Origin of pretruncal nonaneurysmal subarachnoid hemorrhage: ruptured vein, perforating artery, or intramural hematoma?

Pretruncal (perimesencephalic) nonaneurysmal subarachnoid hemorrhage (SAH) is a benign variant of SAH. Although angiography fails to show a source of the hemorrhage, mild basilar artery narrowing may be observed. The cause of pretruncal nonaneurysmal SAH has not been established. Recent imaging studies have demonstrated that the center of this type of SAH is not around the mesencephalon but is in the prepontine or interpeduncular cistern with the hemorrhage closely associated with the basilar artery. We review the possible sources of hemorrhage in these cisterns and hypothesize that pretruncal nonaneurysmal SAH is caused by a primary intramural hematoma of the basilar artery. Such an intramural hematoma would explain bleeding under low pressure, the location of the hemorrhage anterior to the brainstem, and the typical findings of hemorrhage adjacent to the basilar artery lumen on magnetic resonance imaging and mild basilar artery narrowing on angiography. Although an intramural hematoma of the basilar artery would be easily identified at surgical exploration, such surgeries have never included the extensive base-of-the-skull approaches that are necessary to visualize the artery in the prepontine cistern.     

Reversible unilateral brain edema presenting with major neurologic deficit after valve repair

Brain edema after cardiac surgery is unusual and often asymptomatic. We encountered a 34-year-old man who had postoperative left flaccid hemiplegia and anosognosia after undergoing composite root replacement and closure of a patent foramen ovale. Computed tomographic and magnetic resonance imaging (MRI) scans showed profound white matter changes indicative of brain edema predominantly in the right hemisphere. His symptoms resolved spontaneously within 3 days with resolution of MRI abnormality. No evidence of cerebral infarction was documented on diffusion-weighted imaging and apparent diffusion coefficient mapping, or on the follow-up MRI obtained 25 days after presentation. The cause for the unilateral brain edema is unknown, but the patient's clinical course and imaging are supportive for a variant of a hyperperfusion syndrome or reversible encephalopathy. The outcome was excellent.     

The Physiology of the Apnea Test for Brain Death Determination in ECMO: Arguments for Blending Carbon Dioxide

Neurocritical Care -     

Lactulose: A Simple Sugar in a Complex Encephalopathy

Hepatic encephalopathy is a common encephalopathy and one of the very few that are treatable. Lactulose has remained a standard pharmaceutical intervention and is listed as one of the World Health Organization’s Essential Medicines. The discovery of lactulose, the acid dialysis proof of concept, and the role of Bircher are not well known. This historical vignette reviews the gradual understanding of the complex liver–brain connection, the effective treatment of hepatic stupor with lactulose, and the immediate relevance of lactulose to the practice of consultative neurocritical care.     

Metabolic Encephalopathy: Behind the Name

Metabolic encephalopathy may be the most common diagnosis in consultative acute neurology. The origin of this term is not generally known but can be traced back. The term replaced more commonly used designations such as organic or functional. The term metabolic encephalopathy was originally linked to organ dysfunction but subsequently became more imprecise. When it expanded to include a large number of diseases, it evolved to “metabolic neuronal dysfunction” and soon could not be distinguished from “quiet delirium” and other designations. This vignette summarizes why the terminology has confused more than clarified but also why it will likely stay in the neurologist’s vernacular.     

The FOUR Score Predicts Outcome in Patients after Cardiac Arrest

Background  

Prognostication for survivors of cardiac arrest is a frequent challenge to neurologists. Our aim was to determine whether the FOUR (Full Outline of UnResponsiveness) score is an accurate predictor of outcome in patients after cardiac arrest and to compare its performance to the Glasgow Coma Scale (GCS).