Abnormal Pain Response to Visual Feedback During Cervical Movements in Chronic Whiplash: An Experimental Study.

BACKGROUND: Whiplash-associated disorders (WAD) are a debilitating condition. In chronic WAD, sensorimotor incongruence exacerbates symptoms. Sensorimotor incongruence occurs when somatosensory input and predicted motor output are in conflict, which can trigger pain. On the other hand, there is evidence that visual feedback can decrease pain in certain chronic pain conditions. Therefore, the aim of this study was to examine the effect of visual feedback and sensorimotor incongruence on pain thresholds in chronic WAD. METHODS: Sixty-four participants (healthy controls and patients with chronic WAD) were subjected to six experimental conditions. Participants watched correct real-time or modified visual feedback of the neck or hand (without movement as well as during repetitive neck lateroflexion). Sensorimotor incongruence was induced by manipulating visual feedback. Pressure pain thresholds were measured at baseline and during each condition. RESULTS: Marked between-group differences were observed. Visual feedback of the neck-correct or modified-did not influence pain thresholds in chronic WAD. In contrast, healthy controls had significantly higher pain thresholds when provided with the correct or modified visual feedback. When a movement of the neck was added during visual feedback, patients with chronic WAD showed no significant difference in pain thresholds, while an increase in pain thresholds was found in the healthy control group. CONCLUSION: In contrast to the healthy controls, visual feedback and sensorimotor incongruence did not alter pain thresholds in patients with chronic WAD. These findings suggest an abnormal pain response to visual feedback and somatosensory incongruence as well as failing mechanisms of pain inhibition in chronic WAD.

Exercise and Cognitive Functioning in People With Chronic Whiplash-Associated Disorders: A Controlled Laboratory Study.

STUDY DESIGN: Controlled laboratory study. BACKGROUND: In addition to persistent pain, people with chronic whiplash-associated disorders (WAD) commonly deal with cognitive dysfunctions. In healthy individuals, aerobic exercise has a positive effect on cognitive performance, and preliminary evidence in other chronic pain conditions reveals promising results as well. However, there is evidence that people with chronic WAD may show a worsening of the symptom complex following physical exertion. OBJECTIVE: To examine postexercise cognitive performance in people with chronic WAD. METHODS: People with chronic WAD (n = 27) and healthy, inactive, sex- and age-matched controls (n = 27) performed a single bout of an incremental submaximal cycling exercise. Before and after the exercise, participants completed 2 performance-based cognitive tests assessing selective and sustained attention, cognitive inhibition, and simple and choice reaction time. RESULTS: At baseline, people with chronic WAD displayed significantly lower scores on sustained attention and simple reaction time (P<.001), but not on selective attention, cognitive inhibition, and choice reaction time (P>.05), compared with healthy controls. Postexercise, both groups showed significantly improved selective attention and choice reaction time (chronic WAD, P = .001; control, P<.001), while simple reaction time significantly increased (P = .037) only in the control group. In both groups, no other significant changes in sustained attention, cognitive inhibition, pain, and fatigue were observed (P>.05). CONCLUSION: In the short term, postexercise cognitive functioning, pain, and fatigue were not aggravated in people with chronic WAD. However, randomized controlled trials are required to study the longer-term and isolated effects of exercise on cognitive functioning.

Dysfunctional pain inhibition in patients with chronic whiplash-associated disorders: an experimental study.

Inefficient endogenous pain inhibition, in particular impaired conditioned pain modulation (CPM), may disturb central pain processing in patients with chronic whiplash-associated disorders (WAD). Previous studies revealed that abnormal central pain processing is responsible for a wide range of symptoms in patients with chronic WAD. Hence, the present study aimed at examining the functioning of descending pain inhibitory pathways, and in particular CPM, in patients with chronic WAD. Thirty-five patients with chronic WAD and 31 healthy controls were subjected to an experiment evaluating CPM. CPM was induced by an inflated occlusion cuff and evaluated by comparing temporal summation (TS) of pressure pain prior to and during cuff inflation. Temporal summation was provoked by means of 10 consecutive pressure pulses at upper and lower limb location. Pain intensity of first, fifth, and 10th pressure pulse was rated. During heterotopic noxious conditioning stimulation, TS of pressure pain was significantly depleted among healthy controls. In contrast, TS was quite similar prior to and during cuff inflation in chronic WAD, providing evidence for dysfunctional CPM in patients with chronic WAD. The present study demonstrates a lack of endogenous pain inhibitory pathways, and in particularly CPM, in patients with chronic WAD, and hence provides additional evidence for the presence of central sensitization in chronic WAD.

Sensorimotor incongruence exacerbates symptoms in patients with chronic whiplash associated disorders: an experimental study.

OBJECTIVES: Incongruence between sensory feedback and motor output may serve as an ongoing source of nociception inside the CNS, and hence may contribute to the development of chronic whiplash associated disorder (WAD). It has been demonstrated that sensorimotor incongruence exacerbates symptoms and provokes additional sensations in patients with chronic pain. This study aimed to evaluate whether a visually mediated incongruence between motor output and sensory input aggravates symptoms and triggers additional sensations in patients with chronic WAD. METHODS: Thirty-five patients with chronic WAD and 31 healthy controls were subjected to a coordination test. They performed congruent and incongruent arm movements while viewing a whiteboard or mirror. RESULTS: All patients with chronic WAD (n = 35) reported sensory changes such as increased pain, tightness, loss of control, dizziness or feelings of peculiarity at some stage of the test protocol. No significant differences in frequency and intensity of sensory changes were found between the various test stages (P > 0.05). In the healthy control group, 18 (58%) subjects reported sensory changes at some stage of the test protocol, with the highest number during the incongruent mirror stage (n = 17), corresponding to the highest level of sensorimotor incongruence. The pattern of reported sensory changes during the congruent and incongruent stages was significantly different between both groups (P < 0.05). CONCLUSION: This study demonstrates an exacerbation of symptoms and/or additional sensory changes due to reducing or disturbing the visual input during action, indicating altered sensorimotor central nervous processing and altered perception of distorted visual feedback in chronic WAD.

Lack of endogenous pain inhibition during exercise in people with chronic whiplash associated disorders: an experimental study.

UNLABELLED: A controlled experimental study was performed to examine the efficacy of the endogenous pain inhibitory systems and whether this (mal)functioning is associated with symptom increases following exercise in patients with chronic whiplash-associated disorders (WAD). In addition, 2 types of exercise were compared. Twenty-two women with chronic WAD and 22 healthy controls performed a submaximal and a self-paced, physiologically limited exercise test on a cycle ergometer with cardiorespiratory monitoring on 2 separate occasions. Pain pressure thresholds (PPT), health status, and activity levels were assessed in response to the 2 exercise bouts. In chronic WAD, PPT decreased following submaximal exercise, whereas they increased in healthy subjects. The same effect was established in response to the self-paced, physiologically limited exercise, with exception of the PPT at the calf which increased. A worsening of the chronic WAD symptom complex was reported post-exercise. Fewer symptoms were reported in response to the self-paced, physiologically limited exercise. These observations suggest abnormal central pain processing during exercise in patients with chronic WAD. Submaximal exercise triggers post-exertional malaise, while a self-paced and physiologically limited exercise will trigger less severe symptoms, and therefore seems more appropriate for chronic WAD patients. PERSPECTIVE: The results from this exercise study suggest impaired endogenous pain inhibition during exercise in people with chronic WAD. This finding highlights the fact that one should be cautious when evaluating and recommending exercise in people with chronic WAD, and that the use of more individual, targeted exercise therapies is recommended.

Seizures and hyponatremia after excessive intake of diet coke.

We describe a case of epileptic seizures after a massive intake of diet coke. Apart from the hyponatremia due to water intoxication the convulsions can be potentiated by the high dose of caffeine and aspartame from the diet coke. To our knowledge this is the first report of seizures due to excessive diet coke intake.