Symptoms of Cauda Equina Syndrome
Cauda equina syndrome presents with a constellation of symptoms including bilateral radiculopathy, new changes in bladder function (especially urinary retention with 90% sensitivity), saddle anesthesia, bowel dysfunction, and progressive lower extremity weakness. 1, 2
Early "Red Flag" Symptoms (Require Immediate Action)
These symptoms indicate incomplete cauda equina syndrome and represent the critical window for intervention before irreversible damage occurs:
- Bilateral radiculopathy - bilateral radicular pain and/or bilateral sensory disturbance or motor weakness in the legs 1, 2
- New changes in bladder function with preserved control - hesitancy, poor stream, urgency, or any new difficulty with micturition 1, 3
- Subjective and/or objective loss of perineal sensation - numbness in the saddle/perineal/genital region 1, 2, 3
- Progressive neurological deficits in the legs - worsening motor weakness over time 1, 3
- Low back pain with sciatica - pain in typical lumbar nerve root distribution 1, 2
Late "White Flag" Symptoms (Often Indicate Irreversible Damage)
These symptoms represent complete cauda equina syndrome with retention and signal that permanent neurological damage may have already occurred:
- Urinary retention or incontinence - especially painless retention, which is the most frequent finding with 90% sensitivity in established cases 1, 2, 3
- Complete perineal anesthesia - total loss of sensation in the saddle region 1, 3
- Fecal incontinence - loss of bowel control 1, 2
- Patulous anus - decreased or absent rectal tone 1
- Sexual dysfunction - loss of sexual function 2, 4
Critical Clinical Considerations
The gradual nature of symptom progression is a major diagnostic pitfall. Symptoms typically develop over weeks to months, which can lead to attribution to more benign causes and delayed diagnosis 1. No single symptom or sign has high positive predictive value in isolation, making early diagnosis challenging 1, 3.
Waiting for complete urinary retention before referral is the most common and dangerous pitfall, as retention is a late sign indicating that irreversible damage may have already occurred 1. Patients presenting with any combination of red flag symptoms require immediate emergency MRI and neurosurgical consultation, even without urinary retention 1, 2.
The probability of cauda equina syndrome is approximately 1 in 10,000 among patients with low back pain, but this low prevalence should not delay imaging when red flag symptoms are present 2, 3. Sensory testing is subjective and subtle perineal sensation impairment is easily missed, while anal tone assessment has low interobserver reliability, especially among inexperienced clinicians 1.
Atypical Presentations
Some patients may present with isolated bladder-bowel dysfunction without lower limb motor weakness, which often leads to late presentation to orthopedic surgeons and delayed surgical intervention 5. These atypical cases may initially present to urology or other specialties, further delaying appropriate diagnosis and treatment 5.