What is the first test to rule out cauda equina syndrome in the emergency department?

From the Guidelines

The first test to rule out cauda equina syndrome in the emergency department should be an MRI of the lumbar spine without IV contrast, as it is the most accurate and efficient method for evaluating soft-tissue pathology and assessing spinal canal patency. This recommendation is based on the most recent and highest quality study, which suggests that MRI lumbar spine without IV contrast is the preferred initial study for evaluating suspected cauda equina syndrome 1. The study highlights the importance of urgent MRI assessment in patients presenting with new-onset urinary symptoms in the context of low back pain or sciatica 1.

Key Points to Consider

• Cauda equina syndrome is a rare but serious condition that requires prompt diagnosis and treatment to prevent permanent neurological deficits 1.
• MRI lumbar spine without IV contrast is the imaging modality of choice for evaluating suspected cauda equina syndrome due to its ability to accurately depict soft-tissue pathology and assess spinal canal patency 1.
• A recent retrospective review showed that CT lumbar spine without IV contrast can answer the question of whether or not cauda equina compression is present, but it is not the preferred initial study 1.
• CT myelography of the lumbar spine can be useful for surgical planning in patients with cauda equina syndrome, but it is not the first line of imaging 1.

Clinical Implications

While waiting for the MRI, a thorough neurological examination focusing on perineal sensation, anal tone, and bladder function should be performed, but these clinical findings alone are not sufficient to rule out the condition without appropriate imaging 1. The urgency of obtaining an MRI cannot be overstated, as delays in diagnosis and treatment can lead to permanent neurological deficits 1. In summary, an MRI of the lumbar spine without IV contrast is the first test that should be ordered to rule out cauda equina syndrome in the emergency department, due to its high sensitivity and ability to accurately depict soft-tissue pathology.

From the Research

Diagnostic Approach for Cauda Equina Syndrome

The first test to rule out cauda equina syndrome in the emergency department is a topic of interest due to the urgency and potential consequences of delayed diagnosis.

• Magnetic Resonance Imaging (MRI): MRI is considered the gold standard for diagnosing cauda equina syndrome due to its ability to provide detailed images of the spinal cord and nerves 2, 3, 4.
• Limited Sequence MRI: A limited sequence MRI has been proposed as a quicker alternative to a full MRI scan, taking significantly less time to perform and potentially reducing the pressure on resources 3.
• Computed Tomography (CT): CT scans can also be used to evaluate spinal stenosis and cauda equina impingement, with a high sensitivity and negative predictive value for detecting significant spinal stenosis 5.
• Clinical Assessment: Clinical assessment by neurosurgical residents or orthopedic doctors can help predict the likelihood of cauda equina syndrome, but MRI scanning is still recommended due to the complexity of the condition and the potential for false negatives 6, 4.

Key Findings

• A study found that out of 441 patients referred with suspected acute cauda equina syndrome, only 16 (4.7%) had positive MRI scans for cauda equina compression, necessitating prompt decompressive surgery 2.
• The introduction of an orthopedic doctor in the emergency department was found to reduce waiting times for MRI scans and inpatient stays for patients with suspected cauda equina syndrome 6.
• CT percentage thecal sac effacement of <50% appears to reliably rule out cauda equina impingement, potentially serving as an additional tool for deciding whether MRI imaging can be deferred 5.