Papers of the Week

Pain alters motor function. This is supported by studies showing reduced corticomotor excitability in response to experimental pain lasting <90 minutes. Whether similar reductions in corticomotor excitability are present with pain of longer durations or whether alterations in corticomotor excitability are associated with pain severity is unknown. Here we evaluated the evidence for altered corticomotor excitability in response to experimental pain of differing durations in healthy individuals. Databases were systematically searched for eligible studies. Measures of corticomotor excitability and pain were extracted. Meta-analyses were performed to examine i) group-level effect of pain on corticomotor excitability and ii) individual-level associations between corticomotor excitability and pain severity. 49 studies were included. Corticomotor excitability was reduced when pain lasted milliseconds-seconds (hedges g's = -1.26 to -1.55) and minutes-hours (g's = -0.55 to -0.9). When pain lasted minutes-hours, a greater reduction in corticomotor excitability was associated with lower pain severity (g = -0.24). For pain lasting days-weeks, there were no group level effects (g = -0.03 to 0.27). However, a greater reduction in corticomotor excitability was associated with higher pain severity (g = 0.26). In otherwise healthy individuals, suppression of corticomotor excitability may be a beneficial short-term strategy with long-term consequences.