Types of Spinal Disc Herniation

Disc Extrusion, Protrusion, and Sequestration

spinal disc

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A spinal herniation occurs when a disc—the soft cushion between two vertebrae—pushes outward beyond the normal boundaries of a healthy disc. Medical professionals use several terms to describe the extent of a spinal disc herniation seen on an MRI examination: disc protrusion, disc extrusion, and disc sequestration.

A herniation's classification depends on the condition of two disc parts: the annulus fibrosus (the disc's tough outer covering) and the nucleus pulposus (the jelly-like center of the disc). The disc can bulge and remain intact, or the nucleus can leak out from a tear in the annulus.

Also Known As

A herniated disc is sometimes called "a slipped disc" or "throwing out your back." Herniation types are sometimes called "phases."

Disc Protrusion

In this type of herniation, the spinal disc and the associated ligaments remain intact but form an outpouching that can press against nerves. Technically speaking, the farthest edge of the herniation measures smaller than the herniation's origin at the base of the disc.

A disc protrusion can remain as is, but it can also progress into one or both of the following two herniation phases.

Disc Extrusion

This kind of herniation occurs when the nucleus squeezes through a weakness or tear in the annulus, but the soft material is still connected to the disc.

Your body considers the nucleus material to be a foreign invader, which triggers an immune response and inflammation. This can bring about additional pain and swelling.

As with protrusion, an extrusion can remain as it is, but can also progress to the next phase of herniation.

Disc Sequestration

Disc sequestration is a subtype of extrusion occurring when the nucleus not only squeezes out but separates from the main part of the disc. This is also known as a free fragment.

The free fragment can migrate and aggravate spinal nerves, but there is no way to predict where or how severely. Any symptoms, if they occur, depend on where the fragment settles. Symptoms generally appear in one extremity (one arm for a neck herniation, or one leg for a lower back herniation).

As with extrusion, sequestration can also trigger an immune response to the nucleus material, bringing inflammation to the area.

Ruptured disc is not an accepted medical term and suggests trauma when none has occurred. The technical term is displacement of disc material.

Herniation Symptoms

The hallmark of disc herniation is pain. Any of the three herniation types have the potential to cause it and other symptoms.

For example, depending on its location, a protrusion can come in contact with spinal nerves just as easily as an extrusion or sequestration can. The amount of pain and other symptoms will depend on how the nerves have been compromised.

Along with pain, herniations can press against the spinal cord or nerves and cause radiculopathy, the neuromuscular symptoms typical of a disc herniation.

For a lumbar herniation, these include back spasms, sciatica, tingling, numbness, pain down the back of the legs, and possible muscle weakness and loss of lower-body motor function.

For a cervical herniation, these include neck spasms, pain/tingling/numbness down one arm, shoulder pain and/or weakness, and weakened reflex response in these areas.

All that said, it's still common to have protrusions, extrusions, or sequestrations with no symptoms whatsoever. One review of 33 studies found that 37% of 20-year-olds may have herniations without symptoms, and the number rises with age to 96% of 80-year-olds.

Diagnosis

Most terminology surrounding spinal discs are based on measurements, as well as the size and shape of the displaced disc material. While some using the terms bulging disc and herniated disc interchangeably, there are clinical distinctions between the two based on these factors:

  • A herniation measures less than 25% of the total disc circumference.
  • A bulge measures greater than 25% of the total disc circumference.

Bulges also don't extend very far beyond the normal boundaries of a healthy disc, usually 3 millimeters or less, and generally cause fewer symptoms than herniations.

Magnetic resonance imaging (MRI) is often the tool of choice when trying to assess the discs of the spinal column. However, it has its challenges.

Non-Definitive Findings

Since disc degeneration naturally worsens with age, it's actually common to find disc abnormalities on MRI tests. This is an issue when working to diagnose a herniation as subtle findings may not be clinically important, but may lead people to invasive or expensive treatments that they don't really need.

For example, someone may have back pain, as well as a disc abnormality on their MRI, but that does not necessarily mean the two are related. They can be, but presuming the two are related can lead to poor treatment results.

A skilled clinician can help you determine if the disc problem seen on an MRI is truly the cause of your symptoms. It may help to seek a second opinion.

To further complicate matters, the specific type of disc problem seen on an MRI does not necessarily dictate treatment, which makes next steps uncertain.

A doctor must correlate the MRI results with your complaints and examination findings. If these don't all point to the same underlying problem, treatment is less likely to be effective.

Disc Herniation Treatment

Most lower back pain resolves itself in four to six weeks even if you don't seek treatment.

Oddly enough, the more damage to a disc, the faster spontaneous healing seems to occur. One review of 31 studies found the rates for spontaneous regression of herniated discs to be 96% for sequestration, 70% for extrusion, and 41% for protrusion. This could be because the body absorbs the nucleus material that's leaked from the disc, relieving nerve pressure/irritation.

Treatment for all types of disc herniation is generally conservative and includes:

Surgery is generally recommended only when conservative treatments are ineffective after six weeks or more, if you have significant muscle weakness from nerve damage, or when motor functions are compromised.

One herniation-related condition of the lower back, cauda equina, is considered a medical emergency and requires immediate care. It can cause urinary or bowel dysfunction, numbness around the anus, along with traditional herniation symptoms.

A Word From Verywell

Mild back or neck pain may not be a reason to see a doctor unless it persists for several weeks, but more severe symptoms including radiculopathy warrant care. Back pain and injuries can be complex, challenging, and frustrating. If your doctor suspects disc herniation, no matter the type, your diagnosis should combine MRI results along with your specific symptoms and how they progress over time.

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Article Sources

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