The Late Whiplash Syndrome: Current Aspects of Functional Neuroimaging

Abstract

Patients with persisting symptoms after a whiplash injury (the so-called late whiplash syndrome) are often left alone. However, their complaints are not only limited to neuropathic pain in the head and neck region, but there are also symptoms, which proceed from the brain. These brain symptoms comprise vertigo, dizziness, tinnitus, as well as concentration, attention and memory disturbances; also visual problems such as blurred vision and oscillopsia can occur. The whiplash injury is frequent, although only a small proportion of the patients develop the late whiplash syndrome. The incidence of whiplash injury in the industrialized countries is estimated up to 3.8 cases per 1,000 inhabitants per year. Rear-end car collisions are the most frequent causes of whiplash injury and only low speeds between 10 and 20 km/h are necessary to cause large acceleration forces on the head. The usual methods for the diagnosis of whiplash injury such as the neurological investigation or radiography of the cervical spine unfortunately forget that the brain (in addition to the cervical spine) can be damaged by an acceleration trauma. Therefore, research methods are necessary which objectively represent the condition of the brain. Conventional radiological imaging such as computerized tomography or magnetic resonance tomography of the brain can, however, only represent the morphological structures and not the possible functional alterations of the brain, as caused by whiplash injury. In contrast, the relatively new methods of nuclear medicine currently offer the only possibility of imaging such functional changes. In patients with late whiplash syndrome, a statistically significant metabolic reduction in the posterior parietal occipital region of the brain is found. This was shown in several studies with over 500 patients investigated by both cerebral blood flow single-photon emission computed tomography and fluorodeoxyglucose positron emission tomography. In individual cases, patients also showed regions with decreased metabolism which were not in the posterior parietal occipital location, but no statistically significant group differences could be determined between these patients and a healthy control group. In a further study from a research group in Zurich, somewhat different results were found; the results of this study seem, however, doubtful. — Posterior parietal occipital findings can also be observed in other diseases with brain affection, for example, in systemic lupus erythematosus, Alzheimer’s disease or migraine. Other diseases can easily be excluded by a purposeful clinical and neurological assessment. There are also diseases which show a similar clinical component like the late whiplash syndrome, for instance, primary depression. In these diseases, the posterior parietal occipital region is not affected however. In light of the ongoing medico-legal discussion in the field, a critical approach to the interpretation of these new research data from functional neuroimaging is of utmost importance. All treating physicians in the field should be familiar with these tools.