Brain Death Diagnosis in Primary Posterior Fossa Lesions.

Background: New controversies have raised on brain death (BD) diagnosis when lesions are localized in the posterior fossa. Objective: The aim of this study was to discuss the particularities of BD diagnosis in patients with posterior fossa lesions. Materials and Methods: The author made a systematic review of literature on this topic. Results and Conclusions: A supratentorial brain lesion usually produces a rostrocaudal transtentorial brain herniation, resulting in forebrain and brainstem loss of function. In secondary brain lesions (i.e., cerebral hypoxia), the brainstem is also affected like the forebrain. Nevertheless, some cases complaining posterior fossa lesions (i.e., basilar artery thrombotic infarcts, or hemorrhages of the brainstem and/or cerebellum) may retain intracranial blood flow and EEG activity. In this article, I discuss that if a posterior fossa lesion does not produce an enormous increment of intracranial pressure, a complete intracranial circulatory arrest does not occur, explaining the preservation of EEG activity, evoked potentials, and autonomic function. I also addressed Jahi McMath, who was declared braindead, but ancillary tests, performed 9 months after initial brain insult, showed conservation of intracranial structures, EEG activity, and autonomic reactivity to "Mother Talks" stimulus, rejecting the diagnosis of BD. Jahi McMath's MRI study demonstrated a huge lesion in the pons. Some authors have argued that in patients with primary brainstem lesions it might be possible to find in some cases partial recovery of consciousness, even fulfilling clinical BD criteria. This was the case in Jahi McMath.

Neurovascular and perfusion imaging findings in coronavirus disease 2019: Case report and literature review.

Central nervous system involvement in severe acute respiratory syndrome caused by coronavirus disease 2019 (COVID-19) has increasingly been recognised in the literature, and possible mechanisms of neuroinvasion, neurotropism and neurovirulence have been described. Neurological signs have been described in 84% of COVID-19 intensive care unit patients, and haemostatic abnormalities in such patients may play an important role, with a broad spectrum of neuroimaging findings. This report describes the magnetic resonance imaging neurovascular findings in an acutely ill patient with COVID-19, including perfusion abnormalities depicted in the arterial spin labelling technique.

Real-Time Non-invasive Assessment of Cerebral Hemodynamics With Diffuse Optical Spectroscopies in a Neuro Intensive Care Unit: An Observational Case Study.

Prevention of secondary damage is an important goal in the treatment of severe neurological conditions, such as major head trauma or stroke. However, there is currently a lack of non-invasive methods for monitoring cerebral physiology. Diffuse optical methods have been proposed as an inexpensive, non-invasive bedside monitor capable of providing neurophysiology information in neurocritical patients. However, the reliability of the technique to provide accurate longitudinal measurement during the clinical evolution of a patient remains largely unaddressed. Here, we report on the translation of a hybrid diffuse optical system combining frequency domain diffuse optical spectroscopy (FD-DOS) and diffuse correlation spectroscopy (DCS) for real-time monitoring of cerebral physiology in a neuro intensive care unit (neuro-ICU). More specifically, we present a case study of a patient admitted with a high-grade aneurysmal subarachnoid hemorrhage, who was monitored throughout hospitalization. We show that the neurophysiological parameters measured by diffuse optics at the bedside are consistent with the clinical evolution of the patient at all the different stages following its brain lesion. These data provide support for clinical translation of DOS/DCS as a useful biomarker of neurophysiology in the neuro-ICU, particularly in locations where other clinical resources are limited.

Comportamiento fractal espacial en la expansión de la distribución del flujo sanguíneo cerebral en Alzheimer / Spatial fractal behavior in the lengthening of cerebral bloodstream distribution in Alzheimer disease

El Alzheimer es una enfermedad neurodegenerativa que afecta a millones de personas alrededor del mundo. Las causas de esta aún son desconocidas. La geometría fractal es una teoría matemática que permite medir objetivamente la irregularidad de los objetos o procesos naturales; las estructuras y los comportamientos fisiológicos del cuerpo humano se pueden caracterizar matemáticamente a través de la dimensión fractal, la cual mide el grado de irregularidad o complejidad del fractal. La distribución del flujo sanguíneo cerebral en Alzheimer es notablemente irregular, por ello la dimensión fractal es una medida objetiva, la cual suponemos, cuantifica esta distribución. El coeficiente de expansión fractal se define para aquellos objetos dinámicos que poseen dimensión fractal y estima la expansión del fractal sobre su espacio circundante. Este coeficiente se asocia con el grado de conectividad que pueda poseer el fractal para expandirse. En el presente trabajo se determinaron los coeficientes de expansión fractal para la distribución del flujo sanguíneo cerebral en 21 pacientes con Alzheimer y en 11 sujetos normales en las zonas cerebrales posterior y anterior (tomados de la literatura). Los valores de los coeficientes resultaron ser mayores en Alzheimer respecto a los normales en las dos zonas, valores comparados respecto al espacio circundante en que sucede la expansión. Esto último sugiere el comportamiento de las conexiones neuronales en las zonas evaluadas.

Alzheimer disease is a neurodegenerative process affecting millions of persons at world scale. Even nowadays its causes are unknown. The fractal geometry is a mathematical theory allows to measure objectively the irregularity of objects or the natural processes; structures and physiologic behaviors of human body may be in a mathematical way be characterized through the fractal dimension, which to measure the irregularity or complexity degree of fractal. Distribution of cerebral blood flow in Alzheimer's disease is very irregular, thus the fractal dimension is an objective measure, which supposedly to quantify this distribution. The fractal expansion coefficient is defined for those dynamic objects having fractal dimension and estimates the fractal expansion on its surrounding space. This coefficient is associated with the connection that may to has the fractal for its expansion. The objective of present paperwas to determine the fractal expansion coefficients for the cerebral blood flow distribution in 21 patients presenting with Alzheimer's disease and in 11 normal subjects in the posterior and anterior cerebral zones, compared values regarding the surrounding space where expansion occur. This latter suggest the behavior of neuronal connections in assessed zones.