Pseudoradicular and Radicular Low Back Pain
Typically, pain that radiates into an extremity is divided into radicular and pseuodradicular syndromes. Treatment presently differs, depending on the classification of pain as radicular or pseudoradicular. The pain is distinguished as nociceptive versus neuropathic. While radicular pain has traditionally been attributed to nerve root compression and is considered neuropathic, pseudoradicular pain has been attributed to non-nerve related structures such as facet joints, and piriformis syndrome and is considered nociceptive.

The authors of this study propose that current sensory testing is not adequate to appropriately distinguish between the two syndromes. Subclinical sensory loss in pseudoradiculopathy could mean that appropriate treatment is not being considered. The authors feel that Quantitative Sensory Testing, QST, is a reliable test of large and small fiber sensory nerve function in the two syndromes. They feel that it is comparable to nerve conduction studies.

Thirty patients with chronic low back pain radiating into parts of one leg were evaluated. Four independent experienced clinicians classified their pain as radicular or pseudoradicular. The clinicians agreed on the classification of 27 of the 30 subjects. The 27 were then included in the study. They administered the QST which consists of seven tests measuring 13 different sensory parameters. Sensitivity of the QST was verified for radiculopathy as well as pseudoradiculopathy.

The authors were able to demonstrate that subclincial sensory deficits in the pseudoradicular low back pain group were present using QST. In fact, profound sensory loss was detected in both the radicular and pseudoradicular pain groups. Vibration detection seemed to be the most sensitive of the parameters tested. Vibration sense was abnormal in 73 percent of the radicular subjects, and 47 percent of the pseudoradicular subjects. As a result of the study, the authors question whether there is a clear distinction between radicular and pseudoradicular syndromes. If this is the case, pseudoradicular low back pain might also require treatments to address neuropathic pain.
References
R. Freynhagen et al. Pseudoradicular and radicular low back pain: A disease continuum rather than different entities? Answers from quantitative sensory testing. Pain. 2008. Vol 135. Pp. 65-74.