Use of Muscle Functional Magnetic Resonance Imaging to Compare Cervical Flexor Activity Between Patients With Whiplash-Associated Disorders and People Who Are Healthy

Background. Chronic whiplash-associated disorders (WAD) have been shown to be associated with motor dysfunction. Increased electromyographic (EMG) activity in neck and shoulder girdle muscles has been demonstrated during different tasks in participants with persistent WAD. Muscle functional magnetic resonance imaging (rnfMRI) is an innovative technique to evaluate muscle activity and differential recruitment of deep and superficial muscles following exercise. Objective. The purpose of this study was to compare the recruitment pattern of deep and superficial neck flexors between patients with WAD and controls using mfMRI. Design. A cross-sectional design was used. Method. The study was conducted in a physical and rehabilitation medicine department. The participants were 19 controls who were healthy (10 men, 9 women; mean [+/- SD] age = 22.2 +/- 0.6 years) and 16 patients with WAD (5 men, 11 women; mean [+/- SD] age = 32.9 +/- 12.7 years). The T2 values were calculated for the longus coil (Lco), longus capitis (Lca), and stemocleidomastoicl (SCM) muscles at rest and following cranio-cervical flexion (CCF). Results. In the overall statistical model for T2 shift, there was a significant main effect for muscle (F = 3.906, P = .033) but not for group (F = 2.855, P = .101). The muscle X group interaction effect was significant (F = 3.618, P = .041). Although not significant, there was a strong trend for lesser Lco (P = .061) and Lca (P = .060) activity for the WAD group compared with the control group. Although the SCM showed higher T2 shifts, this difference was not significant (P = .291). Limitations. Although mfMRI is an innovative and useful technique for the evaluation of deep cervical muscles, consideration is required, as this method encompasses a postexercise evaluation and is limited to resistance types of exercises. Conclusions. Muscle functional magnetic resonance imaging demonstrated a difference in muscle recruitment between the Lco, Lca, and SCM during CCF in the control group, but failed to demonstrate a changed activity pattern in the WAD group compared with the control group. The mild symptoms in the WAD group and the wide variability in T2 values may explain the lack of significance.