Sensor Technologies to Manage the Physiological Traits of Chronic Pain: A Review

Non-oncologic chronic pain is a common high-morbidity impairment worldwide and acknowledged as a condition with significant incidence on quality of life. Pain intensity is largely perceived as a subjective experience, what makes challenging its objective measurement. However, the physiological traces of pain make possible its correlation with vital signs, such as heart rate variability, skin conductance, electromyogram, etc., or health performance metrics derived from daily activity monitoring or facial expressions, which can be acquired with diverse sensor technologies and multisensory approaches. As the assessment and management of pain are essential issues for a wide range of clinical disorders and treatments, this paper reviews different sensor-based approaches applied to the objective evaluation of non-oncological chronic pain. The space of available technologies and resources aimed at pain assessment represent a diversified set of alternatives that can be exploited to address the multidimensional nature of pain.

A comprehensive literature review of chronic pain and memory

Chronic pain patients often complain of their "poor memory" and numerous studies objectively confirmed such difficulties in reporting working memory (WM) and long-term memory (LTM) dysfunctions. This paper provides a comprehensive review of the literature on memory impairment in chronic pain (CP) patients. Twenty-four observational studies evaluating WM or/and LTM in a chronic pain group and a control group were included in this review. Results showed that studies consistently reported a moderate decline, in both WM and LTM performances in CP patients. Even if CP patients complained about forgetfulness, objective measurements did not permit to conclude to a long-term storage impairment. CP patients exhibited more specifically encoding or retrieving difficulties compared to controls. Results showed that chronic pain selectively impacted the most attention-demanding memory processes, such as working memory and recollection in long-term memory. Results also demonstrated that CP patients exhibited a memory bias directed towards painful events compared to control subjects. Several authors have suggested that CP could be a maladaptive consequence of memory mechanisms. The long-lasting presence of pain continuously reinforces aversive emotional associations with incidental events. The inability to extinguish this painful memory trace could explain the chronic persistence of pain even when the original injury has disappeared. A major concern is the need to extricate pain-related cognitive effects from those resulting from all the co-morbidities associated with CP which both have a deleterious effect on cognitive function.

The relative importance of anxiety and depression in pain impact in individuals with migraine headaches

BACKGROUND

Psychological factors are thought to impact headache as triggering, maintaining, and exacerbating factors. A better understanding of the role that modifiable factors, such as anxiety or depression, play in the impact of migraine could help identify potential treatment targets in this population.

OBJECTIVES

The objective of this study was to evaluate the relative importance of anxiety and depression as predictors of the impact of migraine on function. Thus, we aim to understand the relative importance that anxiety and depression have on the impact of migraines by assessing both and some life domains.

METHODS

Cross-sectional study involving forty-three individuals, mostly females (93%), with migraine headaches aged between 20 and 60 years old. Participants answered questions about headache pain intensity at the time of data collection and the usual in the past 30 days (0-10 Numerical Rating Scales) as well as other pain characteristics (i.e., duration, frequency, and duration), headache impact (vitality and social, role, and cognitive functioning), anxiety and depression by using the Hospital Anxiety and Depression Scale.

RESULTS

Anxiety (r=0.56, p<.001), but not depression (r=0.09, p=.59), was significantly associated with headache impact. Thus showing the relative importance that anxiety has on headache impact.

CONCLUSIONS

The findings support a larger role for anxiety than depression in the impact of migraine headaches on patient function. There are a number of mechanisms by which anxiety could potentially influence the impact of headache on patient function, and this study highlights that anxiety could potentially be a trigger of headache activity.

IMPLICATIONS

The findings thus suggest the possibility that treatments that focus on anxiety might be potentially more important for individuals with migraine than treatments that focus on depression, at least with respect to having a beneficial impact on the interference of headache with activity. Research is needed to evaluate the beneficial impact of anxiety treatment in individuals with migraine headaches. Clinicians should evaluate and consider treating, as appropriate and necessary, anxiety in patients with migraine.

Responsiveness of the autonomic nervous system during paced breathing and mental stress in migraine patients

Background

Migraine is a stress-related disorder, suggesting that there may be sympathetic hyperactivity in migraine patients. However, there are contradictory results concerning general sympathetic activation in migraine patients. To shed more light on the involvement of the autonomic nervous system (ANS) in migraine pathophysiology, we investigated cardiac and cardiovascular reactions during vagal (paced breathing) and sympathetic activation (mental stress test).

Methods

Heart rate variability parameters and skin conductance responses were recorded interictally in 22 episodic migraine patients without aura and 25 matched controls during two different test conditions. The paced breathing test consisted of a five-minute baseline, followed by two minutes of paced breathing (6 breathing cycles per minute) and a five-minute recovery phase. The mental stress test consisted of a five-minute baseline, followed by one minute of stress anticipation, three and a half minutes of mental stress and a five-minute recovery phase. Furthermore we measured blood pressure and heart rate once daily over 2 weeks. Subjects rated their individual current stress level and their stress level during paced breathing and during the mental stress test.

Results

There were no significant differences between migraine patients and controls in any of the heart rate variability parameters in either time domain or frequency domain analysis. However, all parameters showed a non-significant tendency for larger sympathetic activation in migraine patients. Also, no significant differences could be observed in skin conductance responses and average blood pressure. Only heart rates during the 2-week period and stress ratings showed significantly higher values in migraine patients compared to controls.

Conclusions

Generally there were no significant differences between migraine patients and controls concerning the measured autonomic parameters. There was a slight but not significant tendency in the migraine patients to react with less vagal and more sympathetic activation in all these tests, indicating a slightly changed set point of the autonomic system. Heart rate variability and blood pressure in migraine patients should be investigated for longer periods and during more demanding sympathetic activation.