Do patients with interictal migraine modulate pain differently from healthy controls? A psychophysical and brain imaging study

Pain profiling in migraine: a systematic review of Quantitative Sensory Testing (QST), Conditioned Pain Modulation (CPM), and Corneal Confocal Microscopy (CCM)

OBJECTIVE

The aim of this systematic review is to identify pain profiling parameters that are reliably different between patients with migraine and healthy controls, using Quantitative Sensory Testing (QST) including Temporal Summation (TS), Conditioned Pain Modulation (CPM), and Corneal Confocal Microscopy (CCM).

METHODS

A comprehensive literature search was conducted (up to 23 May 2024). The quality of the research was assessed using the Newcastle-Ottawa Scale (NOS) for non-randomized studies.

RESULTS

Twenty-eight studies were included after screening. The QST studies indicate that migraine patients exhibit lower pressure pain thresholds (PPT), particularly in the trigeminal region. A previous meta-analysis reported lower heat pain thresholds (HPT). CPM studies suggest a (mild) inhibitory or absent response in migraine patients, not different from controls. High-frequency and chronic migraine patients may exhibit a facilitatory CPM response. With repeated executions of CPM, migraine patients display a diminishing CPM response, a phenomenon not observed in control subjects. CCM investigations in migraine patients revealed conflicting outcomes, likely as a result of small sample sizes and limited characterization of migraine features.

CONCLUSION

Pain profiling migraine patients varies due to sensory modality, applied methods, anatomical sites, and migraine features. Understanding pain profiling offers insights into migraine pathophysiology, requiring careful selection of parameters and differentiation among migraine subtypes.

Endogenous pain modulation after sleep restriction in migraine: a blinded crossover study

BACKGROUND

Patients with migraine are vulnerable to insufficient sleep, but the impact of sleep restriction is largely unknown. In addition, the importance of sleep may be different in patients with migraine who mostly have attack onsets during sleep, so called sleep-related migraine, compared to patients with non-sleep-related migraine. In this study we investigate the effect of sleep restriction on endogenous pain modulation in patients with migraine and healthy controls. We also compared the effect of sleep restriction in sleep-related and in non-sleep-related migraine.

METHODS

Measurements were conducted in 39 patients with migraine between attacks and 31 controls, once after habitual sleep and once after two consecutive nights of partial sleep restriction. There were 29 and 10 patients with non-sleep-related and sleep-related migraine respectively. Test stimulus was 2-min tonic noxious heat to the left volar forearm. Temporal summation was calculated as the regression coefficient for rated pain in the late part of this 2-min stimulation. Conditioning stimulus was right hand-immersion in 7 °C water. Conditioned pain modulation was defined as the difference in rated pain with and without the conditioning stimulus and was calculated for temporal summation and mean rated pain for the test stimulus. The effect of sleep restriction on temporal summation and conditioned pain modulation was compared in migraine subjects and controls using two-level models with recordings nested in subjects.

RESULTS

Conditioned pain modulation for temporal summation of heat pain tended to be reduced after sleep restriction in patients with migraine compared to controls (p = 0.060) and, in an exploratory analysis, was reduced more after sleep restriction in sleep-related than in non-sleep-related migraine (p = 0.017). No other differences between groups after sleep restriction were found for temporal summation or conditioned pain modulation.

CONCLUSION

Patients with migraine may have a subtly altered endogenous pain modulation system. Sleep restriction may have an increased pronociceptive effect on this system, suggesting a mechanism for vulnerability to insufficient sleep in migraine. This effect seems to be larger in sleep-related migraine than in non-sleep-related migraine.

Central generators of migraine and autonomic cephalalgias as targets for personalized pain management: Translational links

BACKGROUND AND OBJECTIVE

Migraine oscillates between different states in association with internal homeostatic functions and biological rhythms that become more easily dysregulated in genetically susceptible individuals. Clinical and pre-clinical data on migraine pathophysiology support a primary role of the central nervous system (CNS) through 'dysexcitability' of certain brain networks, and a critical contribution of the peripheral sensory and autonomic signalling from the intracranial meningeal innervation. This review focuses on the most relevant back and forward translational studies devoted to the assessment of CNS dysfunctions involved in primary headaches and discusses the role they play in rendering the brain susceptible to headache states.

METHODS AND RESULTS

We collected a body of scientific literature from human and animal investigations that provide a compelling perspective on the anatomical and functional underpinnings of the CNS in migraine and trigeminal autonomic cephalalgias. We focus on medullary, hypothalamic and corticofugal modulation mechanisms that represent strategic neural substrates for elucidating the links between trigeminovascular maladaptive states, migraine triggering and the temporal phenotype of the disease.

CONCLUSION

It is argued that a better understanding of homeostatic dysfunctional states appears fundamental and may benefit the development of personalized therapeutic approaches for improving clinical outcomes in primary headache disorders.

SIGNIFICANCE

This review focuses on the most relevant back and forward translational studies showing the crucial role of top-down brain modulation in triggering and maintaining primary headache states and how these central dysfunctions may interact with personalized pain management strategies.

Harnessing the conditioned pain modulation response in migraine diagnosis, outcome prediction, and treatment-A narrative review

OBJECTIVE

To present the potential use and relevance of the conditioned pain modulation (CPM) response to migraine diagnosis, outcome prediction, and treatment.

BACKGROUND

The CPM response is a widely used laboratory test to examine inhibitory pain modulation capabilities.

METHODS

This narrative review summarizes and synthesizes the findings on the CPM response in patients with migraine.

RESULTS

For diagnosis, we summarized the studies comparing CPM responses between patients with migraine and individuals without migraine or with other headache syndromes, as well as between patients with subtypes of migraine. For prediction, we summarized the studies utilizing the CPM response to predict migraine outcome, such as response to interventions. For treatment, we described a device that utilizes the CPM response for acute and preventative migraine treatment. In addition, we suggest the requirements needed for the CPM response to be used for migraine diagnosis, outcome prediction, and treatment.

CONCLUSIONS

Although more research is needed, the CPM response could be a useful tool for improving migraine management.

Neural mechanisms underlying the conditioned pain modulation response: a narrative review of neuroimaging studies

ABSTRACT

Processing spatially distributed nociceptive information is critical for survival. The conditioned pain modulation (CPM) response has become a common psychophysical test to examine pain modulation capabilities related to spatial filtering of nociceptive information. Neuroimaging studies have been conducted to elucidate the neural mechanisms underlying the CPM response in health and chronic pain states, yet their findings have not been critically reviewed and synthesized before. This narrative review presents a simplified overview of MRI methodology in relation to CPM assessments and summarizes the findings of neuroimaging studies on the CPM response. The summary includes functional MRI studies assessing CPM responses during scanning as well as functional and structural MRI studies correlating indices with CPM responses assessed outside of the scanner. The findings are discussed in relation to the suggested mechanisms for the CPM response. A better understanding of neural mechanisms underlying spatial processing of nociceptive information could advance both pain research and clinical use of the CPM response as a marker or a treatment target.

Descending pain modulatory efficiency in healthy subjects is related to structure and resting connectivity of brain regions

The descending pain modulatory system in humans is commonly investigated using conditioned pain modulation (CPM). Whilst variability in CPM efficiency, i.e., inhibition and facilitation, is normal in healthy subjects, exploring the inter-relationship between brain structure, resting-state functional connectivity (rsFC) and CPM readouts will provide greater insight into the underlying CPM efficiency seen in healthy individuals. Thus, this study combined CPM testing, voxel-based morphometry (VBM) and rsFC to identify the neural correlates of CPM in a cohort of healthy subjects (n =40), displaying pain inhibition (n = 29), facilitation (n = 10) and no CPM effect (n = 1). Clusters identified in the VBM analysis were implemented in the rsFC analysis alongside key constituents of the endogenous pain modulatory system. Greater pain inhibition was related to higher volume of left frontal cortices and stronger rsFC between the motor cortex and periaqueductal grey. Conversely, weaker pain inhibition was related to higher volume of the right frontal cortex - coupled with stronger rsFC to the primary somatosensory cortex, and rsFC between the amygdala and posterior insula. Overall, healthy subjects showed higher volume and stronger rsFC of brain regions involved with descending modulation, while the lateral and medial pain systems were related to greater pain inhibition and facilitation during CPM, respectively. These findings reveal structural alignments and functional interactions between supraspinal areas involved in CPM efficiency. Ultimately understanding these underlying variations and how they may become affected in chronic pain conditions, will advance a more targeted subgrouping in pain patients for future cross-sectional studies investigating endogenous pain modulation.

Conditioned Pain Modulation (CPM) Effects Captured in Facial Expressions

Purpose

Conditioned pain modulation (CPM) is most often assessed using self-report of pain. However, self-report of pain is not always available (eg in individuals with cognitive impairment) and is susceptible to report bias. In comparison, the facial expression of pain is more reflex-like and represents one of the most sensitive and specific non-verbal signals of pain. The aim of the present study was to investigate whether the facial expression of pain is sensitive enough to capture endogenous pain inhibition as elicited during CPM paradigms.

Patients and Methods

In total, 26 female participants took part in this study. Facial and verbal responses to phasic heat pain were assessed once while participants immersed their hand in a hot water bath and once without additional stimulation. Facial responses were analyzed using the Facial Action Coding System (FACS). Verbal responses were assessed using a Numerical Rating Scale (NRS).

Results

Pain-relevant facial responses as well as pain ratings to phasic heat pain were significantly reduced when participants simultaneously immersed their hand in a hot water bath compared to baseline. Thus, CPM effects could be demonstrated both on subjective as well as on facial responses. Moreover, CPM-induced changes in pain-relevant facial responses and in NRS ratings were significantly correlated.

Conclusion

The present study shows that facial expressions of pain are sensitive enough to capture CPM effects. Given the proven clinical usefulness of assessing CPM, the parallel assessment of verbal and facial CPM effects might be a promising approach with wider scope of applications. Further research in other demographic healthy participant and clinical cohorts is warranted.

Slowly repeated evoked pain (SREP) as a central sensitization marker in episodic migraine patients

Migraine headache is a pain condition characterized by severe and recurrent unilateral head pain. Among other mechanisms, central pain sensitization processes seem to be involved in the disorder. An experimental protocol based on slowly repeated evoked pain (SREP) has been shown to indicate pain sensitization in fibromyalgia patients and differentiate these patients from healthy individuals and rheumatoid arthritis patients. This study examined SREP sensitization in migraine patients and explored its potential usefulness as a central sensitization marker. The SREP protocol was administered to 40 episodic migraine (EM) patients not currently experiencing a headache and 40 healthy controls. SREP consisted of a series of 9 suprathreshold painful pressure stimuli of 5 s duration and a 30 s interstimulus interval. SREP sensitization was indexed by the increase in pain ratings across the stimuli. Pain threshold, pain tolerance and temporal summation of pain were also assessed. SREP sensitization was observed in EM, but not in healthy individuals (p < .001). SREP differentiated between EM and healthy individuals with up to 75% diagnostic accuracy. Pain threshold, pain tolerance and temporal summation of pain did not show significant discriminative ability. An SREP index value of 0.5 was the most sensitive cut-off for detecting central pain sensitization when prioritizing diagnostic sensitivity (0.88). Results provide evidence for SREP as a possible central sensitization marker with potential clinical utility in migraine patients. Inclusion of SREP in Quantitative Sensory Testing protocols may enhance the assessment of altered pain modulation in different pain conditions.

Identification of neural and psychophysical predictors of headache reduction after cognitive behavioral therapy in adolescents with migraine

ABSTRACT

Cognitive behavioral therapy (CBT) is a psychological intervention that involves development of coping strategies to reduce the experience of pain. Although CBT is a promising intervention to reduce headache days in patients with migraine, it may not be effective for all patients. Thus, there is a need to identify markers that could predict which patients will respond to CBT. We aimed to determine whether baseline brain function and amygdalar connectivity, assessed by functional magnetic resonance imaging, or pain modulation capacities, assessed by the conditioned pain modulation (CPM) response, can predict a reduction in headache days after CBT in adolescents with migraine. Patients with migraine (n = 20; age range 10-17 years) completed 8 weekly CBT sessions. The CPM response was examined in the trapezius and the leg. Headache days significantly decreased after CBT (P < 0.001). Greater functional connectivity before CBT between the right amygdala and frontal gyrus, anterior cingulate cortex, and precentral gyrus was related to greater headache reduction after CBT. Greater reduction in headache days after CBT was related with less efficient CPM response before CBT at the trapezius (r = -0.492, P = 0.028) but not at the leg. This study found that headache reduction after CBT was related to right amygdala connectivity with frontal and sensorimotor regions at baseline as well as baseline pain modulation capacities. These findings suggest that individual differences in brain function and pain modulation can be associated with clinical improvements and help with determination of CBT responsiveness.

Spatial aspects of pain modulation are not disrupted in adolescents with migraine

OBJECTIVE

To compare spatial pain modulation capabilities between adolescents with and without migraine.

BACKGROUND

Conditioned pain modulation (CPM) responses at the leg are similar in adolescents with versus without migraine. However, the anatomical region of testing may affect spatial pain modulation capabilities as differences in nociceptive processing between patients with migraine and healthy controls are found in local areas that are near the site of clinical pain but not in nonlocal areas. This study aimed to examine spatial pain modulation capabilities tested by the CPM paradigm using test stimulus applied to a local body area.

METHODS

Nineteen adolescents with migraine (age 14.9 ± 2.3, mean ± SD; 16 female) and 20 healthy adolescents (age 13.8 ± 2.5, mean ± SD; 16 female) completed this case-control study at Cincinnati Children's Hospital Medical Center. Pressure pain thresholds (PPT) were assessed at the trapezius before and during immersion of the foot in a cold water bath (8°C).

RESULTS

In the migraine group (146.0 ± 79.1, mean ± SD), compared to healthy controls (248.0 ± 145.5, mean ± SD), significantly lower PPT (kilopascal) values were found (estimate = 124.28, 95% CI: 58.98, 189.59, p < 0.001; effect size: d = 1.40). No differences between the groups were found for pain intensity and unpleasantness ratings of cold-water immersion nor the CPM response.

CONCLUSIONS

This study found altered ascending nociceptive processing of mechanical stimuli at the neck in adolescents with migraine. However, endogenous pain modulatory mechanisms were functional and not altered. In light of other studies, impairments in inhibitory control may not be involved in migraine pathophysiology in pediatric patients regardless of stimulus location.

Individual variability and sex differences in conditioned pain modulation and the impact of resilience, and conditioning stimulus pain unpleasantness and salience

Distinct pain experiences are shaped both by personal attributes and characteristics of noxious stimuli. An Individual's capacity for endogenous pain inhibition (reflected by conditioned pain modulation [CPM]), their resilience, and the pain unpleasantness and salience of painful stimuli can impact their pain perception. Here, we aimed to determine how individual variability in CPM relates to sex and resilience as personal attributes, and pain unpleasantness and salience of the CPM conditioning stimulus (CS). We evaluated CPM in 106 healthy participants (51 female and 55 male) based on the change in test stimulus pain applied concurrently with a painful CS, both delivered by painful heat. The CS reduced test stimulus pain in only half of the participants (CPM subgroup), but did not do so for the other half (no-CPM subgroup), many who exhibited pain facilitation. A regression model explained CPM effects after accounting for sex, resilience, CS pain unpleasantness and salience. In the CPM subgroup regression model, the CPM effect was positively related to CS pain unpleasantness, while the CPM effect was not related to any variable in the no-CPM subgroup model. Correlation analyses revealed that the CPM effect was anticorrelated with resilience in males with no-CPM. The CPM effect was correlated with CS pain unpleasantness in males with CPM and in females with no-CPM. The CPM effect and CS salience were correlated in the whole group more strongly than in the subgroups. These data reveal that the complexity of contributors to CPM variability include both personal attributes and attributes of the CS.

Brain Functional Alternations of the Pain-related Emotional and Cognitive Regions in Patients with Chronic Shoulder Pain

Objective

Chronic shoulder pain (CSP) is a common health problem associated with shoulder dysfunction and persistent pain for many different reasons. However, the studies of pain-related functional brain regions in CSP have been poorly investigated. The main purpose of our study was to observe whether there are abnormal functional changes in brain regions in patients with CSP by using functional magnetic resonance imaging (fMRI).

Patients and Methods

We compared the differences of brain regions between 37 patients with CSP and 24 healthy controls (HC) using regional homogeneity (ReHo) method. The patients with chronic shoulder pain and healthy controls were matched for age and gender. Brain regions which had abnormal ReHo values were defined as seed region of interests. The approach of seed-based functional connectivity (FC) was further performed to analyze the connectivity between the seeds and whole brain regions. The relationship between abnormal regions and current clinical pain was also evaluated.

Results

Compared to healthy controls, the patients with CSP showed increased ReHo values in the left middle temporal gyrus and decreased ReHo values in right orbitofrontal cortex (OFC). The seed-based analyses demonstrated decreased connectivity between the right OFC and right rectus, superior frontal gyrus in patients with chronic shoulder pain. However, a correlation between ReHo values and clinical characteristics in CSP patients was not found.

Conclusion

The observed results indicate that there are abnormal ReHo values in brain regions of patients with CSP, especially in the OFC and middle temporal gyrus. Our findings demonstrate that the experience of CSP patients may be mainly associated with cognitive-affective pain processing, rather than nociception.

The Endogenous Analgesia Signature in the Resting Brain of Healthy Adults and Migraineurs

Altered pain modulation and resting state functional connectivity (rsFC) were found to be related to migraine pathology and clinical manifestation. We examined how pain modulation psychophysical measures are related to resting-state networks and rsFC between bottom-up and top-down pain modulation areas. Thirty-two episodic migraineurs and 23 age-matched healthy individuals underwent temporal summation of pain (TSOP) and conditioned pain modulation (CPM) tests, followed by a resting-state imaging scan. No differences in temporal summation of pain and CPM were found between groups. However, in healthy individuals, more efficient CPM was correlated with 1) stronger rsFCs of the posterior cingulate cortex, with the ventromedial prefrontal cortex and with the pregenual anterior cingulate cortex; 2) weaker rsFC of the anterior insula with the angular gyrus. Conversely, in migraineurs, the association between CPM and rsFC was altered. Our results suggest that the functional connectivity within the default mode network (DMN) components and the functional coupling between the DMN and pain inhibitory brain areas is linked with pain inhibition efficiency. In migraineurs, this interplay is changed, yet enables normal pain inhibition. Our findings shed light on potential functional adaptation of the DMN and its role in pain inhibition in health and migraine. PERSPECTIVE: This article establishes evidence for the relationship between the resting-state brain and individual responses in psychophysical pain modulation tests, in both migraine and healthy individuals. The results emphasize the significant role of the default mode network in maintaining pain inhibition efficiency in health and in the presence of chronic pain.

Altered Resting State Functional Activity and Microstructure of the White Matter in Migraine With Aura

Introduction: Brain structure and function were reported to be altered in migraine. Importantly our earlier results showed that white matter diffusion abnormalities and resting state functional activity were affected differently in the two subtypes of the disease, migraine with and without aura. Resting fluctuation of the BOLD signal in the white matter was reported recently. The question arising whether the white matter activity, that is strongly coupled with gray matter activity is also perturbed differentially in the two subtypes of the disease and if so, is it related to the microstructural alterations of the white matter.

Methods: Resting state fMRI, 60 directional DTI images and high-resolution T1 images were obtained from 51 migraine patients and 32 healthy volunteers. The images were pre-processed and the white matter was extracted. Independent component analysis was performed to obtain white matter functional networks. The differential expression of the white matter functional networks in the two subtypes of the disease was investigated with dual-regression approach. The Fourier spectrum of the resting fMRI fluctuations were compared between groups. Voxel-wise correlation was calculated between the resting state functional activity fluctuations and white matter microstructural measures.

Results: Three white matter networks were identified that were expressed differently in migraine with and without aura. Migraineurs with aura showed increased functional connectivity and amplitude of BOLD fluctuation. Fractional anisotropy and radial diffusivity showed strong correlation with the expression of the frontal white matter network in patients with aura.

Discussion: Our study is the first to describe changes in white matter resting state functional activity in migraine with aura, showing correlation with the underlying microstructure. Functional and structural differences between disease subtypes suggest at least partially different pathomechanism, which may necessitate handling of these subtypes as separate entities in further studies.

Increased pain sensitivity but normal pain modulation in adolescents with migraine

Inhibitory pain modulation has been reported to be deficient in adults across different types of chronic pain, including migraine. To determine whether a similar phenomenon occurs in youth, we performed a quantitative sensory testing investigation in adolescents with migraine (N = 19). These patients were compared to healthy adolescents with (Fam-His; N = 20) or without (Healthy; N = 29) a family history of migraine (eg, first-degree relative with migraine). Subjects were first familiarized with the stimuli and visual analogue rating scales using graded noxious stimuli (0°C, 43-49°C range). These data were used to explore potential pain sensitivity differences between the groups. Pain inhibition was assessed by conditioned pain modulation (CPM), which used both suprathreshold heat pain (heat CPM) and pressure pain thresholds (pressure CPM) as the test stimuli before and during cold-water immersion (8°C). In response to the graded heat stimuli, Fam-His participants reported higher pain intensity ratings compared with patients with migraine, who in turn reported higher pain intensity ratings than the healthy controls (F = 3.6, [df = 2, 459], P = 0.027). For heat and pressure CPM, there was no significant group difference in the magnitude of CPM responses. Thus, adolescents with migraine and healthy adolescents have similar inhibitory pain modulation capability, despite having marked differences in pain sensitivity. Although Fam-His participants are asymptomatic, they demonstrate alterations in pain processing, which may serve as markers for prediction of migraine development.

Experimental evaluation of central pain processes in young women with primary dysmenorrhea

Primary dysmenorrhea (PD; menstrual pain without an underlying medical condition) is associated with enhanced pain sensitivity and temporal summation (TS) in adult women, which may reflect the presence of central pain processes. Research in this area has been limited by focusing on only adult populations and incomplete assessments of central sensitization. The current study explored both excitatory and inhibitory measures of pain processing in girls and young adult women with and without PD. Thirty-two young women with PD and 34 healthy controls underwent laboratory pain testing during each of 3 menstrual cycle phases (menstrual, ovulatory, and midluteal), which included measures of pain tolerance and threshold, TS, and conditioned pain modulation. Results indicated enhanced pain sensitivity in young women with PD as measured by heat pain tolerance and Average Pain50 (P50), compared with healthy controls. These group differences were evident at all phases of the menstrual cycle. No group differences in cold pain tolerance, TS, or conditioned pain modulation were evident at any phase of the menstrual cycle. These data suggest some evidence of central sensitization in young women with PD, although no evidence of enhanced excitatory or deficient inhibitory mechanisms were observed. Future research should focus on identifying other potential phenotypes for PD to determine those at risk of developing other pain problems.