Introduction
In primary care, cauda equina syndrome (CES) is rare but GPs are often the front line for the recognition of possible CES. Since 2020, national guidance for GPs has stated that symptoms of CES are sufficient to mandate emergency referral for imaging even in the absence of objective signs of CES (such as altered perianal sensation [PAS] or anal tone [AT]). Indeed, rectal (PR) examination to determine altered PAS and AT is not recommended in primary care. This article reviews the recent national guidelines and offers a perspective for the management of patients with possible CES in primary care.
Prevalence
The commonest cause of CES is a large central disc prolapse that compresses the cauda equina nerve roots. A significant central disc prolapse is present in about 2%–3% of all lumbar disc prolapses (PLIDs). CES occurs in about 0.12% of PLIDs. The incidence of CES in previously asymptomatic community populations is 0.5–0.6 per 100 000 patient years. In working adults it is 7/100 000 patient years. Of all patients with low back pain, 0.3% will have CES. In clinically suspected CES, 19% have clinical and radiological confirmation of CES.1 Although the commonest cause of CES is an acute disc prolapse, CES can be caused by lumbar spinal stenosis (LSS), which is common in general practice, and with an ageing population the prevalence of LSS is increasing. In primary care, clinical evidence of LSS, typically neurogenic claudication, is found in 11%–39% of all patients with suspected CES.2 Radiological diagnosis of LSS varies between 11% and 38%;2 45%–60% of patients aged ≥65 years have magnetic resonance imaging (MRI) evidence of LSS.2 The reality is that GPs see patients with low back pain and sciatica every day. On average they might see a presentation of CES once in their career. Identifying the rare presentation of CES is a challenge for GPs.
Clinical diagnosis
CES is a syndrome of symptoms and signs. There is no universally agreed definition of CES. Symptoms and/or signs range from modest cauda equina irritation through to catastrophic neurological and visceral injury. In cases of acute CES caused by a disc prolapse, the following symptoms are found:3 back pain, often severe (96%); sciatica (93%), more often unilateral (54%) than bilateral (46%); urinary retention (41%); other bladder symptoms including incontinence (40%), altered sensation (22%), poor stream (37%), and urinary urgency or frequency (9%); and bowel dysfunction (39%). On examination, saddle anaesthesia (complete loss of saddle sensation) was uncommon; there was reduced saddle sensation (67%) of cases (bilaterally in 63%, unilaterally in 37%). Similar symptoms and signs are found in patients with LSS but symptoms are often chronic. Urinary incontinence is present in 14% of men and 48% of women over the age of 70 years.
GPs must ask all patients with low back pain and sciatica if they have new urinary problems and/or new altered saddle area sensation. It is essential to record such questioning. In most patients CES can be quickly excluded. In GP medicolegal practice the most common problem is no record of questioning about the symptoms of CES. Unfortunately, some GPs think they can exclude CES if the patient can pass urine and is not incontinent. This is incorrect. GP examination findings of normal saddle sensation and AT, both very difficult assessments to make, do not exclude CES.
Change in UK national guidelines
Since 2020, three national guidelines4–6 state that 1) symptoms of CES in the absence of objective signs mandate an urgent MRI; 2) rectal examination is not necessary in primary care so the assessment of PAS and AT is not required to diagnose CES clinically — an urgent same-day MRI should be requested on the basis of symptoms alone; and 3) a history to elicit early symptoms of CES is required.
Red flags
Definitive guidance can be straightforward in young patients with an acute presentation. There is considerably more diversity in the presentation of CES in older patients where chronic low back pain and bladder problems are common.
Acute presentation
Many, typically young, patients present acutely with symptoms present for hours, days, or weeks. Under the revised national guidance,4–6 in the context of a patient with low back pain and/or sciatica, any new symptom of bladder dysfunction should now prompt an urgent same-day MRI regardless of objective signs. Symptoms include any change in the pattern of micturition, hesitancy, frequency, dribbling, incomplete emptying, loss of the sensation of passing urine, retention, or incontinence, or any subjective change in saddle sensation (genital and/or perianal sensation, including paraesthesia and/or numbness). The latest National Institute for Health and Care Excellence (NICE) guidance of 2025 emphasises ‘[d]ifficulty initiating micturition or impaired sensation of urinary flow’ as early symptoms. If those early symptoms are untreated this can lead to ‘irreversible urinary retention with overflow urinary incontinence’.
Chronic presentation
Chronic urinary problems and low back pain are common in general practice, particularly in older patients. Longstanding bladder problems do not require urgent referral even if there is back pain if there are no other symptoms of CES. It is an acute or recent change in bladder (and less commonly sexual) function in the context of, typically severe, back pain and/or sciatica that should be identified, prompting urgent referral. Although an acute disc prolapse is a more common cause of CES than LSS, LSS is common in general practice. In a patient with neurogenic claudication or known radiological evidence of LSS, new bladder dysfunction or altered saddle sensation should prompt urgent referral.7 Similar symptoms presenting chronically typically in an older patient require more careful thought. In LSS gradual progression of symptoms over several months or a stable picture probably warrants routine MRI.7 In patients with LSS the urgency of an MRI is determined by the duration, onset, or speed of change in possible CES symptoms.7
Referral from primary care
In a patient with low back pain, sciatica, or neurogenic claudication, it is essential to establish:
If the answer to either of these questions is ‘yes’ the patient must be referred for urgent same-day MRI scanning. Examination for PAS and AT cannot exclude CES, and these examinations do not need to be made in primary care.
It is essential to record what symptoms were asked about. Delayed diagnosis is a major cause of clinical negligence claims. GPs commonly record ‘no red flags’. The wise GP will now record that there was an enquiry into early symptoms of CES. If there is litigation in respect of an alleged delay in referral, GPs should be able to show that such an enquiry was made (and not just questions about symptoms of late CES such as urinary incontinence or saddle anaesthesia). Referral will usually be to orthopaedics or accident and emergency (A&E) depending on the local pathway of referral. In reality, hospital doctors do not always know that CES symptoms without signs mandate same-day MRI scanning and they might try to refuse referrals from GPs. If an orthopaedic registrar refuses to see the patient they must be sent to A&E.
Subsequent management
Following referral from primary care, a patient with suspected CES should have an MRI within 4 hrs.4–6 About 19% of the MRIs will be positive, demonstrating compression of the cauda equina nerve roots; the commonest pathology is a large central lumbar disc prolapse. Referral to a spinal service will follow; this could be an orthopaedic or neurosurgical spinal service depending on local arrangements. Surgery will follow, usually as an emergency. In the cohort study 90% of cases were operated on within 24 hrs of referral.3 In the more distant past some spinal surgeons would not operate in the absence of objective signs, but that is no longer good practice. In the cohort study (which was recruited in 2019) 27% had symptoms of CES with normal PAS on examination (symptom-only CES).3
Outcomes
Early diagnosis is associated with better outcomes. Surgery usually prevents further neurological deterioration. Delayed referral, diagnosis, and treatment often cause avoidable progressive neurological injury, which can be very rapid. If a patient with CES is treated when they have symptoms of CES without objective signs, most will have excellent outcomes, many with no long-term neurological deficits.
Box 1. Key guidelines for primary care
In a patient with back pain, sciatica, or neurogenic claudication, the GP should identify or exclude early cauda equina syndrome (CES) symptoms and refer if present. Recognition of CES in young patients with acute symptoms can be straightforward. In older patients with chronic symptoms diagnosis is more difficult and management more nuanced.
Is there any new bladder dysfunction? This includes urinary hesitancy, dribbling, incomplete emptying, and loss of sensation of bladder fullness or when passing urine. The GP should ask about urinary retention or incontinence but be aware these are late CES symptoms.
Is there any alteration in saddle area sensation? Any subjective change in saddle sensation, for example, when wiping, is relevant, including paraesthesia. Saddle anaesthesia is a late CES symptom.
Rectal examination for altered perianal sensation and anal tone is no longer required in primary care. It cannot exclude CES.
The GP should refer for same-day magnetic resonance imaging scanning any patient with CES symptoms, however mild and regardless of objective CES signs. It is impossible for a GP to exclude CES in these patients.
The GP should ask about all early CES symptoms in all patients with low back pain, sciatica, or neurogenic claudication and record doing so. Patients should be safety netted about the symptoms of CES and advised to seek emergency care if symptoms are present.
Lumbar spinal stenosis (LSS) is common in general practice and it can cause CES. If there are acute symptoms of CES in a patient with LSS, the GP should refer urgently. In LSS with chronic symptoms referral should reflect the nature, duration, and progression of possible CES symptoms.
Notes
Provenance
Freely submitted; externally peer reviewed.
Competing interests
The authors have declared no competing interests.
- Received February 24, 2025.
- Revision received April 1, 2025.
- Accepted May 22, 2025.
- © British Journal of General Practice 2025
References
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