The Influence of Photophobia on Postural Control in Patients With Migraine

Human RAMP1 overexpressing mice are resistant to migraine therapies for motion sensitivity: a mouse model of vestibular migraine

Both enhanced motion-induced nausea and increased static imbalance are \observed symptoms in migraine and especially vestibular migraine (VM). Motion-induced nausea and static imbalance were investigated in a mouse model, nestin/hRAMP1, expressing elevated levels of human RAMP1 in the CNS, which enhances CGRP signaling in the nervous system. Behavioral surrogates such as the motion-induced thermoregulation and postural sway center of pressure (CoP) assays were used to assess motion sensitivity. Tail vasodilation analysis revealed that this model exhibits an increased sensitivity to CGRP's effects at lower doses compared to control mice. In addition, the nestin/hRAMP1 mice exhibit a higher dynamic range in postural sway than their wildtype counterparts, along with increased sway observed in nestin/hRAMP1 male mice that was not present in male littermate controls. Results from migraine blocker experiments were challenging to interpret, but the data suggests that olcegepant is incapable of reversing CGRP-induced alterations in the nestin/hRAMP1 mice, while rizatriptan was ineffective in both the nestin/hRAMP1 and control mice. The results indicate that overexpression of hRAMP1 leads to heightened endogenous CGRP signaling. Results also suggest that both olcegepant and rizatriptan are ineffective in reducing CGRP-triggered nausea and sway in this hypersensitive CGRP mouse model. This study suggests that hypersensitivity to CGRP may be a mouse model for difficult to treat cases of vestibular migraine.

Balance disorders and migraine

BACKGROUND

Migraine is associated with motion sensitivity symptoms such as kinetosis, vestibular symptoms and balance alterations. While focus is given to headache management, addressing these symptoms is often neglected, although they are related to additional migraine burden and increased disability.

PURPOSE

Our aim is to disseminate the current understanding of the motion sensitivity symptoms among patients with migraine, with focus on balance impairments. We discuss the susceptibility of migraine to motion sensitivity, its suggested mechanisms, the balance alterations during quiet standing, mobility tasks and reactions to external perturbations. The role of migraine subdiagnosis, implications for clinical practice and future perspectives are also acknowledged.

IMPLICATIONS

Balance disorders are one of the signs reflecting a broader and complex spectrum of motion sensitivity, which are present even between attacks. Migraineurs are especially inherent to these symptoms probably due to brain hyperexcitability and to shared pathophysiological mechanisms. Patients, especially with aura and chronic migraine, exhibit balance instability during quiet standing under different surface and visual input conditions. Migraineurs demonstrated reduced limits of stability and lower performance on walk, transposing obstacles and sit to stand tasks. Only patients with aura present impairment of motor control reactions following external perturbations. Balance alterations are associated with falls and are influenced by aura, migraine frequency and psychosocial aspects, but not by vestibular symptoms or vestibular migraine diagnosis. There is a high demand for high quality of evidence regarding the assessment and care of motion sensitivity symptoms in migraineurs, considering approaches to manage not just the pain, but its associated symptoms.

Connection between right-to-left shunt and photosensitivity: a community-based cross-sectional study

Background

Hypersensitivity to light is a common symptom associated with dysfunction of the occipital region. Earlier studies also suggested that clinically significant right-to-left shunt (RLS) could increase occipital cortical excitability associated with the occurrence of migraine. The aim of this study was to investigate the relationship between RLS and photosensitivity.

Methods

This cross-sectional observational study included the residents aged 18-55 years living in the Mianzhu community between November 2021 and October 2022. Photosensitivity was evaluated using the Photosensitivity Assessment Questionnaire along with baseline clinical data through face-to-face interviews. After the interviews, contrast-transthoracic echocardiography (cTTE) was performed to detect RLS. Inverse probability weighting (IPW) was used to reduce selection bias. Photosensitivity score was compared between individuals with and without significant RLS using multivariable linear regression based on IPW.

Results

A total of 829 participants containing 759 healthy controls and 70 migraineurs were finally included in the analysis. Multivariable linear regression analysis showed that migraine (β = 0.422; 95% CI: 0.086-0.759; p = 0.014) and clinically significant RLS (β = 1.115; 95% CI: 0.760-1.470; p < 0.001) were related to higher photosensitivity score. Subgroup analysis revealed that clinically significant RLS had a positive effect on hypersensitivity to light in the healthy population (β = 0.763; 95% CI: 0.332-1.195; p < 0.001) or migraineurs (β = 1.459; 95% CI: 0.271-2.647; p = 0.010). There was also a significant interaction between RLS and migraine for the association with photophobia (p_interaction = 0.009).

Conclusion

RLS is associated with photosensitivity independently and might exacerbate photophobia in migraineurs. Future studies with RLS closure are needed to validate the findings.

Trial registration

This study was registered at the Chinese Clinical Trial Register, Natural Population Cohort Study of West China Hospital of Sichuan University, ID: ChiCTR1900024623, URL: https://www.chictr.org.cn/showproj.html?proj=40590.

Involvement of the cerebellum in migraine

Migraine is a disabling neurological disease characterized by moderate or severe headaches and accompanied by sensory abnormalities, e.g., photophobia, allodynia, and vertigo. It affects approximately 15% of people worldwide. Despite advancements in current migraine therapeutics, mechanisms underlying migraine remain elusive. Within the central nervous system, studies have hinted that the cerebellum may play an important sensory integrative role in migraine. More specifically, the cerebellum has been proposed to modulate pain processing, and imaging studies have revealed cerebellar alterations in migraine patients. This review aims to summarize the clinical and preclinical studies that link the cerebellum to migraine. We will first discuss cerebellar roles in pain modulation, including cerebellar neuronal connections with pain-related brain regions. Next, we will review cerebellar symptoms and cerebellar imaging data in migraine patients. Lastly, we will highlight the possible roles of the neuropeptide calcitonin gene-related peptide (CGRP) in migraine symptoms, including preclinical cerebellar studies in animal models of migraine.

Frequency of migraine according to the ICHD-3 criteria and its association with sociodemographic and triggering factors in Pakistan: A cross-sectional study

Background

Migraine is a primary headache disorder marked by episodes of moderate to severe headache that is unilateral, throbbing in character, having a duration of 4 h to three days, and associated with nausea, vomiting, photophobia, and phonophobia.

Aims

Our study aims to determine the frequency of migraine in Pakistan, its association with sociodemographic variables and triggering factors, and the coping mechanisms used.

Methods

A cross-sectional study was conducted through an online survey from March 19, 2022, to June 15, 2022. The snowball sampling technique was used for data collection. The questions asked included those on sociodemographic information, screening questions, and questions on triggering factors and coping mechanisms. The screening was done using the ICHD-3 criteria and percentages were calculated using SPSS.

Results

Of the 986 respondents, 393 suffered from migraine. The majority of them were female (78.1%), belonged to the age group 20–29 years (69.2%), and were students (76.1%). 32.8% of the migraineurs had a family history of migraine. Most frequent triggers included sleep disturbance (70.5%), stress (66.7%) and fatigue (64.4%). Of the female migraineurs, 31.8% had menstruation as a trigger. The coping mechanisms used included taking rest, medication, staying in a quiet and dark place, and doing massage.

Conclusion

The findings suggest that young adults, especially females, with a stressful and sleep-deprived lifestyle are more vulnerable to migraine. However, further studies must focus on trigger synergy and interrelation of triggers that precipitate migraine so a better understanding can be developed for the prevention, diagnosis, and treatment of migraine.

•

Females, majorly students, of the age group 20–29 years were the most affected by migraine.

•

The migraine attacks were mostly triggered by sleep disturbance, stress, excess screen time, loud noise, and missed meals.

•

The most frequently used coping mechanism by the migraineurs to relieve pain was taking rest.

Stimulation of CGRP-expressing neurons in the medial cerebellar nucleus induces light and touch sensitivity in mice

Calcitonin gene-related peptide (CGRP) is considered a major player in migraine pathophysiology. However, the location and mechanisms of CGRP actions in migraine are not clearly elucidated. One important question yet to be answered is: Does central CGRP signaling play a role in migraine? One candidate site is the cerebellum, which serves as a sensory and motor integration center and is activated in migraine patients. The cerebellum has the most CGRP binding sites in the central nervous system and a deep cerebellar nucleus, the medial nucleus (MN), expresses CGRP (MN^CGRP). A previous study demonstrated that CGRP delivery into the cerebellum induced migraine-like behaviors. We hypothesized that stimulation of MN^CGRP neurons might induce migraine-like behaviors. To test the hypothesis, we used an optogenetic strategy using Calca^Cre/+ mice to drive Cre-dependent expression of channelrhodopsin-2 selectively in CGRP neurons in the cerebellar MN. A battery of behavioral tests was done to assess preclinical behaviors that are surrogates of migraine symptoms, including light aversion, cutaneous allodynia, and spontaneous pain when MN^CGRP neurons were optically stimulated. Motor functions were also assessed. Optical stimulation of MN^CGRP neurons decreased the time spent in the light, which was coupled to increased time spent resting in the dark, but not the light. These changes were only significant in female mice. Plantar tactile sensitivity was increased in the ipsilateral paws of both sexes, but contralateral paw data were less clear. There was no significant increase in anxiety-like behavior, spontaneous pain (squint), or changes in gait. These discoveries reveal that MN^CGRP neurons may contribute to migraine-like sensory hypersensitivity to light and touch.

CGRP Administration Into the Cerebellum Evokes Light Aversion, Tactile Hypersensitivity, and Nociceptive Squint in Mice

The neuropeptide calcitonin gene-related peptide (CGRP) is a major player in migraine pathophysiology. Previous preclinical studies demonstrated that intracerebroventricular administration of CGRP caused migraine-like behaviors in mice, but the sites of action in the brain remain unidentified. The cerebellum has the most CGRP binding sites in the central nervous system and is increasingly recognized as both a sensory and motor integration center. The objective of this study was to test whether the cerebellum, particularly the medial cerebellar nuclei (MN), might be a site of CGRP action. In this study, CGRP was directly injected into the right MN of C57BL/6J mice via a cannula. A battery of tests was done to assess preclinical behaviors that are surrogates of migraine-like symptoms. CGRP caused light aversion measured as decreased time in the light zone even with dim light. The mice also spent more time resting in the dark zone, but not the light, along with decreased rearing and transitions between zones. These behaviors were similar for both sexes. Moreover, significant responses to CGRP were seen in the open field assay, von Frey test, and automated squint assay, indicating anxiety, tactile hypersensitivity, and spontaneous pain, respectively. Interestingly, CGRP injection caused significant anxiety and spontaneous pain responses only in female mice, and a more robust tactile hypersensitivity in female mice. No detectable effect of CGRP on gait was observed in either sex. These results suggest that CGRP injection in the MN causes light aversion accompanied by increased anxiety, tactile hypersensitivity, and spontaneous pain. A caveat is that we cannot exclude contributions from other cerebellar regions in addition to the MN due to diffusion of the injected peptide. These results reveal the cerebellum as a new site of CGRP actions that may contribute to migraine-like hypersensitivity.

Gait control of migraine patients with increasing light and sound levels

BACKGROUND

Under a typical light and sound environment context, individuals with migraine showed balance control deficits on a series of functional activities, which helps to explain why migraineurs report more falls. it isn't established, the effects of intensity light and sound in migraineurs during functional tasks.

RESEARCH QUESTION

Based on the hypersensitivity to light and sound in migraineurs, not only during the attack but also in the interictal period, does the exposure to bright light and loud sound impact motor control in this population?

METHODS

This cross-sectional study consisted of 51 women with migraine and 22 healthy women. They performed three walking tasks: crossing an obstacle, stepping-up and stepping-down a curb, in a control situation with ambient lighting (≅350 lux), bright light (≅1200 lux), and loud sound (≅90 dBa). For statistical analysis, a t-test, a Spearman correlation test, and a repeated measures mixed ANOVA were applied.

RESULTS

Migraineurs presented higher discomfort induced by light (p ≤ 0.0001) and sound (p = 0.001). In the obstacle task, migraineurs had greater step width than controls in the ambient light condition (p = 0.038) and participants of both groups placed their leading foot farther away from the obstacle in the light (p = 0.033) than in the ambient light condition. For the step-up task, this distance increased for both groups and limbs in the light (leading limb: p = 0.015; trailing limb: p = 0.002) and sound (leading limb: p = 0.010; trailing limb: p ≤ 0.0001) conditions compared to the ambient light condition. Step speed increased for light and sound conditions compared to ambient light condition, except for the sound condition in the step-down task.

SIGNIFICANCE

Despite the higher discomfort induced by light and sound in the migraineurs, the effects of these sensory manipulations were similar for both migraineurs and controls, except for step width. Light and sound manipulation induced a less conservative strategy to deal with uneven terrain in both groups.