Quantification of stroke lesion volume using epidural EEG in a cerebral ischaemic rat model

Development of an equation to predict delta bilirubin levels using machine learning

OBJECTIVE

Delta bilirubin (albumin-covalently bound bilirubin) may provide important clinical utility in identifying impaired hepatic excretion of conjugated bilirubin, but it cannot be measured in real-time for diagnostic purposes in clinical laboratories.

METHODS

A total of 210 samples were collected, and their delta bilirubin levels were measured four times using high-performance liquid chromatography. Data collected included age, sex, diagnosis code, delta bilirubin, total bilirubin, direct bilirubin, total protein, albumin, globulin, aspartate aminotransferase, alanine transaminase, alkaline phosphatase, gamma-glutamyl transferase, lactate dehydrogenase, hemoglobin, serum hemolysis value, hemolysis index, icterus value (Iv), icterus index (Ii), lipemia value (Lv), and lipemia index. To conduct feature selection and identify the optimal combination of variables, linear regression machine learning was performed 1,000 times.

RESULTS

The selected variables were total bilirubin, direct bilirubin, total protein, albumin, hemoglobin, Iv, Ii, and Lv. The best predictive performance for high delta bilirubin concentrations was achieved with the combination of albumin-direct bilirubin-hemoglobin-Iv-Lv. The final equation composed of these variables was as follows: delta bilirubin = 0.35 × Iv + 0.05 × Lv - 0.23 × direct bilirubin - 0.05 × hemoglobin - 0.04 × albumin + 0.10.

CONCLUSION

The equation established in this study is practical and can be easily applied in real-time in clinical laboratories.

An Alternative Photothrombotic Model of Transient Ischemic Attack

Animal models mimicking human transient ischemic attack (TIA) and cerebral microinfarcts are essential tools for studying their pathogenetic mechanisms and finding methods of their treatment. Despite its advantages, the model of single arteriole photothrombosis requires complex experimental equipment and highly invasive surgery, which may affect the results of further studies. Hence, to achieve high translational potential, we focused on developing a TIA model based on photothrombosis of arterioles to combine good reproducibility and low invasiveness. For the first time, noninvasive laser speckle contrast imaging (LSCI) was used to monitor blood flow in cerebral arterioles and reperfusion was achieved. We demonstrate that irradiation of mouse cerebral cortical arterioles using a 532-nm laser with a 1-mm-wide beam at 2.4 or 3.7 mW for 55 or 40 s, respectively, after 15 mg/kg intravenous Rose Bengal administration, induces similar ischemia-reperfusion lesions resulting in microinfarct formation. The model can be used to study the pathogenesis of spontaneously developing cerebral microinfarcts in neurodegeneration. Reducing the exposure times by 10 s while maintaining the same other parameters caused photothrombosis of the arteriole with reperfusion in less than 1 h. This mode of photodynamic exposure caused cellular and subcellular level ischemic changes in neurons and promoted the activation of astrocytes and microglia in the first day after irradiation, but not later, without the formation of microinfarcts. This mode of photodynamic exposure most accurately reproduced human TIA, characterized by the absence of microinfarcts.

Constructing a Transient Ischemia Attack Model Utilizing Flexible Spatial Targeting Photothrombosis with Real-Time Blood Flow Imaging Feedback

Transient ischemic attack (TIA) is an early warning sign of stroke and death, necessitating suitable animal models due to the associated clinical diagnostic challenges. In this study, we developed a TIA model using flexible spatially targeted photothrombosis combined with real-time blood flow imaging feedback. By modulating the excitation light using wavefront technology, we precisely created a square light spot (50 × 250 µm), targeted at the distal middle cerebral artery (dMCA). The use of laser speckle contrast imaging (LSCI) provided real-time feedback on the ischemia, while the excitation light was ceased upon reaching complete occlusion. Our results demonstrated that the photothrombus formed in the dMCA and spontaneously recanalized within 10 min (416.8 ± 96.4 s), with no sensorimotor deficits or infarction 24 h post-TIA. During the acute phase, ischemic spreading depression occurred in the ipsilateral dorsal cortex, leading to more severe ischemia and collateral circulation establishment synchronized with the onset of dMCA narrowing. Post-reperfusion, the thrombi were primarily in the sensorimotor and visual cortex, disappearing within 24 h. The blood flow changes in the dMCA were more indicative of cortical ischemic conditions than diameter changes. Our method successfully establishes a photochemical TIA model based on the dMCA, allowing for the dynamic observation and control of thrombus formation and recanalization and enabling real-time monitoring of the impacts on cerebral blood flow during the acute phase of TIA.

Modeling transient ischemic attack via photothrombosis

The health significance of transient ischemic attacks (TIAs) is largely underestimated. Often, TIAs are not given significant importance, and in vain, because TIAs are a predictor of the development of serious cardiovascular diseases and even death. Because of this, and because of the difficulty in diagnosing the disease, TIAs and related microinfarcts are poorly investigated. Photothrombotic models of stroke and TIA allow reproducing the occlusion of small brain vessels, even single ones. When dosing the concentration of photosensitizer, intensity and irradiation time, it is possible to achieve occlusion of well-defined small vessels with high reproducibility, and with the help of modern methods of blood flow assessment it is possible to achieve spontaneous restoration of blood flow without vessel rupture. In this review, we discuss the features of microinfarcts and the contemporary experimental approaches used to model TIA and microinfarcts, with an emphasis on models using the principle of photothrombosis of brain vessels. We review modern techniques for in vivo detection of blood flow in small brain vessels, as well as biomarkers of microinfarcts.

Dexmedetomidine-mediated sleep phase modulation ameliorates motor and cognitive performance in a chronic blast-injured mouse model

Multiple studies have shown that blast injury is followed by sleep disruption linked to functional sequelae. It is well established that improving sleep ameliorates such functional deficits. However, little is known about longitudinal brain activity changes after blast injury. In addition, the effects of directly modulating the sleep/wake cycle on learning task performance after blast injury remain unclear. We hypothesized that modulation of the sleep phase cycle in our injured mice would improve post-injury task performance. Here, we have demonstrated that excessive sleep electroencephalographic (EEG) patterns are accompanied by prominent motor and cognitive impairment during acute stage after secondary blast injury (SBI) in a mouse model. Over time we observed a transition to more moderate and prolonged sleep/wake cycle disturbances, including changes in theta and alpha power. However, persistent disruptions of the non-rapid eye movement (NREM) spindle amplitude and intra-spindle frequency were associated with lasting motor and cognitive deficits. We, therefore, modulated the sleep phase of injured mice using subcutaneous (SC) dexmedetomidine (Dex), a common, clinically used sedative. Dex acutely improved intra-spindle frequency, theta and alpha power, and motor task execution in chronically injured mice. Moreover, dexmedetomidine ameliorated cognitive deficits a week after injection. Our results suggest that SC Dex might potentially improve impaired motor and cognitive behavior during daily tasks in patients that are chronically impaired by blast-induced injuries.

The focused quantitative EEG bio-marker in studying childhood atrophic encephalopathy

Although it is a normal involution process in advanced age, brain atrophy—also termed atrophic encephalopathy—can also occur prematurely in childhood as a consequential effect of brain tissues injury through trauma or central nervous system infection, though in both normal and premature occurrences this condition always presents with loss of volume relative to the skull. A common tool for the functional study of brain activities is an electroencephalogram, but analyses of this have reportedly identified mismatches between qualitative and quantitative forms, particularly in the use of Delta-alpha ratio (DAR) indices, meaning that the values may be case dependent. The current study thus examines the value of Focused Occipital Beta-Alpha Ratio (FOBAR) as a modified biomarker for evaluating brain functional changes resulting from brain atrophy. This cross-sectional design study involves 260 patients under 18 years of age. Specifically, 207 patients with brain atrophy are compared with 53 control subjects with CT scan-proven normal brain volume. All the children underwent digital electroencephalography with brain mapping. Results show that alpha posterior dominant rhythm was present in 88 atrophic children and 44 controls. Beta as posterior dominant rhythm was present in an overwhelming 91.5% of atrophic subjects, with 0.009 p-values. The focused occipital Beta-alpha ratio correlated significantly with brain volume loss presented in diagonal brain fraction. The FOBAR and DAR values of the QEEG showed no significant correlation. This work concludes that QEEG cerebral dysfunctional studies may be etiologically and case dependent from the nature of the brain injury. Also, the focused Beta-alpha ratio of the QEEG is a prospective and potential biomarker of consideration in studying childhood atrophic encephalopathy.