The spinal cord tapers and also ends at the level in between the first and second lumbar vertebrae in an median adult. The most distal bulbous part of the spinal cord is called the conus medullaris, and its tapering end continues as the filum terminale. Distal to this finish of the spinal cord is a collection of nerve roots, which room horsetail-like in appearance and hence referred to as the cauda equina (Latin for horse"s tail). (See the photo of cauda equina anatomy below.)

Illustration demonstrating the pertinent anatomy the the cauda equina an ar

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These nerve root constitute the anatomic connection between the main nervous device (CNS) and also the peripheral nervous system (PNS). They space arranged anatomically follow to the spinal segments from which lock originated and also are in ~ the cerebrospinal fluid (CSF) in the subarachnoid space with the dural sac ending at the level of second sacral vertebra.

Cauda equina syndrome describes a characteristic pattern of neuromuscular and urogenital symptom resulting from the simultaneous compression of lot of lumbosacral nerve roots listed below the level that the conus medullaris (see the image below). These symptoms incorporate low earlier pain, sciatica (unilateral or, usually, bilateral), saddle sensory disturbances, bladder and bowel dysfunction, and variable lower extremity motor and also sensory ns (see Clinical).

Although the lesion is technically involves nerve roots and represents a "peripheral" nerve injury, damages may it is in irreversible and also cauda equina syndrome may be a operation emergency (see Treatment). <1>

Illustration demonstrating an example of cauda equina syndrome second to a spinal neoplasm

Lesions entailing the termination of the spinal cord (conus medullaris) space not discussed in this article. Please watch the post Spinal Cord Injuries.

The spinal cord, i m sorry is the downward extension of medulla the starts just listed below the foramen magnum, serves together a conduit for the ascending and also descending fiber tracts that affix the peripheral and spinal nerves to the brain. The cord tasks 31 bag of spinal nerves top top either side (8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 coccygeal) that are connected to the peripheral nerves.

A cross-section the the spinal cord discover butterfly-shaped gray matter in the middle, surrounded by white matter. Together in the cerebrum, the gray matter is created of cabinet bodies. The white matter consists of assorted ascending and descending tracts that myelinated axon fibers, each with particular functions.

During development, the vertebral tower grows much more rapidly 보다 the spinal cord. Spinal nerves leave the vertebral shaft at progressively much more oblique angles because of the raising distance in between the spinal cord segments and the equivalent vertebrae. Lumbar and also sacral nerves travel virtually vertically under the spinal canal to reach their exiting foramen.

The spinal cord end at the intervertebral disc between the an initial and 2nd lumbar vertebrae as a tapered structure referred to as the conus medullaris, consists of sacral spinal cord segments. The upper border the the conus medullaris is regularly not fine defined. The fibrous expansion of the cord, the filum terminale, is a nonneural aspect that extends under to the coccyx.

The cauda equina (CE) is a bundle that intradural nerve root at the finish of the spinal cord, in the subarachnoid room distal come the conus medullaris. Cauda is Latin because that tail, and also equina is Latin for steed (ie, the "horse"s tail"). The CE gives sensory innervation to the saddle area, motor innervation to the sphincters, and parasympathetic innervation come the bladder and also lower bowel (ie, from the left splenic flexure come the rectum). <100>

The nerves in the CE region include lower lumbar and all of the sacral nerve roots. The pelvic splanchnic nerves carry preganglionic parasympathetic fibers from S2-S4 to innervate the detrusor muscle of the urinary bladder. Whereas somatic lower motor neurons indigenous S2-S4 innervate the voluntary muscle of the external anal sphincter and also the urethral sphincter via the worse rectal and the perineal branches the the pudendal nerve, respectively.

Hence, the nerve root in the CE an ar carry emotion from the lower extremities, perineal dermatomes, and also outgoing engine fibers come the reduced extremity myotomes.

The conus medullaris obtains its blood supply primarily from 3 spinal arterial vessels: the anterior typical longitudinal arterial trunk and also 2 posterolateral trunks. Less prominent sources that blood supply incorporate radicular arterial branches from the aorta, lateral sacral arteries, and the 5th lumbar, iliolumbar, and middle sacral arteries. The latter contribute much more to the vascular it is provided of the cauda equina, although not in a segmental fashion, uneven the blood it is provided to the peripheral nerves.

The nerve root may also be supplied by diffusion native the neighboring CSF. Moreover, a proximal area the the nerve roots may have a region of family member hypovascularity.

In expertise the pathological basis of any an illness involving the conus medullaris, keep in mind that this framework constitutes part of the spinal cord (the distal component of the cord) and also is in proximity to the nerve roots. Thus, injuries to this area frequently yield a mix of top motor neuron (UMN) and also lower engine neuron (LMN) symptoms and signs in the dermatomes and also myotomes of the influenced segments. On the various other hand, a cauda equina lesion is one LMN lesion due to the fact that the nerve roots are component of the PNS.

Cauda equina syndrome may an outcome from any kind of lesion that compresses CE nerve roots. This nerve root are an especially susceptible to injury, due to the fact that they have a poorly arisen epineurium. A well-developed epineurium, as peripheral nerves have, protects versus compressive and also tensile stresses. <2>

The microvascular solution of nerve roots have a an ar of family member hypovascularity in your proximal third. Raised vascular permeability and also subsequent diffusion native the surrounding cerebral spinal liquid supplement the nutritional supply. This home of enhanced permeability may be regarded the propensity toward edema development of the nerve roots, i beg your pardon may result in edema compounding initial and also sometimes seemingly slight injury.

Several research studies in different animal models have assessed the pathophysiology of cauda equina syndrome. <3, 4> Olmarker et al, making use of a graded balloon pressure technique in a porcine model, reported the the venules in the CE an ar begin come compress in ~ a pressure as low together 5 mm Hg and also the arterioles begin to occlude as the balloon push surpasses the average arterial pressure. <5, 6, 7, 3, 8> regardless of this, also a press as high as 200 mm Hg failed to totally shut off nutritional it is provided to the CE.

These studies showed that not just the size but additionally the length and also the rate of obstruction were also important in damaging the CE region. <9> similar results to be reported in various other studies. Takahashi et al reported a reduction in blood flow to the intermediary nerve segment when 2 pressure points were used along the course of the nerve in the CE. <10>

Others have actually studied compound action potentials in afferent and also efferent segments of nerves in the CE region after application of balloon compression. <11, 12, 13> These researchers reported that 0-50 mm Hg of push did not impact the action potentials (the threshold for disturbances in action potentials was 50-75 mm Hg), and far-reaching deficits to be observed as soon as pressure rose to 100-200 mm Hg.



Cauda equina syndrome is led to by any type of narrowing the the spinal canal the compresses the nerve roots listed below the level the the spinal cord. <14> Numerous reasons of cauda equina syndrome have been reported, including disc herniation, intradural key rupture, spinal stenosis secondary to other spinal conditions, traumatic injury, primary tumors such as ependymomas and also schwannomas, metastatic tumors, infectious conditions, arteriovenous malformation or hemorrhage, and iatrogenic injury. <14, 15>

The many common reasons of cauda equina and also conus medullaris syndromes space the following:

Lumbar stenosis (multilevel)

Neoplasm, including metastases, astrocytoma, neurofibroma, and meningioma; 20% of all spinal tumors impact this area

Other, rare reasons include the following:

Spinal hemorrhage, especially subdural and also epidural hemorrhage causing compression within the spinal canal

Intravascular lymphomatosis

Congenital anomalies the the spine/filum terminale, consisting of tethered cord syndrome

Conus medullaris lipomas

Multiple sclerosis

Spinal arteriovenous malformations

Late-stage ankylosing spondylitis


Deep venous thrombosis of the spinal veins (propagated)

A retrospective study of 66 consecutive situations of patients admitted come a neurosurgical unit through suspected cauda equina syndrome found that almost fifty percent had no evidence of structural pathology ~ above MRI. <24> these researchers argued that the symptoms have a functional beginning in such cases.


Traumatic occasions leading to fracture or subluxation can lead come compression the the cauda equina. <16, 25, 26, 27, 28> Penetrating trauma can reason damage or compression of the cauda equina. Spinal manipulation bring about subluxation has actually caused cauda equina syndrome. <29> Rare instances of sacral insufficiency fractures have been reported to reason cauda equina syndrome. <30> Acute and delayed gift of CES as result of hematomas and also posttraumatic arachnoid cysts have additionally been reported. <31, 32, 33>

Herniated disk

The reported incidence of cauda equina syndrome resulting from herniated lumbar decaying (see the image below) varies from 1-15%. <34, 35, 19> Ninety percent that lumbar decaying herniations take place either at L4-L5 or L5-S1. <36, 37>

Sagittal MRI that a patient with cauda equina syndrome secondary to a huge lumbar disc herniation
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Of instances of herniated disks bring about cauda equina syndrome, 70% happen in patients through a history of chronic low earlier pain; in 30%, cauda equina syndrome is the first symptom of lumbar disk herniation. <18> guys in the fourth and also fifth years of life are most prone come cauda equina syndrome an additional to disk herniation. <38>

Most instances of cauda equina syndrome second to decaying herniation involve either a large central disc or an extruded disc fragment that compromises a far-reaching amount of the spinal canal diameter. <39> The presentation may be acute or the of a much more protracted course, with the last bearing a better prognosis. <35> individuals with congenital stenosis that sustain a decaying herniation are much more likely to develop cauda equina syndrome due to the fact that even a small herniation can substantially limit the space available for the nerve roots.

Rare instances of intradural disc herniations have actually been report to reason cauda equina syndrome. <40> Myelography in this instances generally demonstrates a finish block the the contrast material. If an intradural key fragment is identified, transdural remove of the extruded bowl fragment may be beneficial to prevent further stretching of the already compromised nerve root.

Spinal stenosis

Narrowing the the spinal canal can be due to a developmental abnormality or degenerative process. Return unusual, cauda equina syndrome indigenous spinal stenosis second to spinal obstacle such together ankylosing spondylitis, spondylosis, and spondylolisthesis have actually all been reported. <41, 42, 43, 44, 45, 46, 47>


Cauda equina syndrome deserve to be brought about by main or metastatic spinal neoplasms. Amongst the primary tumors able to reason CES incorporate myxopapillary ependymoma, schwannoma, and paraganglioma.

Myxopapillary ependymoma is the most typical tumor that the filum. Recovery of the function after surgery counts on the duration of symptoms and the visibility or lack of sphincter dysfunction <48> Paraganglioma the the filum, as soon as present, requirements to be differentiated from various other tumors the this region. <49> return rare, this entity may present as CES.

Schwannomas room benign encapsulated neoplasms that are structurally the same to a syncytium of Schwann cells. <50> these growths might arise indigenous peripheral or forgiveness nerves. Schwannomas, even if it is solitary or as a component of a syndrome, may cause CES if current at the level the the conus or filum terminale. Major tumors that affect the sacrum, such as chordoma and giant cabinet tumor of the bone, may produce similar symptoms as a result of bony destruction and also collapse. <51>

Ependymomas room gliomas acquired from fairly undifferentiated ependymal cells. They frequently originate native the central canal of the spinal cord and tend come be i ordered it radially about blood vessels. Ependymomas are discovered most typically in patient aged around 35 years. They deserve to lead to enhanced intracranial pressure (ICP), and cerebrospinal liquid (CSF) has actually an raised protein level.

Metastatic lesions the the spine room being reported with enhancing frequency because of earlier diagnosis, much better imaging, and an ext effective therapy modalities. Back metastasis account for most tumors in the spine in general, metastatic tumors in the cauda equina are fairly rare contrasted with major tumors.

For the spine in general, resources of spinal metastases are as follows <52> :

Lung cancer (40-85%)

Breast cancer (11%)

Renal cabinet carcinoma (4%)

Lymphatic cancer (3%)

Colorectal cancer (3%)

Although lung cancer is the most common source of spine metastases, in one study, just 0.7% the the lung cancer metastases to the spine produced cauda equina syndrome; most of the metastatic lesions were no at the level that the cauda equina. <52> approximately 8% the patients with prostate cancer suffer malignant spinal cord compression; however, the percent of instances involving cauda equina syndrome is unknown. <53>

The CE an ar is additionally a favored site for fall metastases from intracranial ependymoma, germinoma, and other tumors. <54> various other unusual metastatic spread from genitourinary and gynecologic cancer have also been report at the conus region, leading to neurological compromise. <55, 56>

Inflammatory and also infectious conditions

Long-lasting inflammatory problems of the spine, including Paget condition and ankylosing spondylitis, can lead come cauda equina syndrome secondary to spinal stenosis or fracture.

Infectious conditions, consisting of epidural abscess, deserve to lead to deformity the the nerve roots and also spinal cord. <57> symptom generally include severe back pain and also a rapidly proceeding motor weakness.

Infectious reasons for cauda equina syndrome may be pyogenic or nonpyogenic. Pyogenic abscesses space generally uncovered in one immunocompromised or poorly nourished host. Staphylococcus aureus reasons epidural abscesses in 25-60% the cases, but, recently, boosting incidence of infections with methicillin-resistant S aureus, Pseudomonas species, and Escherichia coli have actually been recorded. A high table of contents of uncertainty is advantageous in exactly diagnosis and management. <57>

Nonpyogenic reasons for abscess are rare and include tuberculosis. Renewal of tuberculosis secondary to immunocompromise in individuals with HIV infection requires a high table of contents of suspicion, together the development of cauda equina syndrome might follow one indolent course. <58> other uncommon organisms, such as Nocardia asteroides and Streptococcus milleri, have additionally been reported together a reason of abscess that leads come the advancement of CES. <59, 60>

Iatrogenic causes

Complications that spinal instrumentation have actually been report to cause cases of cauda equina syndrome, including misplaced pedicle screws <61> and also laminar hooks. <62, 63> continuous spinal anesthesia likewise has been linked to instances of cauda equina syndrome. <64>

Rare situations of cauda equina syndrome led to by epidural steroid injections, fibrin adhesive injection, <65> and also placement the a free-fat graft have actually been reported. <66>

Several situations have involved the usage of hyperbaric 5% lidocaine because that spinal anesthesia. Recommendations are that hyperbaric lidocaine not be administered in concentrations higher than 2%, with a total dose not to exceed 60 mg. <67, 68>

Medical and surgical instances such as bone screw fixation, fat grafts, lumbar arthrodesis for spondylolisthesis, lumbar discectomy, intradiscal therapy, lumbar puncture forming an epidural hematoma, chiropractic manipulation, and also a bolus injection the anesthetic throughout spinal anesthesia have been pertained to the development of cauda equina syndrome–like syndromes. <35, 69, 70, 71, 72, 73>



Cauda equina and also conus medullaris syndromes space classified together clinical syndromes of the spinal cord; epidemiological data top top the 2 syndromes are often not obtainable separately native the basic data ~ above spinal cord injury.

Cauda equina syndrome is uncommon, both atraumatically as well as traumatically. That is frequently reported together a instance report as result of its rarity. Back infrequent, that is a diagnosis that must be thought about in patients who complain that low back pain coupled with neurologic complaints, particularly urinary symptoms.

Age-related distinctions in incidence

Traumatic cauda equina syndrome is not period specific. Atraumatic cauda equina syndrome occurs mainly in adults as a result of operation morbidity, spinal decaying disease, metastatic cancer, or epidural abscess.



Morbidity and also especially mortality rates are figured out by the underlying etiology. Multiple problems can an outcome in cauda equina or conus medullaris syndrome. The prognosis enhances if a definitive cause is identified and appropriate therapy occurs early in the course. Surgical decompression might be performed emergently, or, in part patients, delayed, depending on the etiology. Residual weakness, incontinence, impotence, and/or sensory abnormalities are potential problems if treatment is delayed.

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Investigators have attempted to identify particular criteria the can help in predicting the prognosis that patients with cauda equina syndrome. Patients v bilateral sciatica have actually been reported to have actually a much less favorable prognosis 보다 patients with unilateral pain. Patient with finish perineal anesthesia are an ext likely to have actually permanent paralysis the the bladder. <39>

The degree of perineal or saddle sensory deficit has actually been reported to it is in the most essential predictor that recovery. <74> Patients v unilateral deficits have actually a better prognosis 보다 patients v bilateral deficits. Females and patients through bowel dysfunction have been report to have worse outcomes postoperatively. <75>

Prognosis have the right to be predicted through the American Spinal Injury combination (ASIA) special needs scale (see physical Examination ), as follows:

ASIA A: 90% the patients continue to be incapable of practical ambulation (reciprocal gait that 200 feet or more)

ASIA B: 72% of patients are unable to achieve functional ambulation

ASIA C/D: 13% are unable to obtain functional ambulation 1 year after injury

Ambulatory motor index additionally is offered to suspect ambulatory capability. That is calculation by scoring hip flexion, hip abduction, i know good extension, knee extension, and also knee flexion on both sides, using a 4-point range (0=absent, 1=trace/poor, 2=fair, 3=good or normal); the score is expressed as a percent of the preferably score that 30. Prognostic significance is as follows:

A patient with a score the 60% or an ext has a an excellent chance for community ambulation with no much more than one knee-ankle-foot orthosis (KAFO)

A patient with a score that 79% or greater may not need an orthosis

A patient through a score that 40% or much less may need 2 KAFOs for community ambulation


Patient Education

Patient education needs will certainly vary v the form and severity that persistent deficits, and also may encompass the following:

Training in self-catheterization and also finger fecal disimpaction, if required

Use of actions to prevent pressure ulcers, such together skin inspection/care, positioning, transforming and moving tactics, use of skin protectors, or pressure-reducing assistance surfaces

Maintenance that endurance and strength-training exercises

Regular follow-up by the consulting teams who treated the patience in the hospital

Instructions top top how and also when medicines should be taken and when follow-up laboratory tests should be performed

For patient education and learning information, view the Erectile Dysfunction center and mind and Nervous mechanism Center, as well as Impotence/Erectile Dysfunction, Erectile Dysfunction FAQs, and also Cauda Equina Syndrome.

Clinical Presentation

Scott PJ. Bladder paralysis in cauda equina lesions native disc prolapse. J Bone joint Surg. 1965. 47B:224-235.

Ginsberg D, et al. Step 3 Efficacy and also Safety research of OnabotulinumtoxinA in Patients through Urinary Incontinence due to Neurogenic Detrusor Overactivity. Presented in ~ 107th yearly Meeting that the American Urological Association, Washington, DC. May, 2011.

Media collection
Muscle groups, surface anatomy, peripheral sensory innervation, and dermatomes the the anterior reduced limb. This photo should be associated with Tables 1 and 2 in the text. Image courtesy of Nicholas Y. Lorenzo, MD.
Muscle groups, surface anatomy, peripheral sensory innervation, and dermatomes of the posterior lower limb. This picture should be associated with Tables 1 and also 2 in the text. Picture courtesy the Nicholas Y. Lorenzo, MD.
Conus/epiconus infarction in the setting of sickle cabinet crisis. Image courtesy the Matthew J. Baker, MD.
Conus/epiconus infarction in the setup of sickle cell situation in the same patient presented in the over image. Photo courtesy that Matthew J. Baker, MD.
Conus/epiconus infarction in the setting of sickle cell situation in the very same patient displayed in the pictures above. Picture courtesy of Matthew J. Baker, MD.
Illustration demonstrating the appropriate anatomy of the cauda equina region
Illustration demonstrating an instance of cauda equina syndrome secondary to a spinal neoplasm
Sagittal MRI the a patient v cauda equina syndrome second to a big lumbar disc herniation
Epidural abscess through effacement that thecal sac in a 56-year-old man.
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Table 1. Symptoms and Signs that Conus Medullaris and Cauda Equina Syndromes

Conus Medullaris Syndrome

Cauda Equina Syndrome


Sudden and also bilateral

Gradual and also unilateral


Knee jerks preserved however ankle jerks affected

Both ankle and knee jerks affected

Radicular pain

Less severe

More severe

Low ago pain



Sensory symptoms and also signs

Numbness tends to be an ext localized come perianal area; symmetrical and also bilateral; sensory dissociation occurs

Numbness tends to be much more localized to saddle area; asymmetrical, may be unilateral; no sensory dissociation; lose of sensation in details dermatomes in reduced extremities with numbness and also paresthesia; feasible numbness in pubic area, including glans prick or clitoris

Motor strength

Typically symmetric, hyperreflexic distal paresis of reduced limbs that is less marked; fasciculations may be present

Asymmetric areflexic paraplegia that is an ext marked; fasciculations rare; atrophy much more common



Less frequent; erectile dysfunction that has inability to have actually erection, i can not qualify to keep erection, absence of emotion in pubic area (including glans dick or clitoris), and also inability to ejaculate

Sphincter dysfunction

Urinary retention and atonic anal sphincter cause overflow urinary incontinence and also fecal incontinence; have tendency to existing early in food of disease

Urinary retention; often tends to current late in food of disease


Cauda Equina Syndrome

Conus Medullaris

Vertebral level



Spinal level

Injury to the lumbosacral nerve roots

Injury the the sacral cord segment (conus and epiconus) and also roots

Severity of symptoms and also signs

Usually severe

Usually no severe

Symmetry that symptoms and signs

Usually asymmetric

Usually symmetric


Prominent, asymmetric, and radicular

Usually bilateral and also in the perineal area


Weakness come flaccid paralysis

Normal motor duty to mild or middle weakness


Saddle anesthesia, may be asymmetric

Symmetric saddle distribution, sensory ns of pin prick, and temperature sensations (Tactile emotion is spared.)


Areflexic reduced extremities; bulbocavernosus reflex is missing in low CE (sacral) lesions

Areflexic reduced extremities

(If the epiconus is involved, patellar reflex may be absent, whereas bulbocavernosus reflex might be spared.)

Sphincter and sexual function

Usually late and also of lesser magnitude;

lower sacral root involvement can cause bladder, bowel, and also sexual dysfunction

Early and also severe bowel, bladder, and sexual dysfunction that results in a reflexic bowel and bladder v impaired erection in males