Topographic Analysis of Electroencephalographic Changes during Photic Driving Responses in Patients with Migraine

EEG Changes in Migraine-Can EEG Help to Monitor Attack Susceptibility?

Migraine is a highly prevalent brain condition with paroxysmal changes in brain excitability believed to contribute to the initiation of an attack. The attacks and their unpredictability have a major impact on the lives of patients. Clinical management is hampered by a lack of reliable predictors for upcoming attacks, which may help in understanding pathophysiological mechanisms to identify new treatment targets that may be positioned between the acute and preventive possibilities that are currently available. So far, a large range of studies using conventional hospital-based EEG recordings have provided contradictory results, with indications of both cortical hyper- as well as hypo-excitability. These heterogeneous findings may largely be because most studies were cross-sectional in design, providing only a snapshot in time of a patient's brain state without capturing day-to-day fluctuations. The scope of this narrative review is to (i) reflect on current knowledge on EEG changes in the context of migraine, the attack cycle, and underlying pathophysiology; (ii) consider the effects of migraine treatment on EEG features; (iii) outline challenges and opportunities in using EEG for monitoring attack susceptibility; and (iv) discuss future applications of EEG in home-based settings.

Single-trial EEG analysis reveals burst structure during photic driving

OBJECTIVE

Photic driving in the human visual cortex evoked by intermittent photic stimulation is usually characterized in averaged data by an ongoing oscillation showing frequency entrainment and resonance phenomena during the course of stimulation. We challenge this view of an ongoing oscillation by analyzing unaveraged data.

METHODS

64-channel EEGs were recorded during visual stimulation with light flashes at eight stimulation frequencies between 7.8 and 23 Hz for fourteen healthy volunteers. Time-frequency analyses were performed in averaged and unaveraged data.

RESULTS

While we find ongoing oscillations in the averaged data during intermittent photic stimulation, we find transient events (bursts) of activity in the unaveraged data. Both resonance and entrainment occur for the ongoing oscillations in the averaged data and the bursts in the unaveraged data.

CONCLUSIONS

We argue that the continuous oscillations in the averaged signal may be composed of brief, transient bursts in single trials. Our results can also explain previously observed amplitude fluctuations in averaged photic driving data.

SIGNIFICANCE

Single-trial analyses might consequently improve our understanding of resonance and entrainment phenomena in the brain.

Application of EEG in migraine

Migraine is a common disease of the nervous system that seriously affects the quality of life of patients and constitutes a growing global health crisis. However, many limitations and challenges exist in migraine research, including the unclear etiology and the lack of specific biomarkers for diagnosis and treatment. Electroencephalography (EEG) is a neurophysiological technique for measuring brain activity. With the updating of data processing and analysis methods in recent years, EEG offers the possibility to explore altered brain functional patterns and brain network characteristics of migraines in depth. In this paper, we provide an overview of the methodology that can be applied to EEG data processing and analysis and a narrative review of EEG-based migraine-related research. To better understand the neural changes of migraine or to provide a new idea for the clinical diagnosis and treatment of migraine in the future, we discussed the study of EEG and evoked potential in migraine, compared the relevant research methods, and put forwards suggestions for future migraine EEG studies.

Evaluation of Electroencephalogram Using Exact Low-Resolution Electromagnetic Tomography During Photic Driving Response in Patients with Migraine

BACKGROUND

Photophobia is a common feature of migraine, which may involve abnormal cortical information processing. In electroencephalograms (EEG), photic driving is known as a reaction to visual stimulation. Both photophobia and photic driving response are present during light stimulation. We hypothesized that cortical response to photic stimulation would differ between migraine patients with and without aura.

METHODS

We recruited 50 migraine patients (migraine with aura [MWA] = 21; migraine without aura [MWOA] = 29). Spontaneous eyes-closed resting EEG from 20 electrodes on the scalp during the interictal phase was recorded. After recording, each photic stimulation was separately selected. We analyzed EEG by fast Fourier transform and observed the spectrum frequency peaks and topographies in response to photic stimulation. Exact low-resolution electromagnetic tomography (eLORETA) was used to compute the 3-dimensional intracerebral distribution of EEG activity.

RESULTS

Photic stimulation at frequencies 5, 8, 15, and 20 Hz showed significant differences between migraine patients with and without aura. MWOA patients consistently had a stronger response to photic stimulation than MWA patients. In all patients, the differential response was located in the visual cortex, except for the stimulation at 20 Hz, where the difference at subharmonic 10 Hz was located in the parietal cortex (Brodmann Area 7).

CONCLUSION

We confirmed high incidences of photic hypersensitivity and photic driving responses in migraine patients. We suggest that repeated occurrences of cortical spreading depression in MWA may suppress cortical function, thus contributing to a weaker visual cortical response to photic stimulation in MWA patients compared with MWOA patients.

Subclinical vestibular dysfunction in migraineurs without vertigo: A Clinical study

OBJECTIVES

This observational study aimed to investigate the presence of potential vestibular system subclinical dysfunction among migraineurs without a history of vertigo and dizziness compared with healthy controls.

METHODS

Patients diagnosed with episodic migraine with and without aura were enrolled. All patients and healthy controls underwent vestibular examination using the following conventional tests: sitting position, Pagnini-McClure's, Dix-Hallpike's, head hanging, video head impulse, subjective visual vertical, Romberg, Fukuda, and caloric vestibular stimulation by Fitzgerald-Hallpike's tests. Nystagmus and angular velocity of the slow phase during culmination phase was analyzed by video-nystagmography.

RESULTS

Overall, 33 patients (76% female, 7 with aura and 26 without aura; mean age (mean ± SD): 29.1 ± 4.3 years) and 22 controls (33% female, mean age: 30.8 ± 9.4 years) were enrolled. There were no statistically significant differences in demographic features between patients and controls. Caloric vestibular stimulation test results were found to differ among patients and controls. In particular, right and left angular velocity (AV) were highly correlated one another (r = 0.88, P < .001). Right AV (53.0 ± 6.7 vs 44.0 ± 9.6) and left AV (54.3 ± 5.3 vs 43.3 ± 9.0) were statistically higher in migraineurs as compared to controls (P < .001). Also right V-HIT (1.1 ± 0.1 vs 0.8 ± 0.4) and left V-HIT (1.1 ± 0.1 vs 0.7 ± 0.2) were statistically higher in migraineurs compared to controls (P < .001).

CONCLUSION

Our findings suggest a subclinical alteration of vestibular pathway in migraineurs who have never complained vertigo or postural imbalance. This finding supports the hypothesis of a vestibular-cerebellar dysfunction in migraineurs, particularly among those with aura.