Visual system dysfunction in migraine: a review of clinical and psychophysical findings

Hyperactivity of the medial thalamus in patients with photophobia-associated migraine

OBJECTIVE

To examine cerebral functional alterations associated with sensory processing in patients with migraine and constant photophobia.

BACKGROUND

Migraine is a common headache disorder that presents with photophobia in many patients during attacks. Furthermore, some patients with migraine experience constant photophobia, even during headache-free intervals, leading to a compromised quality of life.

METHODS

This prospective, case-control study included 40 patients with migraine (18 male and 22 female) who were recruited at an eye hospital and eye clinic. The patients were divided into two groups: migraine with photophobia group, consisting of 22 patients (10 male and 12 female) with constant photophobia, and migraine without photophobia group, consisting of 18 patients (eight male and 10 female) without constant photophobia. We used 18F-fluorodeoxyglucose and positron emission tomography to compare cerebral glucose metabolism between the two patient groups and 42 healthy participants (16 men and 26 women).

RESULTS

Compared with the healthy group, both the migraine with photophobia and migraine without photophobia groups showed cerebral glucose hypermetabolism in the bilateral thalamus (p < 0.05, family-wise error-corrected). Moreover, the contrast of migraine with photophobia minus migraine without photophobia patients showed glucose hypermetabolism in the bilateral medial thalamus (p < 0.05, family-wise error-corrected).

CONCLUSIONS

The medial thalamus may be associated with the development of continuous photophobia in patients with migraine.

Application of EEG in the Diagnosis and Classification of Migraine: A Scoping Review

Migraine is a chronic debilitating disease affecting a significant number of people, more often women than men. The gold standard for diagnosis is the International Classification of Headache Disorders-3 (ICHD-3). Authors have identified multiple tight spots in the present method of diagnosis. An alternative method of diagnosis has always been coveted. Electroencephalogram (EEG) is one of the most researched of such alternatives. The visually evoked potential is the most studied; auditory evoked potentials and transcranial direct current stimulation are also being studied. Cortical hyperexcitability and habituation deficit to sensory stimuli are some of the consistent findings. Alpha oscillations are among the most frequently studied bands; spectral analysis of EEG waves has often shown more reliable and consistent results than features read off the EEG directly. EEG microstate is a novel and promising method showing characteristic identifiable features that may help diagnose Migraine patients. An alternative to the ICHD-3 criterion for diagnosing Migraines would be instrumental in promptly diagnosing the disease. EEG is one of the most explored alternatives within which enumerable features can be used to identify Migraines, of which the most promising are EEG microstates.

Resting-state electroencephalography microstate dynamics altered in patients with migraine with and without aura-A pilot study

OBJECTIVE

To evaluate electroencephalography (EEG) microstate differences between patients with migraine with aura (MWA), patients with migraine without aura (MWoA), and healthy controls (HC).

BACKGROUND

Previous research employing microstate analysis found unique microstate alterations in patients with MWoA; however, it is uncertain how microstates appear in patients with MWA.

METHODS

This study was conducted at the Headache Clinic of the First Affiliated Hospital of Xi'an Jiaotong University. In total, 30 patients with MWA, 30 with MWoA, and 30 HC were enrolled in this cross-sectional study. An EEG was recorded for all participants under resting state. The microstate parameters of four widely recognized microstate classes A-D were calculated and compared across the three groups.

RESULTS

The occurrence of microstate B (MsB) in the MWoA group was significantly higher than in the HC (p = 0.006, Cohen's d = 0.72) and MWA (p = 0.016, Cohen's d = 0.57) groups, while the contribution of MsB was significantly increased in the MWoA group compared to the HC group (p = 0.016, Cohen's d = 0.64). Microstate A (MsA) displayed a longer duration in the MWA group compared to the MWoA group (p = 0.007, Cohen's d = 0.69). Furthermore, the transition probability between MsB and microstate D was significantly increased in the MWoA group compared to the HC group (p = 0.009, Cohen's d = 0.68 for B to D; p = 0.007, Cohen's d = 0.71 for D to B). Finally, the occurrence and contribution of MsB were positively related to headache characteristics in the MWoA group but negatively in the MWA group, whereas the duration of MsA was positively related to the visual analog scale in the MWA group (all p < 0.05).

CONCLUSIONS

Patients with MWA and MWoA have altered microstate dynamics, indicating that resting-state brain network disorders may play a role in migraine pathogenesis. Microstate parameters may have the potential to aid clinical management, which needs to be investigated further.

Correlation between higher-order aberration and photophobia after cataract surgery

Cataract surgery impinges on the spatial properties and wavelength distribution of retinal images, which changes the degree of light-induced visual discomfort/photophobia. However, no study has analyzed the alteration in photophobia before and after cataract surgery or the association between retinal spatial property and photophobia. Here, we measured the higher-order aberrations (HOAs) of the entire eye and the subjective photophobia score. This study investigated 71 eyes in 71 patients who received conventional cataract surgery. Scaling of photophobia was based on the following grading system: when the patient is outdoor on a sunny day, score of 0 and 10 points were assigned to the absence of photophobia and the presence of severe photophobia prevents eye-opening, respectively. We decomposed wavefront errors using Zernike polynomials for a 3-mm pupil diameter and analyzed the association between photophobia scores and HOAs with Spearman’s rank sum correlation (rs). We classified patients into two groups: photophobia (PP) unconcerned included patients who selected 0 both preoperatively or postoperatively and PP concerned included the remaining patients. After cataract surgery, photophobia scores increased, remained unchanged (stable), and decreased in 3, 41, and 27 cases, respectively. In the stable group, 35 of 41 cases belonged to PP unconcerned. In PP concerned, there were significant correlations between photophobia score and postoperative root-mean-square values of total HOAs (rs = 0.52, p = 0.002), total coma (rs = 0.52, p = 0.002), total trefoil (rs = 0.47, p = 0.006), and third-order group (rs = 0.53, p = 0.002). In contrast, there was no significant correlation between photophobia scores and preoperative HOAs. Our results suggest that the spatial properties of retinal image modified by HOAs may affect the degree of photophobia. Scattering light due to cataracts could contribute to photophobia more than HOAs, which may mask the effect of HOAs for photophobia preoperatively.

Abnormalities in resting-state EEG microstates are a vulnerability marker of migraine

Background

Resting-state EEG microstates are thought to reflect brief activations of several interacting components of resting-state brain networks. Surprisingly, we still know little about the role of these microstates in migraine. In the present study, we attempted to address this issue by examining EEG microstates in patients with migraine without aura (MwoA) during the interictal period and comparing them with those of a group of healthy controls (HC).

Methods

Resting-state EEG was recorded in 61 MwoA patients (50 females) and 66 HC (50 females). Microstate parameters were compared between the two groups. We computed four widely identified canonical microstate classes A-D.

Results

Microstate classes B and D displayed higher time coverage and occurrence in the MwoA patient group than in the HC group, while microstate class C exhibited significantly lower time coverage and occurrence in the MwoA patient group. Meanwhile, the mean duration of microstate class C was significantly shorter in the MwoA patient group than in the HC group. Moreover, among the MwoA patient group, the duration of microstate class C correlated negatively with clinical measures of headache-related disability as assessed by the six-item Headache Impact Test (HIT-6). Finally, microstate syntax analysis showed significant differences in transition probabilities between the two groups, primarily involving microstate classes B, C, and D.

Conclusions

By exploring EEG microstate characteristics at baseline we were able to explore the neurobiological mechanisms underlying altered cortical excitability and aberrant sensory, affective, and cognitive processing, thus deepening our understanding of migraine pathophysiology.

Exploration of anomalous perceptual experiences in migraine between attacks using the Cardiff Anomalous Perceptions Scale

Distortions in sensory experiences that precede a migraine attack have been extensively documented, the most well-known being the visual aura. Distortions in the experience of other senses are also reported as part of an aura, albeit less frequently, together with changes in the perception or ownership of the body or body parts. There are many examples of differences in aspects of visual perception between migraine and control groups, between attacks, but not as much on unusual experiences involving other senses, the sense of the body or the experience of the environment. Seventy-seven migraine (33 with aura) and 74 control participants took part. Anomalous perceptions were experienced by both migraine and control groups, but more with migraine experienced them and rated them as more distressing, intrusive and frequent. Associations with reports of visual triggers of migraine and visual discomfort are presented. This study is the first to show relationships between these factors.

Relating excitatory and inhibitory neurochemicals to visual perception: A magnetic resonance study of occipital cortex between migraine events

Certain perceptual measures have been proposed as indirect assays of brain neurochemical status in people with migraine. One such measure is binocular rivalry, however, previous studies have not measured rivalry characteristics and brain neurochemistry together in people with migraine. This study compared spectroscopy-measured levels of GABA and Glx (glutamine and glutamate complex) in visual cortex between 16 people with migraine and 16 non-headache controls, and assessed whether the concentration of these neurochemicals explains, at least partially, inter-individual variability in binocular rivalry perceptual measures. Mean Glx level was significantly reduced in migraineurs relative to controls, whereas mean occipital GABA levels were similar between groups. Neither GABA levels, nor Glx levels correlated with rivalry percept duration. Our results thus suggest that the previously suggested relationship between rivalry percept duration and GABAergic inhibitory neurotransmitter concentration in visual cortex is not strong enough to enable rivalry percept duration to be reliably assumed to be a surrogate for GABA concentration, at least in the context of healthy individuals and those that experience migraine.

Automated instrument designed to determine visual photosensitivity thresholds

The Ocular Photosensitivity Analyzer (OPA), a new automated instrument to quantify the visual photosensitivity thresholds (VPT) in healthy and light sensitive subjects, is described. The OPA generates light stimuli of varying intensities utilizing unequal ascending and descending steps to yield the VPT. The performance of the OPA was evaluated in healthy subjects, as well as light sensitive subjects with achromatopsia or traumatic brain injury (TBI). VPT in healthy, achromatopsia, and TBI subjects were 3.2 ± 0.6 log lux, 0.5 ± 0.5 log lux, and 0.4 ± 0.6 log lux, respectively. Light sensitive subjects manifested significantly lower VPT compared to healthy subjects. Longitudinal analysis revealed that the OPA reliably measured VPT in healthy subjects.

Preventive drugs restore visual evoked habituation and attention in migraineurs

Visual system pathway dysfunction has been postulated in migraineurs. We wanted to investigate if any difference exists interictally in visual attention and visual evoked habituation of frequently attacked migraineurs compared to the healthy control group. The effects of 3-month prophylactic migraine treatment on these parameters were also assessed. The migraineurs at headache-free interval (n = 52) and age, sex-matched healthy controls (n = 35) were compared by habituation response to 10 blocks of repetitive pattern-reversal visual stimuli (each block consisted 100 responses). The amplitude changes of 5th and 10th blocks were further compared with that of block 1 to assess the response of habituation (i.e., decrease) or potentiation (i.e., increase). The level of sustained visual attention was assessed by Cancellation test. Migraineurs were randomized to three different preventive treatments: propranolol 40 mg tid, flunarizine 5 mg bid, or topiramate 50 mg bid. After 3 months of preventive treatment, migraineurs data were compared with their baseline values. The groups did not differ by sex and age. In electrophysiological studies, the habituation ability observed in the healthy group was not observed in migraineurs. However, it was restored 3 months after preventive treatment. In migraineurs, compared to their baseline values, the distorted visual attention parameters also improved after treatment. All drugs were effective. The loss of habituation ability and low visual attention performance in migraineurs can be restored by migraine preventive treatment. This electrophysiological study accompanied by neuropsychological test may aid an objective and quantitative assessment tool for understanding migraine pathophysiology.

Pathophysiology of Migraine: A Disorder of Sensory Processing

Plaguing humans for more than two millennia, manifest on every continent studied, and with more than one billion patients having an attack in any year, migraine stands as the sixth most common cause of disability on the planet. The pathophysiology of migraine has emerged from a historical consideration of the "humors" through mid-20th century distraction of the now defunct Vascular Theory to a clear place as a neurological disorder. It could be said there are three questions: why, how, and when? Why: migraine is largely accepted to be an inherited tendency for the brain to lose control of its inputs. How: the now classical trigeminal durovascular afferent pathway has been explored in laboratory and clinic; interrogated with immunohistochemistry to functional brain imaging to offer a roadmap of the attack. When: migraine attacks emerge due to a disorder of brain sensory processing that itself likely cycles, influenced by genetics and the environment. In the first, premonitory, phase that precedes headache, brain stem and diencephalic systems modulating afferent signals, light-photophobia or sound-phonophobia, begin to dysfunction and eventually to evolve to the pain phase and with time the resolution or postdromal phase. Understanding the biology of migraine through careful bench-based research has led to major classes of therapeutics being identified: triptans, serotonin 5-HT1B/1D receptor agonists; gepants, calcitonin gene-related peptide (CGRP) receptor antagonists; ditans, 5-HT1F receptor agonists, CGRP mechanisms monoclonal antibodies; and glurants, mGlu5 modulators; with the promise of more to come. Investment in understanding migraine has been very successful and leaves us at a new dawn, able to transform its impact on a global scale, as well as understand fundamental aspects of human biology.

Objective Assessment of Cortical Excitability in Migraine With and Without Aura

Recent progress in the genetics of migraine has refocused attention on cortical dysfunction as an important component of the pathophysiology of this disorder. In previous work, we have demonstrated functional changes in the visual cortex of migraine patients, using an objective transcranial magnetic stimulation technique, termed magnetic suppression of perceptual accuracy (MSPA). This study aimed to replicate previous findings in migraine with aura (MA) and to use the technique to examine migraine without aura (MoA). Eight MA patients, 14 MoA patients and 13 migraine-free controls participated. MSPA assessments were undertaken using a standardized protocol in which computer-presented letter targets were followed at a variable delay interval by a single magnetic pulse delivered over the occiput. MSPA performance is expressed as a profile of response accuracy across target-pulse delay intervals. The profiles of migraine-free controls exhibited a normal U-shape. MA patients had significantly shallower profiles, showing little or no suppression at intermediate delay intervals. MoA patients had profiles that were similar to controls. Recent animal evidence strongly indicates that the U-shape of the normal MSPA function is caused by preferential activation of inhibitory neurons. Shallower MPSA profiles in MA patients are therefore likely to indicate a functional hyperexcitability caused by impaired inhibition. The finding of normal MPSA profiles in MoA patients is novel and will require further investigation.

Ophthalmological Assessment of OCT and Electrophysiological Changes in Migraine Patients

BACKGROUND

A cross-sectional study to investigate the morphological and functional changes of the visual pathway taking place in patients with migraine.

METHODS

Fifteen patients (14 female, 1 male) diagnosed with migraine with aura and 23 patients (21 female, 2 male) diagnosed with migraine without aura were compared with 20 healthy volunteers (18 female, 2 male). All the participants underwent optical coherence tomography scan, electroretinogram (ERG), visual evoked potentials, and multifocal electroretinogram (mf-ERG) recording.

RESULTS

Assessing ERG recordings, no significant differences in mean N1-P1 amplitudes were measured among the groups. The mean visual evoked potentials N80-P100 amplitudes were not significantly different among the three groups (one way analysis of variance: P = 0.075, F = 2.718). No significant difference was found in P100 latency times among groups. The mean retinal response density of mf-ERG in ring 1 was higher in healthy individuals compared with migraineurs, with statistical significance (Kruskal-Wallis analysis of variance and Dunn multiple comparisons test; P < 0.001, mean rank difference = -24.857 and P < 0.001, mean rank difference = -20.9, for migraine with aura-control and migraine without aura-control comparisons, respectively). In migraine with aura subjects, retinal nerve fiber layer thickness in superior and inferior quadrants was significantly decreased compared with healthy individuals, whereas in migraine without aura group, only the superior quadrant was significantly thinner compared with the control group.

CONCLUSIONS

Retinal response density in mfERG of all migraineurs was significantly lessened compared with healthy individuals. There was no significant difference in visual evoked potentials N80-P100 amplitudes or P100 latencies among the groups. Moreover, retinal nerve fiber layer thinning observed in patients with migraine compared with control subjects, appeared statistically significant in some quadrants. The authors may be able to defend the retinal blood flow decrease theory in migraine. The results also indicate that several levels of the visual pathway seem to be affected in migraineurs.

An experimental study of the neurophysical mechanisms of photophobia induced by subarachnoid hemorrhage

BACKGROUND

Photophobia is defined as a painful psychosomatic discomfort triggered by intense light flow through the pupils to the brain, but the exact mechanism through which photophobia is induced by subarachnoid hemorrhage (SAH) is not well understood. In this study, we aimed to investigate whether there was any relationship between the mydriasis induced by the degeneration of the ciliary ganglion (CG) and photophobia in instances of SAH.

MATERIALS AND METHODS

Five of a total of 25 rabbits were used as the intact control group; five were used in the sham-operated control group; and the remaining 15 were used as the SAH group, which was created by injecting autologous blood into their cisterna magna. All animals were examined daily for 20days to evaluate their level of photophobia, after which their brains, CGs and superior cervical ganglia (SCGs) were extracted bilaterally. The densities of normal and degenerated neurons in these ganglia were examined by stereological methods.

RESULTS

In SAH animals with a high photophobia score, the mean pupil diameter and density of degenerated neurons density in the CG were greater than in cases with a low photophobia score (p<0.05). Further analysis revealed that the increase in the density of degenerated neurons in the CG following SAH resulted in the paralysis of the parasympathetic pathway of the pupillary muscles and mydriasis, which facilitates the excessive transfer of light to the brain and photophobia.

CONCLUSION

Our findings indicate that SAH results in a high density of degenerated neurons in the CG, which induces mydriasis and is an important factor in the onset of photophobia. This phenomenon is likely due to more light energy being transferred through mydriatic pupils to the brain, resulting in vasospasm of the supplying arteries.

Time Perception in Migraine Sufferers: An Experimental Matched-Pairs Study

Despite occasional case reports, the influence of migraine on time perception has not been systematically investigated. We used an experimental technique to study the estimation of auditory duration in 40 migraineurs at different tone intervals in the ms and in the 1-s range and compared their performance with 40 matched normal subjects. With a time awareness questionnaire we also evaluated the subjective experience of elapsing time for long durations involving long-term memory processes. Migraine did not influence temporal judgements in either of the tests, suggesting that migraineurs do not generally over- or underestimate temporal events. The subgroup of migraineurs with a depressive disorder, however, showed a marked speeding up of their internal timekeeping mechanisms, pointing to depression as an important covariable in time perception.

Headache Related to a Specific Screen Flickering Frequency Band

The case of a 25-year-old white male, who had migrainous headaches each time he sat in front of his personal computer screen, is described. Changing the screen frequency from 60 to 75 Hz through a Windows command could abolish the headaches. In several surveys, computer screens have been reported to be a migraine trigger. We hypothesize that this environmental trigger may be related to the abnormal flicker fusion thresholds that have been described in migraineurs. It may be that modifying the frequencies of light sources, such as computer screens, could become a non-pharmacological approach to prevent migraine attacks.

Interictal Abnormalities of Gamma Band Activity in Visual Evoked Responses in Migraine: An Indication of Thalamocortical Dysrhythmia?

Between attacks, migraineurs lack habituation in standard visual evoked potentials (VEPs). Visual stimuli also evoke high-frequency oscillations in the gamma band range (GBOs, 20–35 Hz) assumed to be generated both at subcortical (early GBOs) and cortical levels (late GBOs). The consecutive peaks of GBOs were analysed regarding amplitude and habituation in six successive blocks of 100 averaged pattern reversal (PR)-VEPs in healthy volunteers and interictally in migraine with (MA) or without aura patients. Amplitude of the two early GBO components in the first PR-VEP block was significantly increased in MA patients. There was a significant habituation deficit of the late GBO peaks in migraineurs. The increased amplitude of early GBOs could be related to the increased interictal visual discomfort reported by patients. We hypothesize that the hypo-functioning serotonergic pathways may cause, in line with the thalamocortical dysrhythmia theory, a functional disconnection of the thalamus leading to decreased intracortical lateral inhibition, which can induce dishabituation.

Critical Flicker Frequency in Migraine. A Controlled Study in Patients without Prophylactic Therapy

The critical flicker frequencies (CFF) of individuals with migraine with and without aura were determined and compared to those of normal controls. Twenty-six migraine patients, 12 with aura and 14 without aura and 30 healthy controls were included. Migraineurs were tested during a migraine-free period, through both the continuous flicker method (CFM) and the forced choice method (FCM). Migraineurs presented a mean flickering fusion threshold lower than healthy controls with the CFM (40.45 vs. 44.33, respectively; P = 0.019) and with the FCM (34.16 Hz vs. 38.5 Hz, respectively, P = 0.019). Both groups of migraineurs had significantly lower thresholds as compared to controls, migraineurs with aura presenting the lowest thresholds for the fusion of flickering ( P = 0.008 and P = 0.0001 with the CFM and the FCM, respectively). Results confirmed and extended previous observations of abnormal flicker fusion thresholds in migraineurs. We hypothesize that this finding might be related to a shorter cortical stimulation silent period.

Melatonin Secretion is Supersensitive to Light in Migraine

The present study examined the sensitivity to light of melatonin (MLT) secretion in familial migraine during a headache-free interval. Twelve female patients and 12 healthy controls were included in the trial. All subjects were studied twice. In each session, light exposure (300 lx) or placebo was randomly administered for 30 min between 00.30 and 01.00 h. Blood was sampled hourly between 20.00 and 24.00 h, and 02.00 and 04.00 h and every 15 min between 00.30 and 01.30 h. Plasma MLT levels were determined by radioimmunoassay. MLT suppression was more marked in the migraine group than in the control group [difference of area under curve (δAUC) = −53.8 ± 16.2 vs. 18.5 ± 12.7 pg/h/ml, P < 0.005; maximum of MLT suppression (δ) = −35.7 ± 10.2 vs.- 6.7 ± 5.8 pg/ml, P < 0.05]. These findings show a clear hypersensitivity to light in young female migraineurs during the headache-free period.

Visual motion processing in migraine: Enhanced motion after-effects are related to display contrast, visual symptoms, visual triggers and attack frequency

Background Visual after-effects are illusions that occur after prolonged viewing of visual displays. The motion after-effect (MAE), for example, is an illusory impression of motion after viewing moving displays: subsequently, stationary displays appear to drift in the opposite direction. After-effects have been used extensively in basic vision research and in clinical settings, and are enhanced in migraine. Objective The objective of this article is to assess associations between ( 1 ) MAE duration and visual symptoms experienced during/between migraine/headache attacks, and ( 2 ) visual stimuli reported as migraine/headache triggers. Methods The MAE was elicited after viewing motion for 45 seconds. MAE duration was tested for three test contrast displays (high, medium, low). Participants also completed a headache questionnaire that included migraine/headache triggers. Results For each test contrast, the MAE was prolonged in migraine. MAE duration was associated with photophobia; visual triggers (flicker, striped patterns); and migraine or headache frequency. Conclusions Group differences on various visual tasks have been attributed to abnormal cortical processing in migraine, such as hyperexcitability, heightened responsiveness and/or a lack of intra-cortical inhibition. The results are not consistent with hyperexcitability simply from a general lack of inhibition. Alternative multi-stage models are discussed and suggestions for further research are recommended, including visual tests in clinical assessments/clinical trials.

The visual system in migraine: from the bench side to the office

BACKGROUND

Throughout history, migraine-associated visual symptoms have puzzled patients, doctors, and neuroscientists. The visual aspects of migraine extend far beyond the aura phenomena, and have several clinical implications.

METHODS

A narrative review was conducted, beginning with migraine mechanisms, then followed by pertinent aspects of the anatomy of visual pathways, clinical features, implications of the visual system on therapy, migraine on visually impaired populations, treatment of visual auras and ocular (retinal) migraine, effect of prophylactic migraine treatments on visual aura, visual symptoms induced by anti-migraine or anti-headache drugs, and differential diagnosis.

RESULTS

A comprehensive narrative review from both basic and clinical standpoints on the visual aspects of migraine was attained; however, the results were biased to provide any useful information for the clinician.

CONCLUSION

This paper achieved its goals of addressing and condensing information on the pathophysiology of the visual aspects of migraine and its clinical aspects, especially with regards to therapy, making it useful not only for those unfamiliar to the theme but to experienced physicians as well.

Refractive Errors in Patients with Migraine Headache

PURPOSE

To evaluate refractive errors in patients with migraine headache and to compare with healthy subjects.

MATERIALS AND METHODS

This prospective case-control study includes patients with migraine and age- and sex-matched healthy subjects. Clinical and demographic characteristics of the patients were noted. Detailed ophthalmological examinations were performed containing spherical refractive error, astigmatic refractive error, spherical equivalent (SE), anisometropia, best-corrected visual acuity, intraocular pressure, slit lamp biomicroscopy, fundus examination, axial length, anterior chamber depth, and central corneal thickness. Spectacle use in migraine and control groups was compared. Also, the relationship between refractive components and migraine headache variables was investigated.

RESULTS

Seventy-seven migraine patients with mean age of 33.27 ± 8.84 years and 71 healthy subjects with mean age of 31.15 ± 10.45 years were enrolled (p = 0.18). The migraine patients had higher degrees of astigmatic refractive error, SE, and anisometropia when compared with the control subjects (p = 0.01, p = 0.03, p = 0.02, respectively).

CONCLUSION

Migraine patients may have higher degrees of astigmatism, SE, and anisometropia. Therefore, they should have ophthalmological examinations regularly to ensure that their refractive errors are appropriately corrected.

Headache and sleep: shared pathophysiological mechanisms

OBJECTIVE

The objective of the current article is to review the shared pathophysiological mechanisms which may underlie the clinical association between headaches and sleep disorders.

BACKGROUND

The association between sleep and headache is well documented in terms of clinical phenotypes. Disrupted sleep-wake patterns appear to predispose individuals to headache attacks and increase the risk of chronification, while sleep is one of the longest established abortive strategies. In agreement, narcoleptic patients show an increased prevalence of migraine compared to the general population and specific familial sleep disorders have been identified to be comorbid with migraine with aura.

CONCLUSION

The pathophysiology and pharmacology of headache and sleep disorders involves an array of neural networks which likely underlie their shared clinical association. While it is difficult to differentiate between cause and effect, or simply a spurious relationship the striking brainstem, hypothalamic and thalamic convergence would suggest a bidirectional influence.

An inability to exclude visual noise in migraine

PURPOSE

People with migraine are relatively poor at judging the direction of motion of coherently moving signal dots when interspersed with noise dots drifting in random directions, a task known as motion coherence. Although this has been taken as evidence of impoverished global pooling of motion signals, it could also arise from unreliable coding of local direction (of each dot), or an inability to segment signal from noise (noise-exclusion). The aim of this study was to determine how these putative limits contribute to impoverished motion processing in migraine.

METHODS

Twenty-two participants with migraine (mean age, 34.7 ± 8.3 years; 16 female) and 22 age- and sex-matched controls (mean age, 34.4 ± 6.2 years) performed a motion-coherence task and a motion-equivalent noise task, the latter quantifying local and global limits on motion processing. In addition, participants were tested on analogous equivalent noise paradigms involving judgments of orientation and size, so that the specificity of any findings (to visual dimension) could be ascertained.

RESULTS

Participants with migraine exhibited higher motion-coherence thresholds than controls (P = 0.01, independent t-test). However, this difference could not be attributed to deficits in either local or global processing since they performed normally on all equivalent noise tasks (P > 0.05, multivariate ANOVA).

CONCLUSIONS

These findings indicate that motion perception in the participants with migraine was limited by an inability to exclude visual noise. We suggest that this is a defining characteristic of visual dysfunction in migraine, a theory that has the potential to integrate a wide range of findings in the literature.

Interictal neurocognitive processing of visual stimuli in migraine: evidence from event-related potentials

Research has established decreased sensory habituation as a defining feature in migraine, while decreased cognitive habituation has only been found with regard to cognitive assessment of the relative probability of the occurrence of a stimulus event. Our study extended the investigation of interictal habituation in migraine to include cognitive processing when viewing of a series of visually-complex images, similar to those we encounter on the internet everyday. We examined interictal neurocognitive function in migraine from a habituation perspective, using a novel paradigm designed to assess how the response to a series of images changes over time. Two groups of participants--migraineurs (N = 25) and non-migraine controls (N = 25)--were asked to view a set of 232 unfamiliar logos in the context of a target identification task as their brain electrical responses were recorded via event-related potentials (ERPs). The set of logos was viewed serially in each of 10 separate trial blocks, with data analysis focusing on how the ERP responses to the logos in frontal electrodes from 200-600 ms changed across time within each group. For the controls, we found that the amplitude of the late positive potential (LPP) ERP component elicited by the logos had no significant change across trial blocks. In contrast, in migraineurs we found that the LPP significantly increased in amplitude across trial blocks, an effect consistent with a lack of habituation to visual stimuli seen in previous research. Our findings provide empirical support abnormal cognitive processing of complex visual images across time in migraineurs that goes beyond the sensory-level habituation found in previous research.

Migraine and triggers: post hoc ergo propter hoc?

The influence of environmental factors on the clinical manifestation of migraine has been a matter of extensive debate over the past decades. Migraineurs commonly report foods, alcohol, meteorologic or atmospheric changes, exposure to light, sounds, or odors, as factors that trigger or aggravate their migraine attacks. In the same way, physicians frequently follow this belief in their recommendations in how migraineurs may reduce their attack frequency, especially with regard to the consumption of certain food components. Interestingly, despite being such a common belief, most of the clinical studies have shown conflicting results. The aim of the review is to critically analyze clinical and pathophysiological facts that support or refute a correlation between certain environmental stimuli and the occurrence of migraine attacks. Given the substantial discrepancy between patients' reports and objective clinical data, the methodological difficulties of investigating the link between environmental factors and migraine are highlighted.

Recurrent headache in pediatric outpatients at a public hospital in Delhi

This observational, descriptive study was conducted to study the clinical profile of children presenting with recurrent headaches to the general pediatric services of a tertiary-care, public hospital in northern India. 43 children, 3-18 year old (23 females, median age 10 years), were enrolled between April, 2011 to January, 2012. History, clinical examination (including fundus evaluation and detailed ophthalmological evaluation) and follow-up were done using a structured proforma. Headache diagnosis was made on the basis of International Classification of Headache Disorders, 2nd edition (ICHD-II). Headache disability and severity were assessed by pedMIDAS, and Visual analog scale and Faces scale, respectively. 26 patients (60.5%) had headache with migraine features (20, migraine without aura), 11 (25.6%) had Tension type headache (TTH), and 4 (9.3%) children had non-specific headache. Stress was the commonest (42.3%) trigger identified by children with migraine. No patient in the study had an ophthalmological problem as cause of headache. 69.2% of migraine patients and 36% of TTH patients had been suffering from it for 1-2 years before reporting to the hospital. Majority of children with recurrent headache present late for medical attention. Ophthalmological problems are an infrequent cause of recurrent headache in these children.

Primary headache disorders and neuro-ophthalmologic manifestations

Headache is an extraordinarily common complaint presenting to medical practitioners in all arenas and specialties, particularly primary care physicians, neurologists, and ophthalmologists. A wide variety of headache disorders may manifest with a myriad of neuro-ophthalmologic symptoms, including orbital pain, disturbances of vision, aura, photophobia, lacrimation, conjunctival injection, ptosis, and other manifestations. The differential diagnosis in these patients is broad and includes both secondary, or symptomatic, and primary headache disorders. Awareness of the headache patterns and associated symptoms of these various disorders is essential to achieve the correct diagnosis. This paper reviews the primary headache disorders that prominently feature neuro-ophthalmologic manifestations, including migraine, the trigeminal autonomic cephalalgias, and hemicrania continua. Migraine variants with prominent neuro-ophthalmologic symptoms including aura without headache, basilar-type migraine, retinal migraine, and ophthalmoplegic migraine are also reviewed. This paper focuses particularly on the symptomatology of these primary headache disorders, but also discusses their epidemiology, clinical features, and treatment.

Shedding light on photophobia

Photophobia is a common yet debilitating symptom seen in many ophthalmic and neurologic disorders. Despite its prevalence, it is poorly understood and difficult to treat. However, the past few years have seen significant advances in our understanding of this symptom. We review the clinical characteristics and disorders associated with photophobia, discuss the anatomy and physiology of this phenomenon, and conclude with a practical approach to diagnosis and treatment.

Light-induced trigeminal sensitization without central visual pathways: another mechanism for photophobia

PURPOSE

The authors investigated whether trigeminal sensitization occurs in response to bright light with the retina disconnected from the rest of the central nervous system by optic nerve section.

METHODS

In urethane-anesthetized rats, trigeminal reflex blinks were evoked with air puff stimuli directed at the cornea in darkness and at three different light intensities. After normative data were collected, the optic nerve was lesioned and the rats were retested. In an alert rat, reflex blinks were evoked by stimulation of the supraorbital branch of the trigeminal nerve in the dark and in the light.

RESULTS

A 9.1 × 10(3) μW/cm(2) and a 15.1 × 10(3) μW/cm(2) light significantly enhanced the magnitude of reflex blinks relative to blinks evoked by the same trigeminal stimulus when the rats were in the dark. In addition, rats exhibited a significant increase in spontaneous blinking in the light relative to the blink rate in darkness. After lesioning of the optic nerve, the 15.1 × 10(3) μW/cm(2) light still significantly increased the magnitude of trigeminal reflex blinks.

CONCLUSIONS

Bright lights increase trigeminal reflex blink amplitude and the rate of spontaneous blinking in rodents. Light can modify trigeminal activity without involving the central visual system.

Advances in understanding the mechanisms of migraine-type photophobia

PURPOSE OF REVIEW

Historically, photophobia was studied in patients and attempts to explain the underlying mechanisms have been speculative. Efforts to understand better the neural substrate of photophobia paved a way to the development of different animal models and the publication of several articles (all in 2010) on the mechanism by which light exacerbates migraine headache.

RECENT FINDINGS

Observations made in blind migraine patients devoid of any visual perception and blind migraine patients capable of detecting light have led to the discovery of a novel retino-thalamo-cortical pathway that carries photic signal from the retina to thalamic trigeminovascular neurons believed to play a critical role in the perception of headache intensity during migraine. Evidence for modulation of the trigeminovascular pathway by light and identification of the pathway through which photic signals converge on the nociceptive pathway that mediates migraine headache provide first set of scientific data on the mechanism by which light intensifies migraine headache.

SUMMARY

The findings provide a neural substrate for migraine-type photophobia. This may lead to identification and development of molecular targets for selective prevention of photophobia during migraine.

Visual metacontrast masking in migraine

Background: In visual metacontrast masking, the visibility of a brief target stimulus can be reduced substantially if it is preceded (forward masking) or followed (backward masking) by a non-overlapping mask. These effects have been attributed to inhibitory processes within the visual system. Two previous studies have used metacontrast masking to assess inhibitory function in migraine and control groups, however, each used different types of masking and obtained different results.

Subjects and Methods: Forward, backward and combined forward and backward masking were compared in migraine (15 with visual aura, 15 without) and control ( n = 15) groups. Baseline trials were also included (target only).

Results: For all types of masking, both migraine groups were more accurate than the control group. When performance for the masking trials was expressed relative to baseline, however, there were no significant group differences. Performance in certain conditions nevertheless correlated significantly with migraine frequency and with the recency of the last attack.

Conclusions: The inhibitory processes involved in the masking tasks employed in this study do not appear to be impaired in migraine. Their better overall performance may reflect a sensitivity difference, perhaps as a consequence of a heightened neuronal response, which varies with the migraine cycle.

Perceptive aspects of visual aura

Visual aura is the most common feature associated with migraine, though it can occur separately. In both cases it often represents a dramatic event, especially for patients who experience it for the first time. Besides, its subjective characteristics may illuminate on the functional architecture of the visual cortex. Repetitive events of migraine and visual aura have been suggested to affect the visual system in the long run, both on the cortical and precortical level. In effect, objective investigation of visual functions in patients support the idea that a selective damage does occur, so that more attention to visual examination seems to be justified. In this paper, subjective and psychophysical aspects of visual aura are examined, lastly highlighting and discussing the interesting correlations found between this condition and normal-tension glaucoma.

Sunrise-Related Headache: Case Report

A male, 34 years of age, suffers from headaches, red and watery eyes. The headaches began in childhood; the frequency of headaches has increased over the years and in the last decade headaches have occurred on a daily basis. If he wakes up before sunrise he feels much better and free of a headache; however, once he continues to sleep during and after sunrise, he suffers from tiredness, headache and nervousness. On magnetic resonance imaging (MRI), benign neuroepithelial cysts or a chronic infarct area was reported at the junction of the left medio-lateral zone of hypothalamus. After repeated MRI examinations, it was decided that the lesion on the left medio-lateral zone of hypothalamus may have disrupted the pineal gland and changed melatonin secretion. It was decided to treat him with 3 mg melatonin daily before going to bed. After a week of treatment, the patient reported that he felt very fresh and was virtually free of headaches.

Usefulness of a photophobia questionnaire in patients with migraine

Photophobia is an important criterion for the diagnosis of migraine. However, several Asian epidemiological surveys about migraine have shown lesser prevalence of photophobia than that of Western studies. This discrepancy is probably caused by underestimation of photophobia due to inappropriate questioning of patients by physicians. To investigate this issue, we developed a questionnaire about photophobia and evaluated its usefulness in 103 patients with migraine. In phase 1 of the study, we found good repeatability of the questionnaire with a 0.826 kappa coefficient. In phase 2, the prevalence of photophobia from interviews and that from the questionnaire were compared. The prevalence of interview-documented photophobia was 51.5% and of questionnaire-documented photophobia 82.5% (P < 0.001). In phase 3, we attempted to make a short-form questionnaire with the same detection power of the questionnaire study. Two short-form questionnaires were identified as a useful method for detecting photophobia. The prevalence of photophobia could be underreported via interview, especially in Asian migraineurs. Using this questionnaire to test for photophobia, the diagnostic rate of photophobia and migraine could be improved.

Sympathetic Skin Responses From Frontal Region in Migraine Headache: A Pilot Study

Frontal sympathetic skin responses (F-SSRs) were recorded to investigate sympathetic nervous system activity in migraine headache (MH). Thirty-five patients with unilateral MH and 10 healthy volunteers were studied by evoking bilateral F-SSRs with electrical stimulation of the median nerve in attack, post-attack and interictal periods. The mean latencies were longer and the maximum amplitudes were smaller on the symptomatic side compared with the asymptomatic side ( P < 0.05 for both amplitude and latency) in attack and in interictal periods. In five patients, F-SSRs were absent bilaterally, in four patients the responses were absent only on the symptomatic side during the attack period. In the post-attack period, F-SSRs on the symptomatic side had higher amplitudes and shorter latencies compared with the asymptomatic side ( P < 0.01 for both amplitude and latency). There is an asymmetric sympathetic hypofunction on the symptomatic side in attack and interictal periods, whereas there is a hyperfunction in the post-attack period.

Translational imaging studies of cortical spreading depression in experimental models for migraine aura

This perspective discusses cortical spreading depression (CSD) phenomena and their translational significance for human migraine aura and the peri-infarct events following cerebral ischemia and injury. They begin with interstitial K(+) release and accumulation following neuronal stimulation, and a buffering astrocytic K(+) influx and remote liberation propagating waves of neuronal hyperexcitability and depression. Diffusion-weighted echoplanar MRI demonstrates CSD features in gyrencephalic brains recapitulating human migraine aura, spatial and temporal features of single primary events and multiple secondary events, their stimulus dependence, pharmacological properties, and their relationship to blood oxygenation level-dependent signals and late cerebrovascular changes. The article finally explores prospects for physiological studies of CSD gaining fuller insights both into mechanisms underlying the pathology of the corresponding human condition and possible approaches to management.

Role of melatonin in the eye and ocular dysfunctions

Melatonin is a ubiquitous molecule and widely distributed in nature, with functional activity occurring in unicellular organisms, plants, fungi, and animals. Several studies have indicated that melatonin synthesis occurs in the retina of most vertebrates, including mammals. The retinal biosynthesis of melatonin and the mechanisms involved in the regulation of this process have been extensively studied. Circadian clocks located in the photoreceptors and retinal neurons regulate melatonin synthesis in the eye. Photoreceptors, dopaminergic amacrine neurons, and horizontal cells of the retina, corneal epithelium, stroma endothelium, and the sclera all have melatonin receptors, indicating a widespread ocular function for melatonin. In addition, melatonin is an effective antioxidant which scavenges free radicals and up-regulates several antioxidant enzymes. It also has a strong antiapoptotic signaling function, an effect that it exerts even during ischemia. Melatonin cytoprotective properties may have practical implications in the treatment of ocular diseases, like glaucoma and age-related macular degeneration.

Ocular motor measures in migraine with and without aura

The purpose of this study was to examine basic ocular motor function in individuals with migraine. We used an infrared eye-tracking system to measure horizontal smooth pursuit to a sinusoidal target, saccades to horizontal target displacements of 5-20 degrees , and the stability of fixation in 19 migraine without aura (MoA), 19 migraine with aura (MA) and 19 headache-free control (C) subjects. Eye movement measurements were made at two target displacement rates and against both homogeneous grey and patterned backgrounds. We found no statistically significant differences between migraine and control subjects in any of the eye movement parameters measured, but did find highly significant effects of both target speed and background pattern in all groups. Our results do not provide support for subclinical cerebellar impairment in migraineurs, and do provide evidence that previously described visual abnormalities in migraine are not artefacts of abnormal fixation or eye movements.

Migraine: a review and future directions for treatment

Migraine is a chronic, neurological disorder generally manifesting itself in attacks with severe headache, nausea and an increased reactivity to sensory stimuli. A low migraine threshold is set by genetic factors, although the phenotype also modulates the manifestations. The 1-year prevalence is approximately 13% and is higher among women. Patients usually experience neuropsychological dysfunction, and sometimes also reversible focal neurological symptoms. The trajectories of the characteristic symptoms of acute migraine usually follow a similar time course, indicating a reciprocal underlying mechanism. A central nervous system hyperexcitability has been demonstrated in neurophysiological studies. The dibilitating effects of migraine are not confined to the attacks per se. Many individuals do not recover completely between the attacks and most report a negative impact on the most important life domains, and an interest in testing other treatments. Young persons have a higher frequency of attacks. Acute treatment should routinely be initiated with an analgesic plus a prokinetic anti-emetic. Triptans must not be provided early during the attack to ensure their efficacy. The natural course of attacks is commonly only temporarily altered by acute treatment. Non-pharmacological treatment and drugs may be equally viable in prophylaxis for migraine. In more complicated cases, conjoint therapy should be considered. New strategies to improve adherence with existing therapeutic regimens might yield greater benefits than will new pharmacological agents.