A higher prevalence of dementia in individuals with fewer years of education has suggested that education may protect against Alzheimer's disease (AD). We tested whether individuals with more years of education have a more advanced AD before it is clinically evident. As a measure of pathophysiological severity, we quantified regional cerebral blood flow (rCBF), by the 133Xenon inhalation technique; a specific pattern of flow reduction in the parietotemporal cortex corresponds to AD pathology. In 3 groups of patients with probable AD, matched for clinical measures of dementia severity but with varying levels of education, whole-cortex mean flows were comparable. However, the parietotemporal perfusion deficit was significantly greater in the group with the highest level of education, indicating that AD was more advanced in this group. We conclude that education or its covariates or both may provide a reserve that compensates for the neuropathological changes of AD and delays the onset of its clinical manifestations.

Cocaine cues lead to abnormally high cingulate and low frontal lobe activation in cocaine addicts. Addicts also show more general abnormalities in affect-related brain activation.

Patients with end-stage renal disease (ESRD) undergoing hemodialysis are known to suffer cognitive deficits and stroke of unknown etiology. It has been suspected that the treatment itself may contribute to the syndrome by unknown mechanisms, which we investigated in this study. Endstage renal disease patients on hemodialysis (n = 19) or peritoneal dialysis (PD, n = 5) were compared with 14 healthy controls. Subjects participated in magnetic resonance imaging (MRI) measurements of cerebral atrophy, cerebral blood flow (CBF) arterial spin labeled-MRI (ASL-MRI), quantitative Doppler blood flow through the internal carotid artery, and cerebral oxymetry. The Doppler and oxymetry procedures were also performed at the beginning and end of a single hemodialysis session. End-stage renal disease patients on hemodialysis showed significant cerebral atrophy, associated with longer hemodialysis duration and cognitive deficits, including focal bilateral lesions in the caudate nucleus and midbrain. Cerebral oxygenation was extremely low before dialysis (rSO 2 41613, compared with 7062 in controls, P < 0.02) and improved only slightly after dialysis. Carotid blood flow was also very low at the start of dialysis (115628 mL/sec, versus 193656 in controls, P < 0.005) but normalized at the end of the session (181 mL/sec). The PD patients showed intermediate values, between the hemodialysis and controls. Notably, duration of hemodialysis treatment predicted global gray-matter volume (r = À0.74), change of blood flow during dialysis (r = À0.65), and baseline rSO 2 (r = À0.65). The findings suggest that ESRD patients on hemodialysis suffer low CBF during the interdialytic cycle. Coupled with low cerebral oxygenation levels and atherosclerosis, this may contribute significantly to the etiology of the observed cerebral atrophy, cognitive deficits, and high stroke prevalence.

Emotional instability is a hallmark feature of borderline personality disorder (BPD), yet its biological underpinnings are poorly understood. We employed functional MRI to compare patterns of regional brain activation in BPD patients and healthy volunteers as they process positive and negative social emotional stimuli. fMRI images were acquired while 19 BPD patients and 17 healthy controls (HC) viewed emotion-inducing pictures from the IAPS set. Activation data were analyzed with SPM5 ANCOVA models to derive the effects of diagnosis and stimulus type. BPD patients demonstrated greater differences in activation than controls, when viewing negative pictures compared to rest, in the amygdala, fusiform gyrus, primary visual areas, superior temporal gyrus (STG), and premotor areas, while healthy controls showed greater differences than BPD’s in the insula, middle temporal gyrus and dorsolateral prefrontal cortex (BA46). When viewing positive pictures compared to rest, BPD patients showed greater differences in the STG, premotor cortex, and ventrolateral prefrontal cortex. These findings suggest that BPD patients show greater amygdala activity and heightened activity of visual processing regions than HC’s, when processing negative social emotional pictures compared to rest. They activate neural networks in emotion processing that are phylogenetically older and more reflexive than healthy controls.

We examined six patients with an abrupt change in behavior after infarction involving the inferior genu of the internal capsule. The acute syndrome featured fluctuating alertness, inattention, memory loss, apathy, abulia, and psychomotor retardation, suggesting frontal lobe dysfunction. Contralateral hemiparesis and dysarthria were generally mild, except when the infarct extended into the posterior limb. Neuropsychological testing in five patients with left-sided infarcts revealed severe verbal memory loss. Additional cognitive deficits consistent with dementia occurred in four patients. A right-sided infarct caused transient impairment in visuospatial memory. Functional brain imaging in three patients showed a focal reduction in hemispheric perfusion most prominent in the ipsilateral inferior and medial frontal cortex. We infer that the capsular genu infarct interrupted the inferior and anterior thalamic peduncles, resulting in functional deactivation of the ipsilateral frontal cortex. These observations suggest that one mechanism for cognitive deterioration from a lacunar infarct is thalamocortical disconnection of white-matter tracts, in some instances leading to "strategic-infarct dementia."

To investigate cerebral hemodynamics in sickle cell disease (SCD), we used the 133Xenon inhalation technique of quantifying cerebral blood flow (CBF) in 67 patients. Clinical examinations and cerebral magnetic resonance imaging also were performed in all patients. Compared with age-matched healthy controls, CBF was elevated by 68% in patients, and inversely related to hematocrit. An experimental index of cerebral blood volume, pr4, was also elevated in the patients in a similar manner. Cerebral blood volume was positively correlated to CBF in SCD patients but not in controls. History of stroke and current neurologic symptoms were associated with lower flow and higher cerebral blood volume. Transfusion therapy reduced the hyperemia, the reduction being greater than expected by hematocrit elevation alone. These findings document a vasodilatory hyperemia in SCD. This dilatation may be a risk factor for ischemic distal-field infarctions, as visualized by MRI, due to a limitation of cerebrovascular reserve capacity.

Elevation of blood flow velocity in the large cerebral vessels is known to be of substantial pathophysiologic and prognostic significance in sickle-cell disease (SCD). Its precise cause is not established, but the two obvious proximal mechanisms are obstructive vascular stenosis and hemodynamic dilatation. Here we revisit this distinction by analyzing cerebrovascular reserve capacity. Forty-two patients with SCD underwent measurements of global cerebral blood flow in grey matter by the 133 Xe inhalation method during normocapnia and hypercapnia to quantify cerebrovascular reactivity. Cerebral blood flow was significantly higher in SCD patients (120±31 ml/ 100 g/min) than in controls (76 ± 20 ml/100 g/min). Reactivity was significantly lower in SCD patients (1.06±1.92 versus 2.16±1.15%/mm Hg). Stepwise multiple regressions within the SCD sample determined that normocapnic cerebral blood flow was largely predicted by hematocrit (r = À0.59; P < 0.0001), whereas hypercapnic reactivity was only predicted by normocapnic flow across all subjects (r = À0.52; P < 0.0001). None of the controls, but 24% of the SCD patients showed 'steal' (negative reactivity, v 2 = 6.05; P < 0.02). This impairment of vasodilatory capacity, occurring at perfusion levels above 150 ml/100 g/min, may reflect intrinsic limitations of the human cerebrovascular system and can explain both the elevated blood flow velocities and the high risk of stroke observed in such patients.

The genetic cause of sickle cell disease has been known for decades, yet the reasons for its clinical variability are not fully understood. The neurological complications result from one point mutation that causes vasculopathy of both large and small vessels. Anemia and the resultant cerebral hyperemia produce conditions of hemodynamic insufficiency. Sickled cells adhere to the endothelium, contributing to a cascade of activated inflammatory cells and clotting factors, which result in a nidus for thrombus formation. Because the cerebrovascular reserve becomes exhausted, the capacity for compensatory cerebral mechanisms is severely limited. There is evidence of small-vessel sludging, and a relative deficiency of nitric oxide in these vessels further reduces compensatory vasodilatation. Both clinical strokes and silent infarcts occur, affecting motor and cognitive function. New data suggest that, in addition to sickle cell disease, other factors, both environmental (eg, hypoxia and inflammation) and genetic (eg, mutations resulting in thrombogenesis), may contribute to a patient's stroke risk. The stroke risk is polygenic, and sickle cell disease can be considered a model for all cerebrovascular disease. This complex disease underscores the potential intellectual and practical distance between the determination of molecular genetics and effective clinical application and therapeutics.