Behavioral measures of cortical hyperexcitability assessed in people who experience visual snow

McKendrick, Allison M; Chan, Yu Man; Tien, Melissa Yixin; Millist, Lynette; Clough, Meaghan; Mack, Heather G; Fielding, Joanne; White, Owen B

doi:10.1212/wnl.0000000000003784

Cited by 55 publications

(62 citation statements)

References 35 publications

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“…The present results were consistent with those in previous studies. 2,4 Flickering and floaters were present in all VS patients. Nyctalopia was frequently reported by VS wom patients, but no statistically significant differences were observed.…”

Section: Discussionmentioning

confidence: 91%

“…A previous functional brain imaging study revealed hypermetabolism of the supplementary visual cortex in VS patients . In a recent study, abnormal visual perceptual measures and elevated excitability in the primary visual cortex were observed in VS patients . In our study, using TMS induced magnetophosphene thresholds, we also demonstrated the occipital cortex hyperexcitability in VS patients.…”

Section: Discussionmentioning

confidence: 96%

“…In our VS patients, floaters, flickering, blue field entoptic phenomenon, photopsia, palinopsia, tinnitus, photophobia, and concentration difficulty were the most reported symptoms. The present results were consistent with those in previous studies . Flickering and floaters were present in all VS patients.…”

Section: Discussionmentioning

confidence: 99%

“…The exact pathophysiology of this syndrome is still unknown, but it is believed that this syndrome may originate from the overactive neuronal structures within the primary visual cortex . Although VS and migraine aura are distinct disorders, the prevalence of migraine aura has been reported to be very high in VS patients .…”

Section: Introductionmentioning

confidence: 99%

“…3 The exact pathophysiology of this syndrome is still unknown, but it is believed that this syndrome may originate from the overactive neuronal structures within the primary visual cortex. 4 Although VS and migraine aura are distinct disorders, the prevalence of migraine aura has been reported to be very high in VS patients. 5 In migraine patients, low phosphene thresholds (PTs) 6 and loss of habituation to repetitive pattern visual evoked potentials (rVEP) 7 have been shown to be correlated with occipital cortex hyperexcitability.…”

Section: Introductionmentioning

confidence: 99%

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The Clinical Characteristics and Neurophysiological Assessments of the Occipital Cortex in Visual Snow Syndrome With or Without Migraine

2019

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Objective Visual snow syndrome (VS) is mainly characterized by flickering, little dots in both visual fields. The recognition of the clinical entity of VS has been increasing recently. Diagnosis is based on patient reports and not better accounted for by another diagnosis. Background The exact pathophysiology of this syndrome is still unknown. In this study, our aim was to investigate the role of neurophysiological assessments of the occipital cortex in VS patients with (VSm) or without migraine (VSwom) and the healthy control (HC). Methods To assess the occipital cortex hyperexcitability, we conducted a prospective, observational study to investigate the habituation/potentiation response by repetitive pattern reversal visual evoked potentials (rVEP) and examined the phosphene thresholds (PT) by transcranial magnetic stimulation in VS patients with or without migraine who were admitted to our tertiary headache clinic and the healthy control. Results Twenty‐nine volunteers were recruited. The VSm (n = 10), the VSwom (n = 7), and the HC group (n = 12) did not differ demographically. Flickering and floaters were reported in all VS patients and flickering in the dark was the most distressing symptomatology in both VS groups. Higher VAS scores for palinopsia (trailing), photophobia, and concentration difficulty were more frequently self‐reported by VSm patients. The HC demonstrated habituation; however, there was loss of habituation response and decreased PTs in both groups of VS patients. The N1P1 VEP amplitude ratios of the 10th/1st block from right and left eye stimulation disclosed higher values (lack of habituation) in VSm (1.04 ± 0.2 and 1.06 ± 0.2) and the VSwom (1.05 ± 0.2 and 0.96 ± 0.08) patients compared to the healthy control (0.75 ± 0.1 and 0.79 ± 0.1), P = .002 from right eye and P = .003 from left eye. In the post hoc analysis the VS patients did not differ according to the presence of migraine from right or left eye stimulations (both P > .999). The left occipital cortex PTs were lower in VSm (58.00 ± 6.60) and VSwom (62.14 ± 11.53) and higher in the HC (71.33 ± 5.56) P = .009. In the post hoc analysis the VS patients did not differ according to the presence of migraine (P > .999). The right occipital cortex PTs were lower in VSm (60.30 ± 8.15) and VSwom (62.00 ± 10.95), higher in the HC (69.67 ± 8.04); however, statistically, groups did not differ (P = .087). Conclusions The loss of habituation and lower threshold for occipital cortex excitability were demonstrated electrophysiologically in VS patients. While statistically significant loss of habituation was seen in both VS patients (with or without migraine) in the right eye, statistically significant loss of habituation in the left eye and decreased threshold of left occipital cortex excitability was seen in visual snow with migraine patients. These findings may provide new insights on “visual snow” pathophysiology and serve as an objective and quantitative assessment tool in VS patients.

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Section: Discussionmentioning

confidence: 91%

Section: Discussionmentioning

confidence: 96%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

The Clinical Characteristics and Neurophysiological Assessments of the Occipital Cortex in Visual Snow Syndrome With or Without Migraine

2019

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Disrupted connectivity within visual, attentional and salience networks in the visual snow syndrome

Puledda

O’Daly

Schankin

et al. 2021

Human Brain Mapping

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Here we investigate brain functional connectivity in patients with visual snow syndrome (VSS). Our main objective was to understand more about the underlying pathophysiology of this neurological syndrome. Twenty‐four patients with VSS and an equal number of gender and age‐matched healthy volunteers attended MRI sessions in which whole‐brain maps of functional connectivity were acquired under two conditions: at rest while watching a blank screen and during a visual paradigm consisting of a visual‐snow like stimulus. Eight unilateral seed regions were selected a priori based on previous observations and hypotheses; four seeds were placed in key anatomical areas of the visual pathways and the remaining were derived from a pre‐existing functional analysis. The between‐group analysis showed that patients with VSS had hyper and hypoconnectivity between key visual areas and the rest of the brain, both in the resting state and during a visual stimulation, compared with controls. We found altered connectivity internally within the visual network; between the thalamus/basal ganglia and the lingual gyrus; between the visual motion network and both the default mode and attentional networks. Further, patients with VSS presented decreased connectivity during external sensory input within the salience network, and between V5 and precuneus. Our results suggest that VSS is characterised by a widespread disturbance in the functional connectivity of several brain systems. This dysfunction involves the pre‐cortical and cortical visual pathways, the visual motion network, the attentional networks and finally the salience network; further, it represents evidence of ongoing alterations both at rest and during visual stimulus processing.

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Brain network dynamics in people with visual snow syndrome

Strik

Clough

Solly

et al. 2022

Human Brain Mapping

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Visual snow syndrome (VSS) is a neurological disorder characterized by a range of continuous visual disturbances. Little is known about the functional pathological mechanisms underlying VSS and their effect on brain network topology, studied using high‐resolution resting‐state (RS) 7 T MRI. Forty VSS patients and 60 healthy controls underwent RS MRI. Functional connectivity matrices were calculated, and global efficiency (network integration), modularity (network segregation), local efficiency (LE, connectedness neighbors) and eigenvector centrality (significance node in network) were derived using a dynamic approach (temporal fluctuations during acquisition). Network measures were compared between groups, with regions of significant difference correlated with known aberrant ocular motor VSS metrics (shortened latencies and higher number of inhibitory errors) in VSS patients. Lastly, nodal co‐modularity, a binary measure of node pairs belonging to the same module, was studied. VSS patients had lower modularity, supramarginal centrality and LE dynamics of multiple (sub)cortical regions, centered around occipital and parietal lobules. In VSS patients, lateral occipital cortex LE dynamics correlated positively with shortened prosaccade latencies (p = .041, r = .353). In VSS patients, occipital, parietal, and motor nodes belonged more often to the same module and demonstrated lower nodal co‐modularity with temporal and frontal regions. This study revealed reduced dynamic variation in modularity and local efficiency strength in the VSS brain, suggesting that brain network dynamics are less variable in terms of segregation and local clustering. Further investigation of these changes could inform our understanding of the pathogenesis of the disorder and potentially lead to treatment strategies.

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Behavioral measures of cortical hyperexcitability assessed in people who experience visual snow

Cited by 55 publications

References 35 publications

The Clinical Characteristics and Neurophysiological Assessments of the Occipital Cortex in Visual Snow Syndrome With or Without Migraine

The Clinical Characteristics and Neurophysiological Assessments of the Occipital Cortex in Visual Snow Syndrome With or Without Migraine

Disrupted connectivity within visual, attentional and salience networks in the visual snow syndrome

Brain network dynamics in people with visual snow syndrome

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