Generalized Hypoesthesia Occurs After Acute WhiplashAs researchers learn more about whiplash and whiplash-associated disorders, they have learned about a group of patients who, after sustaining whiplash, end up with chronic whiplash-associated disorders, including hypersensitivity (being too sensitive) and hypoesthesia (a dulled sensitivity to touch).
Earlier studies have shown a connection between high sensitivity to heat, vibration, and electrical stimulation following whiplash and as part of the whiplash-associated disorder. However, although these studies have been done, they were generally done with chronic whiplash-associated disorders, not acute whiplash. One study that ventured into the acute area, done by Kasch and colleagues, did find that people with acute whiplash with high levels of whiplash pain showed signs of hyperalgesia, or increased sensitivity to pain, more than those with lower levels of whiplash pain. They wrote that this could be a predictors of poor recovery from whiplash.
The authors of this study wanted to find out if hyperalgesia occurred in patients with acute whiplash injury, using a quantitative sensory testing (QST), which examines the level of pain experienced with temperature, vibration, and electrical stimulation. To do this, researchers studied 52 volunteers with neck pain following motor vehicle accidents and 31 controls, people who had not injured their neck.
In order to determine the pain thresholds, the researchers used a probe that provided pressure in certain levels of the spine, the elbow, and the abdomen. Cold thresholds were measured using a probe that applied cold directly to the skin on the top part of the hand. Another test, called the brachial plexus provocation test measured pain while the arm was being straightened at the elbow. Vibration sensation and threshold was measured using a vibrometer applied to the hand. Hot and cold detection was measured using another prove on the hand with which temperatures were either increased or decreased, depending on the test. Finally, the electrical stimulation was done with a device that emitted various frequencies and this was applied to various parts of the cervical spine, or neck.
The patients were asked to complete questionnaires about their symptoms, the Neck Disability Index (NDI), as well as the General Health Questionnaire 28 (GHQ-28). All participants then had a full physical examination to be sure that they qualified for the study. At this point, the patients' group was split into to, with 17 of the patients being assigned to the high-risk group. The study tests were done by the same examiners for all the patients and controls.
The researchers found that there were significant differences between all three groups, the two patient groups and the control group. Both patient groups had higher detection thresholds than the controls but there wasn't a significant difference between the two patient groups. For the hot and cold detection, there wasn't much difference in the heat detection threshold between any group, but there was a difference between the patient groups and the controls. The patients had a slower response in detecting the cold sensations and more so in the high-risk group. The electrical stimulation was much higher in the high risk group, followed by the low-risk group, with the controls being significantly lower.
These findings led the authors to conclude that there was an effect of generalized hypoesthesia not only among people who sustain chronic whiplash-associated disorders, but those who have acute whiplash-associated disorders as well.
Andy Chien, BPhty (Hons), et al. Hypoesthesia Occurs in Acute Whiplash Irrespective of Pain and Disability Levels and the Presence of Sensory Hypersensitivity. In Clinical Journal of Pain. November/December 2008. Vol. 24. No. 9. Pp. 759-766.
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