What is your diagnosis?

Lumbar disc extrusion with clinical findings concerning for Cauda Equina Syndrome

• Pearl: Cauda equina syndrome occurs due to compression of the nerve roots, usually at the L4-5 region (less commonly L5-S1), and is most often due to acute disc herniation. However, cauda equina syndrome can occur with any space-occupying lesion in that region of the lumbosacral canal, such as epidural tumors, abscesses, or hematomas [2]. Patients typically present with low back pain, and often have associated lower extremity pain/weakness. Additionally, saddle anesthesia, bladder dysfunction, and other sensory changes can occur as well. 

• Pearl: Saddle anesthesia is a less common finding, and therefore not sensitive for cauda equina. However, it is more specific, and should prompt more emergent intervention if present [1]. 

What is the preferred imaging modality to make this diagnosis?

MRI lumbar spine

• Pearl: MRI lumbar spine is the preferred imaging modality for identification of suspected Cauda Equina Syndrome. IV contrast may be used in certain situations based on the clinical context (ie. if concerned about infectious or metastatic etiology) [4]. Most times, sagittal and axial T1/T2 sequences are sufficient for making the diagnosis [2].

• Pearl: If MRI is contraindicated or not available, the next best imaging modality is a CT myelogram (sagittal and axial reconstructions). This is, however, more invasive, and requires contrast to be injected directly into the spinal canal for image attainment [3]. 

 

Image 2: Case courtesy of Dr. Robert Jesinger, Medpix.nlm.nih.gov

Image 2 above shows an axial CT myelogram at the level of L4-5, with evidence of disc protrusion and subsequent mass effect on the L5 nerve roots, as well as some associated central canal stenosis. When performing a myelogram, the diagnosis may be confirmed with partial or complete obstruction of contrast, which may take on an hour-glass appearance as shown in the radiograph below (Image 3). 

Image 3. Case courtesy of Dr. Robert Jesinger, Medpix.nlm.nih.gov

What is your initial management in the ED? Do I need to consult Orthopaedics?

Yes! Management is with surgical consultation (orthopaedics vs neurosurgery), due to likely need for emergent surgical decompression. Bladder decompression in the interim may be needed. 

• Pearl: Surgery should ideally be performed within 24 hours of symptoms with abrupt onset, and definitely within 48 hours to have the highest likelihood of avoiding permanent dysfunction [1]. 

• Pearl: Steroids, such as dexamethasone, can be considered in certain clinical contexts (such as metastatic compression). However, this should be used judiciously, as it can worsen the clinical picture in some situations, such as an epidural abscess. 

What alternative diagnosis can present similarly to this, and how do you differentiate them?

Conus Medullaris Syndrome, which is often due to compression at the L2 vertebral level. 

• Pearl: The main differentiation is that conus medullaris syndrome can have a combination of upper and lower motor nerve findings, whereas cauda equina syndrome is typically only lower motor neuron dysfunction. Saddle anesthesia, bowel/bladder dysfunction, and extremity sensory changes can all occur with both syndromes [5].

• Pearl: Differentiating the two syndromes can be subtle, and is often not clinically relevant for an emergency department provider, as both require urgent surgical consultation for initial management.