Prognostic Value of Measures of the Central Hypersensitivity in Patients With Acute Low Back Pain

Background. Patients with chronic low back pain display hyperexcitability of the central nervous system (central hypersensitivity). Such hypersensitivity may occur in the acute phase and represent a risk factor for the development of chronic pain. Objective. To determine the prognostic value of central hypersensitivity for the development of chronic low back pain. Design. Prospective cohort study. Setting. Primary care. Patients. 140 individuals with acute low back pain and no history of chronic pain. Outcomes. Primary prognostic variable will be the pain tolerance threshold at the second toe (the pressure intensity at which a further increase in pressure is deemed intolerable). Exploratory secondary prognostic variables are measures of mechanisms related to central hypersensitivity: stimulus-specific hypersensitivity (pressure, electrical, heat and cold stimulation); tissue-specific hypersensitivity (skin vs. muscle stimulation); localized vs. widespread hypersensitivity; spinal cord modulation (electrophysiological measures of hypersensitivity and changes in receptive fields); modulation at brain level (descending modulation of nociceptive input and cortical plasticity). Clinical primary outcome will be the occurrence of chronic low back pain at follow-up. Main analysis. The investigators will use least square logistic regression models to determine the association of central hypersensitivity with prognosis. Relevance. An understanding of the prognostic value of central hypersensitivity may allow an early stratification for treatment of individuals at risk of developing chronic low back pain. Subgroups of patients may be selected for clinical trials on novel pharmacological approaches for the prevention and treatment of central hypersensitivity.