Etiology

In an adult, the spinal cord terminates in a tapering fashion as the conus medullaris (T12-S4) at the L1-L2 vertebral level. The collection of spinal nerves below this point (eg, L3-S4) exit inferiorly through their respective intervertebral foramina and are referred to as the cauda equina (ie, horse’s tail).
It constitutes a surgical emergency as delayed treatment can lead to irreversible neurological damage, including paralysis and incontinence.
Most common cause: Massive central lumbar disc herniation, typically at L4/L5 or L5/S1.
Other causes: Spinal stenosis, tumors (metastatic or primary), trauma/fractures, spinal epidural abscess, or epidural hematoma.

Functions

“Red Flag” Symptoms: This constellation of symptoms is critical to recognize.
- Saddle Anesthesia: Numbness in the perineum, buttocks, and inner thighs (S3-S5 dermatomes) is a classic and significant finding. A common history question is asking if it feels normal when wiping after a bowel movement.
- Bowel/Bladder Dysfunction: This is a hallmark of CES. It typically begins with urinary retention (difficulty starting a stream, loss of sensation of fullness) and can progress to overflow incontinence. Fecal incontinence and loss of anal sphincter tone are also key features.
- Bilateral Sciatica: Severe, progressive, bilateral leg pain, numbness, and weakness.
- Lower Extremity Weakness: Presents as asymmetric, areflexic paraplegia (LMN signs).
Physical Exam:
- LMN Signs: Hyporeflexia/areflexia (e.g., decreased or absent patellar and Achilles reflexes), decreased muscle tone, and potential muscle atrophy.
- Sensory Deficit: Check for perianal and “saddle” distribution numbness.
- Rectal Exam: Decreased or absent rectal tone is a critical finding.

Clinical Suspicion: Diagnosis is suspected based on the characteristic history and physical exam findings. There should be a low threshold for investigation.
Imaging: Urgent MRI is the gold standard and is required to confirm the diagnosis and identify the cause of compression.
CT Myelogram can be used if MRI is contraindicated or unavailable.

Surgical Emergency: Immediate hospital admission and neurosurgical consultation are required.
Treatment: Urgent surgical decompression (e.g., laminectomy) is the definitive treatment to relieve pressure on the nerve roots.
Timing: Surgery is ideally performed as soon as possible, with better outcomes generally seen if done within 24-48 hours of symptom onset.
Adjunctive Tx: High-dose corticosteroids may be used to reduce inflammation and swelling.

Prognosis: Even with prompt surgery, recovery is variable. Permanent deficits can include urinary/bowel incontinence, sexual dysfunction, chronic pain, and leg weakness.
CES-I vs. CES-R:
- CES-I (Incomplete): Patient has altered urinary sensation but no established urinary retention. This has a better prognosis if operated on urgently.
- CES-R (Retention): Patient has painless urinary retention and overflow incontinence. Prognosis is significantly worse.