Pain-induced changes in the activity of the cervical extensor muscles evaluated by muscle functional magnetic resonance imaging

Objectives: To investigate the effect of experimental neck muscle pain on the activation of the cervical extensor muscles during the performance of a cervical extension exercise by the use of muscle functional magnetic resonance imaging. Methods: The activity of the multifidus, semispinalis cervicis, semispinalis capitis, and splenius capitis muscles was investigated bilaterally at 2 cervical levels (C2 to C3 and C7 to T1) in 15 healthy individuals. Measurements were taken at rest and after the performance of a cervical extension exercise without and with induced pain of the right upper trapezius (intramuscular injection of hypertonic saline). Results: In the pain condition, the activity of the multifidus/semispinalis cervicis was reduced bilaterally at the C7 to T1 level (P = 0.045). For the semispinalis capitis, there were no significant differences between both conditions. The splenius capitis showed a significantly higher T2 shift at the left side at the C2 to C3 level (P = 0.008) and a lower T2 shift at the right side at the C7 to T1 level (P = 0.023). Discussion: This is the first study that has shown pain to immediately affect the activity of both deep and superficial cervical extensor muscle layers during a cervical extension exercise. The findings support recommendations for evaluation of cervical extensor muscle function early in the management of painful cervical spine injuries