key: cord-0030710-89vhv3rd authors: White, Owen B.; Fielding, Joanne; Pelak, Victoria Susan; Schankin, Christoph J. title: Editorial: Visual Snow: Old Problem, New Understanding date: 2022-04-15 journal: Front Neurol DOI: 10.3389/fneur.2022.884752 sha: c75272656cf8039afbf8bfbeb99f9f3f339fcb6e doc_id: 30710 cord_uid: 89vhv3rd nan more severe presentation in patients who have both (5, 19) . The pathophysiological link has been investigated by Eren et al. who, in an electrophysiological study, assessed magnetic suppression of perceptual accuracy, which is reduced in patients with migraine with aura and chronic migraine (19) . In patients with VSS, this is not the case, suggesting that occipital cortex inhibition is not affected, and that the mechanisms of VSS and migraine with aura are different. In contrast, a predisposition to VSS might exist for patients with episodic visual snow as nicely shown in the case report by Puledda et al. (20) . In this manuscript, a 44-year-old man had an acute stroke in the right superior cerebellar artery territory and immediately developed all the symptoms of VSS. Prior to the stroke, he had the same symptoms in an episodic manner about once per month. This means that episodic visual snow might not be so uncommon (21) and may be a risk factor for VSS. This is important for counseling patients with episodic visual snow. Another focus of this Research Topic was brain physiology in VSS. Harris et al. analyzed double-pulse visual evoked potentials (VEPs) and found a differential pattern of VEP attenuation and potentiation in one patient suggesting that multiple mechanisms of neuronal responsiveness to visual stimulation might exist in VSS. In a psychophysical experiment, attention was investigated by Foletta et al., who assessed eye movements toward and away from target stimuli using an "inhibition of return" paradigm. This study raises the potential for a distinct saccadic behavioral profile in VSS that might serve as a biomarker for VSS for future therapeutic studies, and suggests that attention is impacted in VSS. From a neuroimaging perspective, Michels et al. investigated the white matter in VSS. They found widespread alterations in prefrontal, temporal, and occipital areas, supporting the fact that atypical visual processing and conceptualization might be an important mechanism in this disorder. Taken together, VSS might be regarded as a particular form of network disorder as carved out in a systematic review by Klein and Schankin (7). The authors presented and combined what is known from clinical, neurophysiological, functional, and structural imaging in visual and extra-visual areas. They conclude that VSS is a network disorder with key structures in pre-cortical and attentional networks, where filtering and prioritizing might happen. Despite all these advances in our clinical and pathophysiological understanding of VSS, therapy remains a substantial challenge. Against this background, Solly et al. profiled patients with VSS in respect of psychiatric and neuropsychological symptoms with a focus on depression, anxiety, depersonalization, sleep, fatigue, and quality of life. Although VSS is clearly not a psychiatric disorder, patients with VSS show high rates of psychiatric symptoms and a reduction of quality of life (Solly et al.) . For clinical practice, this is highly important. Currently, we cannot offer evidence-based treatment for the key visual symptoms of VSS. However, the psychiatric comorbidities can be identified and addressed specifically with the aim of increasing overall quality of life in our patients. Another important therapeutic option is non-pharmacological. Hepschke et al. (22) applied intuitive colorimetry in a psychophysical experiment. They found that VSS discomfort exacerbates with short-wave (i.e., "blue") cone activation, which is important for two reasons. First, the koniocellular pathway might be affected in VSS; and second, intuitive colorimetry starting in the blue filter area should be offered to patients with the aim of reducing visual discomfort. Although symptomatic therapy and consideration of psychiatric comorbidity is important, etiological treatment will be the ultimate goal in VSS research. Also in this Research Topic, Grande et al. In the last decade, the establishment of clinical criteria for VSS has taken the disorder out of the area of psychiatric or psychological disease, as shown in this Research Topic, and set the stage for a rapid growth in research in many domains of neurology and neurosciences that might 1 day lead to a better understanding of and treatment for VSS and other disorders with similar underlying "network" mechanisms. Our previous nodal concept of cerebral function is inadequate to explain the brain's function. We need to move away from the Charcot-based evaluation of cerebral function, recognizing that it represents no more than 10% of cerebral circuits, and look at more in-depth studies. We must reorientate toward a concept of interactive networks which are neither sensory nor motor but are in fact sensorimotor. There are afferent components, efferent components, and central processing, about which we have much to learn but for which we have sufficient tools to make a start. Visual snow syndrome is a condition where we can start to gain these insights, and it will be exciting to go along with the development of this field in the coming years. OW was responsible for setting up the introduction to the editorial and subsequent combination of all author contributions. JF and VP reviewed articles for the Research Topics and reviewed the manuscript. CS reviewed articles for the Research Topics, reviewed the manuscript, and substantially modified the initial concept of the editorial. All authors contributed to the article and approved the submitted version. Persistent positive visual phenomena in migraine Visual snow-persistent positive visual phenomenon distinct from migraine aura Visual snow: a new disease entity distinct from migraine aura Field-testing the criteria for visual snow (positive persistent visual disturbance) Visual snow'-a disorder distinct from persistent migraine aura Visual snow: visual misperception Visual snow syndrome, the spectrum of perceptual disorders, and migraine as a common risk factor: a narrative review IHS. The International Classification of Headache Disorders Prevalence of visual snow syndrome in the UK Visual snow: a thalamocortical dysrhythmia of the visual pathway? Abnormal connectivity and brain structure in patients with visual snow Sustained visual cortex hyperexcitability in migraine with persistent visual aura Diffusion-and perfusion-weighted MR imaging in persistent migrainous visual disturbances White matter abnormalities in a patient with visual snow syndrome: new evidence from a diffusion tensor imaging study Disrupted connectivity within visual, attentional and salience networks in the visual snow syndrome Ocular motor measures of visual processing changes in visual snow syndrome Eye movement characteristics provide an objective measure of visual processing changes in patients with visual snow syndrome Contrast-processing dysfunction in both magnocellular and parvocellular pathways in migraineurs with or without aura The relation between migraine, typical migraine aura and "visual snow Visual snow syndrome: a clinical and phenotypical description of 1,100 cases Episodic visual snow associated with migraine attacks The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.