Brain Dysfunction and Whiplash
Some of the most controversial study in whiplash literature is centered on the issue of cognitive disturbances. Some people in the medico-legal community don't even believe in physical symptoms after whiplash; when a patient complains of poor concentration, insomnia, dizziness, or fatigue, it may be considered exaggeration or malingering.
A number of theories have been put forth to explain the existence of these symptoms. Some have suggested brain injury; some have investigated the role of the inner ear and the role that the cervical neck musculature plays in balance. A new study by a team of Swiss researchers looks further into this problem by examining how the cortex of the brain functions, as measured by eye movements—or saccades.
The Merriam-Webster dictionary describes a saccade (pronounced sa-'käd) as, "a small rapid jerky movement of the eye especially as it jumps from fixation on one point to another (as in reading)."
Saccades are key to this new study, because there are two different kinds of saccade: reflexive saccades, which are "externally triggered by the sudden appearance of a visual target;" and intentional or voluntary saccades, which are "triggered internally by the subject." These two different types of saccade are important, because each is controlled by a different part of the cerebral cortex. By a careful analysis of saccades, the authors of this study hoped to determine if there were indeed signs of brain injury in patients with whiplash.
Three different groups were studied:
- "The symptomatic group consisted of 11 subjects (eight women and three men; mean age 38.8 years, range 21-54 years) complaining of persistent dizziness of non-specific character, poor concentration, and neck pain or headache. The interval between the accident and the examination in this group averaged 2.8 years..."
- The "recovered" group, which consisted of 10 patients with a history of whiplash injury, but who had recovered completely at the time of examination. The mean interval between the accident and examination was just slightly more than in the symptomatic patients—3.0 years.
- A group of 16 healthy control subjects who were matched for age.
The researchers then tested all of the subjects with a battery of saccade tests (two reflexive and two voluntary tests), and—because previous studies have found that depression can affect saccades—all participants underwent an in-depth clinical interview with a psychiatrist.
The researchers found significant differences between the symptomatic group and the other two groups, but only on the intentional (voluntary) tests:
"The results of the present study suggest that subjects with persistent complaints after whiplash injury may have a particular pattern of eye movement disturbance. This disturbance pattern is characterized by a dissociation in performance of reflexive and intentional saccade paradigms and is significantly different from the performance of the recovered group and the control group. There were no significant differences between the last two groups, with respect to any of the eye movement assessment paradigms used."
"...dissociation of the performance of reflexive and intentional saccades, with normal performance of reflexive saccades and impaired performance of intentional saccades...was found in the symptomatic group. This pattern may be explained by a dysfunction of frontal, especially prefrontal, cortical structures, which remains open to further examination and aetiological consideration."
In summary, symptomatic whiplash patients exhibit objective differences in eye movements. This study's findings are relevant for a few very important reasons.
First, the "Swiss accident insurance scheme does not provide compensation for non-economic loss such as pain and suffering, and it is considered that the scheme does not primarily promote malingering."
Second, "In addition, the particular pattern of eye movement disturbance in the symptomatic group of the present study cannot be explained by malingering, since faking performance in the respective paradigms would require considerable knowledge of how to perform and the ability to do so."
Mosimann UP, Muri RM, Felblinger J, Radanov BP. Saccadic eye movement disturbances in whiplash patients with persistent complaints. Brain 2000;123:828-835.
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