Neuropsychological complaints are common after whiplash injury. These include headache, vertigo, auditory disturbances, tinnitus, disturbances in concentration and memory, and impaired vision. The problem to date has been in correlating these symptoms to some type of physical lesion. CT and MRI are ineffective in this role, as they can only show physical anatomy. Newer, more sophisticated imaging techniques, however, such as PET and SPECT scans can provide images of cellular metabolism and blood flow. These types of images may be an important method of determining the injury mechanism of whiplash.
A new study by Otte et al (building on some previous work that these researchers have done) used PET and SPECT scans to image the brains of six chronic whiplash patients and to compare them to twelve healthy control subjects. The goal was to examine cerebral blood perfusion and glucose metabolism in "whiplash brain."
In this current study, the researchers performed PET and SPECT scans on both groups of subjects. The images were then compared.
"This pilot study indicates for the first time that there are abnormalities in glucose metabolism in 'whiplash brain.' The findings provide evidence that in most of the patients studied there is a characteristic pattern of bilateral hypometabolism—in addition to hypoperfusion—in the parieto-occipital regions of the brain. Thus brain injury in whiplash patients might have been underreported in the past. As CT and MRI showed normal brain findings in all investigated patients, combined functional imaging using PET or SPECT may be more appropriate than morphological imaging alone." In some patients, other areas of the brain also showed hypometabolism.
What is the origin of these changes in whiplash patients' brains? The authors state that:
"[Our] hypothesis is that parieto-occipital hypometabolism may be caused by activation of nociceptive afferences from the upper cervical spine. By contrast, the areas of hypometabolism seen in areas other than parieto-occipital may mainly be explained by brain contusion and not by the effects of activated nociceptive afferences on brain metabolism. In addition, hypometabolism in parieto-occipital regions cannot be excluded in some cases as part or entirely a consequence of diffuse axonal lesions due to acceleration forces."
The authors also suggest that lowered glucose metabolism in these parts of the brain may also be responsible for some of the cognitive disturbances experienced by patients.
In the future, SPECT and PET may provide imporant information for individual whiplash patients. At this time, the price of a PET scan is about $2,200.Otte A, Ettlin TM, Nitzsche EU, et al. PET and SPECT in whiplash syndrome: a new approach to a forgotten brain? Journal of Neurology, Neurosurgery, and Psychiatry 1997;63:368-372.