Understanding the clinical diagnosis of a herniated disc

Integrated findings form the clinical diagnosis
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.
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.

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).

Typical symptoms of a herniated disc
A herniated disc most often occurs in the lumbar spine (lower back) or the cervical spine (neck), but it can also occur in the thoracic spine (upper back). Each location for a herniated disc produces different symptoms of pain.

Lumbar herniated disc
Leg pain (also known as sciatica) is the most common symptom associated with a herniated disc in the lumbar spine. Approximately 90% of herniated discs occur at L4-L5 and L5-S1, causing pain in the L5 or S1 nerve that radiates down the sciatic nerve. Symptoms of a herniated disc at these locations are described below:

A herniated disc at lumbar segment 4 and 5 (L4-L5) usually causes L5 nerve impingement. In addition to sciatica pain, this type of herniated disc can lead to weakness when raising the big toe and possibly in the ankle, also known as foot drop. Numbness and pain can also be felt on top of the foot.

A herniated disc at lumbar segment 5 and sacral segment 1 (L5-S1) usually causes S1 nerve impingement. In addition to sciatica, this type of herniated disc can lead to weakness when standing on the toes. Numbness and pain can radiate down into the sole of the foot and the outside of the foot.

Cervical herniated disc
A cervical herniated disc is less common than a lumbar herniated disc because there is less disc material and substantially less force across the cervical spine. The pain and other symptoms from a cervical herniated disc differ by level:

A herniated disc at cervical segment 4 and 5 (C4-C5) causes C5 nerve root impingement. Patients may feel weakness in the deltoid muscle in the upper arm but do not usually feel numbness or tingling sensations. A cervical herniated disc at this level can also cause shoulder pain.

A herniated disc at cervical segment 5 and 6 (C5-C6) causes C6 nerve root impingement. This level is one of the most common areas for a cervical herniated disc to occur. It can cause weakness in the biceps (the muscles in the front of the upper arms) and in the wrist extensor muscles. Pain, numbness and tingling can radiate to the thumb side of the hand.

A herniated disc at cervical segment 6 and 7 (C6-C7) causes C7 nerve root impingement and is another common type of cervical herniated disc. It can cause weakness in the triceps (the muscles in the back of the upper arm and extending to the forearm) and in the extensor muscles of the fingers. Numbness and tingling along with pain can radiate down the triceps and into the middle finger.

A herniated disc at cervical segment 7 and thoracic segment 1 (C7-T1) causes C8 nerve root impingement. This may lead to weakness when gripping with the hand, along with numbness, pain, and tingling that radiates down the arm and to the little finger side of the hand.

Thoracic herniated disc
Herniated discs in the upper back are rarely symptomatic and rarely produce pain, but if they are symptomatic, the pain is usually felt in the upper back and/or chest area.

Diagnosis of a herniated disc guides treatment
Obtaining correct clinical diagnosis is crucial, as the choice of treatment options will be guided by the diagnosis. Patients are well advised to never accept a diagnosis based solely on findings from an MRI scan or other radiographic test. Instead, an accurate clinical diagnosis must be based primarily on the patient’s symptoms and other information from the patient’s medical history as well as a thorough physical exam from a spine care professional. For further information, patients may read Getting an accurate back pain diagnosis.