Does This Patient Have Cauda Equina?

Written by Rachel Jennings

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This retrospective review demonstrated that bilateral lower extremity pain, sensory loss in a dermatomal distribution, and loss of bilateral ankle or knee reflexes were the best correlates to a radiographic diagnosis of CEC (cauda equina compression). Also, rectal exam had little to no diagnostic utility.

Why does this matter
Atraumatic back pain is an incredibly common complaint in the ED, and it is our job as ED providers to rule out the big emergencies – with cauda equina syndrome (CES) being at the top of the list. Diagnosis is time critical, but unfortunately requires significant resources (boarding time, transport, MRI techs, radiologists). Accurate and timely diagnosis of CES is challenging, as classic symptoms are often not strong predictors, and data is limited on the prognostic accuracy of individual clinical features. This study provides guidance on which symptoms and clinical findings should carry more weight when deciding what to include in your work up.

But doc…is that…necessary?

Design: This was a 4-year retrospective review within a single tertiary referral center in the UK.  Self-reported symptoms along with objective physical exam findings were collected prospectively by treating clinicians within a structured clinical proforma. Inclusion criteria were limited to patients presenting with atraumatic back pain suspected to have CEC who subsequently underwent MRI imaging to establish a “definitive” diagnosis.

Results: Of the 996 patients that met inclusion criteria, 111 (11.1%) had CEC on MRI. Authors used univariate logistic regression to identify which individual factors were associated with radiographic CEC, then subsequently performed a multivariate analysis to determine relative significance of each factor. Data from the multivariate analysis suggested that the most frequent self-reported symptom suggestive of CEC was bilateral leg pain (OR 1.9) with the most frequent objective examination findings being dermatomal loss of sensation (OR 1.7) and absent bilateral ankle or ankle and knee jerks (OR 3.4). They did not demonstrate any benefit to digital rectal examination in identifying CES. It is important to note that when the various clinical findings were described for sensitivity and specificity, the individual performance of all history or exam elements was poor.

Limitations: This was a single-center, retrospective study. Selection bias was introduced, as not all patients who presented to the ED with atraumatic back pain got an MRI; thus, there was no data on these patients to determine clinical outcome. The study also used radiographic evidence of CES as a “gold standard,” as opposed to operative findings.

Implications:  While it is certainly interesting to know which symptoms correlate most often to CEC, it might be equally important to note that the evidence also demonstrated the relative lack of importance of each individual factor when it comes to specificity and sensitivity. Knowing this, we shouldn’t rely on the presence or absence of specific clinical symptoms to rule in or rule out CES. The evidence demonstrating the limited diagnostic utility of the digital rectal exam provides an opportunity for shared decision making prior to performing this invasive exam, and, if validated in the future, could possibly be completely avoided.

Source
Determination of potential risk characteristics for cauda equina compression in emergency department patients presenting with atraumatic back pain: a 4-year retrospective cohort analysis within a tertiary referral neurosciences centre. Emerg Med J. 2021 Oct 12;emermed-2020-210540. doi: 10.1136/emermed-2020-210540. Online ahead of print.

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