Sciatica
Encyclopedia
Sciatica is a set of symptoms including pain
that may be caused by general compression or irritation of one of five spinal nerve roots that give rise to each sciatic nerve
, or by compression or irritation of the left or right or both sciatic nerves. The pain is felt in the lower back, buttock, or various parts of the leg and foot. In addition to pain, which is sometimes severe, there may be numbness, muscular weakness, pins and needles or tingling and difficulty in moving or controlling the leg. Typically, the symptoms are only felt on one side of the body. Pain can be severe in prolonged exposure to cold weather.
Although sciatica is a relatively common form of low back pain
and leg pain, the true meaning of the term is often misunderstood. Sciatica is a set of symptoms rather than a diagnosis for what is irritating the root of the nerve, causing the pain. This point is important, because treatment for sciatica or sciatic symptoms often differs, depending upon the underlying cause of the symptoms and pain levels.
The first known use of the word sciatica dates to 1451.
L4 or L5 or sacral nerves
S1, S2, or S3, or by compression of the sciatic nerve
itself. When sciatica is caused by compression of a dorsal nerve root
(radix
) it is considered a lumbar radiculopathy
(or radiculitis when accompanied with an inflammatory response). This can occur as a result of a spinal disk bulge or spinal disc herniation
(a herniated intervertebral disc
), or from roughening, enlarging, or misalignment (spondylolisthesis
) of the vertebrae, or as a result of degenerated discs
that can reduce the diameter of the lateral foramen through which nerve roots exit the spine. The intervertebral discs consist of an annulus fibrosus, which forms a ring surrounding the inner nucleus pulposus. When there is a tear in the annulus fibrosus
, the nucleus pulposus (pulp) may extrude through the tear and press against spinal nerves within the spinal cord, cauda equina
, or exiting nerve roots, causing inflammation, numbness or excruciating pain. Sciatica due to compression of a nerve root is one of the most common forms of radiculopathy
.
Pseudosciatica or non-discogenic sciatica, which causes symptoms similar to spinal nerve root compression, is most often referred pain
from damage to facet joints
in the lower back and is felt as pain in the lower back and posterior upper legs. Pseudosciatic pain can also be caused by compression of peripheral sections of the nerve, usually from soft tissue tension in the piriformis or related muscle
s (see piriformis syndrome
and see below).
pressing on one of the sciatic nerve roots. The spinal discs are composed of a tough spongiform ring of cartilage (annulus fibrosus
) with a more malleable center (nucleus pulposis). The discs separate the vertebrae, thereby allowing room for the nerve roots to properly exit through the spaces between the L4, L5, and sacral vertebrae. The discs cushion the spine from compressive forces, but are weak to pressure applied during rotational movements. That is why a person who bends to one side, at a bad angle to pick something up, may more likely herniate a spinal disc than a person jumping from a ladder and landing on his or her feet.
Herniation of a disc occurs when the liquid center of the disc bulges outwards, tearing the external ring of fibers, extrudes into the spinal canal, and compresses a nerve root against the lamina or pedicle of a vertebra, thus causing sciatica. This extruded liquid from the nucleus pulposus
may cause inflammation and swelling of surrounding tissue, which may cause further compression of the nerve root in the confined space in the spinal canal.
Sciatica caused by pressure from a disc herniation and swelling of surrounding tissue can spontaneously subside if the tear in the disc heals and pulposis extrusion and inflammation cease.
Sciatica can be caused by tumours impinging on the spinal cord or the nerve roots. Severe back pain extending to the hips and feet, loss of bladder or bowel control, or muscle weakness, may result from spinal tumours. Trauma to the spine, such as from a car accident, may also lead to sciatica.
, or sciatic nerve roots. This narrowing can be caused by bone spurs, spondylolisthesis
, inflammation, or herniated disc, which decreases available space for the spinal cord, thus pinching and irritating nerves from the spinal cord that travel to the sciatic nerves.
rather than beneath it. When the muscle shortens or spasms due to trauma or overuse, it can compress or strangle the sciatic nerve beneath the muscle. Conditions of this type are generally referred to as entrapment neuropathies; in the particular case of sciatica and the piriformis muscle, this condition is known as piriformis syndrome
. It has colloquially been referred to as "wallet sciatica" since a wallet carried in a rear hip pocket will compress the muscles of the buttocks and sciatic nerve when the bearer sits down. Piriformis syndrome may be a cause of sciatica when the nerve root is normal.
The most applied diagnostic test is the straight leg rising test, or Lasègue's sign, which is considered positive if pain in the sciatic nerve is reproduced with between 30 and 70 degrees passive flexion of the straight leg
Diagnosis of sciatica through imaging can be achieved either with computerised tomography or with magnetic resonance imaging
. MR neurography
has been shown to diagnose 95% of severe sciatica patients, while as few as 15% of sciatica sufferers in the general population are diagnosed with disc-related problems. MR neurography may help diagnose piriformis syndrome—another cause of sciatica that does not involve disc herniation.
90% of disc prolapses resolve with no intervention. Treatment of the underlying cause of the compression is needed in cases of epidural abscess, epidural tumors, and cauda equina syndrome
.
Although medications are commonly prescribed for the treatment of sciatica, evidence from clinical trials to guide the use of analgesics to relieve pain and disability is lacking. Research has shown no significant difference between placebo
s, NSAIDs, analgesics, and muscle relaxants. Evidence is lacking in use of opioid
s and compound drugs.
Research has failed to show a significant difference in outcomes between advice to stay active and recommendations of bed rest. Similarly, physical therapy (exercises) has not been found better than bed rest.
Elective surgery is the main option for unilateral sciatica and focuses on removal of the underlying cause by removing disk herniation and eventually part of the disc. In a controlled study, surgical intervention was found to have better results after one year but after four and ten year follow ups no significant differences were found.
Moderate quality evidence suggests that spinal manipulation
is effective for the treatment of acute sciatica, however, only low level evidence was found to support spinal manipulation for the treatment of chronic sciatica. Spinal manipulation has been found safe for the treatment of disc-related pain.
Pain
Pain is an unpleasant sensation often caused by intense or damaging stimuli such as stubbing a toe, burning a finger, putting iodine on a cut, and bumping the "funny bone."...
that may be caused by general compression or irritation of one of five spinal nerve roots that give rise to each sciatic nerve
Sciatic nerve
The sciatic nerve is a large nerve fiber in humans and other animals. It begins in the lower back and runs through the buttock and down the lower limb...
, or by compression or irritation of the left or right or both sciatic nerves. The pain is felt in the lower back, buttock, or various parts of the leg and foot. In addition to pain, which is sometimes severe, there may be numbness, muscular weakness, pins and needles or tingling and difficulty in moving or controlling the leg. Typically, the symptoms are only felt on one side of the body. Pain can be severe in prolonged exposure to cold weather.
Although sciatica is a relatively common form of low back pain
Back pain
Back pain is pain felt in the back that usually originates from the muscles, nerves, bones, joints or other structures in the spine.The pain can often be divided into neck pain, upper back pain, lower back pain or tailbone pain...
and leg pain, the true meaning of the term is often misunderstood. Sciatica is a set of symptoms rather than a diagnosis for what is irritating the root of the nerve, causing the pain. This point is important, because treatment for sciatica or sciatic symptoms often differs, depending upon the underlying cause of the symptoms and pain levels.
The first known use of the word sciatica dates to 1451.
Cause
Sciatica is generally caused by the compression of lumbar nervesLumbar nerves
The lumbar nerves are the five spinal nerves emerging from the lumbar vertebrae. They are divided into posterior and anterior divisions.-Posterior divisions:...
L4 or L5 or sacral nerves
Sacral nerves
The five sacral nerves emerge from the sacrum. Although the vertebral components of the sacrum are fused into a single bone, the sacral vertebrae are still used to number the sacral nerves....
S1, S2, or S3, or by compression of the sciatic nerve
Sciatic nerve
The sciatic nerve is a large nerve fiber in humans and other animals. It begins in the lower back and runs through the buttock and down the lower limb...
itself. When sciatica is caused by compression of a dorsal nerve root
Dorsal root
In anatomy and neurology, the dorsal root is the afferentsensory root of a spinal nerve.At the distal end of the dorsal root is the dorsal root ganglion, which contains the neuron cell bodies of the nerve fibres conveyed by the root.If the dorsal root of a spinal nerve were severed it would lead...
(radix
Radix (disambiguation)
Radix refers to the number b in an expression of the form bnRadix may also refer to:- Biology :*Radix, the root of a plant in botany**Also used for dorsal root and ventral root in anatomy. Derived terms e.g...
) it is considered a lumbar radiculopathy
Radiculopathy
Radiculopathy is not a specific condition, but rather a description of a problem in which one or more nerves are affected and do not work properly . The emphasis is on the nerve root...
(or radiculitis when accompanied with an inflammatory response). This can occur as a result of a spinal disk bulge or spinal disc herniation
Spinal disc herniation
A spinal disc herniation , informally and misleadingly called a "slipped disc", is a medical condition affecting the spine due to trauma, lifting injuries, or idiopathic, in which a tear in the outer, fibrous ring of an intervertebral disc allows the soft, central portion A spinal disc herniation...
(a herniated intervertebral disc
Intervertebral disc
Intervertebral discs lie between adjacent vertebrae in the spine. Each disc forms a cartilaginous joint to allow slight movement of the vertebrae, and acts as a ligament to hold the vertebrae together.-Structure:...
), or from roughening, enlarging, or misalignment (spondylolisthesis
Spondylolisthesis
Spondylolisthesis describes the anterior or posterior displacement of a vertebra or the vertebral column in relation to the vertebrae below. It was first described in 1782 by Belgian obstetrician, Dr. Herbinaux. He reported a bony prominence anterior to the sacrum that obstructed the vagina of a...
) of the vertebrae, or as a result of degenerated discs
Degenerative disc disease
Degeneration of the intervertebral disc, often called "degenerative disc disease" of the spine, is a condition that can be painful and can greatly affect the quality of one's life...
that can reduce the diameter of the lateral foramen through which nerve roots exit the spine. The intervertebral discs consist of an annulus fibrosus, which forms a ring surrounding the inner nucleus pulposus. When there is a tear in the annulus fibrosus
Annulus fibrosus disci intervertebralis
Each intervertebral fibrocartilage is composed, at its circumference, of laminæ of fibrous tissue and fibrocartilage, forming the annulus fibrosus.-Spelling notes:...
, the nucleus pulposus (pulp) may extrude through the tear and press against spinal nerves within the spinal cord, cauda equina
Cauda equina
The cauda equina is a structure within the lower end of the spinal column of most vertebrates, that consists of nerve roots and rootlets from above...
, or exiting nerve roots, causing inflammation, numbness or excruciating pain. Sciatica due to compression of a nerve root is one of the most common forms of radiculopathy
Radiculopathy
Radiculopathy is not a specific condition, but rather a description of a problem in which one or more nerves are affected and do not work properly . The emphasis is on the nerve root...
.
Pseudosciatica or non-discogenic sciatica, which causes symptoms similar to spinal nerve root compression, is most often referred pain
Referred pain
Referred pain is pain perceived at a location other than the site of the painful stimulus. An example is the case of ischemia brought on by a myocardial infarction , where pain is often felt in the neck, shoulders, and back rather than in the chest, the site of the injury...
from damage to facet joints
Zygapophysial joint
A zygapophysial joint is a synovial joint between the superior articular process of one vertebra and the inferior articular process of the vertebra directly above it...
in the lower back and is felt as pain in the lower back and posterior upper legs. Pseudosciatic pain can also be caused by compression of peripheral sections of the nerve, usually from soft tissue tension in the piriformis or related muscle
Muscle
Muscle is a contractile tissue of animals and is derived from the mesodermal layer of embryonic germ cells. Muscle cells contain contractile filaments that move past each other and change the size of the cell. They are classified as skeletal, cardiac, or smooth muscles. Their function is to...
s (see piriformis syndrome
Piriformis syndrome
Piriformis syndrome is a neuromuscular disorder that occurs when the sciatic nerve is compressed or otherwise irritated by the piriformis muscle causing pain, tingling and numbness in the buttocks and along the path of the sciatic nerve descending down the lower thigh and into the leg...
and see below).
Spinal disc herniation
One of the possible causes of sciatica is a spinal disc herniationSpinal disc herniation
A spinal disc herniation , informally and misleadingly called a "slipped disc", is a medical condition affecting the spine due to trauma, lifting injuries, or idiopathic, in which a tear in the outer, fibrous ring of an intervertebral disc allows the soft, central portion A spinal disc herniation...
pressing on one of the sciatic nerve roots. The spinal discs are composed of a tough spongiform ring of cartilage (annulus fibrosus
Annulus fibrosus disci intervertebralis
Each intervertebral fibrocartilage is composed, at its circumference, of laminæ of fibrous tissue and fibrocartilage, forming the annulus fibrosus.-Spelling notes:...
) with a more malleable center (nucleus pulposis). The discs separate the vertebrae, thereby allowing room for the nerve roots to properly exit through the spaces between the L4, L5, and sacral vertebrae. The discs cushion the spine from compressive forces, but are weak to pressure applied during rotational movements. That is why a person who bends to one side, at a bad angle to pick something up, may more likely herniate a spinal disc than a person jumping from a ladder and landing on his or her feet.
Herniation of a disc occurs when the liquid center of the disc bulges outwards, tearing the external ring of fibers, extrudes into the spinal canal, and compresses a nerve root against the lamina or pedicle of a vertebra, thus causing sciatica. This extruded liquid from the nucleus pulposus
Nucleus pulposus
Nucleus pulposus is the jelly-like substance in the middle of the spinal disc. It is the remnant of the notochord . It functions to distribute hydraulic pressure in all directions within each disc under compressive loads. The nucleus pulposus consists of chondrocyte-like cells, collagen fibrils,...
may cause inflammation and swelling of surrounding tissue, which may cause further compression of the nerve root in the confined space in the spinal canal.
Sciatica caused by pressure from a disc herniation and swelling of surrounding tissue can spontaneously subside if the tear in the disc heals and pulposis extrusion and inflammation cease.
Sciatica can be caused by tumours impinging on the spinal cord or the nerve roots. Severe back pain extending to the hips and feet, loss of bladder or bowel control, or muscle weakness, may result from spinal tumours. Trauma to the spine, such as from a car accident, may also lead to sciatica.
Spinal stenosis
Other compressive spinal causes include lumbar spinal stenosis, a condition in which the spinal canal (the spaces through which the spinal cord runs) narrows and compresses the spinal cord, cauda equinaCauda equina
The cauda equina is a structure within the lower end of the spinal column of most vertebrates, that consists of nerve roots and rootlets from above...
, or sciatic nerve roots. This narrowing can be caused by bone spurs, spondylolisthesis
Spondylolisthesis
Spondylolisthesis describes the anterior or posterior displacement of a vertebra or the vertebral column in relation to the vertebrae below. It was first described in 1782 by Belgian obstetrician, Dr. Herbinaux. He reported a bony prominence anterior to the sacrum that obstructed the vagina of a...
, inflammation, or herniated disc, which decreases available space for the spinal cord, thus pinching and irritating nerves from the spinal cord that travel to the sciatic nerves.
Piriformis syndrome
In 15% of the population, the sciatic nerve runs through the piriformis musclePiriformis muscle
The piriformis is a muscle in the gluteal region of the lower limb. It was first named by Spigelius, a professor from the University of Padua in the 16th century.- Origin and insertion :...
rather than beneath it. When the muscle shortens or spasms due to trauma or overuse, it can compress or strangle the sciatic nerve beneath the muscle. Conditions of this type are generally referred to as entrapment neuropathies; in the particular case of sciatica and the piriformis muscle, this condition is known as piriformis syndrome
Piriformis syndrome
Piriformis syndrome is a neuromuscular disorder that occurs when the sciatic nerve is compressed or otherwise irritated by the piriformis muscle causing pain, tingling and numbness in the buttocks and along the path of the sciatic nerve descending down the lower thigh and into the leg...
. It has colloquially been referred to as "wallet sciatica" since a wallet carried in a rear hip pocket will compress the muscles of the buttocks and sciatic nerve when the bearer sits down. Piriformis syndrome may be a cause of sciatica when the nerve root is normal.
Diagnosis
Sciatica is diagnosed by physical examination, neurological testing and patient history. Generally if a patient reports the typical radiating pain in one leg as well as one or more neurological indications of nerve root tension or neurological deficit, sciatica can be diagnosed.The most applied diagnostic test is the straight leg rising test, or Lasègue's sign, which is considered positive if pain in the sciatic nerve is reproduced with between 30 and 70 degrees passive flexion of the straight leg
Diagnosis of sciatica through imaging can be achieved either with computerised tomography or with magnetic resonance imaging
Magnetic resonance imaging
Magnetic resonance imaging , nuclear magnetic resonance imaging , or magnetic resonance tomography is a medical imaging technique used in radiology to visualize detailed internal structures...
. MR neurography
Magnetic resonance neurography
Magnetic resonance neurography is the direct imaging of nerves in the body by optimizing selectivity for unique MRI water properties of nerves. It is a modification of magnetic resonance imaging. This technique yields a detailed image of a nerve from the resonance signal that arises from in the...
has been shown to diagnose 95% of severe sciatica patients, while as few as 15% of sciatica sufferers in the general population are diagnosed with disc-related problems. MR neurography may help diagnose piriformis syndrome—another cause of sciatica that does not involve disc herniation.
Treatment
When the cause of sciatica is due to a prolapsed or lumbar disc herniationSpinal disc herniation
A spinal disc herniation , informally and misleadingly called a "slipped disc", is a medical condition affecting the spine due to trauma, lifting injuries, or idiopathic, in which a tear in the outer, fibrous ring of an intervertebral disc allows the soft, central portion A spinal disc herniation...
90% of disc prolapses resolve with no intervention. Treatment of the underlying cause of the compression is needed in cases of epidural abscess, epidural tumors, and cauda equina syndrome
Cauda equina syndrome
Cauda equina syndrome ' is a serious neurologic condition in which there is acute loss of function of the lumbar plexus, neurologic elements of the spinal canal below the termination of the spinal cord.-Causes:...
.
Although medications are commonly prescribed for the treatment of sciatica, evidence from clinical trials to guide the use of analgesics to relieve pain and disability is lacking. Research has shown no significant difference between placebo
Placebo
A placebo is a simulated or otherwise medically ineffectual treatment for a disease or other medical condition intended to deceive the recipient...
s, NSAIDs, analgesics, and muscle relaxants. Evidence is lacking in use of opioid
Opioid
An opioid is a psychoactive chemical that works by binding to opioid receptors, which are found principally in the central and peripheral nervous system and the gastrointestinal tract...
s and compound drugs.
Research has failed to show a significant difference in outcomes between advice to stay active and recommendations of bed rest. Similarly, physical therapy (exercises) has not been found better than bed rest.
Elective surgery is the main option for unilateral sciatica and focuses on removal of the underlying cause by removing disk herniation and eventually part of the disc. In a controlled study, surgical intervention was found to have better results after one year but after four and ten year follow ups no significant differences were found.
Moderate quality evidence suggests that spinal manipulation
Spinal manipulation
Spinal manipulation is a therapeutic intervention performed on spinal articulations which are synovial joints . These articulations in the spine that are amenable to spinal manipulative therapy include the z-joints, the atlanto-occipital, atlanto-axial, lumbosacral, sacroiliac, costotransverse...
is effective for the treatment of acute sciatica, however, only low level evidence was found to support spinal manipulation for the treatment of chronic sciatica. Spinal manipulation has been found safe for the treatment of disc-related pain.