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Cauda Equina Syndrome Overview
The spinal cord extends from the brain down through the
spinal canal inside the vertebral column. Nerves that branch
off of the spinal cord (also called nerve roots) are an
extension of the spinal cord and are responsible for sending
signals to and from the muscles and other structures
throughout the body. These signals allow the brain to
interpret information from the body including pain, touch,
and sense of position. Outgoing signals allow the brain to
control actions of the organs and muscle movements.
The spinal cord ends near the first lumbar vertebra in
the lower back, forming the conus medullaris. The fibrous
extension of the spinal cord is the filum terminale. The
bundle of nerve roots below the conus medullaris is named
the cauda equina (see Multimedia File 1).
Compression or inflammation of the nerve roots can cause
symptoms of pain, altered reflexes, decreased strength, and
decreased sensation. Although these symptoms can become
severe, and in some cases disabling, most are self-limiting
and respond to conservative care.
An extreme version of nerve compression or inflammation
is cauda equina syndrome. Cauda equina syndrome is a serious
condition caused by compression of the nerves in the lower
portion of the spinal canal (see Multimedia File 2). Cauda
equina syndrome is considered a surgical emergency because
if left untreated it can lead to permanent loss of bowel and
bladder control and paralysis of the legs.
Cauda Equina Syndrome Causes
Cauda equina syndrome is caused by significant narrowing
of the spinal canal that compresses the nerve roots below
the level of the spinal cord. Numerous causes of cauda
equina syndrome have been reported, including traumatic
injury, disk herniation, spinal stenosis, spinal tumors (neoplasms),
such as metastatic tumors, meningiomas, schwannomas, and
ependymomas, inflammatory conditions, infectious conditions,
and accidental causes by medical intervention (iatrogenic
causes).
Trauma
- Traumatic events leading to fracture or partial
dislocation (subluxation) of the low back (lumbar spine)
result in compression of the cauda equina.
- A collection of blood surrounding the nerves
following trauma (epidural hematoma) in the low back
area can lead to compression of the cauda equina.
- Penetrating trauma (gunshot or stab wounds) can
cause damage or compression of the cauda equina.
- A rare complication of spinal manipulation is
partial dislocation (subluxation) of the low back
(lumbar spine) that can cause cauda equina syndrome.
Herniated Disk
- Most disk herniations will improve on their own (are
self-limiting) and respond well to conservative
treatment, including antiinflammatory medications,
physical therapy, and short periods of rest (one to two
days).
- Cauda equina syndrome results from a herniated
lumbar disk in 1-15% of cases.
- Of lumbar disk herniations, 90% occur either at the
vertebral levels L4-L5 or L5-S1.
- Seventy percent of cases of herniated disks leading
to cauda equina syndrome occur in people with a history
of chronic low back pain, and 30% develop cauda equina
syndrome as the first symptom of lumbar disk herniation.
- Males in their 30s and 40s are most prone to cauda
equina syndrome caused by disk herniation.
- Most cases of cauda equina syndrome caused by disk
herniation involve large particles of disk material that
have completely separated from the normal disk and
compress the nerves (extruded disk herniations). In most
cases, the disk material takes up at least one-third of
the canal diameter.
Spinal Stenosis
- Spinal stenosis is any narrowing of the normal front
to back distance (diameter) of the spinal canal.
- Narrowing of the spinal canal can be caused by a
developmental abnormality or degenerative process.
- The abnormal forward slip of one vertebral body on
another is called spondylolisthesis. Severe cases can
cause a narrowing of the spinal canal and lead to cauda
equina syndrome (see Multimedia File 3).
Tumors (Neoplasms)
- Cauda equina syndrome can be caused by isolated
tumors (primary neoplasms) or from tumors that have
spread to the spine from other parts of the body
(metastatic spinal neoplasms). Metastatic spine tumors
are most commonly from the prostate or lung in males and
from the lung and breast in females.
- The most common initial symptom of people with cauda
equina syndrome caused by a tumor (spinal neoplasm) is
severe low back and leg pain.
- Later findings include lower extremity weakness.
- Loss of feeling in the legs (sensory loss) and loss
of bowel or bladder control (sphincter dysfunction) are
also common.
Inflammatory Conditions
- Long-lasting inflammatory conditions of the spine,
including Paget's disease and ankylosing spondylitis,
can cause a narrowing of the spinal canal and lead to
cauda equina syndrome.
Infectious Conditions
- Infections in the spinal canal (spinal epidural
abscess) can cause deformity of the nerve roots and
spinal column.
- Symptoms generally include severe back pain and
rapidly worsening muscle weakness.
Accidental Medical Causes (Iatrogenic Causes)
- Poorly positioned screws placed in the spine can
compress and injure nerves and cause cauda equina
syndrome.
- Continuous spinal anesthesia has been linked to
cases of cauda equina syndrome.
- Lumbar puncture (spinal tap) can cause a collection
of blood in the spinal canal (spontaneous spinal
epidural hematoma) in patients receiving medication to
thin the blood (anticoagulation therapy). This
collection of blood can compress the nerves and cause
cauda equina syndrome.
Cauda Equina Syndrome Symptoms
Symptoms of cauda equina syndrome include the following:
- Low back pain
- Pain in one leg (unilateral) or both legs
(bilateral) that starts in the buttocks and travels down
the back of the thighs and legs (sciatica)
- Numbness in the groin or area of contact if sitting
on a saddle (perineal or saddle paresthesia)
- Bowel and bladder disturbances
- Lower extremity muscle weakness and loss of
sensations
- Reduced or absent lower extremity reflexes
Low back pain can be divided into local and radicular pain.
- Local pain is generally a deep, aching pain
resulting from soft tissue and vertebral body
irritation.
- Leg pain (radicular pain) is generally a sharp,
stabbing pain resulting from compression of the nerve
roots. Radicular pain projects along the specific areas
controlled by the compressed nerve (known as a
dermatomal distribution).
Bladder disturbance (urinary manifestations) related to
cauda equina syndrome include the following:
- Inability to urinate (urinary retention)
- Difficulty initiating urination (urinary hesitancy)
- Decreased sensation when urinating (decreased
urethral sensation)
- Inability to stop or control urination
(incontinence)
Bowel disturbances may include the following:
- Inability to stop or feel a bowel movement
(incontinence)
- Constipation
- Loss of anal tone and sensation
When to Seek Medical Care
Cauda equina syndrome is a surgical emergency. Persons
should seek immediate medical care or go to the emergency
department if they believe they have symptoms of cauda
equina syndrome. Some of the early symptoms related to cauda
equina syndrome, including low back pain and muscle
weakness, are more often caused by simple disk herniation,
which does not require urgent attention. However, if you
develop severe pain or loss of sensation or bowel or bladder
disturbances, you should contact your physician immediately.
Your chances of regaining normal function and having a
positive outcome are related to how long you have had
symptoms of cauda equina syndrome. Most experts agree that
people with cauda equina syndrome should undergo surgery to
make more space for the nerves (lumbar decompression) within
48 hours in order to have the best chance for complete
recovery.
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