Understanding the Clinical Diagnosis of a Herniated Disc

By: John P. Revord, MD

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A physician’s clinical diagnosis focuses on determining the source of a patient’s pain. For this reason, the clinical diagnosis of pain from a herniated disc is based on more than just the findings from a diagnostic test, such as an MRI scan or CT scan. Instead, the spine care professional arrives at a clinical diagnosis of the cause of the patient’s pain through a combination of findings from a thorough medical history, conducting a complete physical exam, and, if appropriate, conducting one or more diagnostic tests.

Medical history. The physician will take the patient’s medical history, such as a description of when the low back pain, sciatica or other symptoms occur, a description of how the pain feels, what activities, positions or treatments make the pain feel better and more.
Physical exam. The physicians will conduct a thorough physical exam of the patient, such as testing nerve function and muscle strength in certain parts of the leg or arm, testing for pain in certain positions and more. Usually, this series of physical tests will give the spine professional a good idea of the type of back problem the patient has.

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Diagnostic tests. After the physician has a good idea of the source of the patient’s pain, a diagnostic test, such as a CT scan or an MRI scan, is often ordered to confirm the presence of an anatomical lesion in the spine. The tests can give a detailed picture of the location of the herniated disc and impinged nerve roots.

It is important to emphasize that MRI scans and other diagnostic tests are not used to diagnose the patient’s pain; rather, they are only used to confirm the presence of an anatomical problem that was identified or suspected through the medical history and physical exam. For this reason, while the radiographic findings on an MRI scan or other tests are important, they are not as significant in diagnosing the cause of the patient’s pain (the clinical diagnosis) as are the findings from the medical history and physical exam. Often, an MRI scan or other type of test will be used mainly for the purpose of surgical planning—for example, so the surgeon can see exactly where the herniated disc is and how it is impinging on the nerve root.

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What happens when a disc herniates

While the spinal discs are designed to withstand significant amounts of force, injury and other problems with the disc can occur. When the disc ages or is injured, the outer portion (annulus fibrosus) of a disc may be torn and the disc’s inner material (nucleus pulposus) can herniate or extrude out of the disc. Each spinal disc is surrounded by highly sensitive nerves, and the inner portion of the disc that leaks out contains inflammatory proteins, so when this material comes in contact with a nerve it can cause pain that can travel down the length of the nerve. Even a small disc herniation that allows a small amount of the inner disc material to just touch the nerve can cause significant pain.

Pain from a herniated disc vs. degenerative disc disease

A herniated disc will typically produce a different type of pain than degenerative disc disease (another common disc problem).

When a patient has a symptomatic degenerated disc (one that causes pain or other symptoms), it is the disc space itself that is painful and is the source of pain. This type of pain is typically called axial pain.
When a patient has a symptomatic herniated disc, it is not the disc space itself that hurts, but rather the disc problem is causing pain in a nerve in the spine. This type of pain is typically called radicular pain (nerve root pain, or sciatica from a lumbar herniated disc).