Functional MRI as a biomarker for evaluation and prediction of effectiveness of migraine prophylaxis

Central effects of galcanezumab in migraine: a pilot study on Steady State Visual Evoked Potentials and occipital hemodynamic response in migraine patients

BACKGROUND

The discovery of the prominent action of Calcitonin Gene Related Peptide -CGRP- on trigeminal afferents and meningeal vessels, opened a new era in migraine treatment. However, how the block of nociceptive afferents could act on central mechanisms of migraine is still not clear. In this pilot study we aimed to test the effect of 3 months Galcanezumab (CGA) therapy on occipital visual reactivity in migraine patients, using the Steady State Visual Evoked Potentials-SSVEPs and Functional Near Infrared Spectroscopy -fNIRS.

METHOD

Thirteen migraine patients underwent clinical and neurophysiological examination in basal condition (T0), 1 h after GCA injection (T1) and after 3 months of GCA treatment (T2). Ten healthy volunteers were also evaluated.

RESULTS

At T2, there was a reduction of headache frequency and disability. At T2, the EEG power significantly diminished as compared to T0 and T1 at occipital sites, and the topographical analysis confirmed a restoration of SSVEPs within normal values. The Oxyhemoglobin levels in occipital cortex, which were basically increased during visual stimulation in migraine patients, reverted to normal values at T2.

CONCLUSIONS

The present pilot study indicates that Galcanezumab could act on cortical targets located beyond the pain network, restoring the abnormal occipital reactivity. This effect could indicate the possible disease modifying properties of CGRP related monoclonal antibodies.

The perception threshold of the panda illusion, a particular form of 2D pulse-width-modulated halftone, correlates with visual acuity

To call attention to the danger of extinction of the panda bear, the Lithuanian artist Ilja Klemencov created the artwork “They can disappear”. The illustration is composed of black-and-white zigzagged lines, which form the famous panda logo of the World Wild Fund For Nature (WWF) when seen from a distance. If one is too close to the artwork, it is difficult to spot the bear, however, if one steps back or takes off one’s glasses the panda suddenly appears. This led us to ask if the ability to see the panda is related to the visual acuity of the observer and if therefore, the panda illusion can be used to assess the spatial resolution of the eye. Here we present the results of the comparison between visual acuity determined using the Landolt C and that predicted from the panda illusion in 23 healthy volunteers with artificially reduced visual acuity. Furthermore, we demonstrate that the panda illusion is based on a 2D pulse-width modulation, explain its technical history, and provide the equations required to create the illusion. Finally, we explain why the illusion indeed can be used to predict visual acuity and discuss the neural causes of its perception with best-corrected visual acuity.

Functional Neuroimaging Biomarkers in Migraine: Diagnostic, Prognostic and Therapeutic Implications

BACKGROUND

In current migraine clinical practice, conventional neuroimaging examinations are often sought to exclude possible causes of secondary headaches or migraineassociated disorders. Contrariwise, although advanced Magnetic Resonance Imaging (MRI) has improved tremendously our understanding of human brain processes in migraine patients, to the state of the art they have not superseded the conventional neuroimaging techniques in the migraine clinical setting.

METHODS

A comprehensive review was conducted of PubMed citations by entering the keyword "marker" and/or "biomarker" combined with "migraine" and/or "headache". Other keywords included "imaging" or "neuroimaging", "structural" or "functional". The only restriction was English-language publication. The abstracts of all articles meeting these criteria were reviewed, and the full text was retrieved and examined for relevant references.

RESULTS

Several authors tried to identify imaging biomarkers able to identify different migraine phenotypes or, even better, to follow-up the same migraine patients during the course of the disease, to predict the evolution into more severe phenotypes and, finally, the response to specific treatment.

CONCLUSION

The identification of diagnostic, prognostic and therapeutic advanced neuroimaging biomarkers in the migraine clinical setting, in order to approach to patients in a more and more rational and "tailored" way, is extremely intriguing and futuristic. Unfortunately, reliable and robust neuroimaging biomarkers are still lacking for migraine, probably due to both not completely understood pathogenesis and clinical and neuroimaging heterogeneity. Although further longitudinal advanced neuroimaging studies, aimed to identify effective neuroimaging biomarkers, are needed, this review aims to collect the main and most recent works on this topic.

Visually stressful striped patterns alter human visual cortical functional connectivity

Visually stressful striped patterns with a spatial frequency (SF) of around 3 cycles per degree (cpd) can induce perceptual illusions/distortions and visual discomfort in most people, headaches in patients with migraine, and seizures in patients with photosensitive epilepsy. Patterns with SF ∼0.3 cpd have no such effects and are not uncomfortable to look at (non-stressful). The effects of the striped patterns on visual cortical activation have been investigated, but their effects on the visual cortical network remain to be studied. A prolonged visual stimulation with stressful patterns may alter the functional connections within the visual system, and their relationship with other networks. Using resting-state fMRI, this study revealed that the functional connections within the visual system were significantly enhanced by visually stressful stimulation. The functional connectivity between V1 and other brain regions was also significantly modified. Non-stressful stimulation produced no such significant effects. More importantly, the effects outlasted the stimulation, and this applied both to those effects within and those beyond the visual cortex, suggesting that repeated prolonged visual stimulation with stressful patterns may alter functional connections of the brain and this might be utilized as a visual neuromodulation approach for treatments of visually triggered headaches in migraine patients and visually induced seizures in patients with photosensitive epilepsy. Hum Brain Mapp 38:5474-5484, 2017. © 2017 Wiley Periodicals, Inc.

Insights and advances in post-traumatic headache: research considerations

Despite the growing awareness of mild traumatic brain injury in military and civilian populations, understanding of the acute and chronic effects of concussion on central nervous system structure and function is limited. Even less is understood about the underpinnings of the cardinal postconcussive symptom, post-traumatic headache (PTH). Here, we review recent advances in PTH, with special emphasis on the migraine-like phenotype, the most disabling form. Considerations for future research in PTH are discussed, including diagnostic classification, and applications with advanced neuroimaging techniques, biomarkers, and treatments.

Pharmacological neuroimaging in headache and pain

PURPOSE OF REVIEW

The current review gives an overview about recent advances in neuroimaging studies with specific emphasis on pharmacological modulation of pain and headache. Further, we want to highlight how imaging methods have changed our understanding of chronic pain and discuss how pharmacological MRI could lead to new insights into underlying mechanisms of headache and pain.

RECENT FINDINGS

Several studies from different imaging laboratories have highlighted the outstanding role of imaging in getting a deeper insight regarding the central mechanisms of drugs. Neuroimaging techniques start to unravel how analgesic drugs, antidepressants or NSAIDs act on pain perception and in particular on central pain processes. Furthermore, the studies included in this review show how context dependent drugs act and how differently they reveal their action in the human brain.

SUMMARY

Imaging techniques give us the opportunity to gain a better understanding of drug processes in the central nervous system and help to understand where drugs reveal their therapeutic effect. While some substances work on the emotional-affective component of pain, others modulate sensory-discriminative pain pathways. Especially in the field of headache research, still a lot has to be done to understand how preventatives and acute medication modulate the human brain. Future studies should also replicate and extend recent findings.