Delayed Endovascular Thrombectomy for Ischemic Stroke in a Young Woman with No Known Risk Factors: A Case Report.

BACKGROUND National guidelines and consensus statements suggest a 24-hour window for endovascular recanalization in patients presenting with acute ischemic stroke due to large-vessel occlusion. However, the safety and efficacy of extending the window for intervention remains to be definitively established. CASE REPORT A healthy 26-year-old woman presented with headache, left-sided hemiplegia, and rightward gaze palsy 2 days after a minor trauma. Time last known well was approximately 50 hours prior to presentation. Computed tomography angiography revealed dissection of the distal right internal carotid artery and occlusion of the M1 segment of the right middle cerebral artery. Magnetic resonance imaging showed a small area of acute infarct in the right basal ganglia and right insular cortex, but suggested a large ischemic penumbra; this was confirmed with cerebral perfusion analysis. In light of the patient's young age and potential for penumbral salvage, mechanical thrombectomy of an M1 thrombus and stenting of an internal carotid artery dissection were performed nearly 60 hours after the onset of symptoms. The patient demonstrated marked clinical improvement over the following days and was discharged home in excellent condition one week after presentation. Based on our clinical experience and other emerging data, we propose that extension of the 24-hour window for endovascular intervention may improve functional outcomes among select individuals. CONCLUSIONS A 24-hour window for endovascular thrombectomy is appropriate for many patients presenting with acute ischemic stroke. However, in select individuals, extension of the window to 48 hours or beyond may improve functional outcomes.

Quantifying anatomical shape variations in neurological disorders.

We develop a multivariate analysis of brain anatomy to identify the relevant shape deformation patterns and quantify the shape changes that explain corresponding variations in clinical neuropsychological measures. We use kernel Partial Least Squares (PLS) and formulate a regression model in the tangent space of the manifold of diffeomorphisms characterized by deformation momenta. The scalar deformation momenta completely encode the diffeomorphic changes in anatomical shape. In this model, the clinical measures are the response variables, while the anatomical variability is treated as the independent variable. To better understand the "shape-clinical response" relationship, we also control for demographic confounders, such as age, gender, and years of education in our regression model. We evaluate the proposed methodology on the Alzheimer's Disease Neuroimaging Initiative (ADNI) database using baseline structural MR imaging data and neuropsychological evaluation test scores. We demonstrate the ability of our model to quantify the anatomical deformations in units of clinical response. Our results also demonstrate that the proposed method is generic and generates reliable shape deformations both in terms of the extracted patterns and the amount of shape changes. We found that while the hippocampus and amygdala emerge as mainly responsible for changes in test scores for global measures of dementia and memory function, they are not a determinant factor for executive function. Another critical finding was the appearance of thalamus and putamen as most important regions that relate to executive function. These resulting anatomical regions were consistent with very high confidence irrespective of the size of the population used in the study. This data-driven global analysis of brain anatomy was able to reach similar conclusions as other studies in Alzheimer's disease based on predefined ROIs, together with the identification of other new patterns of deformation. The proposed methodology thus holds promise for discovering new patterns of shape changes in the human brain that could add to our understanding of disease progression in neurological disorders.

Fractal dimension analysis of the cortical ribbon in mild Alzheimer's disease.

Fractal analysis methods are used to quantify the complexity of the human cerebral cortex. Many recent studies have focused on high resolution three-dimensional reconstructions of either the outer (pial) surface of the brain or the junction between the gray and white matter, but ignore the structure between these surfaces. This study uses a new method to incorporate the entire cortical thickness. Data were obtained from the Alzheimer's Disease (AD) Neuroimaging Initiative database (Control N=35, Mild AD N=35). Image segmentation was performed using a semi-automated analysis program. The fractal dimension of three cortical models (the pial surface, gray/white surface and entire cortical ribbon) were calculated using a custom cube-counting triangle-intersection algorithm. The fractal dimension of the cortical ribbon showed highly significant differences between control and AD subjects (p<0.001). The inner surface analysis also found smaller but significant differences (p<0.05). The pial surface dimensionality was not significantly different between the two groups. All three models had a significant positive correlation with the cortical gyrification index (r>0.55, p<0.001). Only the cortical ribbon had a significant correlation with cortical thickness (r=0.832, p<0.001) and the Alzheimer's Disease Assessment Scale cognitive battery (r=-0.513, p=0.002). The cortical ribbon dimensionality showed a larger effect size (d=1.12) in separating control and mild AD subjects than cortical thickness (d=1.01) or gyrification index (d=0.84). The methodological change shown in this paper may allow for further clinical application of cortical fractal dimension as a biomarker for structural changes that accrue with neurodegenerative diseases.

Regionally selective atrophy after traumatic axonal injury.

OBJECTIVES: To determine the spatial distribution of cortical and subcortical volume loss in patients with diffuse traumatic axonal injury and to assess the relationship between regional atrophy and functional outcome. DESIGN: Prospective imaging study. Longitudinal changes in global and regional brain volumes were assessed using high-resolution magnetic resonance imaging-based morphometric analysis. SETTING: Inpatient traumatic brain injury unit. PATIENTS OR OTHER PARTICIPANTS: Twenty-five patients with diffuse traumatic axonal injury and 22 age- and sex-matched controls. MAIN OUTCOME MEASURE: Changes in global and regional brain volumes between initial and follow-up magnetic resonance imaging were used to assess the spatial distribution of posttraumatic volume loss. The Glasgow Outcome Scale-Extended score was the primary measure of functional outcome. RESULTS: Patients underwent substantial global atrophy with mean whole-brain parenchymal volume loss of 4.5% (95% confidence interval, 2.7%-6.3%). Decreases in volume (at a false discovery rate of 0.05) were seen in several brain regions including the amygdala, hippocampus, thalamus, corpus callosum, putamen, precuneus, postcentral gyrus, paracentral lobule, and parietal and frontal cortices, while other regions such as the caudate and inferior temporal cortex were relatively resistant to atrophy. Loss of whole-brain parenchymal volume was predictive of long-term disability, as was atrophy of particular brain regions including the inferior parietal cortex, pars orbitalis, pericalcarine cortex, and supramarginal gyrus. CONCLUSION: Traumatic axonal injury leads to substantial posttraumatic atrophy that is regionally selective rather than diffuse, and volume loss in certain regions may have prognostic value for functional recovery.

Impact of positive pressure ventilation on thoracostomy tube removal.

BACKGROUND: Little data exist examining the impact of positive pressure ventilation on safe thoracostomy tube removal. We sought to evaluate the impact of positive-pressure ventilation (PPV) on recurrent pneumothoraces (PTX) after removal of thoracostomy tubes (TT). METHODS: A retrospective cohort analysis was performed evaluating all trauma patients requiring TT drainage of PTX or hemothoraces during a 3-year period. All chest radiographs before and after TT removal were reviewed to identify PTX recurrence. The principle outcome was recurrent PTX after TT removal. The 95% confidence intervals were calculated to assess for significance. RESULTS: We studied 234 TT removals in 190 patients. One hundred thirty-six (58%) TTs were removed under PPV. PTX recurred in 15 (11%) and 6 (4%) required reinsertion. In 10 patients (7.4%), there was a radiographically stable small PTX before and after removal not requiring TT reinsertion. In comparison, 98 (42%) TTs were removed under spontaneous ventilation. PTX recurred in 16 (16%) and 3 (3%) required reinsertion. There were 25 (25.5%) stable small PTXs before and after removal. The overall recurrence rate difference was -5.3% (confidence interval: -14.8 to 3.5) and reinsertion rate difference was 1.35% (confidence interval: -4.7 to 6.6). CONCLUSIONS: The rate of recurrent PTX or TT replacement after removal is not associated with PPV status. The slightly lower recurrence rate on PPV combined with the smaller proportion of patients with stable small PTX before removal may reflect more careful clinician selection of ideal patients or technique of TT removal among patients on PPV. Prospective data are needed to clarify these associations.

Characterization of Atrophic Changes in the Cerebral Cortex Using Fractal Dimensional Analysis.

The purpose of this project is to apply a modified fractal analysis technique to high-resolution T1 weighted magnetic resonance images in order to quantify the alterations in the shape of the cerebral cortex that occur in patients with Alzheimer's disease. Images were selected from the Alzheimer's Disease Neuroimaging Initiative database (Control N=15, Mild-Moderate AD N=15). The images were segmented using a semi-automated analysis program. Four coronal and three axial profiles of the cerebral cortical ribbon were created. The fractal dimensions (D(f)) of the cortical ribbons were then computed using a box-counting algorithm. The mean D(f) of the cortical ribbons from AD patients were lower than age-matched controls on six of seven profiles. The fractal measure has regional variability which reflects local differences in brain structure. Fractal dimension is complementary to volumetric measures and may assist in identifying disease state or disease progression.

Hyperscanning: simultaneous fMRI during linked social interactions.

"Plain question and plain answer make the shortest road out of most perplexities." Mark Twain-Life on the Mississippi. A new methodology for the measurement of the neural substrates of human social interaction is described. This technology, termed "Hyperscan," embodies both the hardware and the software necessary to link magnetic resonance scanners through the internet. Hyperscanning allows for the performance of human behavioral experiments in which participants can interact with each other while functional MRI is acquired in synchrony with the behavioral interactions. Data are presented from a simple game of deception between pairs of subjects. Because people may interact both asymmetrically and asynchronously, both the design and the analysis must accommodate this added complexity. Several potential approaches are described.