Last Updated on November 22, 2023
Spinal disc herniation is a condition in which a tear in the annulus fibrosus (Outer firmer ring) of an intervertebral disc allows the soft, central portion (nucleus pulposus) to bulge out. Due to that adjacent neural structures may get compressed and produce symptoms of radiculopathy.
The following diagram would make it easier to comprehend how a spinal disc herniation can affect nerve roots. On the left side is a normal disc and on the right side is a herniated disc.
Spinal disc herniation is most common in the lumbar followed by the cervical spine. L4-L5 and L5-S1 discs are most common to herniate in the lumbar spine. In the cervical spine, C5-C6 and C6-C7 discs are most commonly involved.
Spinal disc herniation is rare in the thoracic spine.
Mostly, spinal disc herniations occur in young people. With age, the nucleus pulposus dries and the risk of herniation is reduced.
It is now being recognized in addition to compression of the nerve root there is the release of inflammatory mediator with herniation of the disc. This mediator is recognized as tumor necrosis factor-alpha (TNF). This molecule is released not only by the herniated disc, but also in cases of disc tear, by facet joints, and in spinal stenosis.
Relevant Anatomy and Structure of Intervertebral Disc
The Intervertebral disc is present between two vertebrae except those that are fused [for example, sacral and coccygeal]. The disc serves as a kind of shock absorber and provides cushion during the motion of vertebrae. Thus it prevents grinding of vertebrae against each other.
Discs are attached to vertebral bodies by hyaline cartilage.
Each disc is made up of two parts: the annulus fibrosus and the nucleus pulposus.
The disc is sandwiched between two vertebral bodies. The discs are in contact with vertebral endplates.
Vertebral endplates have a cortical rim and compressed cancellous bone in the central disc area, which covers nearly 70% of the disk.
The outer 30% consists of a dense cortical margin and is the strongest area of the endplate.
The annulus is a ring-like tough structure that surrounds and encases the other structure of the intervertebral disc, called the nucleus pulposus.
The annulus fibrosis is tough and provides rotational stability. It also resists compressive stress.
The annulus is made of water, proteoglycans, and type I collagen fibers. These fibres are oriented at different angles horizontally to create strength.
Multiple layers of collagen fibers are arranged in a unique circumferential orientation along the disc periphery. Each layer is called lamella.
The outer collagen fibers attach to the ring apophysis, and the inner layers attach to the endplate surrounding the nucleus.
The high collagen/ low proteoglycan ratio of these makes the disc flexible enough.
It is the gel-like elastic substance within the annulus fibrous and is composed of the same material as annulus fibrosis – water, collagen, and proteoglycans but in different concentrations and structural arrangements.
The nucleus pulposus is composed of type II collagen, water, and proteoglycans. Nucleus pulposus contains approximately 88% water. It maintains the disc height and compressibility.
Viscoelastic matrix makes the annulus fibrous elastic and enables the distribution of the forces smoothly to the annulus and the endplates.
Overall, the disc gradients from the fibrous well-organized periphery to the randomly organized gelatinous center.
Pathophysiology of Disc Herniation
Recurrent loading of the spine leads to recurrent torsional strain causing tears of the outer annulus. This tear makes herniation of the disc more likely. The most common site of disc herniation is posterolateral or paracentral [see below] as the posterior longitudinal ligament is weakest there.
Sinuvertebral nerves innervate the annulus on the posterior part and carry the pain sensation.
Microscopically, age-related cell cycle stoppage [senescence] of fibrochondrocytes leads to loss of proteoglycan production causing loss of disc height which causes strain on annulus fibrosus.
This leads to tears in the annulus where the nucleus pulposus may herniate through repetitive loading or sudden acute load.
The symptoms result from a combination of
- Mechanical compression
Cause of Spinal Disc Herniation
Usually, there is a history of strain on the back which may be in the form of lifting heavy weights or sudden movement. In some patients, no cause or antecedent event could be elicited.
A preexisting protrusion of the disc might be there before the disc herniation takes place. A protrusion is one in which fibers of annulus fibrosus are not torn but on increase in internal pressure, it bulges out. The following diagram shows stages of disc herniation
Minor back pain and chronic back tiredness are indicators of general wear and tear that make one susceptible to herniation on the occurrence of a traumatic event from bending or a traumatic injury from a fall.
Classification of Disc Herniation
Disc herniation can be classified by many factors.
Depending on the Site of the Herniation
The disc prolapses in the midline. As the roots are lateral, radiculopathy [referral is not common and this type is associated with back pain only.
In case, the disc is big in size the herniation may affect the cord when cord tissue is present. This is often seen in cauda equina syndrome. Cauda equina is a surgical emergency.
Posterolateral or Paracentral
This is the most common type of spinal disc herniation in lumbar spine. It is so because the posterior longitudinal is the weakest here.
It often causes the compression of nerve roots.
Foraminal or Far Lateral
The herniation is more lateral than the previous. It is less common and affects the nerve exiting from the foramen. It can directly compress the dorsal root ganglion. This type is more painful than other types.
In the axillary type, the disc material travels posteriorly into the axilla between the nerve roots laterally and thecal sac medially.
In the shoulder type, the disc material lies lateral or ventral to the nerve root.
Classification Depending on the Extent of Herniation
- A bugle with an intact annulus
- The annulus is torn and the disc herniates but stays in the disc space
- Sequestered fragment
- Disc out of disc space after extrusion
- May migrate proximally or distally
Contained Vs Uncontained
- Disc materials contained beneath the posterior longitudinal ligament
- Disc material passes dorsal to the posterior longitudinal ligament
- Disc material passes dorsal to the posterior longitudinal ligament
Acute vs Chronic
- herniation of recent origin – 3-6 months is called acute
- >6 months chronic
- herniations present < 3-6 months
The lumbar disc herniation can present with
- Axial pain
- Pain in the lower back
- This may start before the actual herniation
- Radicular pain
- Pain that radiates
- Seen in the buttocks, and thighs, and may radiate into the foot and/or toe
- Pain gets worsened with anything that leads to an increase in abdominal pressure
- Pain does not get worse with ambulation
- Cauda Equina Syndrome
- Seen in less than 10%
- Disc herniation compresses the cauda equina region of the cord
- Typical presentation
- Bilateral lower limb pain
- saddle anesthesia [numbness in the perineal area]
- bladder or bowel complaints
The severity of symptoms may range from little or no pain to severe and unrelenting back pain that will radiate into the regions of affected nerve roots.
It may be accompanied by neural deficits in the form of muscle weakness.
There could be a history of [though it may not be elicited in a substantial number of the patients].
- Sudden pain that started after lifting a heavy object
- Repetitive injury to the spine as occupational exposure [for example, exposure to vibrations in a sitting position for prolonged times
The pain improves when the patient lies down, especially with knees and hips flexed.
To sum up, most commonly a patient with lumber disc herniation may present with
- Back pain
- Pain that radiates to one or both limbs, usually single-limb involvement
- Numbness and/or tingling over the region of the nerve involved [see physical examination]
- Muscle weakness
- Involvement of bladder/ bowel should arouse suspicion of cauda equina syndrome.
Note: The patients with severe radiating pain have difficulty in sitting, standing, and walking and prefer to lie down. So that part of the examination may have to be omitted in these cases.
On examination, there would be a decrease in range of motion due to accompanying pain and spasms.
The patient may lean to one side, usually away from the side of radiculopathy. This is often, a protective mechanism, to decrease the irritation/compression of the involved nerve.
This phenomenon is also called the lateral shift or trunk list.
Back on examination may show paraspinal spasm as indicated by muscle tightness. There could be vague nonspecific tenderness lover the area too.
L5 involvement may show Trendelenber gait suggesting weakness of gluteus medius muscles.
Neural Examination is conducted thoroughly to find the nerve root being compressed. Different nerve roots have different profiles of function and their compression is presented as detailed below.
- Pain in the lateral thigh, leg, and medial aspect of the foot
- Diminished extensor patellar tendon reflex
- Weakness in ankle dorsiflexors [both L4, L5 contribute; L4 slightly more]
- Pain in the anterolateral aspect of the leg and dorsum of the foot
- Weakness of extensor hallucis longus muscle
- Weak ankle dorsiflexor/invertors
- hip abduction weakness (L5)
- Pain in calf on posterior aspect and lateral foot
- Weakness of plantar flexors
- Diminished Achilles tendon reflex
These tests are done to reproduce the symptoms and signs by provoking nerve compression
Straight leg raise Test
It is also called Lasegue’s sign and is a stretch test to tense the nerve roots L4, L5, and S1. It can be done in a sitting or supine position.
The test reproduces the pain and tingling sensation in leg by making the hip position in 30-70 degrees of flexion.
The test is sensitive but not very specific. There is another version of the test where instead of the examiner raising the leg, the patient actively raises the leg to its position. It is called the active straight leg raise test or aSLR
Braggard’s sign is a further extension of this maneuver. After SLR is done, the knee is flexed till the point pain goes away. At that point, ankle dorsiflexion is done and pain is exacerbated.
Similarly, Bowstring sign is when an SLR test leads to pain and the pain is worsened by pressure on the popliteal fossa.
Contralateral Leg Raise Test
This is similar to SLR but it is done on the opposite nonsymptomatic limb. When present, the contralateral leg raise is more specific. It is also called the crossed-leg raise test.
Femoral Nerve Stretch Test
It is also called the reverse Lasegue test or Wasserman sign. It tests for compression of L2 and L3. It is performed in a prone or lateral position.
For performing the test, the knee is flexed and then the hip is extended by the examiner. Reproduction of pain in the anterior thigh makes the test positive.
Imaging for Spinal Disc Herniation
Plain X-rays have a limited role in the diagnosis of disc herniation as they are unable to define soft tissues such as discs, muscles, and nerves.
But often these are the initial investigations. AP and lateral radiographs are recommended views. These can identify any bony abnormalities.
Flexion-extension X-rays may be done to look for spinal instability.
The most common findings are
- Mostly normal
- The following abnormal findings are not specific
- Loss of lumbar lordosis
- Lumbar spine degenerative changes
- Reduction of disc height
Magnetic resonance imaging is the investigation of choice to confirm disc pathologies. It can show the spinal cord, nerve roots, and surrounding areas and is a very sensitive investigation to show even a slight bulge of the disc.
The following MRI image shows disc herniation between L5 and S1 vertebrae.
MRI is indicated in
- Pain occurring for more than one month that has not responded to nonoperative treatment
- At the outset, in patients with
- Suspected infection
- Suspected malignancy
- Cauda equina syndrome
MRI has high sensitivity and specificity and is very helpful for preoperative planning. As it is very sensitive, MRI may lead to overdiagnosis and therefore clinical correlation is very important.
MRI with gadolinium enhancement is very useful in revision surgery as the enhancement distinguishes between fibrosis [enhanced with gadlinium] that developed after surgery and repeat herniation [unenhanced].
This investigation is not commonly performed. It is indicated in cases where MRI cannot be done such as patients with vascular or orthopedic implants etc.
It is quite good to pick up herniation but is not able to detect foraminal herniations. It can also tell about any surgical pathology.
Treatment of Spinal Disc Herniation
The majority of herniated discs can be managed with nonoperative treatment.
Following treatment modalities may be used in conjunction to treat disc herniation non-operatively.
- Physical therapy, which may include ultrasound, massage, conditioning, and exercise programs
- Pain relief drugs
- Non-steroidal anti-inflammatory drugs
- Oral steroids
- Lumbosacral back support
This treatment is indicated in
- New onset pain
- No cauda equina syndrome
- No significant neural deficit
Nonoperative treatment has a high success rate but patient cooperation is very important.
Selective nerve root epidural steroids are used as the second line of treatment if the above-listed measures do not bring improvements in about 6 weeks. Steroids can provide long-term relief in about half of the patients.
If nonoperative methods fail even after treatment for 6 weeks, surgery should be considered. However, there are certain conditions where surgery is indicated without considering the option of nonoperative treatment
- Significant neurological deficit
- Cauda equina syndrome [It’s a medical emergency]
Note: Studies have found that 1-year outcomes were similar for patients assigned to early surgery and those assigned to conservative treatment with eventual surgery if needed, but the rates of pain relief and of perceived recovery were faster for those assigned to early surgery. Thus patient decision and pain tolerance become factors for surgical decisions.
Indications, Surgical Goals and Options
Indications for surgery are
- Persistent disabling pain > 6 weeks without improvement with nonoperative treatment
- Significant progressive weakness
- Cauda equina syndrome
- Relief of nerve compression
- Nerve recovery
- Relief of associated back pain
- Restoration of normal function.
Surgical options employed for lumbar disc herniation are
- Laminectomy /Hemilaminectomy
- Intradiscal electrothermal Therapy
- Disc replacement
Discectomy or open discectomy removal of the disc after surgical incision. The procedure involves removing the central portion of an intervertebral disc, the nucleus pulposus, which causes pain by stressing the spinal cord or radiating nerves.
Nowadays a smaller incision is used and the procedure is called microdiscectomy. It uses a loupe or microscope for the procedure.
With the traditional discectomy, a laminotomy [cutting of lamina] is often involved to permit access to the intervertebral disc.
Intradiscal electrothermal annuloplasty is a less invasive and outpatient procedure. The procedure is performed under local anaesthesia.
Under fluoroscopy, a thin electrothermal catheter [heating wire] is passed through the needle into the disc and maneuvered into place around the outer edge of the central nucleus. The wire is heated slowly to a temperature of 90 degrees Celsius for about 15 minutes. Heat can potentially contract and shrink the fibres that make up the disc wall, closing any tears.
It should not be considered in
Transforaminal Endoscopic Surgical System
Also popularly abbreviated to TESS, in this method, the surgeon removes the herniated portions of the disc using an endoscope through intervertebral foramen
Laminectomy means the removal of the lamina, a posterior arch of the vertebral bone lying between the spinous process pedicles and the transverse processes of each vertebra. Laminectomy, conventionally also removes the posterior spinal ligament and the spinous process.
It is a procedure for decompressing the spine or gaining more access to the deeper regions and is now rarely done for herniated discs unless it has resulted in secondary canal stenosis.
Laminotomy is a procedure that removes part of a lamina instead of the whole lamina.
Intervertebral Disc arthroplasty
It is also called artificial disc replacement, or total disc replacement, and is a type of arthroplasty. In intervertebral disc arthroplasty, the degenerated intervertebral disc is replaced with artificial discs.
It is an alternative to spinal fusion which aims at eliminating pain while preserving motion.
- Dural tear – immediate repair should be done
- Vascular Injury – very rare, may be fatal if a major vessel involved
- Epidural fibrosis
- Infectious discitis
- Low back pain
About 90 percent of the patients improve within 3 months of medical treatment.
Non-obese and patients not having radicular pain respond better.
Leg pains respond better to surgery than back pain. Symptoms present for a shorter duration have a better response.
In the long-term context, the results of surgery and nonoperative treatment are equivalent. However, surgery provides faster pain relief.
Prevention of Disc Herniation
It is not possible to prevent the herniated disc altogether. But you can reduce the risk by inculcating some good spine habits
- Good postural habits: A good posture loads the spine in a proper way. It is important to sit, stand, walk, and sleep in the right posture. Learn more about avoiding back pain by correcting postures.
- Proper lifting techniques: First, do not attempt too heavy a load. Secondly, do not bend at the waist to lift something from below. Instead, bend at the knees while keeping the spine straight.
- Stay healthy: An excess weight loads the lower spine unnecessarily.
- Build core strength: Focus on your back and abdominal muscles.
- Quit smoking: Smoking decreases blood supply and has a weakening effect on the tissues, making them vulnerable.
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- Schoenfeld AJ, Weiner BK. Treatment of lumbar disc herniation: Evidence-based practice. Int J Gen Med. 2010 Jul 21;3:209-14.
Kerr D, Zhao W, Lurie JD. What Are Long-term Predictors of Outcomes for Lumbar Disc Herniation? A Randomized and Observational Study. Clin Orthop Relat Res. 2015 Jun;473(6):1920-30. [link]
- Oster BA, Kikanloo SR, Levine NL, Lian J, Cho W. Systematic Review of Outcomes Following 10-Year Mark of Spine Patient Outcomes Research Trial for Intervertebral Disc Herniation. Spine (Phila Pa 1976). 2020 Jun 15;45(12):825-831. [Link]