Cauda equina syndrome: symptoms and treatment

Cauda equina syndrome is an acute or subacute compression of the lumbosacral nerve root bundle in the distal spinal canal, characterized by low back pain radiating to the legs, perineal sensory disturbances, bladder and bowel dysfunction, and sexual dysfunction. This condition is considered a neurosurgical emergency, as delayed diagnosis and decompression increases the risk of permanent neurological loss. [1]

Classic "red flags" include swelling or numbness in the saddle area, progressive leg weakness, loss of urinary control or urinary retention, fecal incontinence, and severe bilateral sciatica. If these signs are present, immediate magnetic resonance imaging of the lumbar spine and consultation with a neurosurgeon are recommended. [2]

Despite its relative rarity, cauda equina syndrome is one of the most legally significant causes of back pain complaints, due to the severity of consequences when delayed. Early recognition of symptoms in primary care and emergency departments plays a key role in preventing disabling outcomes. [3]

Timely surgical decompression, preferably within the first 24–48 hours of the onset of significant pelvic symptoms, is associated with better hospital outcomes and a higher chance of functional recovery, although the details of the optimal “hourly window” remain debated. Therefore, healthcare organizations are implementing expedited diagnostic pathways and 24-hour availability of magnetic resonance imaging. [4]

Code according to ICD-10 and ICD-11

In the International Classification of Diseases, Tenth Revision, cauda equina syndrome is coded under the heading G83.4 "Cauda equina syndrome." This code is used for medical documentation, statistics, and routing of patients with distal spinal radicular syndromes, including neurogenic bladder dysfunction secondary to cauda equina disease. [5]

The International Classification of Diseases, Eleventh Revision, includes the category 8B40 "Cauda equina syndrome" for cauda equina syndrome, located in the "Diseases of the spinal cord, excluding injuries" section. The clarifying codes in the Eleventh Revision help describe clinical features and associated conditions, which is important for research and reporting quality. [6]

Table 1. Classification codes for cauda equina syndrome

Classifier	Code	Description
International Classification of Diseases, 10th revision	G83.4	Cauda equina syndrome
International Classification of Diseases, 11th revision	8B40	Cauda equina syndrome
[7]

Epidemiology

Cauda equina syndrome is rare in the general population. Estimates of annual incidence range from less than 1 case per 100,000 individuals in "asymptomatic" populations to approximately 7 cases per 100,000 in specific age- and sex-specific cohorts of the working-age population. This variability is due to differences in study design and diagnostic criteria. [8]

Among patients seeking medical attention for low back pain, cauda equina syndrome accounts for a fraction of one percent. According to aggregate estimates, its share among secondary care visits does not exceed 0.27%, highlighting the rarity of the diagnosis and the need for high suspicion in the presence of "red flags." [9]

The peak age of onset is between 30 and 49 years, with women being affected somewhat more frequently, partly due to the structure of the underlying causes, including large median disc herniations and stenosis. However, the syndrome can occur in all age groups, particularly with infections, tumors, and epidural hematomas. [10]

The high proportion of persistent pelvic organ dysfunction with late decompression makes cauda equina syndrome an important medical and social problem requiring optimization of logistics of access to emergency magnetic resonance imaging and neurosurgical care. [11]

Table 2. Epidemiological landmarks

Indicator	Grade
Annual incidence in the general population	Less than 1 in 100,000 in some population samples
Share of visits for low back pain	About 0.27% in the secondary level
Age peak	30-49 years old
Gender characteristics	Somewhat more often in women, according to data from individual registries
[12]

Reasons

The most common cause of cauda equina syndrome is a large central lumbar disc herniation compressing multiple nerve roots simultaneously. This typically develops against a background of pre-existing disc degeneration and severe spinal stenosis. [13]

Other significant causes include spinal stenosis due to degenerative changes, epidural abscess in the lumbosacral region, epidural hematoma following trauma or anticoagulant therapy, as well as tumors and metastatic lesions. These options require etiotropic tactics along with decompression. [14]

Cauda equina syndrome can occur following spinal procedures or neuraxial anesthesia. In such situations, rapid recognition and immediate neuroimaging confirmation with referral to a neurosurgeon are critical. [15]

Rare causes include spontaneous epidural hematomas, vascular malformations, and inflammatory processes. Although these conditions are observed infrequently, they are included in the differential diagnosis in cases of closed clinical presentation of pelvic disorders. [16]

Risk factors

Risk factors include severe lumbar stenosis, recurrent episodes of severe sciatica, large midline disc herniations, and conditions that increase the risk of infection and bleeding, including diabetes, immunodeficiency, and anticoagulant therapy. The presence of such factors increases the likelihood of rapid symptom progression. [17]

Invasive spinal procedures and epidural injections increase the risk of epidural hematoma or abscess under certain circumstances. Postoperatively, caution should be maintained for the development of pelvic disorders. [18]

Infectious causes are more common in patients with intravenous drug use, sepsis, chronic wound infections, and long-term catheterization. These conditions create a "portal" for bacteremia and subsequent epidural abscess formation. [19]

The use of anticoagulants increases the risk of spontaneous epidural hematoma, which, when localized in the lumbosacral region, can lead to compression of the cauda equina roots and acute neurological symptoms. [20]

Pathogenesis

The mechanism of the syndrome includes mechanical compression of multiple roots of the lower lumbosacral nerves, ischemia due to increased pressure in the epidural space, and a secondary inflammatory response. These factors combine to disrupt the conduction of impulses along sensory and motor fibers and parasympathetic innervation of the pelvic organs. [21]

In disc herniation, mechanical compression and chemical irritation of the nerve roots by mediators of the nucleus pulposus are combined, which explains the severe pain, paresthesia, and progressive pelvic dysfunction. Unlike lesions of the spinal conus, signs of peripheral nervous system damage predominate. [22]

An epidural abscess causes compression due to the volumetric process and edema, and also triggers a systemic inflammatory response. Without timely decompression and antibacterial therapy, irreversible changes in the nerve roots quickly develop. [23]

An epidural hematoma causes a sudden increase in pressure in the spinal canal. Timing is critical: the shorter the interval before decompression, the higher the likelihood of restoration of bladder function and perineal sensation. [24]

Symptoms

Typical complaints include severe low back pain radiating bilaterally to the legs, paresthesia and numbness in the dermatomes, weakness in the feet and legs, and sensory disturbances in the saddle area. Urinary disturbances are often associated, including retention, difficulty initiating a urinary stream, and overflow incontinence. [25]

Symptoms often develop in stages: first, sciatica and paresthesia intensify, then there is decreased sensitivity in the perineum, followed by pelvic disorders. This scenario requires immediate magnetic resonance imaging. [26]

It is important to remember that individual elements of the "classic triad" may be absent. For example, not all patients have pronounced bilateral sciatica or obvious leg weakness, but the presence of pelvic symptoms and "saddle" hypoesthesia should prompt urgent neuroimaging. [27]

The reliability of digital rectal examination for assessing sphincter tone is limited: sensitivity is low, results vary among examiners, and they do not allow for the exclusion of the syndrome with a normal finding. Therefore, a negative result should not delay magnetic resonance imaging if clinical suspicion exists. [28]

Table 3. Red flags of cauda equina syndrome

Sign	Clinical significance
Numbness or hypoesthesia in the saddle area	Sacral root lesion
Urinary incontinence or urinary retention	High risk of irreversible loss of function
Fecal incontinence, decreased anal tone	Severe damage to the pelvic segments
Bilateral sciatica and weakness in the legs	Compression of multiple roots
[29]

Classification, forms and stages

The practical and prognostic classification divides the syndrome into an incomplete form and a form with urinary retention. The incomplete form is characterized by altered perineal sensitivity and impaired urination, such as difficulty starting and weakening of the stream while maintaining control. The form with retention includes painless urinary retention and bladder overflow. [30]

Some guidelines also distinguish a complete form, in which anal tone, perineal sensation, and any pelvic control are absent. This category is associated with worse long-term outcomes, even with rapid decompression. [31]

Clinical stratification helps determine the urgency of intervention. The incomplete form is considered an emergency, requiring the earliest possible decompression to prevent progression to the delayed and complete form. [32]

Additionally, the following causal factors are described: discogenic, infectious, hematoma, and tumor. These factors determine the need for concomitant antibacterial or oncological therapy and influence the extent of surgical intervention. [33]

Table 4. Classification of cauda equina syndrome

Type	Key Features	Forecast
Incomplete form	Pelvic symptoms without urinary retention, sensory disturbances in the saddle area	Most favorable with early decompression
Form with urinary retention	Painless retention, overflow of the bladder	The risk of persistent disorders is higher
Full form	Lack of anal tone, perineal anesthesia, total pelvic organ dysfunction	The worst prognosis even with early treatment
[34]

Complications and consequences

The main consequences of late diagnosis are chronic neurogenic bladder dysfunction requiring catheterization, fecal incontinence, persistent sensory disturbances and weakness in the legs, and sexual dysfunction. These disorders significantly impair quality of life and work capacity. [35]

If the infection is caused by a disease, without timely decompression and antibacterial therapy, generalization of the infection and septic complications are possible. In some cases, spinal instability and deformities may develop, requiring reconstructive surgery. [36]

Delayed intervention leads to irreversible root ischemia due to compression, increasing the incidence of persistent pelvic dysfunction. This is especially true during anticoagulant therapy. [37]

Even with timely surgery, residual symptoms are possible, so rehabilitation with a program to restore pelvic functions, training in catheterization if necessary, and psychological support should be planned in advance. [38]

When to see a doctor

Immediate medical attention is required for any new urinary retention, sudden incontinence, a cotton-wool sensation or numbness in the perineum, weakness in both legs, or worsening bilateral sciatica. These signs are considered urgent indications for neuroimaging. [39]

Urgent referral is indicated when back pain is accompanied by fever, immunodeficiency, intravenous drug use, or recent invasive procedures. This clinical picture increases the likelihood of an epidural abscess. [40]

Postoperative patients, as well as those receiving anticoagulants, should be promptly evaluated if pelvic symptoms develop, as epidural hematoma requiring decompression is possible.[41]

In the absence of “red flags”, but with persistent bilateral sciatica and sensory disturbances in the perineum, it is necessary to expedite magnetic resonance imaging and specialist consultation, without waiting for spontaneous improvement. [42]

Diagnostics

The first step is clinical recognition. The nature of the pain, symmetry and distribution of symptoms, tenderness in the saddle area, bladder and bowel function, sexual function, and strength and reflexes in the legs are assessed. It should be kept in mind that digital rectal examination has a low diagnostic value for assessing anal tone. [43]

The second step is ultrasound assessment of the residual bladder volume after voiding. A threshold of 200 milliliters is considered a significant indicator of the likelihood of compression on magnetic resonance imaging and a useful risk stratification tool, especially in cases of unresolved clinical presentation. [44]

The third step is emergency magnetic resonance imaging of the lumbar spine, which is the method of choice. If contraindicated or unavailable, computed tomography (CT) myelography may be performed, recognizing the limitations of soft tissue imaging. It is organizationally recommended to have local routing procedures for patients with contraindications to magnetic resonance imaging. [45]

The fourth step is laboratory testing as indicated: inflammatory markers if infection is suspected, blood cultures if fever is present, and baseline coagulation profiles if bleeding is at risk. If compression is detected, the neurosurgical team is immediately notified to decide on decompression. [46]

Table 5. Diagnostic tools and their role

Method	Target	Comment
Clinical assessment of "red flags"	Rapid recognition of the syndrome	Negative anal tone does not exclude the syndrome
Post-micturition residual urine	Risk stratification	The 200 milliliter threshold increases the likelihood of compression
Magnetic resonance imaging	Compression confirmation and surgical plan	Method of choice, perform urgently
Computed tomography myelography	Alternative in case of contraindications	Inferior to magnetic resonance imaging for soft tissues
[47]

Table 6. Differences between cauda equina syndrome and conus medullaris syndrome

Sign	Cauda equina syndrome	Conus medullaris syndrome
Nature of the lesion	Peripheral roots	Combination of peripheral and central lesions
Symmetry	More often asymmetrical deficiencies	More often symmetrical deficits
Reflexes	Reduction of knee and Achilles tendons	Signs of central damage are possible
Pelvic disorders	Expressed, often at a late stage	May occur earlier and be more pronounced
[48]

Differential diagnosis

Cauda equina syndrome should be distinguished from conus medullaris syndrome, in which signs of central involvement and symmetrical abnormalities appear earlier. Neuroimaging and a thorough neurological assessment are critical for this distinction. [49]

Infectious processes, such as epidural abscess, can mimic the clinical presentation of cauda equina syndrome and simultaneously cause it when localized in the lumbosacral region. In such cases, systemic antibacterial therapy is added to decompression. [50]

Epidural hematoma secondary to trauma or anticoagulant therapy is another important differential diagnosis. Symptoms usually progress rapidly, and successful treatment depends on minimizing the time to decompression. [51]

Neurogenic and urological causes of urinary retention without radicular compression, as well as diabetic polyneuropathy and pelvic brachial plexus lesions, require targeted exclusion in the presence of atypical clinical presentation and negative magnetic resonance imaging. [52]

Treatment

The first therapeutic principle is to avoid wasting time between clinical suspicion, magnetic resonance imaging confirmation, and decompression. Large cohort data show that decompression within 0-1 days of hospitalization is associated with a lower complication rate and mortality compared with later surgery. Therefore, the earliest possible neurosurgical evaluation is recommended. [53]

Surgical tactics typically include posterior decompression with removal of the compressing factor, such as laminectomy with microdiscectomy for a herniated disc. The goal is rapid restoration of the spinal canal and unloading of the cauda equina nerve roots. In infectious and tumor-related causes, the scope of the intervention is expanded to include removal of the pathological substrate and stabilization. [54]

Perioperative management is aimed at protecting pelvic organ function. Early catheterization helps prevent bladder overdistension and facilitates recovery monitoring. In cases of severe dysfunction, bladder training programs and subsequent urological support are prescribed. [55]

Antibacterial therapy is indicated for epidural abscesses and is performed in conjunction with surgical decompression. The choice of an empirical regimen and adjustment based on culture results are made under the supervision of an infectious disease specialist. The parenteral course typically lasts for weeks. [56]

In the case of an epidural hematoma while on anticoagulants, immediate correction and emergency decompression are performed. Delay increases the risk of irreversible loss of sensation in the perineal area and persistent neurogenic bladder dysfunction. [57]

The role of glucocorticosteroids is considered on a case-by-case basis. In cases of spinal cord compression due to tumor, steroids reduce swelling and can be used preoperatively, but in cases of infection, they are not standard and require caution. In cases of discogenic compression of the cauda equina roots, systemic steroids have no proven routine benefit. [58]

Pain management is selected taking into account the need to preserve neurological assessment. Multilevel regimens with non-opioid agents that minimally affect consciousness and neurological status are preferred. Long-term use of opioids should be avoided due to risks and lack of long-term benefit. [59]

Rehabilitation begins early and includes neuromuscular activation of the legs, gait training, training in compensation strategies, restoration of pelvic function, and psycho-emotional support. Management is carried out by a multidisciplinary team including a neurosurgeon, physiotherapist, urologist, and psychologist. [60]

In the incomplete form of the syndrome and minimal neurological deficit, rapid decompression is also indicated, as it is at this stage that the chance of full recovery is greatest. Delaying the development of urinary retention worsens the prognosis and increases the risk of persistent impairment. [61]

Finally, in patients in whom compression is not confirmed by magnetic resonance imaging, management includes an active search for alternative causes of pelvic disorders and targeted treatment, but in case of clinical progression, repeat neuroimaging is discussed without delay. [62]

Table 7. Treatment steps for confirmed cauda equina syndrome

Stage	Action	Target
Preoperative period	Catheterization, anesthesia, preparation for anesthesia	Protecting bladder function and comfort
Surgery	Decompression and elimination of the cause	Rapid relief of root compression
Etiotropic therapy	Antibiotics for abscess, correction of anticoagulants	Control of infection and bleeding
Early rehabilitation	Activation and training of pelvic functions	Reducing the risk of persistent deficiencies
[63]

Table 8. Effect of time before surgery on outcomes

Time window	Observed effects
0-1 day from hospitalization	Better hospital outcomes, fewer complications and mortality
Up to 48 hours from the onset of pelvic symptoms	Higher chance of restoring urination and sensitivity
Later than 48 hours	The risk of permanent neurological loss increases
[64]

Prevention

Primary prevention is limited because many causes involve sudden disc herniation or acute space-occupying lesions. However, reducing infection risks, strict aseptic techniques during invasive procedures, and glycemic control in patients with diabetes mellitus reduce the likelihood of epidural abscess. [65]

Rational management of anticoagulant therapy, adherence to periprocedural protocols, and awareness of symptoms after interventions reduce the risk of epidural hematoma. Patient education on signs requiring immediate attention reduces delays. [66]

At the healthcare system level, "fast tracks" with 24-hour availability of magnetic resonance imaging and pre-established routes for patients with contraindications to magnetic resonance imaging serve to prevent severe complications. These organizational measures directly impact outcomes. [67]

For chronic low back pain with a high risk of large disc herniation, programs for early medical attention when pelvic symptoms appear are recommended. This allows for a shorter interval between onset and decompression. [68]

Forecast

The prognosis depends on the severity of the syndrome at the time of surgery and the time to decompression. The best results are observed with the incomplete form, operated on as quickly as possible, and the worst results are observed with the complete form with total perineal anesthesia and the absence of anal tone. [69]

Early surgical treatment is associated with lower complication rates and better hospital outcomes. Pelvic function recovery can take months and requires systematic rehabilitation and urological monitoring. [70]

Even with optimal timing of surgery, some patients still experience residual sensory disturbances, paresis, and sexual dysfunction, but the severity of these symptoms is lower with early decompression and comprehensive rehabilitation. [71]

In cases of infectious and hematoma origin, the prognosis is determined by the speed of decompression and the effectiveness of etiotropic therapy. Without correction of the underlying cause, the risk of relapse and progression remains. [72]

FAQ

Should digital rectal examination (DRE) be relied upon to rule out the syndrome?
No. The sensitivity of anal tone assessment is low, and a normal finding does not rule out the syndrome in the presence of "red flags." A decision to perform neuroimaging should not be delayed because of "normal" tone. [73]

What is the minimum set of examinations that should be performed before magnetic resonance imaging?
A clinical examination with assessment of tenderness in the saddle area and strength in the legs, measurement of residual urine volume after voiding, and a rapid assessment of inflammatory markers if infection is suspected. Magnetic resonance imaging is then performed immediately. [74]

If magnetic resonance imaging is unavailable, what should be done?
If contraindicated or unavailable, computed tomography (CT) myelography is considered; however, it is inferior to MRI in terms of soft tissue detail. A locally prescribed procedure should be considered for these patients. [75]

Are antibiotics always indicated?
Antibiotics are mandatory for infectious causes, especially epidural abscesses, and are used in conjunction with surgical decompression. Antibiotics are not indicated for discogenic compression without infection. [76]

How soon is surgery needed?
Preferably as soon as possible, the ideal goal is within the first 24-48 hours of the onset of pelvic symptoms, as earlier decompression is associated with better outcomes.[77]

Table 9. Choice of imaging modality for suspected cauda equina syndrome

Situation	First line method	Alternative	Notes
Suspected syndrome in the presence of "red flags"	Magnetic resonance imaging of the lumbar spine	Computed tomography myelography	Perform urgently, do not delay due to low-informative tests
Contraindications to magnetic resonance imaging	Computed tomography myelography	Computed tomography	Local routes for patients with implants and claustrophobia
Suspected infection	Soft tissue-focused magnetic resonance imaging	-	Additionally, laboratory markers and cultures
[78]