Contingent negative variation in patients with chronic daily headache

Unveiling the Role of Contingent Negative Variation (CNV) in Migraine: A Review of Electrophysiological Studies in Adults and Children

Migraine has been considered a chronic neuronal-based pain disorder characterized by the presence of cortical hyperexcitability. The Contingent Negative Variation (CNV) is the most explored electrophysiological index in migraine. However, the findings show inconsistencies regarding its functional significance. To address this, we conducted a review in both adults and children with migraine without aura to gain a deeper understanding of it and to derive clinical implications. The literature search was conducted in the PubMed, SCOPUS and PsycINFO databases until September 2022m and 34 articles were retrieved and considered relevant for further analysis. The main results in adults showed higher CNV amplitudes (with no habituation) in migraine patients. Electrophysiological abnormalities, particularly focused on the early CNV subcomponent (eCNV), were especially prominent a few days before the onset of a migraine attack, normalizing during and after the attack. We also explored various modulatory factors, including pharmacological treatments-CNV amplitude was lower after the intake of drugs targeting neural hyperexcitability-and other factors such as psychological, hormonal or genetic/familial influences on CNV. Although similar patterns were found in children, the evidence is particularly scarce and less consistent, likely due to the brain's maturation process during childhood. As the first review exploring the relationship between CNV and migraine, this study supports the role of the CNV as a potential neural marker for migraine pathophysiology and the prediction of pain attacks. The importance of further exploring the relationship between this neurophysiological index and childhood migraine is critical for identifying potential therapeutic targets for managing migraine symptoms during its development.

What has neurophysiology revealed about migraine and chronic migraine?

Since the first electroencephalographic recordings obtained by Golla and Winter in 1959, researchers have used a variety of neurophysiological techniques to determine the mechanisms underlying recurrent migraine attacks. Neurophysiological methods have shown that the brain during the interictal phase of an episodic migraine is characterized by a general hyperresponsiveness to sensory stimuli, a malfunction of the monoaminergic brainstem circuits, and by functional alterations of the thalamus and thalamocortical loop. All of these alterations vary plastically during the phases of the migraine cycle and interictally with the days following the attack. Both episodic migraineurs recorded during an attack and chronic migraineurs are characterized by a general increase in the cortical amplitude response to peripheral sensory stimuli; this is an electrophysiological hallmark of a central sensitization process that is further reinforced through medication overuse. Considering the large-scale functional involvement and the main roles played by the brainstem-thalamo-cortical network in selection, elaboration, and learning of relevant sensory information, future research should move from searching for one specific primary site of dysfunction at the macroscopic level, to the chronic, probably genetically determined, molecular dysfunctions at the synaptic level, responsible for short- and long-term learning mechanisms.

How does the brain change in chronic migraine? Developing disease biomarkers

BACKGROUND

Validated chronic migraine biomarkers could improve diagnostic, prognostic, and predictive abilities for clinicians and researchers, as well as increase knowledge on migraine pathophysiology.

OBJECTIVE

The objective of this narrative review is to summarise and interpret the published literature regarding the current state of development of chronic migraine biomarkers.

FINDINGS

Data from functional and structural imaging, neurophysiological, and biochemical studies have been utilised towards the development of chronic migraine biomarkers. These biomarkers could contribute to chronic migraine classification/diagnosis, prognosticating patient outcomes, predicting response to treatment, and measuring treatment responses early after initiation. Results show promise for using measures of brain structure and function, evoked potentials, and sensory neuropeptide concentrations for the development of chronic migraine biomarkers, yet further optimisation and validation are still required.

CONCLUSIONS

Imaging, neurophysiological, and biochemical changes that occur with the progression from episodic to chronic migraine could be utilised for developing chronic migraine biomarkers that might assist with diagnosis, prognosticating individual patient outcomes, and predicting responses to migraine therapies. Ultimately, validated biomarkers could move us closer to being able to practice precision medicine in the field and thus improve patient care.

Withdrawal from acute medication normalises short-term cortical synaptic potentiation in medication overuse headache

OBJECTIVES

To study the effects of a standard acute medication withdrawal program on short-term cortical plasticity mechanisms in patients with medication overuse headache (MOH).

METHODS

Thirteen patients with MOH and 16 healthy volunteers underwent repetitive transcranial magnetic stimulation (rTMS) over the left motor cortex; in patients with MOH, recordings were performed before and after a 3-week medication withdrawal program. Ten trains of 10 stimuli each (120% resting motor threshold) were delivered at 1 Hz or 5 Hz in two separate sessions in a randomised order. Motor evoked potential (MEP) amplitudes were measured from the right first dorsal interosseous muscle and the slope of the linear regression line from the first to the tenth stimuli was calculated for each participant.

RESULTS

All subjects exhibited MEP amplitude inhibition in response to 1 Hz rTMS. Alternatively, the 5-Hz trains of rTMS inhibited rather than potentiated MEP amplitudes in patients with MOH. The physiological potentiating effect of 5 Hz rTMS on MEP amplitudes was restored after drug withdrawal and in proportion with the percentage reduction in monthly headache days in patients with MOH.

CONCLUSIONS

The results suggest that acute medication withdrawal normalises brain responses in patients with MOH. Clinical improvements after medication withdrawal may reflect the reversal of neurophysiological dysfunction. Accordingly, medication withdrawal should be offered to patients with MOH as early as possible in order to prevent the development of more pronounced alterations in brain plasticity.

Short-term cortical synaptic depression/potentiation mechanisms in chronic migraine patients with or without medication overuse

Objective

To study the effects of trains of repetitive transcranial magnetic stimulation (rTMS) over the motor cortex in patients with chronic migraine (CM) with or without medication overuse (MOH).

Subjects and methods

Thirty-two patients (CM [n = 16]; MOH [n = 16]) and 16 healthy volunteers (HVs) underwent rTMS recording. Ten trains of 10 stimuli each (120% resting motor threshold) were applied over the left motor cortex at 1 Hz or 5 Hz in random order. The amplitude of motor evoked potential (MEP) was evaluated from electromyographic recording in the first dorsal interosseous muscle. The slope of the linear regression line for the 10 stimuli for each participant was calculated using normalized data.

Results

rTMS-1 Hz had a normal depressive effect on MEP amplitude in all groups. rTMS-5 Hz depressed instead of potentiating MEP amplitudes in MOH patients, with a significantly different response from that in HVs and CM patients. The slope of the linear regression of MEP amplitudes was negatively correlated with pain intensity in CM patients, and with the duration of overuse headache in MOH patients.

Conclusions

This different plastic behaviour suggests that MOH and CM, despite exhibiting a similar clinical phenotype, have different neurophysiological learning processes, probably related to different pathophysiological mechanisms of migraine chronification.

Migraine and Meditation: Characteristics of Cortical Activity and Stress Coping in Migraine Patients, Meditators and Healthy Controls-An Exploratory Cross-Sectional Study

The aim of this exploratory cross-sectional study was to investigate the characteristics of cortical activity and stress coping in migraine patients, meditation experienced subjects, and healthy controls. 45 meditation experienced subjects, 46 migraine patients, and 46 healthy controls took part in the study. Cortical activity was measured with the contingent negative variation (CNV), a slow cortical event-related potential. Stress coping was examined with the standardized Stress Coping Questionnaire SVF-78. A one-way analysis of variance was used to investigate possible differences between the groups. CNV-amplitude was significantly higher in migraineurs than in controls. The meditators showed significantly lowest amplitudes. Migraine patients used negative stress-coping strategies significantly more often than meditators and healthy controls. Especially the application of the strategy "rumination" was most frequent in migraine patients and least frequent in meditators. Moreover, frequent rumination was significantly correlated with high CNV-amplitudes. Cortical and stress processing in people with meditation experience was improved compared to migraine patients and healthy controls.

Neural Plasticity in Common Forms of Chronic Headaches

Headaches are universal experiences and among the most common disorders. While headache may be physiological in the acute setting, it can become a pathological and persistent condition. The mechanisms underlying the transition from episodic to chronic pain have been the subject of intense study. Using physiological and imaging methods, researchers have identified a number of different forms of neural plasticity associated with migraine and other headaches, including peripheral and central sensitization, and alterations in the endogenous mechanisms of pain modulation. While these changes have been proposed to contribute to headache and pain chronification, some findings are likely the results of repetitive noxious stimulation, such as atrophy of brain areas involved in pain perception and modulation. In this review, we provide a narrative overview of recent advances on the neuroimaging, electrophysiological and genetic aspects of neural plasticity associated with the most common forms of chronic headaches, including migraine, cluster headache, tension-type headache, and medication overuse headache.

Cortical excitability in chronic migraine

A proportion of episodic migraine patients experiences a progressive increase in attack frequency leading to chronic migraine (CM). The most frequent external factor that leads to headache chronification is medication overuse. The neurobiological bases of headache chronification and of the vicious circle of medication overconsumption are not completely elucidated. More recently, the same neurophysiological methods used to study episodic migraine were applied to CM and medication-overuse headache (MOH). Studies of cortical responsivity tend overall to indicate an increase in excitability, in particular of somatosensory and visual cortices, reflected by increased amplitude of evoked responses, decreased activity of inhibitory cortical interneurons reflected in the smaller magnetic suppression of perceptual accuracy, and, at least for visual responses, an increase in habituation. In MOH, overconsumption of triptans or NSAIDs influences cortical excitability differently. Generalized central sensitization is suggested to play an important role in the pathophysiology of headache chronification.

Psychiatric comorbidity in medication overuse headache patients with pre-existing headache type of episodic tension-type headache

BACKGROUND

Medication overuse headache (MOH) mostly evolves from migraine and episodic tension-type headache (ETTH). Chronic tension-type headache (CTTH) is another headache type that evolves over time from ETTH. It is well known that psychiatric comorbidity is high in MOH patients.

AIM

To investigate the frequency of psychiatric comorbidity, and the intensity of depression and anxiety in MOH patients evolving from ETTH and to compare results with CTTH patients and MOH patients evolving from migraine.

METHODS

Twenty-eight CTTH (Group C) and 89 MOH patients were included into the study. MOH patients were divided into two groups according to their pre-existing headache types: MOH patients with pre-existing ETTH (Group E, n = 31), and with pre-existing migraine (Group M, n = 58). All patients were interviewed with a psychiatrist and SCID-CV and SCID-II were applied. Beck Anxiety Inventory and Beck Depression Inventory scales were also performed.

RESULTS

Eleven patients (39.3%) in Group C, 21 patients (67.7%) in Group E, and 31 patients (53.7%) in Group M were diagnosed to have comorbid psychiatric disorders. The psychiatric comorbidity was found significantly higher in Group E than Group C. In Group E, mood disorders were found significantly higher, but the difference between the two groups with regard to anxiety disorders was insignificant. Mean depression scores were significantly higher in Group E than Group C. The mostly diagnosed type was obsessive-compulsive personality disorder in all the three groups, and was statistically significant in Group M than Group C.

CONCLUSION

Psychiatric comorbidity in MOH patients with pre-existing ETTH is common as in those with pre-existing migraine headache and MOH with regard to developing psychiatric disorders should be interpreted as a risk factor in chronic daily headache patients.

Effects of Rizatriptan on the Contingent Negative Variation in Healthy Women

The effect of the antimigraine drug rizatriptan on the amplitude and habituation of the contingent negative variation (CNV) in healthy women was examined in a randomized, double-blind, placebo-controlled trial. The test persons were assigned either to a drug ( n = 20) or a placebo group ( n = 20). The CNV was recorded three times: before, directly after, and 24 h after drug or placebo intake. The CNV paradigm was presented in a standard, a cued and a choice version. Rizatriptan led to an increase of CNV amplitude that depended on the level of difficulty of the task. Whereas there was no drug effect in the standard version, an amplitude increase was obtained mainly in the choice task. The results are in line with the ceiling theory of migraine, which assumes a rise of CNV amplitude if the serotonin level is lowered.

[Cortical dysbalance in the brain in migraineurs--hyperexcitability as the result of sensitisation?]

A cortical dysbalance has a pivotal role in the pathophysiology of migraine. Numerous electrophysiological and transcranial magnetic stimulation (TMS) studies have investigated the interictal excitability level in migraineurs and have shown a consistent lack of habituation during repetitive stimulation. There is some controversy in the current literature over whether this deficit is based on a lowered or an elevated preactivation level. However, the current discussion may be misguided. It seems that multiple external and intrinsic factors influence the level of cortical excitability and the frequency and intensity of attacks: Habituation is specific neither to migraine nor even to pain; the same phenomenon is found in tinnitus patients, for example. Cortical hyperexcitability is presumably the result of chronicity and the concomitant central sensitisation process.

Low Income and Education Levels May Cause Medication Overuse and Chronicity in Migraine Patients

BACKGROUND

Frequent analgesic drug intake, especially in migraine patients, may induce the risk of medication overuse headache (MOH). The various conditions that may affect the development and the features of MOH have not been determined yet.

AIM

To compare MOH patients with migraine as pre-existing headache and episodic migraine patients according to socioeconomic and educational variables.

METHODS

Forty-six MOH patients with migraine as pre-existing headache and 61 migraine patients were included into study. The headache characteristics, socioeconomic and educational variables of MOH and migraine groups and subgroups divided according to the education (low/high education subgroups), and income (low/high income subgroups) levels were evaluated.

RESULTS

We found that mean duration of education was shorter in MOH patients than migraine patients. There was a negative correlation between duration of education and duration of MOH. The mean duration of MOH was longer and rate of low-income level was higher in patients with low-education level. The duration of education was lower in MOH patients with low income. The frequency of migraine attacks and low-income rate was also higher in low-educated migraine patients. The duration of education was shorter in migraine patients with low income.

CONCLUSION

We report that migraineurs with low socioeconomic status may have risk of developing MOH. A better identification of patients at risk of drug-associated headache may contribute to improved health in a group of patients with MOH.

Scalp-recorded contingent negative variation (CNV) increases during experimentally induced sustained ischemic pain in humans

Contingent negative variations (CNV) after acoustic stimuli (S1) followed by optical ones (S2) were recorded using electroencephalography in 22 healthy students both under control conditions and during ischemic pain to study the effects of sustained pain on CNV. Mean negative CNV-amplitudes and integrated areas below CNV were significantly larger during periods of ischemic pain than under control conditions (16.53 versus 13.11 microV, respectively (P=0.0028) and 8.318 versus 6.357 microV*s, respectively (P=0.00071)). We conclude that deep somatic pain augments CNV. Reduced CNV amplitudes occurring during migraine attacks, however, reflect other mechanisms which may mask the effects of migraine headache on CNV.

Chronic daily headache: a scientist's perspective

Certain features of chronic daily headache, namely, increased headache frequency, expansion of headache area, and cutaneous allodynia, may imply sensitization of central nociceptive neurons in the trigeminal pathway. Repetitive activation of the trigeminal nerve can lead to a biologic and functional change in trigeminal nucleus caudalis neurons, characterized by a decrease in nociceptive threshold and receptive field expansion. Suppression of the endogenous pain control system can facilitate the process of central sensitization. Evidence of such suppression in patients with chronic daily headache includes decreased platelet serotonin, up-regulation of 5-HT2A receptors, increased platelet nitric oxide production, and increased levels of substance P and nerve growth factor in the cerebrospinal fluid. Results from a number of animal experiments have indicated that chronic analgesic exposure leads to changes in serotonin content and density of 5-HT2A receptors in the central nervous system. This plasticity of the serotonin-dependent pain control system may accelerate the process of sensitization; a biologic outcome that is expressed clinically by the development of chronic daily headache associated with analgesic overuse.

Pathophysiology of chronic daily headache

Despite no clear explanation of the mechanism underlying chronic daily headache, sensitization of central nociceptive neurons is one possibility. Either prolonged activation of peripheral nociceptors or any factors that can alter the endogenous pain control system can trigger this process. A decrease in platelet serotonin has been observed in patients with chronic tension-type headache as well as migraine patients with medication-induced headache. It was also shown that chronic analgesic exposure led to changes in the serotonin content and the density of the 5-HT(2A) receptor in the cerebral cortex. The plasticity of the serotonin-dependent pain control system may facilitate the process of sensitization and results in the development of chronic daily headache.

Slow cortical potentials in migraine families

Amplitude and habituation of event-related potentials are abnormal in migraine. We investigated 43 migraine and 41 healthy families to evaluate the influences of age, sex and familial contribution on the variance of amplitude and habituation of the contingent negative variation (CNV). Analysis of individual differences in relation to the CNV habituation was performed. The study demonstrated that habituation of the early CNV component characterizes migraine considerably better than the CNV amplitudes. Habituation, however, is strongly influenced by age. Migraine adults and children generally showed reduced habituation. Surprisingly, more than 30% of the healthy adults demonstrated a marked loss of habituation. The reduced CNV habituation represented a high sensitivity but low specificity to migraine, especially in children. CNV amplitude and habituation parameters revealed a considerable familial contribution associated with migraine. No familial influence on either morphology or habituation of the CNV in healthy families or between healthy members of migraine families was observed. The low specificity and familial transmission of CNV parameters in members of migraine families suggest that increased amplitudes and reduced habituation of CNV do not constitute a primary risk factor for migraine, but rather represent a predisposition. Genetic components probably affect variation of the CNV amplitude and habituation.

Intensity dependence of auditory evoked cortical potentials in migraine families

Intensity dependence of auditory evoked cortical potentials is abnormal in migraine. This study investigated intensity dependence in migraine and healthy families using group comparisons and analysis of individual differences. Migraineurs were characterized by a steeper amplitude/stimulus function slope and more pronounced difference between the amplitudes of N1-P2 on the more and the less intensive tones than healthy age matched subjects. Apart from migraine, the age of the participants was an important predictive variable of intensity dependence. Analysis of individual differences revealed low sensitivity and moderate specificity of intensity dependence for migraine. Familial prevalence of intensity dependence among first-degree relatives in migraine families was equal to that in healthy families. These findings support the assumption that high-intensity dependence reflects a functional CNS trait which is more pronounced and prevalent in migraine, but may also be found in healthy individuals and in other neuropsychiatric disorders. Increased intensity dependence is only one of several factors contributing to the risk for this form of headache.