Functional tests for a herniated disc | How can you recognize a herniated disc?

Functional tests for a herniated disc

Following the doctor-patient consultation, an orienting neurological examination should be carried out. During this examination, the specialist can identify whether and which nerve root is possibly constricted. To check the sensitive nerve conduction paths, the extremities must be stroked.

This special examination must always be carried out in side by side comparison. If there is a deviation in the side-by-side sensation, nerve damage can be assumed. Subsequently, the muscle strength of the most important characteristic muscles (muscles that can be assigned to a spinal segment) should be checked.

Especially a herniated disc, which is already very advanced and/or has existed for a long time, can often be detected in this way. In addition, a possible nerve root compression can be determined by a simple test. In the so-called Lasègue test, the patient is positioned on his back.

The specialist then begins to slowly bend the patient’s stretched leg in the hip joint. This test must be considered positive if the patient feels pain in the lumbar spine when lifting the stretched leg. The classic tests of nerve root compression must be considered positive if pain is felt during passive movement.

However, a positive Lasègue sign does not necessarily indicate a herniated disc. The Lasègue test is also typically positive for inflammatory processes in the area of the meninges (so-called meningitis). However, if the symptoms present indicate a herniated disc in the lumbar spine, the Lasègue test can help to identify the prolapse as such.

In addition, the diagnosis of a suspected herniated disc includes various exercises. These exercises specifically test the functionality of the characteristic muscles of the most important spinal segments. In patients who can walk on their toes and heels without any problems, paralysis of these characteristic muscles can be ruled out.

What imaging techniques are available?

If the suspicion of the presence of a herniated disc is confirmed during the physical examination, further diagnostic measures must be initiated. Only imaging procedures that are suitable for the spinal column and the intervertebral discs can help to identify the herniated disc as such without any doubt and thus confirm the suspected diagnosis. However, the preparation of ordinary x-rays is not considered helpful in the diagnosis of a herniated disc.

To detect a herniated disc, therefore, a computer (CT) or magnetic resonance imaging (MRI) must be initiated. Due to the better visualization of the intervertebral discs, magnetic resonance imaging is considered the method of first choice in the diagnosis of a herniated disc. In addition, nerve conductivity and muscle strength can be checked by means of special tests.

In particular, the so-called electromyography (EMG) can help to detect whether sensitivity disorders and paralysis symptoms are present. Electroneurography (ENG) is also considered a suitable method in the diagnosis of a slipped disc. Although imaging procedures are considered the only way to detect a herniated disc beyond any doubt, they do not have to be performed as a mandatory procedure even if a herniated disc is suspected.

Especially in cases of less pronounced symptoms, images of the spine are often not taken. In a patient who already suffers from sensitivity disorders and limitations of muscle strength, however, imaging procedures cannot be dispensed with. Conventional x-rays are not important in detecting a herniated disc.

The reason for this is that only bony structures can be assessed in a conventional X-ray. Individual nerve roots and the intervertebral disc cannot be imaged in this way. For this reason, the detection of a herniated disc is mainly done by magnetic resonance imaging (MRI).

MRI can be used to visualize bony structures of the spine as well as nerve roots and intervertebral discs. Due to the fact that the preparation of an MRI does not expose the patient to any radiation, the detection of a herniated disc by MRI is considered the diagnostic tool of choice. In principle, the relevant structures can also be displayed by computer tomography (CT).

During this examination procedure, however, the patient is exposed to comparatively high radiation doses. A herniated disc as such cannot be diagnosed by X-ray. The recognition of a herniated disc only by X-ray is for several reasons still not possible today.

Although the spinal column can be perfectly depicted by conventional x-rays, the ability to assess the individual spinal segments is limited only to the bony structures. Neither the nerve roots nor the intervertebral disc itself can be depicted by conventional x-ray. However, to detect a herniated disc, all structures of the individual spinal segments must be assessed.

For this reason, the performance of a magnetic resonance tomography in the diagnosis of a herniated disc is considered the method of first choice. In this context, however, it must be noted that especially herniated discs in the thoracic spine (BWS) are often associated with a previous trauma. In these cases, X-rays can at least help to identify whether a fracture in the area of the bony structures of the spinal column may be present.