Evidence for increased magnetic resonance imaging signal intensity and morphological changes in the brachial plexus and median nerves of patients with chronic arm and neck pain following whiplash injury

BACKGROUND: Whiplash following a motor vehicle accident can result in chronic neck and arm pain. Patients frequently present with cutaneous hypersensitivities and hypoesthesia but without obvious clinical sign of nerve injury. T2-weighted magnetic resonance imaging (MRI) has previously been used to identify nerve pathology. OBJECTIVES: To determine whether there are signs of peripheral nerve pathology on MRI in patients with chronic arm and neck pain following whiplash injury. METHODS: This study used T2-weighted MRI to examine the brachial plexus and median nerve in patients and age-matched healthy control subjects. Clinical examination included tests of plexus and nerve trunk mechanical sensitivity. RESULTS: T2 signal was greater in the brachial plexus and median nerve at the wrist in the patient group (mean intensity ratio = 0.52 (0.13 SD) and 2.09 (0.33 SD) respectively) compared to the control group (mean intensity = 0.45 (0.07 SD) and 1.38 (0.31 SD) respectively; p<0.05). Changes in median nerve morphology were also observed, which included an enlargement (mean area = 8.05 (1.29 SD) mm2 in the patient group and 6.52 (1.08 SD) mm2 in the control group; p<0.05) and flattening at the proximal carpal row (mean aspect ratio = 2.46 (0.53 SD) in the patient group and 1.62 (0.30 SD) in the control group; p < 0.05). All patients demonstrated signs of nerve trunk mechanical sensitivity. CONCLUSION: These findings suggest that patients with chronic whiplash may have inflammatory changes and/or mild neuropathy, which may contribute to symptoms.