Patients with visual snow syndrome (VS) suffer from a debilitating continuous visual disturbance of unknown mechanism. The present study tested the hypothesis of dysfunctional visual processing using visual evoked potentials. Eighteen patients were compared to age‐matched migraineurs (M) and healthy controls (C) using 2‐way analysis of variance with group (VS, M, C) and gender as factors. Visual evoked potentials from patients with VS demonstrated increased N145 latency (in milliseconds, VS: 152.7 ± 7.9 vs M: 145.3 ± 9.8 vs C: 145.5 ± 9.4; F = 3.28; p = 0.046) and reduced N75–P100 amplitudes (in microvolts, VS: 7.4 ± 3.5 vs M: 12.5 ± 4.7 vs C: 10.8 ± 3.4; F = 3.16; p = 0.051). Dunnett post hoc analysis was significant for all comparisons between VS and controls. These findings are in agreement with the idea that the primary disturbance in VS is a dysfunction of the visual association cortex. Ann Neurol 2018;84:946–949
BackgroundMigraine is a stress-related disorder, suggesting that there may be sympathetic hyperactivity in migraine patients. However, there are contradictory results concerning general sympathetic activation in migraine patients. To shed more light on the involvement of the autonomic nervous system (ANS) in migraine pathophysiology, we investigated cardiac and cardiovascular reactions during vagal (paced breathing) and sympathetic activation (mental stress test).MethodsHeart rate variability parameters and skin conductance responses were recorded interictally in 22 episodic migraine patients without aura and 25 matched controls during two different test conditions. The paced breathing test consisted of a five-minute baseline, followed by two minutes of paced breathing (6 breathing cycles per minute) and a five-minute recovery phase. The mental stress test consisted of a five-minute baseline, followed by one minute of stress anticipation, three and a half minutes of mental stress and a five-minute recovery phase. Furthermore we measured blood pressure and heart rate once daily over 2 weeks. Subjects rated their individual current stress level and their stress level during paced breathing and during the mental stress test.ResultsThere were no significant differences between migraine patients and controls in any of the heart rate variability parameters in either time domain or frequency domain analysis. However, all parameters showed a non-significant tendency for larger sympathetic activation in migraine patients. Also, no significant differences could be observed in skin conductance responses and average blood pressure. Only heart rates during the 2-week period and stress ratings showed significantly higher values in migraine patients compared to controls.ConclusionsGenerally there were no significant differences between migraine patients and controls concerning the measured autonomic parameters. There was a slight but not significant tendency in the migraine patients to react with less vagal and more sympathetic activation in all these tests, indicating a slightly changed set point of the autonomic system. Heart rate variability and blood pressure in migraine patients should be investigated for longer periods and during more demanding sympathetic activation.
Deficient VEP habituation in migraine was confirmed. However, the test-retest reliability of VEP habituation was rather weak. Therefore, we suggest that VEP habituation should be used for evaluation of cortical excitability under treatment only at the group level and only when a control group with sham treatment is included.
Patients with ANCA-associated vasculitides commonly have symptoms of autonomic dysfunction that are independent of disease duration and disease severity. However, at least in this single-centre observation, there was no evidence of impaired autonomic regulation in three autonomic function tests in vasculitis patients.
Objective: Patients with visual snow syndrome (VSS) suffer from continuous (“TV snow-like”) visual disturbance of unknown pathoetiology. In VSS, changes in cortical excitability in the primary visual cortex and the visual association cortex are discussed, with recent imaging studies tending to point to higher-order visual areas. Migraine, especially migraine with aura, is a common comorbidity. In chronic migraine and episodic migraine with aura but not in episodic migraine without aura, a reduced magnetic suppression of perceptual accuracy (MSPA) reflects a probably reduced inhibition of the primary visual cortex. Here we investigated the inhibition of the primary visual cortex using MSPA in patients with VSS, comparing that with MSPA in controls matched for episodic migraine.Methods: Seventeen patients with VSS were compared to 17 age- and migraine-matched controls. Visual accuracy was assessed by letter recognition and modulated by transcranial magnetic stimulation delivered to the occipital cortex at different intervals with respect to the letter presentation (40, 100, and 190 ms).Results: Suppression of visual accuracy at the 100-ms interval was present without significant differences between VSS patients and age- and migraine-matched controls (percentage of correctly recognized trigrams, control: 46.4 ± 34.3; VSS: 52.5 ± 25.4, p = 0.56).Conclusions: In contrast to migraine with aura, occipital cortex inhibition, as assessed with MSPA, may not be affected in VSS.
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