Causes of Cauda Equina Syndrome
The most common cause of cauda equina syndrome is lumbar disc herniation at the L4-L5 and L5-S1 levels, accounting for approximately 45% of all cases, with other important etiologies including neoplasm, infection/inflammation, spinal stenosis, and hemorrhage 1.
Primary Etiologic Categories
Compressive Causes (Most Common)
Lumbar disc herniation is the predominant cause, typically presenting as massive midline disc protrusion at the lower lumbar levels 2, 3, 4. This represents nearly half of all CES cases and is the most critical etiology to identify given its surgical urgency.
Neoplastic disease represents a significant proportion of cases and includes:
- Primary spinal tumors affecting the cauda equina region 5
- Metastatic lesions from distant primary malignancies, particularly lung cancer 6
- Leptomeningeal metastases from solid tumors, though rare 6
Spinal stenosis causes gradual compression of the cauda equina nerve roots, typically in older patients with degenerative changes 1, 3.
Infection and inflammation including:
- Epidural abscess
- Discitis osteomyelitis
- Spinal arachnoiditis 3
Hemorrhage into the spinal canal can cause acute compression 1, 3.
Trauma including vertebral fractures with bony fragment displacement into the epidural space 3.
Non-Compressive Causes (Less Common)
Vascular etiologies including ischemic insults to the cauda equina nerve roots 7, 3.
Inflammatory conditions affecting the lumbosacral nerve roots without mechanical compression 7, 3.
Clinical Context
The prevalence of CES in primary care patients with low back pain is extremely low at approximately 0.04% 2. However, when present, it represents a true neurological emergency requiring urgent recognition and intervention to prevent permanent bladder, bowel, and sexual dysfunction 8.
Critical pitfall: The diverse etiologies mean that while disc herniation should be the primary consideration in acute presentations, clinicians must maintain suspicion for neoplastic, infectious, or vascular causes, particularly when the clinical picture is atypical or when contrast-enhanced MRI shows findings inconsistent with simple disc herniation 1.
The distinction between compressive and non-compressive etiologies is essential because it fundamentally changes management—compressive causes typically require urgent surgical decompression, while non-compressive causes may require medical management targeting the underlying pathology 7, 9.