Neurophysiological Factors Associated with Compression and Reflex Mechanisms of Lower Back Pain

Introduction: Vertebrogenic pain syndromes (PSs) in the lower back (LB) are among the most common neurological disorders in the population. Currently, clinical, neurophysiological and neuroimaging characteristics are used as predictors of the course and effectiveness of the treatment for vertebrogenic PSs in the LB.

Aim: To identify the neurophysiological factors associated with compression and reflex mechanisms of PSs in the LB for their differentiation in complicated diagnostic cases.

Materials and methods: The study included 73 patients, 43 of them men and 30 women of the mean age 46.5 years. Based on the results of clinical neurological examination and the magnetic resonance imaging data, reflex vertebrogenic PSs (lumboischialgia) were verified in 40 cases, and radiculopathy of L5 and/or S1 (compression vertebrogenic PSs) in 33 cases. The patients underwent stimulation electroneuromyography with record of motor and sensory responses from the lower limbs, of F- and H-response, and examination of heart rate variability.

Results: Logit regression analysis was used to create models permitting to divide patients into groups with different mechanisms of PSs based on the neurophysiological parameters. The first model demonstrated high sensitivity in the identification of predominantly compression vertebrogenic disorders with the independent factors being the mean F-wave latency and the sensory response amplitude. The second model was more sensitive in identification of reflex PSs with the main predictors being the F-response amplitude and heart rate variability parameters.

Conclusion: The identified factors reflect the role of conduction disorders in compression PSs, as well as the involvement of segmental motor neuronal apparatus and autonomic regulatory mechanisms in the reaction in reflex PSs, which are additional sources of information in taking medical decisions in complicated diagnostic cases.