Are Signs of Central Sensitization in Acute Low Back Pain a Precursor to Poor Outcome?

Central sensitization is considered to have a pathophysiological role in chronic low back pain (LBP). Whether individuals with increased central sensitization early in their condition are more likely to develop persistent pain or whether it increases over time is unclear. This study aimed to determine whether sensory profiles during acute LBP differ between individuals who did and did not recover by 6 months and to identify subgroups associated with outcomes. Individuals with acute LBP (<2 weeks of onset; N = 99) underwent pain threshold (heat/cold/pressure) and conditioned pain modulation testing after completing questionnaires related to pain/disability, sleep, and psychological status. Sensory measures were compared during the acute phase (baseline) and longitudinally (baseline/6 months) between unrecovered (greater or unchanged pain and disability), partially recovered (improved but not recovered pain and/or disability), and recovered (no pain and disability) participants at 6 months. We assessed baseline patterns of sensory sensitivity alone, and with psychological and sleep data, using hierarchical clustering and related the clusters to outcome (pain/disability) at 3 and 6 months. No sensory measure at either time point differed between groups. Two subgroups were identified that associated with more ("high sensitivity") or less ("high sensitivity and negative psychological state") recovery. These data seem to suggest that central sensitization during the acute phase resolves for many patients, but is a precursor to the transition to chronicity when combined with other psychological features. Perspective: Central sensitization signs during early acute LBP does not necessarily precede poor outcome, but may be sustained in conjunction with other psychological factors and facilitate pain persistence. (C) 2019 by the American Pain Society