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Cauda Equina Syndrome – Spoon-Feed Version

October 6, 2023

Written by Jason Lesnick

Spoon Feed
Cauda equina syndrome (CES) is a spinal emergency. This is a practical guide for diagnosis and management as well as review of recent literature published on the topic.

Oh no – the horse’s tail is under pressure!
The authors reference a study that estimates 1 in 300 patients who present to the ED with low back pain have CES. CES refers to the grouping of symptoms that occur when multiple lumbosacral nerve roots are compressed within the vertebral canal. We’ve covered CES before, but we’re due for a refresher.

Symptoms may include saddle sensory changes (on wiping, urinating, or defecating), urinary frequency, incontinence, or retention, bowel incontinence, bilateral lower limb weakness and bilateral radicular leg pain. 

Physical exam should include testing sensation in all lumbar and sacral dermatomes, power in the lower limb myotomes, and lower limb reflexes. Red flags would be lower limb weakness, sensory changes in the perianal area (S2-4), and decreased reflexes (L4 knee, S1 ankle jerk). If upper motor neurologic findings are present such as clonus, hyperreflexia, increased tone – look above the cauda equina (i.e. the cord) for a cause of symptoms. The authors state, “the evidence does not support a need for DRE during the initial assessment or its use in determining whether a patient should undergo MRI scanning.” They note a recent meta-analysis reported low sensitivity for reduced anal tone (23–53%), anal squeeze (29%), and anal canal sensation (40%). Bladder scanning can be used to rule in CES but should not be used to rule it out, as up to 80% of patients with confirmed CES have a post-void residual of < 200 mL, according to three recent publications. 

No single component of history, exam, nor combination of findings is sufficient to exclude CES. Patients with symptoms or exam findings suspicious for the disease should undergo emergent MRI. Limited sequence scans (e.g. T2 sagittal +/- axial sequences) reduce scan time while, according to two published case series, maintaining 100% sensitivity (95%CI 78-100%). CT is not an acceptable alternative, unless MRI is contraindicated, in which case plain CT and CT myelography have been used.

Time is of the essence, as – theoretically – surgical decompression can decrease and halt paralysis, bladder/bowel dysfunction, and sexual dysfunction. Some studies suggest decompression within 48 hours is associated with better outcomes, but this is not consistently observed. Important clinical pitfalls and mimics to consider include cervicothoracic compression, discitis, malignancy, and acute aortic syndromes.

How will this change my practice?
I will continue to have a low threshold for ordering MRIs in patients whom I am concerned may have acute spinal cord compression or CES. The value of a systematic solution to diagnosing this disease centers around emergent access to rapid MRI, and I hope we soon will come up with something similar to what the UK has created – a National Suspected Cauda Equina Syndrome Pathway

Diagnosis of cauda equina syndrome in the emergency department. Emerg Med J. 2023 Sep 5;emermed-2023-213151. doi: 10.1136/emermed-2023-213151. Online ahead of print.

What are your thoughts?