Shiga University of Medical Science

Transient neurological events (TNEs) commonly occur following direct revascularization for moyamoya disease (MMD). Although changes in the cerebral blood flow (CBF) may be linked to TNEs, the underlying mechanism remains unclear. Herein, we investigated the relationship between TNEs and EEG to elucidate the underlying mechanisms and pursue the clinical utility of EEG as a TNE biomarker.

Twenty-six hemispheres in 22 patients with MMD aged ≥15 years who underwent revascularization were analyzed. Scalp electroencephalography (EEG) and single-photon emission computed tomography (SPECT) performed within 7 days postoperatively were analyzed using the clinical information.

Sixteen of 26 hemispheres developed TNEs, of which 12 demonstrated an increased frequency of delta waves (> 0.5, < 4 Hz) on postoperative EEG (P = 0.0002), which was located in an area consistent with each symptom. Infraslow activity (ISA, < 0.33 Hz) was observed in all 4 hemispheres on the day of TNE development. More frequent occurrence of delta wave on postoperative EEG preceded onset in 2 hemispheres. CBF did not differ between the patients with and without TNEs.

ISA may be associated with the pathophysiology of TNEs. Delta waves can be used as clinical biomarkers to predict TNEs.

Slow waves on scalp EEG have the potential can predict and elucidate TNEs. Non-standard Abbreviations and Acronyms. TNEs, transient neurological events; MMD, Moyamoya disease; ISA, infraslow activity; SD, spreading depolarization; TC, time constant.

Evaluation of hemodynamics is crucial to predict growth and rupture of cerebral aneurysms. Variational data assimilation (DA) is a powerful tool to characterize patient-specific intra-aneurysmal flows. The DA inversely estimates a boundary condition in fluid equations using personalized flow data; however, its high computational cost in optimization problems makes its use impractical.

This study proposes a practical strategy for the DA to evaluate patient-specific intra-aneurysmal flows. To estimate personalized flows, a variational DA was combined with computational fluid dynamics (CFD) and four-dimensional flow magnetic resonance imaging (4D flow MRI) for intra-aneurysmal velocity data, and an inverse problem was solved to estimate the spatiotemporal velocity profile at a boundary of the aneurysm neck. To circumvent an ill-posed inverse problem, model order reduction based on a Fourier series expansion was used to describe temporal changes in state variables.

In numerical validation using synthetic data from the CFD, the present DA achieved excellent agreement with the CFD as ground truth, with velocity mismatch within the 4%-7% range. In flow estimations for three patient-specific datasets, the proposed DA shows the velocity mismatch within the 35%-63% range, which is less than half that of the CFD using main vessel branches, and would mitigate unphysical velocity distributions in the 4D flow MRI.

By focusing only on the intra-aneurysmal region, the present strategy based on the DA provides an attractive way to evaluate personalized flows in aneurysms with greater reliability than conventional CFD and better efficiency than existing DA approaches.

A subset of asthmatics suffers from frequent exacerbations. Various features of airway remodeling and the resultant elastic property of airway walls may play pathophysiological roles in these exacerbations. The aim of the study was to examine the collapsibility of airways and sputum biomarkers associated with airway remodeling with different frequencies of exacerbations.

We studied 29 moderate-to-severe asthmatics classified by the number of exacerbations in the previous year as, ≤1: stable, n = 18; ≥2: difficult, n = 11, and 11 healthy controls (HC). The absolute wall area (Awa) and luminal area (Ai) of a segmental bronchus were measured by computed tomography at full inspiration (FI) and full expiration (FE). We examined the %change of Ai (a measure of airway collapsibility) and Awa (a possible measure of vascular/water contents in the airway wall) from FI to FE. Sputum biomarkers associated with fibrosis [TGF-β₁ and matrix metalloproteinase (MMP)-9/tissue inhibitors of metalloproteinase (TIMP)-1 molar ratio] and those associated with angiogenesis/edema [vascular endothelial growth factor (VEGF) and vascular permeability index (sputum/serum ratio of albumin levels)] were examined.

Airway collapsibility was greater in difficult asthmatics than in stable asthmatics and HC. Sputum TGF-β₁ levels were higher and MMP-9/TIMP-1 molar ratios were lower in stable asthmatics than in HC. Sputum VEGF levels and vascular permeability index were higher in difficult asthmatics than in HC.

Collapsibility of thickened airway walls may determine their susceptibility to exacerbations. This may depend on the balance between fibrosis and angiogenesis/edema in the airways.