Motion MRI's and whiplash patients
Proper treatment for victims of an automobile collision depends on a detailed understanding of the extent of the injury. Unfortunately, conventional MRIs are of limited use as an assessment tool for whiplash injury, often failing to show ligament damage in the cervical spine.
"Static imaging does not reveal movement abnormalities," wrote a group of Finnish researchers in its November 2009 study of whiplash patients. The study introduced motion MRI as an effective tool for highlighting abnormal movement patterns that indicate ligament damage. Whiplash injuries which do not appear on static MRI's may be now be measurable by using dynamic imaging of the injury site.
Researchers investigated the differences in movement patterns of the upper cervical spine in whiplash trauma patients and a control group. The study included ten male and 15 female whiplash patients who had been admitted to the ORTON Rehabilitation Centre in Helsinki, Finland because of their severe chronic symptoms. Patients suffered from some combination of severe neck pain, headache, upper and lower limb dysfunction, loss of balance, and numbness of the tongue. Patients participated in the study an average of seven years after the original injury, and were still experiencing symptoms.
The control group consisted of ten male and 15 female volunteers, matched for age and sex with the experimental group. None of the control subjects had any history of neck pain, trauma, or inflammatory diseases such as rheumatoid arthritis.
Researchers focused the motion MRI's on a specific area at the top of the spine. The symptoms exhibited by the whiplash patients indicated a problem in the C0-C2 region of the cervical spine. The C1 and C2, also known as the Atlas and the Axis, are the uppermost vertebrae in the cervical spine. Researchers used dynamic kine magnetic resonance imaging (dMRI) to analyze movement between C1 and C2 during side bending and to assess instability of the C0 and C1 joints. They also measured the signal from the alar ligaments, which connect the C2 vertebra with the occipital bone and control side-to-side movement of the head.
Targeted positioning of the subjects' necks in the motion MRI allowed for more detailed assessment than a static MRI would offer. "The benefits of side bending the cervical spine is illustrated in patients with normal movement because the opposite alar ligament can be seen as it straightens, and possible changes in the signal can be seen more effectively," explained the study's authors.
The results showed significant differences between the whiplash patients and control group. Analysis of the results found abnormal movement in the alar ligaments in 92% of patients compared with 24% of control subjects. Images taken while side bending revealed widening of the C0-C1 joint, an indication of an unstable joint, in seven patients and one control subject. Furthermore, abnormal movements in the C1-C2 were found in 56% of whiplash patients, compared with 20% of the control group.
Overall the whiplash patients with longstanding symptoms had more abnormal signals from the alar ligaments and greater movement disturbances in the C0-C2 level in the dMRI than the control group.
This study has important implications for the assessment of whiplash injury. "Conventional computed tomography and conventional MRI are not appropriate tests with which to rule out pathology," the researchers warned. Whiplash injuries producing significant symptoms may not be visible through conventional imaging. Fortunately for doctors and victims of auto accidents, motion MRI's may be able to demonstrate the nature of whiplash injuries where earlier imaging has failed.
Lindgren K-A, Kettunen JA, Paatelma M, Mikkonen RHM. Dynamic kine magnetic resonance imaging in whiplash patients and in age- and sex-matched controls. Pain Research & Management 2009; 14(6): 427-432.