Back pain with leg pain caused by disc herniation is a complex problem and not one that is easy to diagnose. Physicians rely on the patient’s history, physical examination (including specific neurologic tests), and imaging studies such as X-rays, MRIs, and CT scans. Accurately identifying the problem is one step. Determining the spinal level where the disc is pressing on the spinal nerve is a separate diagnostic step.
It would be helpful for examiners evaluating patients with back and leg pain if they knew which clinical tests are the most accurate and reliable. This is especially true if it turned out that one neurologic testing procedure could provide good overall diagnostic accuracy.
According to this study from New Zealand, current motor, sensory, and reflex testing used to diagnose disc herniation and specific level of pathology are not accurate. In fact, after pooling all the data together and analyzing the studies published so far, it looks like the accuracy value of the tests is poor at best.
After searching six of the most relevant electronic databases, they found 14 studies that matched their inclusion criteria. Their search history, search strategy, and algorithm (flow chart) for the studies was presented as an easily readable diagram. Study characteristics (e.g., author names, tests reported, type of physician examiner, herniation type and level) were presented in an easy-to-read table.
An in-depth description of the problems encountered with each study was provided. This helps explain why the neurologic testing to detect lumbar disc herniation and spinal nerve root involvement is not reliable enough to become a standardized test. Here’s a quick summary:
It is known that the pathology and mechanism of disc herniation can be very complex. People have different responses and symptoms from the same level and degree of herniation. Sometimes there are overlapping symptoms from more than one spinal level. Even when electrodiagnostic tests are done to confirm nerve involvement, severe disc herniation can be present with no signs of weakness or sensory changes.
Currently, there are no neurologic clinical tests that have been shown to conclusively diagnose disc herniation based on the presence of radiculopathy (symptoms from compression on a spinal nerve root). Future studies are needed to find and standardize clinical tests that are valid and reliable in accurately diagnosing nerve root irritation (radiculopathy) associated with disc herniation.