Poor Correlation Between Perihematomal MRI Hyperintensity and Brain Swelling After Intracerebral Hemorrhage

The perihematomal hyperintensity is commonly interpreted to represent cerebral edema following ICH, but the accuracy of this interpretation is unknown. We therefore investigated the relationship between changes in PHH and changes in hemispheric brain volume as a measure of edema during the first week after ICH

Autoregulation after ischaemic stroke

Absent outcome data from randomized clinical trials, management of hypertension in acute ischaemic stroke remains controversial. Data from human participants have failed to resolve the question whether cerebral blood flow (CBF) in the peri-infarct region will decrease due to impaired autoregulation when systemic mean arterial pressure (MAP) is rapidly reduced

Cerebellum as the Normal Reference for the Detection of Increased Cerebral Oxygen Extraction

Hemispheric ratios of oxygen extraction fraction (OEF), a proven methodology for the detection of severe hemodynamic impairment and stroke risk, are not sensitive for detecting bilateral hemispheric increases in OEF. The aim of this study was to investigate the use of cerebellum as the reference normal. We analyzed positron emission tomographic (PET) measurements of count-based OEF and clinical data from 57 patients with unilateral atherosclerotic carotid occlusion and 13 controls enrolled in a prospective study of stroke risk. The ipsilateral, contralateral, and total cerebellum were each evaluated as possible reference regions, and the ratios of the middle cerebral artery (MCA) hemispheric OEF counts against those in each reference region were determined. A statistically significant correlation (P<0.0001) was observed with all three MCA-to-cerebellar ratios when compared with the gold standard of ipsilateral-to-contralateral MCA hemispheric ratio. Kaplan–Meier analyses showed all MCA-to-cerebellar ratios to be predictive of stroke. By using the total cerebellum method, 7 strokes were found to have occurred in 20 patients with increased OEF (P=0.0007), compared with 7 strokes out of 16 patients with elevated OEF using the ipsilateral or contralateral cerebellum methods (P<0.0001). These methods may be useful for categorizing the hemodynamic status of patients with bilateral cerebral occlusive diseases, including atherosclerosis and moyamoya, to determine the association with the risk of subsequent stroke

Attenuation of Counterregulatory Responses to Recurrent Hypoglycemia by Active Thalamic Inhibition: A Mechanism for Hypoglycemia-Associated Autonomic Failure

Hypoglycemia, the limiting factor in the glycemic management of diabetes, is the result of the interplay of therapeutic insulin excess and compromised glycemic defenses. The key feature of the latter is an attenuated sympathoadrenal response to hypoglycemia that typically follows an episode of recent antecedent iatrogenic hypoglycemia, a phenomenon termed hypoglycemia-associated autonomic failure (HAAF) in diabetes. We investigated the role of cerebral mechanisms in HAAF by measuring regional brain activation during recurrent hypoglycemia with attenuated counterregulatory responses and comparing it to initial hypoglycemia in healthy individuals

Cerebral Mitochondrial Metabolism in Early Parkinson's Disease

Abnormal cerebral energy metabolism due to dysfunction of mitochondrial electron transport has been implicated in the pathogenesis of Parkinson Disease (PD). However, in vivo data of mitochondrial dysfunction has been inconsistent. We directly investigated mitochondrial oxidative metabolism in vivo in 12 patients with early, never-medicated PD and 12 age-matched normal controls by combined measurements of the cerebral metabolic rate of oxygen (CMRO2) and the cerebral metabolic rate of glucose (CMRglc) with positron emission tomography. The primary analysis showed a statistically significant 24% increase in bihemispheric CMRO2 and no change in CMRO2/CMRglc. These findings are inconsistent with a defect in mitochondrial oxidative phosphorylation due to reduced activity of the mitochondrial ETS. Since PD symptoms were already manifest, deficient energy production due to a reduced activity of the mitochondrial ETS cannot be a primary mechanism of neuronal death in early PD. Alternatively, this general increase in CMRO2 could be due, not to increased metabolic demand, but to an uncoupling of ATP production from oxidation in the terminal stage of oxidative phosphorylation. Whether this is the case in early PD and whether or not it is important in the pathogenesis of PD will require further study

Thalamic Activation During Slightly Subphysiological Glycemia in Humans

OBJECTIVEThe central nervous system mechanisms of defenses against falling plasma glucose concentrations, and how they go awry and result in iatrogenic hypoglycemia in diabetes, are not known. Hypoglycemic plasma glucose concentrations of 55 mg/dL (3.0 mmol/L) cause symptoms, activate glucose counterregulatory systems, and increase synaptic activity in a network of brain regions including the dorsal midline thalamus in humans. We tested the hypothesis that slightly subphysiological plasma glucose concentrations of 65 mg/dL (3.6 mmol/L), which do not cause symptoms but do activate glucose counterregulatory systems, also activate brain synaptic activities.RESEARCH DESIGN AND METHODSWe measured relative regional cerebral blood flow (rCBF), an index of synaptic activity, in predefined brain regions with [15O]water positron emission tomography, symptoms, and plasma epinephrine and glucagon concentrations during a 2-h euglycemic (90 mg/dL) to hypoglycemic (55 mg/dL) clamp (n = 20) or a 2-h euglycemic to slight subphysiological (65 mg/dL) clamp (n = 9) in healthy humans.RESULTSClamped plasma glucose concentrations of 65 mg/dL did not cause hypoglycemic symptoms, but raised plasma epinephrine and glucagon concentrations and increased rCBF (P = 0.007) only in the dorsal midline thalamus.CONCLUSIONSSlightly subphysiological plasma glucose concentrations increase synaptic activity in the dorsal midline thalamus in humans