Visual snow syndrome: recent advances in understanding the pathophysiology and potential treatment approaches.

PURPOSE OF REVIEW: Visual snow syndrome (VSS) is a disorder characterized by persistent visual disturbances, including the visual snow phenomenon, palinopsia, heightened perception of entoptic phenomena, impaired night vision, and photophobia. The purpose of this review is to provide an update on recent findings over the past 18 months in VSS research and to summarize the current state of treatment approaches. RECENT FINDINGS: Electrophysiological studies have revealed cortical hyperresponsivity in visual brain areas, imaging studies demonstrated microstructural and functional connectivity alterations in multiple cortical and thalamic regions and investigated glutamatergic and serotoninergic neurotransmission. These findings suggest that VSS might be a network disorder.Only few treatment studies are currently available demonstrating limited response to medication and even worsening or triggering of visual symptoms by certain antidepressants. Promising nonpharmacological treatments include mindfulness-based cognitive therapy, the use of chromatic filters, and research on visual noise adaption and neuro-optometric visual rehabilitation therapy (NORT). However, the level of evidence is still low and further research is needed including larger trials and involving objective measures of individual dysfunction. SUMMARY: Although there has been recent progress, we still have not fully understood the nature of VSS. Further research is needed on a clinical and pathophysiological level to successfully treat the condition.

Characteristics of acute ischemic stroke and unusual aura in patients with migraine with aura.

BACKGROUND: Sometimes migraine aura changes from attack to attack, raising the question of whether the change is heralding an ischemic stroke or an unusual aura. Differentiating unusual migraine aura from the onset of an acute ischemic stroke in patients with migraine with aura (MwA) can be challenging. OBJECTIVE: The aim of this cohort study was to assess clinical characteristics that help distinguish between MwA and minor stroke in patients with a previous history of MwA who presented with suspicion of stroke. METHODS: We interviewed patients with MwA and ischemic stroke (MwA + IS) and patients with MwA and unusual aura, but without ischemic stroke (MwA - IS) from a tertiary hospital using a structured questionnaire. We assessed how symptoms of ischemic stroke or unusual aura differed from usual, that is, the typical aura in each patient. Stroke or exclusion of stroke was verified by multimodal magnetic resonance imaging. RESULTS: Seventeen patients with MwA + IS and twelve patients with MwA - IS were included. New focal neurological symptoms (13/17 [76%] vs. 3/12 [25%]), change of the first symptom (10/17 [59%] vs. 1/12 [8%]), and absence of headache (6/15 [40%] vs. 2/10 [20%]) were more often reported during ischemic stroke. The physical examination was normal in 8/17 (47%) MwA + IS and in 6/12 (50%) MwA - IS patients. In 5/17 (29%) patients with MwA + IS, there were unequivocal physical signs suggestive of stroke such as persistent visual loss, ataxia, or paresis. CONCLUSION: There are clues from the history that might help identify stroke in patients with MwA with changed aura symptoms. These might be particularly useful in patients presenting without physical findings suggestive of stroke.

Alterations of the alpha rhythm in visual snow syndrome: a case-control study.

BACKGROUND: Visual snow syndrome is a disorder characterized by the combination of typical perceptual disturbances. The clinical picture suggests an impairment of visual filtering mechanisms and might involve primary and secondary visual brain areas, as well as higher-order attentional networks. On the level of cortical oscillations, the alpha rhythm is a prominent EEG pattern that is involved in the prioritisation of visual information. It can be regarded as a correlate of inhibitory modulation within the visual network. METHODS: Twenty-one patients with visual snow syndrome were compared to 21 controls matched for age, sex, and migraine. We analysed the resting-state alpha rhythm by identifying the individual alpha peak frequency using a Fast Fourier Transform and then calculating the power spectral density around the individual alpha peak (+/- 1 Hz). We anticipated a reduced power spectral density in the alpha band over the primary visual cortex in participants with visual snow syndrome. RESULTS: There were no significant differences in the power spectral density in the alpha band over the occipital electrodes (O1 and O2), leading to the rejection of our primary hypothesis. However, the power spectral density in the alpha band was significantly reduced over temporal and parietal electrodes. There was also a trend towards increased individual alpha peak frequency in the subgroup of participants without comorbid migraine. CONCLUSIONS: Our main finding was a decreased power spectral density in the alpha band over parietal and temporal brain regions corresponding to areas of the secondary visual cortex. These findings complement previous functional and structural imaging data at a electrophysiological level. They underscore the involvement of higher-order visual brain areas, and potentially reflect a disturbance in inhibitory top-down modulation. The alpha rhythm alterations might represent a novel target for specific neuromodulation. TRIAL REGISTRATION: we preregistered the study before preprocessing and data analysis on the platform osf.org (DOI: https://doi.org/10.17605/OSF.IO/XPQHF , date of registration: November 19th 2022).

The "index vein" as a sign for migraine aura in the emergency setting.

Background and objectives To assess the usefulness of the "index vein" for making the diagnosis of migraine aura.Methods 400 patients were included when they: i) presented with an acute neurological deficit, ii) had a brain MRI, and iii) had a discharge diagnosis of migraine aura, ischemic stroke, epileptic seizure or controls (n = 100 per group).Results Compared to stroke (2%), epileptic seizure (4%) and controls (1%), the index vein is more prevalent in migraine aura (17%, p < 0.001). The index vein is highly specific for migraine aura (specificity 97%, 95% CI 95-99). The index vein has a positive predictive value for the diagnosis of migraine aura of 70% (95%CI 48-87). The index vein-score has the ability to diagnose migraine aura with a sensitivity of 94% (95%CI 87.4-97.8) and specificity of 73.5% (95%CI 66.8-79.5) at a cut-off of 4 points.Discussion The index vein serves as a good biomarker for migraine aura in the emergency setting.

Real-world effectiveness of fremanezumab for the preventive treatment of migraine: Interim analysis of the pan-European, prospective, observational, phase 4 PEARL study.

BACKGROUND: The ongoing Pan-European Real Life (PEARL) phase 4 study is evaluating fremanezumab effectiveness and safety for the prevention of episodic and chronic migraine. This interim analysis reports primary, secondary and exploratory endpoints from when 500 participants completed at least six months of treatment. METHODS: Adults with episodic migraine or chronic migraine maintaining daily headache diaries were enrolled upon initiation of fremanezumab. Primary endpoint: proportion of participants with ≥50% reduction in monthly migraine days during the six-month period after fremanezumab initiation. Secondary endpoints: mean change from baseline across months 1-12 in monthly migraine days, acute migraine medication use, and headache-related disability. Exploratory endpoint: mean change in headache severity from baseline across months 1-12. Safety was assessed through adverse events reported. RESULTS: Overall, 897 participants were enrolled and 574 included in the effectiveness analyses (episodic migraine, 25.8%; chronic migraine, 74.2%). Of participants with data available, 175/313 (55.9%) achieved ≥50% monthly migraine days reduction during the six-month period post-initiation. Across months 1-12, there were sustained reductions in mean monthly migraine days, acute medication use, disability scores, and headache severity. Few adverse events were reported. CONCLUSION: PEARL interim results support the effectiveness and safety of fremanezumab for migraine prevention in a real-world population across several European countries.Trial registration: encepp.eu: EUPAS35111.

Response to erenumab assessed by Headache Impact Test-6 is modulated by genetic factors and arterial hypertension: An explorative cohort study.

BACKGROUND AND PURPOSE: Response predictors to erenumab (ERE) in migraine patients would benefit their clinical management. We investigate associations between patients' clinical characteristics and polymorphisms at calcitonin receptor-like receptor (CALCRL) and receptor activity-modifying protein 1 (RAMP1) genes and response to ERE treatment measured as clinically meaningful improvement on the Headache Impact Test-6 (HIT-6) score. METHODS: This post hoc analysis of a prospective, multicenter, investigator-initiated study involves 110 migraine patients starting ERE 70 mg/month. Demographics, medical history, and migraine-related burden measured by HIT-6 score were collected during 3 months before and after ERE start. Selected polymorphic variants of CALCRL and RAMP1 genes were determined using real-time polymerase chain reaction. Logistic regression models identified independent predictors for response to ERE, defined as HIT-6 score improvement ≥ 8 points (HIT-6 responders [HIT-6 RESP] vs. HIT-6 nonresponders). RESULTS: At Month 3, 58 (52.7%) patients were HIT-6 RESP. Comorbid hypertension predicted a lower probability of being HIT-6 RESP (odds ratio [OR] = 0.160, 95% confidence interval [CI] = 0.047-0.548, p = 0.003). Compared to major alleles, minor alleles CALCRL rs6710852G and RAMP rs6431564G conferred an increased probability of being HIT-6 RESP (for each G allele: OR = 2.82, 95% CI = 1.03-7.73, p = 0.043; OR = 2.10, 95% CI = 1.05-4.22, p = 0.037). RAMP1 rs13386048A and RAMP1 rs12465864G decreased this probability (for each rs13386048A, OR = 0.53, 95% CI = 0.28-0.98, p = 0.042; for each rs12465864G, OR = 0.32, 95% CI = 0.13-0.75, p = 0.009). A genetic risk score based on the presence and number of identified risk alleles was independently associated with HIT-6 RESP (OR = 0.49, 95% CI = 0.33-0.72, p = 0.0003), surviving Bonferroni correction. CONCLUSIONS: Response to ERE was associated with comorbid hypertension and specific allelic variants in CALCRL and RAMP1 genes. Results require confirmation in future studies.

Symptomatic visual snow in acute ischemic stroke: A case series.

Visual snow is the main symptom of visual snow syndrome, a disorder of predominantly visual disturbances initially described in patients without abnormalities on ancillary investigations. We present a case series of patients with visual snow in the setting of acute ischemic stroke. The first and second patient reported previous episodic visual snow with migraine attacks. The third patient experienced visual snow for the first time during the ischemic stroke. In the first patient, the ischemic stroke affected the right and left precuneus and the right lingual gyrus. In the second patient, the ischemic stroke was located in the left lingual gyrus, parts of the left fusiform and parahippocampal gyrus, left dorso-lateral thalamus, and left cerebellar hemisphere. In the third patient, occipital pole, trunk of the corpus callosum on the right, right paramedian pons, right cerebellar hemisphere, and vermis were affected. Our case series indicates that the symptom visual snow can be caused by vascular lesions in areas of visual processing. Because patients did not meet criteria for visual snow syndrome, dysfunction in the affected areas might only explain part of the complex pathophysiology of visual snow syndrome.

[Consensus statement of the migraine and headache societies (DMKG, ÖKSG, and SKG) on the duration of pharmacological migraine prophylaxis]. / Konsensusstatement der Migräne- und Kopfschmerzgesellschaften (DMKG, ÖKSG & SKG) zur Therapiedauer der medikamentösen Migräneprophylaxe.

Migraine is the most common neurological disorder and can be associated with a high degree of disability. In addition to non-pharmacological approaches to reduce migraine frequency, pharmacological migraine preventatives are available. Evidence-based guidelines from the German Migraine and Headache Society (DMKG), and German Society for Neurology (DGN), Austrian Headache Society (ÖKSG), and Swiss Headache Society (SKG) are available for indication and application. For therapy-relevant questions such as the duration of a pharmacological migraine prevention, no conclusions can be drawn from currently available study data. The aim of this review is to present a therapy consensus statement that integrates the current data situation and, where data are lacking, expert opinions. The resulting current recommendations on the duration of therapy for pharmacological migraine prophylaxis are shown here.

[Consensus statement of the migraine and headache societies (DMKG, ÖKSG, and SKG) on the duration of pharmacological migraine prophylaxis]. / Konsensusstatement der Migräne- und Kopfschmerzgesellschaften (DMKG, ÖKSG & SKG) zur Therapiedauer der medikamentösen Migräneprophylaxe.

Migraine is the most common neurological disorder and can be associated with a high degree of disability. In addition to non-pharmacological approaches to reduce migraine frequency, pharmacological migraine preventatives are available. Evidence-based guidelines from the German Migraine and Headache Society (DMKG), and German Society for Neurology (DGN), Austrian Headache Society (ÖKSG), and Swiss Headache Society (SKG) are available for indication and application. For therapy-relevant questions such as the duration of a pharmacological migraine prevention, no conclusions can be drawn from currently available study data. The aim of this review is to present a therapy consensus statement that integrates the current data situation and, where data are lacking, expert opinions. The resulting current recommendations on the duration of therapy for pharmacological migraine prophylaxis are shown here.

Changes of migraine aura with advancing age of patients.

AIM: Given the similar presentation of migraine aura and acute ischemic stroke, advancing patient age might change the characteristics of migraine with aura (MA) and be clinically important. Clinical data, however, are limited. Experimental studies indicate a decrease in the magnitude of cortical spreading depression (CSD), the pathophysiological correlate of migraine aura, with advancing age. Our study aimed to assess the influence of age on the clinical features of MA. METHODS: Three hundred and forty-three patients were interviewed using a structured questionnaire. The questions covered the headache characteristics and symptom types including the characteristics of the C-criterion, as defined by the International Classification of Headache Disorders 3rd Edition. The association of age with MA characteristics was assessed. RESULTS: The median age was 29 (IQR 28-52) and 235 of the 343 patients were women (69%). Individual symptoms of the C-criterion such as gradual aura spreading over longer than 5 min (P < 0.001), two or more aura symptoms occurring in succession (P = 0.005), duration of at least one MA symptom for longer than 60 min (P = 0.004), and associated headache (P = 0.01) were more frequent in younger patients. The number of symptoms including the C-characteristics decreased with increasing age (P < 0.001). Patients with sensory (P < 0.001), motor (P = 0.004) and speech disturbance (P = 0.02) were younger, and older patients with headache had less photophobia (P = 0.04) and phonophobia (P = 0.03). Sensitivity analyses yielded similar results. CONCLUSION: The frequency of typical characteristics of migraine aura and migraine headache including photophobia and phonophobia decreases with advancing patient age. This might have potentially difficult implications for the diagnosis of MA in the elderly.

Visual snow syndrome is probably not mediated by CGRP: A case series.

BACKGROUND: Visual snow syndrome is a phenomenon for which no effective treatment is known. It is highly comorbid with migraine, therefore we performed a retrospective chart review of patients with visual snow syndrome treated with a monoclonal antibody against calcitonin gene related peptide or its receptor. FINDINGS: We enrolled 15 patients with visual snow syndrome who received at least once a monoclonal antibody against calcitonin gene related peptide or its receptor. None of the patients reported relief of visual snow syndrome whereas those patients with comorbid migraine reported a very good efficacy of the antibody against the migraine headache but not against the migraine aura. CONCLUSION: The data suggest that visual snow syndrome is not mediated by calcitonin gene related peptide in a relevant way and that the calcitonin gene related peptide receptor is not involved in the network underlying the visual snow syndrome.

Migraine and atrial fibrillation: a systematic review.

BACKGROUND AND PURPOSE: Patients with migraine are at increased risk of stroke. The aim was to systematically review the current literature on the association between migraine and atrial fibrillation, which is a relevant risk factor for stroke. METHODS: PubMed was searched for 'migraine' AND 'atrial fibrillation' and selected original investigations on the association of migraine and atrial fibrillation for our analysis. Articles without original data, such as guidelines, narrative reviews, editorials and others, were excluded. RESULTS: In all, 109 publications were found. Twenty-two were included and analysed for this review. The population-based Atherosclerosis Risk in Communities study showed a significant association of migraine with visual aura and incident atrial fibrillation (hazard ratio 1.30, 95% confidence interval 1.03-1.62, p = 0.02), but not for migraine without aura, compared to non-headache persons after multivariable adjustment for vascular risk factors. An even larger population-based study in Denmark confirmed this association (odds ratio 1.25, 95% confidence interval 1.16-1.36). Studies investigating patients with ischaemic stroke and migraine are methodologically insufficient and provide contradictory results. Ablation therapy for atrial fibrillation in patients with migraine might reduce migraine attacks, but transient post-ablation new-onset migraine-like headaches in persons without a history of migraine have also been reported. CONCLUSION: Population-based studies indicate a significant association of migraine with aura and atrial fibrillation. In practical terms, screening for atrial fibrillation in patients who have a long history of migraine might be reasonable, whereas in patients with stroke or other disorders and migraine extensive screening for atrial fibrillation should be performed as in all patients without migraine.

Swiss QUality of life and healthcare impact Assessment in a Real-world Erenumab treated migraine population (SQUARE study): interim results.

BACKGROUND: The fully human monoclonal antibody erenumab, which targets the calcitonin gene-related peptide (CGRP) receptor, was licensed in Switzerland in July 2018 for the prophylactic treatment of migraine. To complement findings from the pivotal program, this observational study was designed to collect and evaluate clinical data on the impact of erenumab on several endpoints, such as quality of life, migraine-related impairment and treatment satisfaction in a real-world setting. METHODS: An interim analysis was conducted after all patients completed 6 months of erenumab treatment. Patients kept a headache diary and completed questionnaires at follow up visits. The overall study duration comprises 24 months. RESULTS: In total, 172 adults with chronic or episodic migraine from 19 different sites across Switzerland were enrolled to receive erenumab every 4 weeks. At baseline, patients had 16.6 ± 7.2 monthly migraine days (MMD) and 11.6 ± 7.0 acute migraine-specific medication days per month. After 6 months, erenumab treatment reduced Headache Impact Test (HIT-6™) scores by 7.7 ± 8.4 (p < 0.001), the modified Migraine Disability Assessment (mMIDAS) by 14.1 ± 17.8 (p < 0.001), MMD by 7.6 ± 7.0 (p < 0.001) and acute migraine-specific medication days per month by 6.6 ± 5.4 (p < 0.001). Erenumab also reduced the impact of migraine on social and family life, as evidenced by a reduction of Impact of Migraine on Partners and Adolescent Children (IMPAC) scores by 6.1 ± 6.7 (p < 0.001). Patients reported a mean effectiveness of 67.1, convenience of 82.4 and global satisfaction of 72.4 in the Treatment Satisfaction Questionnaire for Medication (TSQM-9). In total, 99 adverse events (AE) and 12 serious adverse events (SAE) were observed in 62 and 11 patients, respectively. All SAE were regarded as not related to the study medication. CONCLUSIONS: Overall quality of life improved and treatment satisfaction was rated high with erenumab treatment in real-world clinical practice. In addition, the reported impact of migraine on spouses and children of patients was reduced. TRIAL REGISTRATION: BASEC ID 2018-02,375 in the Register of All Projects in Switzerland (RAPS).

Localised increase in regional cerebral perfusion in patients with visual snow syndrome: a pseudo-continuous arterial spin labelling study.

OBJECTIVES: We aimed to investigate changes in regional cerebral blood flow (rCBF) using arterial spin labelling (ASL) in patients with visual snow syndrome (VSS), in order to understand more about the underlying neurobiology of the condition, which remains mostly unknown. METHODS: We performed an MRI study in which whole-brain maps of rCBF were obtained using pseudo-continuous ASL. Twenty-four patients with VSS and an equal number of gender and age-matched healthy volunteers took part in the study. All subjects were examined with both a visual paradigm consisting of a visual-snow like stimulus, simulating key features of the snow, and a blank screen at rest, randomly presented. RESULTS: Patients with VSS had higher rCBF than controls over an extensive brain network, including the bilateral cuneus, precuneus, supplementary motor cortex, premotor cortex and posterior cingulate cortex, as well as the left primary auditory cortex, fusiform gyrus and cerebellum. These areas were largely analogous comparing patients either at rest, or when looking at a 'snow-like' visual stimulus. This widespread, similar pattern of perfusion differences in either condition suggests a neurophysiological signature of visual snow. Furthermore, right insula rCBF was increased in VSS subjects compared with controls during visual stimulation, reflecting a greater task-related change and suggesting a difference in interoceptive processing with constant perception of altered visual input. CONCLUSION: The data suggest VSS patients have marked differences in brain processing of visual stimuli, validating its neurobiological basis.

Impact on monthly migraine days of discontinuing anti-CGRP antibodies after one year of treatment - a real-life cohort study.

OBJECTIVE: This study aims to analyse the effect of the discontinuation of anti-calcitonin gene-related peptide antibodies on monthly migraine days after 12 treatment months. BACKGROUND: Anti-calcitonin gene-related peptide antibodies have been a game changer in migraine prophylaxis. However, high treatment costs warrant reducing treatment duration to the essential minimum. METHODS: We collected data of patients with migraine who had received anti-calcitonin gene-related peptide antibodies and had received treatment for 12 months. RESULTS: We included 52 patients. The average number of monthly migraine days was 16 ± 7 days at baseline, 6 ± 6 in the third, and 5 ± 4 in the 12th treatment month. After treatment interruption, the number of monthly migraine days was 6 ± 4 days in the first month, 9 ± 4 days in the second, and 11 ± 5 days in the third month. Most patients (88.9%) restarted treatment. CONCLUSION: Only little of the therapeutic effect of anti-calcitonin gene-related peptide antibodies outlasts their pharmacological effect. After treatment interruption, migraine frequency rose in most patients, and prophylaxis was required again in most cases.Limiting treatment to benefitting patients and confirming the need for prophylaxis periodically is reasonable. However, our data does not support the need for prescheduled treatment discontinuation after 12 months and a fixed duration of the treatment interruption of 3 months.

Visual snow syndrome, the spectrum of perceptual disorders, and migraine as a common risk factor: A narrative review.

OBJECTIVE: The aim of this narrative review is to explore the relationship between visual snow syndrome (VSS), migraine, and a group of other perceptual disorders. BACKGROUND: VSS is characterized by visual snow and additional visual and nonvisual disturbances. The clinical picture suggests a hypersensitivity to internal and external stimuli. Imaging and electrophysiological findings indicate a hyperexcitability of the primary and secondary visual areas of the brain possibly due to an impairment of inhibitory feedback mechanisms. Migraine is the most frequent comorbidity. Epidemiological and clinical studies indicate that other perceptual disorders, such as tinnitus, fibromyalgia, and dizziness, are associated with VSS. Clinical overlaps and parallels in pathophysiology might exist in relation to migraine. METHODS: We performed a PubMed and Google Scholar search with the following terms: visual snow syndrome, entoptic phenomenon, fibromyalgia, tinnitus, migraine, dizziness, persistent postural-perceptual dizziness (PPPD), comorbidities, symptoms, pathophysiology, thalamus, thalamocortical dysrhythmia, and salience network. RESULTS: VSS, fibromyalgia, tinnitus, and PPPD share evidence of a central disturbance in the processing of different stimuli (visual, somatosensory/pain, acoustic, and vestibular) that might lead to hypersensitivity. Imaging and electrophysiological findings hint toward network disorders involving the sensory networks and other large-scale networks involved in the management of attention and emotional processing. There are clinical and epidemiological overlaps between these disorders. Similarly, migraine exhibits a multisensory hypersensitivity even in the interictal state with fluctuation during the migraine cycle. All the described perceptual disorders are associated with migraine suggesting that having migraine, that is, a disorder of sensory processing, is a common link. CONCLUSION: VSS, PPPD, fibromyalgia, and chronic tinnitus might lie on a spectrum of perceptual disorders with similar pathophysiological mechanisms and the common risk factor migraine. Understanding the underlying network disturbances might give insights into how to improve these currently very difficult to treat conditions.

Green Flags and headache: A concept study using the Delphi method.

OBJECTIVE: The aim of this study was to collect and rate Green Flags, that is, symptoms or pieces of information indicating that a patient is more likely to suffer from a primary than from a secondary headache. BACKGROUND: When assessing headaches, a central question to be answered is whether the pain is primary or secondary to another disorder. To maximize the likelihood of a correct diagnosis, relevant signs and symptoms must be sought, identified, and weighed against each other. METHODS: The project was designed as a Delphi study. In the first round, an expert panel proposed green flags that were rated anonymously in two subsequent rounds. Proposals with an average rating of 4.0 and higher on a scale from 0 to 5 reached consensus. RESULTS: Five Green Flags reached consensus: (i) "The current headache has already been present during childhood"; (ii) "The headache occurs in temporal relationship with the menstrual cycle"; (iii) "The patient has headache-free days"; (iv) "Close family members have the same headache phenotype"; and (v) "Headache occurred or stopped more than one week ago." CONCLUSIONS: We propose five Green Flags for primary headache disorders. None being a pathognomonic sign, we recommend searching for both Green Flags and Red Flags. If both are present, a secondary headache should be suspected. Overall, the application of the Green Flag concept in clinical practice is likely to increase diagnostic accuracy and improve diagnostic resource allocation. Prospective studies in clinical populations should be conducted to validate these Green Flags.

Structural and functional footprint of visual snow syndrome.

Patients with visual snow syndrome suffer from a continuous pan-field visual disturbance, additional visual symptoms, tinnitus, and non-perceptional symptoms. The pathophysiology of visual symptoms might involve dysfunctional visual cortex. So far, the extra-visual system has not been investigated. We aimed at identifying structural and functional correlates for visual and non-visual symptoms in visual snow syndrome. Patients were compared to age- and sex-matched controls using 18F-2-fluoro-2-deoxy-d-glucose PET (n = 20 per group) and voxel-based morphometry (n = 17 per group). Guided by the PET results, region of interest analysis was done in voxel-based morphometry to identify structural-functional correspondence. Grey matter volume was assessed globally. Patients had corresponding hypermetabolism and cortical volume increase in the extrastriate visual cortex at the junction of the right lingual and fusiform gyrus. There was hypometabolism in the right superior temporal gyrus and the left inferior parietal lobule. Patients had grey matter volume increases in the temporal and limbic lobes and decrease in the superior temporal gyrus. The corresponding structural and functional alterations emphasize the relevance of the visual association cortex for visual snow syndrome. The broad structural and functional footprint, however, confirms the clinical impression that the disorder extends beyond the visual system.

Age- and frequency-dependent changes in dynamic contrast perception in visual snow syndrome.

OBJECTIVE: Patients with visual snow syndrome (VSS) suffer from a debilitating continuous ("TV noise-like") visual disturbance. They report problems with vision at night and palinopsia despite normal visual acuity. The underlying pathophysiology of VSS is largely unknown. Currently, it is a clinical diagnosis based on the patient's history, an objective test is not available. Here, we tested the hypothesis that patients with VSS have an increased threshold for detecting visual contrasts at particular temporal frequencies by measuring dynamic contrast detection-thresholds. METHODS: Twenty patients with VSS were compared to age-, gender-, migraine- and aura-matched controls in this case-control study. Subjects were shown bars randomly tilted to the left or right, flickering at six different frequencies (15 Hz, 20 Hz, 25 Hz, 30 Hz, 35 Hz, 40 Hz). The contrast threshold (CT) for detection of left or right tilt was measured in a two-alternative adaptive forced-choice procedure (QUEST). The threshold was defined as the Michelson contrast necessary to achieve the correct response in 75% of the cases. RESULTS: The CT increased for higher flicker frequencies (ANOVA: main effect frequency: F (5,180) = 942; p < 0.001), with an additional significant frequency*diagnosis interaction (ANOVA: F (5,180) = 5.00; p < 0.001). This interaction effect was due to an increased CT at a flicker frequency of 15 Hz in the VSS cohort (VSS: MC = 1.17%; controls: MC = 0.77%). At the other frequencies, group comparisons revealed no differences. Furthermore, in the VSS cohort we observed an increase of CT with higher age (r = 0.69; p < 0.001), which was not seen in controls (r = 0.30; p = 0.20). CONCLUSIONS: This study demonstrates a lower visual contrast sensitivity exclusively at 15 Hz in VSS patients and demonstrates frequency-dependent differences in dynamic contrast vision. The peak sensitivities of both parvo- and magnocellular visual pathways are close to a frequency of about 10 Hz. Therefore, this frequency seems to be of crucial importance in everyday life. Thus, it seems plausible that the impairment of contrast sensitivity at 15 Hz might be an important pathophysiological correlate of VSS. Furthermore, the overall age-related decrease in contrast sensitivity only in VSS patients underscores the vulnerability of dynamic contrast detection in VSS patients. Dynamic CT detection seems to be a promising neurophysiological test that may contribute to the diagnosis of VSS.

Delayed headache after COVID-19 vaccination: a red flag for vaccine induced cerebral venous thrombosis.

BACKGROUND: Headache is a frequent symptom following COVID-19 immunization with a typical onset within days post-vaccination. Cases of cerebral venous thrombosis (CVT) have been reported in adenovirus vector-based COVID-19 vaccine recipients. FINDINGS: We reviewed all vaccine related CVT published cases by April 30, 2021. We assessed demographic, clinical variables and the interval between the vaccination and onset of headache. We assessed whether the presence of headache was associated with higher probability of death or intracranial hemorrhage. We identified 77 cases of CVT after COVID-19 vaccination. Patients' age was below 60 years in 74/77 (95.8%) cases and 61/68 (89.7%) were women. Headache was described in 38/77 (49.4%) cases, and in 35/38 (92.1%) was associated with other symptoms. Multiple organ thrombosis was reported in 19/77 (24.7%) cases, intracranial hemorrhage in 33/77 (42.9%) cases and 19/77 (24.7%) patients died. The median time between vaccination and CVT-related headache onset was 8 (interquartile range 7.0-9.7) days. The presence of headache was associated with a higher odd of intracranial hemorrhage (OR 7.4; 95% CI: 2.7-20.8, p < 0.001), but not with death (OR: 0.51, 95% CI: 0.18-1.47, p = 0.213). CONCLUSION: Delayed onset of headache following an adenovirus vector-based COVID-19 vaccine is associated with development of CVT. Patients with new-onset headache, 1 week after vaccination with an adenovirus vector-based vaccine, should receive a thorough clinical evaluation and CVT must be ruled out.