In terms of specific imaging protocols, the American College of Radiology recommends MRI spine area of interest without and with IV contrast or MRI spine area of interest without IV contrast for the initial imaging of patients with acute onset myelopathy 1. However, the choice of imaging protocol may depend on the specific clinical presentation and the availability of imaging modalities.

Overall, MRI of the spine is the recommended initial imaging modality for a female patient with sudden onset painless bilateral leg weakness, due to its excellent visualization of the spinal cord and surrounding structures, and its ability to detect subtle signal changes within the cord. This recommendation is based on the most recent guidelines and evidence, including the American College of Radiology's Appropriateness Criteria for myelopathy 1.

From the Research

Imaging Modalities for Sudden Onset Painless Bilateral Leg Weakness

• The patient's symptoms suggest a possible spinal cord or nerve root pathology, and imaging studies can help identify the underlying cause.
• Magnetic Resonance Imaging (MRI) is a sensitive modality for detecting spinal cord injuries, tumors, and other abnormalities that may cause neurological deficits 2.
• In patients with suspected malignant spinal cord compression, MRI can confirm the presence and level of disease, and may lead to a change in the treatment plan 3.
• For patients with ankylosing spinal disorders, MRI may be useful in identifying noncontiguous fractures or disco-ligamentous injuries that are not visible on computed tomography (CT) scans 4.

Specific Imaging Recommendations

• Whole spine MRI is indicated in most patients with suspected spinal cord compression or other spinal pathologies, as it can provide detailed images of the spinal cord and surrounding structures 3, 2.
• In patients with symptoms that mimic lumbar spine pathology, lumbar spine MRI may be useful in diagnosing sacral insufficiency fractures or other conditions that may cause lower back pain and radiating pain 5.
• Physiologic imaging techniques, such as standing radiographs or dynamic MRI, may be useful in evaluating the dynamic nature of the spine and its mobility across multiple segments 6.

Key Considerations

• The choice of imaging modality depends on the patient's symptoms, medical history, and physical examination findings.
• MRI is a sensitive modality for detecting spinal cord and nerve root pathology, but may not be necessary in all cases.
• CT scans may be useful in evaluating bony structures and detecting fractures, but may not provide detailed images of the spinal cord or surrounding soft tissues 4.