Introduction
Sciatica is a buttock pain radiating
down the back of the thigh and leg and possibly into the calf or foot.
Other characteristics of sciatica include varying degrees of weakness in the
leg muscles and numbness and/or tingling that radiates down the leg.
These symptoms occur because of compression and/or irritation of the sciatic
nerve or nerve roots which are forming the sciatic
nerve. The areas in the buttock and leg affected by this compression
are the areas that the sciatic nerve supplies with messages for normal
function. There are many other names for sciatica including lumbosacral
radicular syndrome, radiating low back pain, nerve root pain, and nerve root
entrapment.
The sciatic nerve is formed in the
pelvis from nerve roots that begin in the lower back vertebrae (lumbar 4 [L4],
lumbar 5 [L5]) and sacrum (sacral 1[S1], sacral 2 [S2], sacral 3 [S3]). It is
the thickest nerve in the body and is 2 cm wide at its origin. It enters
the lower limb via the greater sciatic foramen (opening). The nerve passes
along the back of the thigh, supplying the hamstrings (knee flexors) and all of
the muscles below the knee. It also supplies the skin of entire lower extremity
below the knee and foot with the exception of the inside of the calf and foot.
The impingement or irritation of the sciatic nerve anywhere along its course
would cause pain in the area the nerve supplies.
Sciatica is a relatively common
condition with a lifetime incidence (the number of individuals that have experienced sciatica at some point
in their lives) varying from 13% to 40%. The incidence of sciatica
is related to age. Sciatica is rarely seen before the age of 20 and it most
often occurs in people in their fifties. In addition, there may be a genetic
link with the development of sciatica. It has been shown that the
first-degree relatives of people affected by sciatica have a greater risk of
developing it themselves. Other identified risk factors are largely
work-related and include: awkward working position, working in a flexed or
twisted trunk position, or working with the hand above the shoulder. Heavy
amounts of driving and smoking have also been linked with sciatica. It has been
shown that neither gender nor weight has an influence on the development of
sciatica, although being overweight is often associated with low back pain in
general. For males in the 50-64 year range, body height may be a risk factor
for sciatica. It has been shown that the relative risk increased an average 1.5
fold for every 10 cm increase in body height.
The name sciatica refers to a set of
symptoms caused by an underlying problem and is not the name of the problem
itself.
1. Spinal sciatica: compression
and/or irritation of a nerve root or roots
(which are forming the sciatic nerve) inside of the spine
b) spinal stenosis
d) spondylolysis
and spondylolisthesis
e) scoliosis
f) trauma
g) spinal
tumors and infection
2. Extra-spinal sciatica: compression
and/or irritation of the sciatic nerve
outside of the spine
a) piriformis syndrome
b) gynecological problems: fibroids and
endometriosis
c) bone and soft tissue tumors
d) infection
e) trauma
f) others: vascular and medications
In about 90% of cases, sciatica is
caused by compression and/or irritation of one or more nerve roots in the
lumbar spine, before the sciatic nerve enters the leg. These nerve roots
can become compressed by a herniated disc, spinal canal stenosis (narrowing of
spinal canal where the nerve roots are passing through) or neural foraminal
narrowing (narrowing of the holes where the nerve roots are exiting the spine).
The relationship between compression of the nerve root and sciatica is not
completely understood. Mechanical compression of the nerve root may produce neurologic
deficits, such as numbness and tingling in the leg, but the pain associated
with sciatica is only produced if the nerve root is also irritated or inflamed.
There is no definite, known cause of the inflammation of the nerve associated
with sciatica. However, it is thought that the inflammation could be
caused by decreased blood supply to the nerve or associated nerve roots and/or
direct irritation of nerve roots by disc herniation.
Rarely, the entrapment of the sciatic nerve occurs outside
of the spine along the part of the sciatic nerve that runs through the pelvis
or thigh. This is called extra-spinal sciatica. This type of
entrapment is difficult to diagnose because the symptoms are similar to those
of the more frequent causes of sciatica. Extra-spinal sciatic nerve compression
can be caused by tumors, infections, gynecological problems, and problems
associated with muscles, vascular, and bony structures. Although these
are rare causes of sciatica, they are serious and must be thoroughly
investigated.
Very rarely, bone and soft tissue
tumors along the course of the sciatic nerve can cause sciatica. Patients
suffering from sciatica with a history of neurofibromatosis (a genetic disorder
of the nervous system) or malignant tumors that are prone to skeletal
metastases (e.g., prostate, breast, lung, kidney and thyroid cancers) should be
carefully evaluated for a tumor along the course of the sciatic nerve. The important
risk factors for malignant tumors include age older than 50 years, previous
cancer history, unexplained weight loss, pain not relieved by bed rest,
duration of pain more than six to eight weeks and failure of conservative
therapy after six to eight weeks.
Infection also needs to be excluded
in cases of sciatica. The important risk factors for infection include IV drug
use, active or recent infection elsewhere in the body (e.g., urinary tract,
pulmonary, skin, dental), and immunosuppression (either due to medications or
illness affecting the immune system, like HIV/AIDS). Additional factors to
consider include diabetes and history of tuberculosis.
Piriformis syndrome is another
uncommon cause of sciatica. The sciatic nerve usually passes underneath the
piriformis muscle, but in approximately 15% of the population, it travels
through the muscle. In this case, the symptoms are caused by entrapment of the
sciatic nerve in the buttock by the overlying piriformis muscle. Often, a
history of minor trauma may be described, such as falling onto the buttock.
Gynecological causes are fibroids
and endometriosis (cyclic pain). Sciatic
endometriosis is uncommon but should be considered in a woman who presents with
sciatica associated with menstruation. Additional causes include post-traumatic
or anticoagulant induced hematomas (abnormal collection of blood) of the
sciatic nerve and/or muscles.
Sciatica is usually diagnosed by
taking a history of symptoms and by physical examination. Patients are usually
asked to describe the pattern of the pain and whether it radiates below the
knee; drawings may be used to evaluate the distribution. Patients may also
report sensory symptoms (numbness, tingling) and weakness in the legs. Physical
examination is largely made up of neurological testing, which includes: sensory
and muscle strength testing, reflex testing, and sciatic tension signs.
Sciatic tension signs are frequently
used to assess patients with sciatica. The straight leg raise test is performed
in the supine position by elevating the leg with the knee extended and
assessing whether this movement reproduces the sciatic pain in the leg. The
test is considered positive if the pain occurs between 30 and 70 degrees of
elevation. Variations on this test include raising the leg to the point of
symptom reproduction and then lowering the leg slightly and moving the foot
upward passively (dorsiflexion); a positive sign results in reproduction of
radiating pain down the leg. Additional tests include the crossed straight leg
raise test, in which symptoms are reproduced in the symptomatic leg by
performing a straight leg raise test on the opposite leg. Overall, if a
patient reports the typical radiating pain in one leg combined with a positive
result on one or more neurological tests indicating nerve root tension or
neurological deficit, the diagnosis of sciatica is made.
Imaging studies can help the doctor
to determine the cause of sciatic pain. Diagnostic imaging includes plain
films (x-rays), MRI (magnetic resonance imaging), MR neurography, computerized
tomography (CT)-myelography, and CT scans. Diagnostic imaging is only useful if
the results change the treatment plan.
In acute sciatica (during first six
to eight weeks), the diagnosis is based on history taking and physical
examination, and treatment is conservative. Imaging may be indicated at this
stage only if there are indications or “red flags” that the sciatica may be
caused by underlying disease (infections, malignancy) rather than a disc
herniation. These red flags include a history of significant trauma, cancer,
unexplained weight loss, night pain, immunosuppression, recent infection,
bladder and/or bowel dysfunction, bilateral neurologic deficits, saddle
anesthesia (loss of sensation in the buttocks area), progressive neurologic
deficit, and unremitting pain. Diagnostic imaging is also indicated in
patients with severe symptoms who fail to respond to conservative treatments
for six to eight weeks.
Routine plain films are universally
available and inexpensive, but are limited by an ability to directly visualize
nerves and nerve root compression. They are, however, important in ruling out
obvious underlying problems such as tumors, infections, inflammatory spinal
disorder, traumatic bony injury, or instabilities (e.g., spondylolisthesis,
which is forward slippage of one backbone over another).
MRI has become the examination of
choice for patients with sciatica. It has the advantage of being non-invasive,
and having no known side effects or radiation exposure. MRI is the most
accurate test for disc herniation detection. Routine protocols for MRI of
lumbar spine provide excellent visualization of the spinal axis including
central canal and foramina, but do not show the sciatic nerve as it runs
outside of the spinal column. Unfortunately, for the patients with extra-spinal
sciatica, routine MRI of lumbar spine will not usually reveal the cause of the
pain. For these patients, high-resolution MR neurography may identify the
anatomic abnormalities causing the problem.
Before the advent of MRI, CT was the
imaging modality of choice for patients with sciatica. CT can also be performed
with intrathecal (space around the spinal cord) contrast injection
(CT-myelography). Currently, CT-myelography is used for patients who cannot get
an MRI.
Most patients with acute sciatica
respond to conservative (non-surgical) treatment and their symptoms get better
over a period of six to eight weeks. Approximately 10-30% of people develop
chronic sciatica (sciatica persisting longer than 12 weeks). Unfortunately, it
is difficult to predict at an early stage who is at risk for developing chronic
sciatica.
The most common cause of sciatica is
a disc herniation in the lumbar spine. Generally, 70% of disc herniations
mostly go away in one to two years. In the long term (five years or
more), disc herniations decrease in size in 95% of people. Generally,
large, diffuse disc herniations (rupture of the disc) are the most likely to
decrease in size over the first year. In contrast, focal or localized disc
bulges are more likely to be unchanged.
The mechanism that leads a disc
herniation to cause sciatica is not totally clear. Some disc herniations do not
cause any symptoms. In MRI scans of 67 adults with no history of back or leg
pain, about one-third had a substantial abnormality. Disc herniation was seen
in the absence of symptoms in 21%, 22% and 36% of those aged 20-39, 40-60, and
more than 60 years of age, respectively, whereas generalized disc bulging was
also seen in 56%, 59% and 79% of asymptomatic individuals, respectively. These
findings emphasize the difficulty involved in defining the complex interaction
between nerve root inflammation and the compression that seems to be the cause
of sciatica.
To date, conservative treatments for
sciatica consist of a wide range of methods including: treatment with
medication (oral analgesics [pain relievers], muscle relaxants and medications
for nerve pain), physical therapy, bed rest, epidural steroid injections,
lumbar supports (lower back braces), spinal manipulation, complementary
alternative medicine, behavioral treatment, and multidisciplinary
rehabilitation. Adequately informing patients about the causes and expected
prognosis is an important part of the treatment strategy.
Nonsteroidal anti-inflammatory drugs
(NSAIDs) (e.g., ibuprofen, naproxen, diclofenac) are a large group of drugs
commonly used to treat sciatica. They reduce both pain and inflammation. NSAIDs
can have side effects. A history of gastrointestinal bleeding or peptic ulcers
can be a reason not to use NSAIDs. This risk, however, is reduced with the
NSAID celecoxib (Celebrex). Additionally with NSAIDs, other internal organs,
such as the kidneys and liver, may be detrimentally affected. No specific NSAID
was shown to be superior to another in the treatment of sciatica.
Because in the acute setting sciatic
pain can be severe, short term narcotic use can be useful. These should not be
prescribed for an extended period of time, but should be limited to a two to
three day course. Other types of drugs prescribed for sciatic pain include:
tricyclic antidepressants and other antidepressants, gabapentin and other
anticonvulsants, tramadol, topical lidocaine and baclofen.
If bed rest is prescribed, it should
be limited to no more than two to three days. Greater periods of inactivity can
cause prolonged disability and continued pain. In fact, physical therapy has
been shown to not only reduce pain, but to limit days off from work – and it
has been consistently shown that exercise is the most important component of
the physical therapy. Treatment goals of physical therapy are to restore
strength and function of the core muscles, flexibility of leg and paraspinal
muscles, and also to improve cardiovascular fitness; these are all things that
are often lost due to pain and spasm. However, the patient should not perform
any exercise that provokes their pain. If a specific exercise provokes the
pain, that exercise first should be modified and/or the number of exercises
should be decreased. If it still aggravates the symptoms, the patient should
stop doing that particular exercise. Postural education to avoid activities
that can increase intradiscal pressure and/or sciatic tension should be
provided. Adjunctive modalities (e.g., cold pack, hot pack, ultrasound,
massage) are usually helpful for short term relief of symptoms.
Epidural steroid injections to
decrease inflammation have been increasingly utilized with the growing evidence
that inflammatory agents are a significant contributor to the pain and nerve
root irritation that causes sciatica. Injections are offered to patients who
have failed noninvasive conservative treatments, including physical therapy and
medications. It has been shown that selective transforaminal epidural steroid
injections produce symptomatic relief in 70 to 85% of patients. It also has
been reported that 71% of patients with sciatica who receive transforaminal
epidural injections avoid surgery. Transforaminal epidural injections are also
helpful to determine the prognosis of the surgery if the patient fails
conservative treatments. Patients who have 70-80% relief from the epidural
steroid injections have greater than 95% success in achieving an average of 90%
leg-pain relief after surgery.
There are no studies that show
lumbar supports are more effective than other interventions for treatment of
sciatica. Most published studies of spinal manipulation reported mixed
efficacy. Acupuncture has become a popular alternative for the treatment of
sciatica, but no definitive studies have been done that indicate a clear
benefit of its use as a sole treatment or as an adjunct. Traction has no
benefit except for those patients who experience pain relief during the actual
traction.
We know now that psychosocial
factors can play an important role in patients’ symptoms and signs and also in
patients’ response to both nonoperative and operative treatments. For this
reason, behavioral therapies have had a major impact on the treatment and
understanding of long-term effects of sciatic pain on patients with
psychosocial problems. Patients require both physical treatment of their
problem as well as treatment of the psychosocial and behavior aspects of their
condition.
As mentioned previously, most
patients can be treated successfully by nonoperative treatment if the patient
will comply with physical therapy, medications, and transforaminal epidural
steroids. Most importantly, the patient must allow adequate time to heal.
If the patient does not have a progressive or significant neurologic deficit,
cauda equina syndrome (set of symptoms of saddle anesthesia numbness in the
areas that would touch a saddle if the patient were sitting on one, bowel or
bladder incontinence, new onset sensory deficits in legs, or new or progressive
weakness in legs) or severe pain that will not go away, a minimum of six to
eight weeks should be reserved for nonoperative treatment.
However, nonoperative treatment
should not extend beyond four to six months if the patient shows only minimal
improvement. The absolute indications for the surgery are cauda equina syndrome
or a progressive neurologic deficit that includes weakness in the muscles that
are supplied by the impinged nerve root. The relative indications for surgery
are: 1) failure of an adequate trial of nonoperative treatment, and 2)
intractable pain. A prerequisite is radiologic identification of a compressed
nerve that makes sense with the patient’s physical signs and symptoms. Surgery
provides nearly 85% to 95% of patients with good to excellent results. The type
of surgery performed depends on the diagnosis.
Any invasive procedure, no matter
how carefully it is done has risks. Most complications can be avoided with
proper patient selection, education, preoperative planning and meticulous
attention to anatomy and surgical techniques. Fortunately, the serious risks
associated with surgery are the exception rather than the rule. The most
common complications include: wrong vertebral level operated on (1.2 – 3.3%),
missed pathology and/or retained disc, dural (the sac of tissue that covers the
spine) tear (0.8-7.2%), epidural (the space outside the dura) venous bleeding,
nerve root lesion (0.2%), residual sciatica, recurrent disc herniation, cauda
equina syndrome, epidural hematoma, infection (2-3%), iatrogenic vertebral
instability, thromboembolism (blood clot blocking a blood vessel), and
postoperative epidural fibrosis (scar tissue) and/or arachnoiditis
(inflammation of the delicate membrane enclosing the spinal cord and brain).
The overall complication rate ranges from 1% to 3%.
Recurrent herniations occur with a
frequency of 5-15%, with the risk decreasing over time after surgery. Lack of
physical activity is a significant risk factor for recurrence. Distinguishing
between recurrent disc herniation and epidural fibrosis can be difficult.
Contrast enhanced MRI has become the study of choice to differentiate between
disc herniation and scarring.
Based on the studies, operative
treatment provides more rapid resolution of symptoms and a shorter recovery
period compared with conservative care, but no large differences have been
found in success rates after one or two years of follow-up. Patients and
doctors weigh the benefits and harms of both options to make individual
choices. This is especially relevant because the patients’ preference for
treatment may have a direct positive influence on the magnitude of the
treatment effect.
Sciatica is a fairly common health
problem with a lifetime incidence (the number of individuals that have
experienced sciatica at some point in their lives) varying from 13% to 40%. The
most common cause of sciatica is a herniated disc. The precise mechanism of
sciatica is unclear. In addition to mechanical compression, inflammation may
play a role. The natural history of sciatica is favorable, with resolution of
leg pain within six to eight weeks from onset in the majority of patients.
Consensus is that initial treatment is conservative for about six to eight
weeks. Imaging during this acute phase is indicated only in patients with “red
flag” conditions or who have failed conservative treatments. If symptoms do not
improve after six to eight weeks of conservative treatments, patients may
decide on surgery. Those who are hesitant about surgery and can cope with their
symptoms may choose to continue conservative care. Patient preference is,
therefore, an important feature in the decision process. Only 2% to 4% of
patients with disc herniations are surgical candidates. The surgery may provide
quicker relief of leg pain than nonoperative treatment, but no clear
differences have been found after one or two years.
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