2d:I[856015,["/_next/static/immutable/chunks/1xzisbplk9czp.js","/_next/static/immutable/chunks/3j2i1faptc_-9.js","/_next/static/immutable/chunks/0fma7nlq6immz.js","/_next/static/immutable/chunks/08tq8rmv423j5.js","/_next/static/immutable/chunks/1chr5wkk3j58k.js","/_next/static/immutable/chunks/37kmmh_zm4dov.js","/_next/static/immutable/chunks/311zvdjfxff-f.js","/_next/static/immutable/chunks/1a_hqhrsle_n_.js"],"default"] 2e:T56b1,

Summary Table

Category	Detail
Risk Factors	Adults aged 30 to 50, history of lumbar disc disease, prior lumbar surgery, spinal stenosis, spinal tumors, epidural abscess, trauma
Etiology	Compression of the cauda equina nerve roots below the conus medullaris (L1-L2 level); most commonly from a large central lumbar disc herniation at L4-L5 or L5-S1
Patient Presentation	Acute or progressive low back pain radiating bilaterally to the lower extremities, new onset urinary retention or incontinence, fecal incontinence, sexual dysfunction
Classic Physical Exam	Saddle anesthesia (perineal and perianal numbness), decreased anal sphincter tone on digital rectal exam, bilateral lower extremity weakness or hyporeflexia, absent ankle jerks, positive straight leg raise bilaterally
Key Diagnostic Results	MRI of the lumbar spine showing compression of the cauda equina nerve roots; post-void residual (PVR) volume > 200 mL on bladder scan
Management	Emergency surgical decompression (laminectomy) ideally within 24 to 48 hours; IV dexamethasone if concern for tumor or edema; urgent neurosurgical or orthopedic spine consultation
Keywords	"Saddle anesthesia," "urinary retention," "bilateral leg weakness," "decreased rectal tone," "back pain with bladder dysfunction," "surgical emergency"

1. Pathophysiology

The cauda equina is a bundle of lumbar and sacral nerve roots (L2 through S5) that descends below the termination of the spinal cord at the conus medullaris, which ends approximately at the L1-L2 vertebral level in adults. These nerve roots travel within the lumbar cistern, surrounded by cerebrospinal fluid, before exiting through their respective neural foramina. Because these are peripheral nerve roots and not spinal cord, injury to the cauda equina produces lower motor neuron (LMN) signs rather than upper motor neuron findings.

The most common mechanism is a large central disc herniation, typically at the L4-L5 or L5-S1 level, which compresses multiple nerve roots simultaneously. Other causes include spinal tumors (metastases, ependymomas, schwannomas), epidural abscess, epidural hematoma (particularly in patients on anticoagulation), spinal stenosis, and traumatic fractures. The key concept is that the compression must be central and large enough to affect multiple bilateral nerve roots rather than a single unilateral root.

The sacral nerve roots (S2-S4) carry parasympathetic innervation to the bladder detrusor muscle and the internal anal sphincter, as well as sensory fibers to the perineum. This is why compression of these roots produces the hallmark triad: bladder dysfunction (detrusor areflexia leading to painless urinary retention with overflow incontinence), bowel dysfunction (loss of anal sphincter tone and fecal incontinence), and saddle anesthesia (loss of sensation in the perineal, perianal, and inner thigh regions that would contact a saddle). Students should understand that bladder dysfunction in cauda equina syndrome is retention first, then overflow, not the urgency and frequency pattern seen in upper motor neuron lesions.

The bilateral lower extremity weakness and hyporeflexia result from compression of the L3-S1 motor roots. Because these are LMN lesions, expect flaccid weakness, hyporeflexia or areflexia, and muscle atrophy over time, not the spasticity and hyperreflexia of spinal cord compression.

2. Classification and Clinical Manifestation

Classification	Bladder Status	Clinical Features	Urgency
CES-Incomplete (CES-I)	Subjective urinary difficulty (hesitancy, poor stream, altered sensation) but voluntary voiding preserved	Saddle anesthesia (partial or complete), bilateral radiculopathy, reduced perineal sensation, possible decreased rectal tone	Emergent: surgery within 24 hours recommended
CES-Retention (CES-R)	Painless urinary retention with overflow incontinence; PVR > 200 mL; loss of voluntary bladder control	Full saddle anesthesia, bilateral lower extremity weakness, absent anal tone, fecal incontinence, sexual dysfunction	Emergent: surgery as soon as possible, but prognosis for bladder recovery is significantly worse

The progression from CES-Incomplete to CES-Retention can occur over hours to days. Any patient presenting with bilateral sciatica and even subtle perineal symptoms must be evaluated urgently, because neurological outcomes are markedly better when surgery is performed before retention develops.

Clinical Feature	Nerve Roots Involved	Manifestation
Saddle anesthesia	S2-S5	Numbness in perineum, perianal area, posterior thighs, and genitalia
Urinary retention	S2-S4 (parasympathetic)	Painless retention, overflow incontinence, loss of bladder sensation
Fecal incontinence	S2-S4	Loss of external and internal anal sphincter tone
Sexual dysfunction	S2-S4	Erectile dysfunction, loss of genital sensation
Bilateral leg weakness	L2-S1 (variable)	Flaccid weakness in multiple myotomes, foot drop if L4-L5 involved
Bilateral radiculopathy	L4-S1 (most common)	Pain radiating down both legs, bilateral positive straight leg raise
Low back pain	Variable	Severe midline low back pain, often the initial symptom

3. Diagnostic Workup

Test	Role	Key Findings
MRI lumbar spine without contrast	Best initial and most accurate test	Central disc herniation or mass compressing the cauda equina nerve roots
MRI lumbar spine with gadolinium	When tumor, abscess, or infection is suspected	Enhancing lesion, rim-enhancing abscess, leptomeningeal disease
Bladder scan / post-void residual	Bedside screening for urinary retention	PVR > 200 mL suggests neurogenic bladder
Digital rectal exam	Bedside assessment	Decreased or absent anal sphincter tone
CT myelography	Alternative when MRI is contraindicated	Filling defect or block in the thecal sac
Plain radiographs of the lumbar spine	Limited utility	May show fracture, spondylolisthesis, or destructive lesion; cannot visualize soft tissue compression
Electromyography (EMG) / Nerve conduction studies	Subacute or chronic evaluation	Denervation pattern in lower extremity muscles; not used in acute setting

MRI of the lumbar spine is both the best initial test and the gold standard for diagnosing cauda equina syndrome. It directly visualizes the compressive lesion, shows the degree of neural element compression, and helps guide surgical planning. T2-weighted sequences are particularly valuable because cerebrospinal fluid appears bright, making it easy to see where the thecal sac is compressed and the nerve roots are displaced.

Before or alongside imaging, a bladder scan measuring post-void residual volume should be performed at the bedside. A PVR greater than 200 mL in a patient with bilateral lower extremity symptoms and saddle anesthesia is highly suggestive of cauda equina syndrome and raises the urgency for imaging. The digital rectal exam assessing anal sphincter tone is another essential bedside test; decreased tone indicates involvement of the S2-S4 nerve roots.

If MRI is contraindicated (e.g., certain implanted devices), CT myelography is the next best alternative. It involves injecting contrast into the thecal sac and performing a CT scan, which can demonstrate a block or filling defect at the level of compression. Plain radiographs have limited value and should never be used to rule out cauda equina syndrome, as they cannot visualize disc herniations or soft tissue compression.

The workup should proceed rapidly. A common testing scenario presents a patient with bilateral sciatica and new bladder symptoms, then asks for the next best step. The answer is emergent MRI of the lumbar spine, not conservative management, not plain films, and not outpatient follow-up.

4. Management and Treatment

Phase	Intervention	Details
Immediate stabilization	Foley catheter insertion	Decompress the distended bladder; monitor urine output
Immediate stabilization	IV dexamethasone	Consider 10 mg IV bolus if concern for tumor-related compression or significant edema; role in disc herniation is less established
Definitive treatment	Surgical decompression (laminectomy with discectomy)	Ideally within 24 to 48 hours of symptom onset; earlier surgery correlates with better neurological recovery
Postoperative care	Bladder rehabilitation	Intermittent catheterization if retention persists; urodynamic studies at follow-up
Postoperative care	Physical therapy	Lower extremity strengthening, gait training, bowel and bladder retraining
If infection (epidural abscess)	IV antibiotics + surgical drainage	Empiric coverage with vancomycin plus a third-generation cephalosporin (e.g., ceftriaxone); tailor based on culture results; duration typically 4 to 8 weeks
If tumor	Surgery, radiation, or both	Based on tumor type, extent, and patient goals; corticosteroids (dexamethasone 10 mg IV then 4 mg every 6 hours) for vasogenic edema

Acute stabilization begins with securing the airway, breathing, and circulation as with any emergency, followed by insertion of a Foley catheter if the patient is in urinary retention. Pain control is important but should not delay the workup.

Emergency surgical decompression is the definitive treatment and the single most important management step. For disc herniation, this typically involves a posterior lumbar laminectomy and discectomy at the level of compression. The timing of surgery is heavily tested: outcomes for bladder and bowel function are significantly better when decompression is performed within 48 hours of symptom onset, and many guidelines advocate for surgery within 24 hours when feasible. Patients who progress to complete CES-Retention before surgery have a substantially lower chance of recovering bladder function.

Corticosteroids (typically dexamethasone) are used primarily when the compression is caused by a tumor or when there is concern for significant inflammatory edema around the nerve roots. For straightforward disc herniations, the evidence for steroids is less robust, though many clinicians still use a short course. The standard dosing for tumor-related cord or cauda equina compression is dexamethasone 10 mg IV initially, followed by 4 mg IV or orally every 6 hours, with a taper over 1 to 2 weeks.

Postoperative management includes continued bladder monitoring. Many patients will require intermittent catheterization for days to weeks after surgery. Urodynamic testing may be needed at follow-up to assess bladder recovery. Physical therapy focuses on restoring lower extremity strength and function. Bowel retraining programs may be necessary for patients with persistent fecal incontinence.

Contraindications and considerations: In patients with epidural abscess, surgery should not be delayed for prolonged antibiotic courses alone, as the mechanical compression requires surgical drainage. In patients who are poor surgical candidates, a frank discussion about prognosis is necessary, as nonoperative management carries a high risk of permanent neurological deficit.

5. Differential Diagnosis and Distractors

Differential	Why It Looks Similar	Key Discriminator
Conus medullaris syndrome	Also causes bladder and bowel dysfunction, saddle anesthesia, and lower extremity symptoms	Conus lesions occur at the T12-L2 level and produce a mix of upper and lower motor neuron signs (e.g., hyperreflexia at the knees with areflexia at the ankles, and a positive Babinski sign); onset is often sudden and symmetric; cauda equina syndrome is pure LMN with asymmetric onset
Lumbar disc herniation (without cauda equina syndrome)	Back pain with radiculopathy, positive straight leg raise, lower extremity weakness	Typical disc herniation is unilateral, involves a single nerve root, and does not cause bladder dysfunction, saddle anesthesia, or bilateral symptoms
Spinal cord compression (myelopathy)	Weakness and sensory changes in the lower extremities, possible bladder dysfunction	Produces upper motor neuron signs: spasticity, hyperreflexia, clonus, upgoing Babinski; a clear sensory level on the trunk; occurs above the conus medullaris level
Guillain-Barre syndrome	Bilateral ascending weakness, areflexia, possible autonomic dysfunction	Weakness is ascending and symmetric, starts distally and moves proximally; no back pain; no saddle anesthesia; CSF shows albuminocytologic dissociation (elevated protein with normal cell count)
Peripheral neuropathy (diabetic or other)	Bilateral lower extremity numbness and weakness, decreased reflexes	Follows a stocking-glove distribution, not saddle pattern; gradual onset over months to years; no acute back pain; no bowel or bladder dysfunction
Urinary retention from other causes (anticholinergic medications, BPH)	Urinary retention with overflow incontinence	No neurological deficits: normal sensation, normal rectal tone, no lower extremity weakness; history of medication use or known prostatic enlargement

The highest-yield differential on exams is conus medullaris syndrome versus cauda equina syndrome, as both present with bladder dysfunction and saddle anesthesia. The key distinction lies in the motor neuron pattern: conus produces mixed UMN/LMN findings, while cauda equina is purely LMN.

6. Traps and High-Yield Pearls

The most common way students lose points on cauda equina syndrome questions is by failing to recognize it as a surgical emergency. Test writers frequently construct vignettes where a patient presents with back pain and unilateral leg weakness, and students select conservative management (NSAIDs, physical therapy, outpatient follow-up). However, the vignette includes one or two subtle details that should trigger alarm: the patient mentions difficulty urinating, numbness "down there," or the exam reveals decreased rectal tone. These findings transform a routine back pain case into a neurosurgical emergency, and the next best step becomes emergent MRI, not a trial of conservative therapy.

Another common trap is confusing cauda equina syndrome with conus medullaris syndrome. Vignettes that describe hyperreflexia, an extensor plantar response (Babinski sign), or a sensory level on the trunk point toward conus or spinal cord pathology, not cauda equina. Students who do not pay attention to the motor neuron pattern will select the wrong localization.

A third trap involves the timing of surgery. Some questions will present a patient who already has complete urinary retention and ask about prognosis. The tested concept is that CES-Retention carries a worse prognosis for bladder recovery than CES-Incomplete, reinforcing why early recognition and intervention matter.

The core competency being tested across all cauda equina syndrome questions is pattern recognition of a surgical emergency disguised as routine back pain, followed by the ability to select the correct next step (emergent MRI) and definitive treatment (surgical decompression) without delay.

1e:["$","$L2d",null,{"article":{"id":"57750c43-e220-4ab5-9363-6ed7fd7c6699","title":"Sindrom Kauda Equina","content":"$2e","category":"Neurologi","created_at":"2026-07-29T07:27:37.543414+00:00","status":"published","subcategory":null},"questionCount":1,"sections":[{"id":"section-pathophysiology","num":"01","title":"Pathophysiology"},{"id":"section-classification-and-clinical-manifestation","num":"02","title":"Classification and Clinical Manifestation"},{"id":"section-diagnostic-workup","num":"03","title":"Diagnostic Workup"},{"id":"section-management-and-treatment","num":"04","title":"Management and Treatment"},{"id":"section-differential-diagnosis-and-distractors","num":"05","title":"Differential Diagnosis and Distractors"},{"id":"section-traps-and-high-yield-pearls","num":"06","title":"Traps and High-Yield Pearls"}],"hasSummaryTable":true}]