Resting - State EEG Indicates Unstable Microstates in Visual Snow Syndrome

Background: EEG microstates account for a significant amount of the variance in resting-state EEG activity and are considered the basic building blocks of human neurological processes. We analyzed the characteristics of EEG microstates in patients with visual snow syndrome (VSS) with and without migraine and compared these results with those of a matched control group. VSS is a syndrome characterized by a spectrum of visual symptoms, including photophobia, and enhanced entoptic phenomena. The main symptom of VSS is the perception of flickering dots throughout the visual field, described as looking through a snowy television screen. Cause and pathophysiology of VSS are still unknown. Method: Resting-state EEG recordings were selected from a cohort of 21 subjects with visual snow syndrome (VSSP, 8 females, 33 ± 9.56 years) and 21 control patients (8 females, 33 ± 11.1 years). Matching was based on diagnosed VSS, age, sex, and migraine status. A comparative analysis of microstate (MS) parameters between these two groups was performed. The calculation involved the four widely accepted canonical microstate classes, namely A (auditory & visual processing, arousal), B (visual processing), C (self-reflection, salience), and D (dorsal attention network). Results: We found significant differences between groups and between microstates in resting-state EEG in the life span and amplitude of microstates. VSSP showed an overall shorter duration and lower mean global field power (GFP) of microstates compared to controls. In addition, we found an aberrant syntax of microstate class A. Compared to controls, microstate A changed more often to class B and less frequently to microstate class C in VSSP. Conclusion: By examining resting-state EEG microstate features, we were able to investigate neurobiological mechanisms indicative of altered cortical excitability and aberrant shifts between neural networks in VSSP. Therefore, abnormalities in sensory and cognitive processing are suspected. However, to gain deeper insight into the pathophysiology of VSS, further studies with subjects with homogenous comorbidities are indicated

Modulating cortical responsiveness by tACS in visual snow syndrome - a case report

Background: Studies have shown that migraineurs have an enhanced photic-drive response when exposed to a visual chirp compared to healthy controls. Visual Snow Syndrome (VSS) is associated with migraines, but patients have continuous visual symptoms indicating dysfunction in visual processing. For this reason, we want to determine whether VSS patients show a similar reaction as migraineurs when exposed to visual chirp stimulation. Additionally, we want to see whether t-ACS stimulation lowers their reaction significantly. Method: One VSS patient (female, 37) with comorbid migraines was exposed to visual chirp stimulation (5.55 – 60 Hz) in a dimly lit room in front of a PC monitor (50 cm). There were 66 flashes per trial, totaling 792 flashes. A 64-electrode EEG grid was used for the measurement, with the occipital electrodes used for analysis. Power spectral density was calculated for stimulus responses and corrected for baseline. A wavelet transformation was applied before averaging the data. The patient received a total of 9 t-ACS stimulations over a period of 5 days between measurements. Results: The VSS patient showed a high occipital response to visual chirp stimulation pre-t-ACS stimulation and a lower occipital response to visual chirp stimulation post-t-ACS stimulation across all frequencies. Conclusion: This study shows that visual chirps could serve as a potential biomarker for VSS and that t-ACS stimulation over an extended period of time might be able to lower the photic-drive response, which could represent a novel treatment approach for VSS

Das Modell von Burns und Scapens am Beispiel der IT-Auslagerung bei einem öffentlichen Unternehmen

Der kontinuierliche Wandel in Unternehmen führt auch zu Anpassungen im Controlling. Dies betrifft bei IT-Outsourcing Projekten das IT-Controlling. Bisher findet sich noch keine eindeutige Antwort darauf, ob und warum ein solcher Wandel im IT-Controlling gelingt bzw. nicht gelingt. Auf Basis des Modells von Burns/Scapens [1], das einen strukturationstheoretischen Ansatz zur Interpretation von Veränderungen im Controlling ermöglicht, wird der Fall der IT-Auslagerung bei einem öffentlichen Unternehmen untersucht. Die Daten des Praxisunternehmens stammen von einem deutschen Verkehrsflughafen und werden anhand einer interpretativen Fallstudie ausgewertet. Dabei zeigt sich, dass sich das Burns/Scapens Modell für die Interpretation von Veränderungen im IT-Controlling bei öffentlichen Unternehmen eignet und dazu dienen kann, Erfolgsfaktoren im Veränderungsprozess zu identifizieren

Pseudo-subarachnoid haemorrhage due to chronic hypoxaemia: case report and review of the literature

Background: The specificity of computed tomography (CT) for subarachnoid haemorrhage (SAH) is very high. However, physicians should be aware of rare false positive findings, also referred to as "pseudo-SAH". We present an unusual case in which such a finding was caused by chronic hypoxaemia. Case presentation: A 37-year-old male patient presented with headaches. His CT-scan showed multiple confluent subarachnoid hyperattenuations, which mimicked SAH. However, the headache was chronic and had no features typical for SAH. The patient suffered from severe chronic hypoxaemia due to congenital heart failure. On CT-angiography diffuse intracranial vessel proliferation was found and laboratory results revealed a highly raised level of haematocrit, which had both probably developed as compensatory mechanisms. A combination of these findings explained the subarachnoid hyperdensities. Magnetic resonance imaging (MRI) showed no signs of SAH and visualized hypoxaemia in cerebral veins. A diagnosis of pseudo-SAH was made. The patient's symptoms were likely due to a secondary headache attributed to hypoxia and/or hypercapnia. Therapy was symptomatic. Conclusions: Severe chronic hypoxaemia should be recognised as a rare cause of pseudo-SAH. Clinical evaluation and MRI help differentiate SAH from pseudo-SAH

Efficacy and safety outcomes for acute ischemic stroke patients treated with intravenous infusion of tirofiban after emergent carotid artery stenting

Introduction Emergent stenting of the extracranial internal carotid artery (ICA) in stroke patients requires antiplatelet therapy to prevent in-stent thrombosis with a higher risk of intracranial haemorrhage. Aim of the Study Assess the efficacy and safety of emergent carotid stenting with intravenous tirofiban in acute ischemic stroke patients. Methods Primary endpoint: symptomatic hemorrhage. Secondary endpoints: 90-day functional outcome and mortality. Results Of the 62 patients, 21 (34%) received tirofiban as a single antiplatelet, and 41 (66%) received combined therapy. Premedication with anticoagulants and antiplatelets was significantly more frequent in the tirofiban-only group. The rate of symptomatic haemorrhage was significantly lower in the tirofiban-only group than in the combined group (4.8% vs. 27%, p = 0.046). The patients with tirofiban alone had a significantly better functional outcome at day 90 than the combined group (52% vs. 24%, p = 0.028). Mortality was equal (24%) in both groups. Pre-interventional NIHSS score (p = 0.003), significant blood pressure fluctuations (p = 0.012), tandem occlusion (p = 0.023), and thrombolysis (p = 0.044) showed relevant influence on the rate of symptomatic hemorrhage in the entire patient cohort. Conclusions A single antiplatelet therapy with tirofiban regardless of the premedication may improve the functional outcome in patients with stroke due to acute extracranial carotid lesion and emergent carotid stenting with lower rates of serious intracranial haemorrhage. For patients with high pre-interventional NIHSS score, tandem occlusion and after pre-interventional thrombolysis, caution is advised. Additionally, strict blood pressure monitoring should be conducted during the first 72 h after intervention

Presenilin-1 affects trafficking and processing of βAPP and is targeted in a complex with nicastrin to the plasma membrane

Amyloid β-peptide (Aβ) is generated by the consecutive cleavages of β- and γ-secretase. The intramembraneous γ-secretase cleavage critically depends on the activity of presenilins (PS1 and PS2). Although there is evidence that PSs are aspartyl proteases with γ-secretase activity, it remains controversial whether their subcellular localization overlaps with the cellular sites of Aβ production. We now demonstrate that biologically active GFP-tagged PS1 as well as endogenous PS1 are targeted to the plasma membrane (PM) of living cells. On the way to the PM, PS1 binds to nicastrin (Nct), an essential component of the γ-secretase complex. This complex is targeted through the secretory pathway where PS1-bound Nct becomes endoglycosidase H resistant. Moreover, surface-biotinylated Nct can be coimmunoprecipitated with PS1 antibodies, demonstrating that this complex is located to cellular sites with γ-secretase activity. Inactivating PS1 or PS2 function by mutagenesis of one of the critical aspartate residues or by γ-secretase inhibitors results in delayed reinternalization of the β-amyloid precursor protein and its accumulation at the cell surface. Our data suggest that PS is targeted as a biologically active complex with Nct through the secretory pathway to the cell surface and suggest a dual function of PS in γ-secretase processing and in trafficking