Reduction in regional cerebral blood flow during normal aging in man

The orbitofrontal cortex, real-world decision making, and normal aging

The present series of three studies aims at investigating the hypothesis that some seemingly normal older persons have deficits in reasoning and decision making due to dysfunction in a neural system which includes the ventromedial prefrontal cortices. This hypothesis is relevant to the comprehensive study of aging, and also addresses the question of why so many older adults fall prey to fraud. To our knowledge, this work represents the first of its kind to begin to identify, from an individual-differences perspective, the behavioral, psychophysiological, and consumer correlates of defective decision making among healthy older adults. Our findings, in a cross-sectional sample of community-dwelling participants, demonstrate that a sizeable subset of older adults (approximately 35-40%) perform disadvantageously on a laboratory measure of decision making that closely mimics everyday life, by the manner in which it factors in reward, punishment, risk, and ambiguity. These same poor decision makers display defective autonomic responses (or somatic markers), reminiscent of that previously established in patients with acquired prefrontal lesions. Finally, we present data demonstrating that poor decision makers are more likely to fall prey to deceptive advertising, suggesting compromise of real-world judgment and decision-making abilities.

Congestive heart failure and Alzheimer's disease

The increase in average life expectancy is resulting in an increasing prevalence of major invalidating illnesses, such as cardiovascular disease and dementia. Congestive heart failure (CHF) is a chronic, progressive disease representing the advanced stage of cardiac illnesses. Cognitive impairment is known to be a frequent feature of CHF patients. The epidemiologic pictures of mild cognitive impairment (MCI), Alzheimer's disease (AD) and CHF are predicted to worsen with the demographic expansion of the elderly population. Nevertheless, there has been little structured research on cognitive impairment in patients with CHF. This is unfortunate not only because CHF is the leading cause of hospitalization in the elderly and a leading cause of disability and death, but also for important clinical and socioeconomic implications including those related to comorbidity in advanced age and the need to early detect factors which may precipitate the conversion of MCI to AD. In this review, several aspects of the role of CHF in cognitive impairment are evaluated. Owing to the lack of studies focusing on CHF in AD, the pathophysiology of cardiac failure in cognitive impairment is addressed in light of possible preventive strategies against the onset of AD. These include prevention of oxygen radical and peroxynitrite production, supplementation of nitric oxide (NO) donors, as well as the achievement of an adequate antioxidant supply, better if obtained with a targeted and individualized nutritional approach. A systematic neuropsychologic testing of older patients with heart failure is to identify those with early cognitive impairment and promptly establish traditional therapies such as angiotensin converting enzyme (ACE) inhibitors, digoxin or beta-blockers. The neuropsychologic assessment in CHF patients is also fundamental to disclose conditions potentially favoring the onset of cognitive impairment such as depression. Finally, management schemes should include exercise training programs as well as patient and caregiver education.

Loss of M5 muscarinic acetylcholine receptors leads to cerebrovascular and neuronal abnormalities and cognitive deficits in mice

The M5 muscarinic acetylcholine receptor (M5R) has been shown to play a crucial role in mediating acetylcholine-dependent dilation of cerebral blood vessels. We show that male M5R-/- mice displayed constitutive constriction of cerebral arteries using magnetic resonance angiography in vivo. Male M5R-/- mice exhibited a significantly reduced cerebral blood flow (CBF) in the cerebral cortex, hippocampus, basal ganglia, and thalamus. Cortical and hippocampal pyramidal neurons from M5R-/- mice showed neuronal atrophy. Hippocampus-dependent spatial and nonspatial memory was also impaired in M5R-/- mice. In M5R-/- mice, CA3 pyramidal cells displayed a significantly attenuated frequency of the spontaneous postsynaptic current and long-term potentiation was significantly impaired at the mossy fiber-CA3 synapse. Our findings suggest that impaired M5R signaling may play a role in the pathophysiology of cerebrovascular deficits. The M5 receptor may represent an attractive novel therapeutic target to ameliorate memory deficits caused by impaired cerebrovascular function.

Resting hypofrontality in schizophrenia: A study using near-infrared time-resolved spectroscopy

Hypofrontality has been a major finding obtained from functional neuroimaging studies on schizophrenia, although there have also been contradictory results that have questioned the reality of hypofrontality. In our previous study, we confirmed the existence of activation hypofrontality by using a 2-channel continuous-wave-type (CW-type) near-infrared spectroscopy (NIRS) instrument. In this study, we employed a single-channel time-resolved spectroscopy (TRS) instrument, which can quantify hemoglobin (Hb) concentrations based on the photon diffusion theory, to investigate resting hypofrontality. A pair of incident and detecting light guides was placed on either side of the forehead at approximately Fp2-F8 or Fp1-F7 alternately in 14 male schizophrenic patients and 16 age-matched male control subjects to measure Hb concentrations at rest. The patients were also measured with a 2-channel CW-type NIRS instrument during the performance of a random number generation (RNG) task. A reduced total hemoglobin concentration (t-Hb) less than 60 microM (the mean value of the control subjects-1.5 SD) was observed bilaterally in 4 patients and only in the left side in 3 patients. Activation hypofrontality was more manifest in these patients than in the remaining 7 patients despite the same task performance. This decreased t-Hb was related to the duration of illness, and it was not observed in patients whose duration of illness was less than 10 years. These results indicate that resting hypofrontality is a chronically developed feature of schizophrenia. This does not necessarily represent frontal dysfunction, but may reflect anatomical and/or functional changes in frontal microcirculation.

Age-related differences in response regulation as revealed by functional MRI

This fMRI study studied age-related differences in neural activities during response regulation. Twenty-one male participants from two age groups, a younger group and an older group (mean ages: 29.9 and 65.2 years, respectively), were scanned while performing a task with response compatibility manipulation. They were presented with a sequence of arrowheads that pointed either upward or downward. In the "Response Compatible" condition, they were required to press an up or a down button consistent with the direction of the arrowhead. In the "Response Incompatible" condition, they were required to press the button opposite to the arrowhead direction so that an upward arrow should elicit a down response, and vice versa. Findings showed age-related differences in response regulation in several brain regions, including the right frontal, the right cingulate, and the left inferior parietal cortexes. The findings suggested a higher level of neural activity in the right prefrontal and left inferior parietal regions during response regulation for the older adults than for the younger adults.

Transcranial Doppler in Adult Patients with Sickle Cell Disease

BACKGROUND

Transcranial Doppler (TCD) is the key test in determining the need for prophylactic blood transfusion to prevent stroke in children with sickle cell disease (SCD). The role of TCD in assessing stroke risk in adults with SCD as well as the pattern of TCD velocities in these patients are still undetermined.

METHODS

The authors compared TCD velocities in SCD adults (n=56) with those of healthy controls (n=56).

RESULTS

Velocities in SCD adults were lower than those found in children and higher than in controls and negatively correlated to hematocrit in both groups.

CONCLUSION

The pattern of TCD velocities in adults with SCD is different from that described in children. Age-specific TCD criteria may assist the detection of stroke risk in these patients.

The ability to decide advantageously declines prematurely in some normal older persons

The prefrontal region of the brain, including the ventromedial sector which supports reasoning and decision-making, may undergo disproportionate aging in some older persons, but the empirical evidence is decidedly mixed. To help resolve this, we tested 80 neurologically and psychiatrically healthy Younger (aged 26-55) and Older (aged 56-85) adults on a "Gambling Task", which provides a close analog to real-world decision-making by factoring in reward, punishment, and unpredictability, yielding a sensitive index of ventromedial prefrontal function. A subset of the Older group manifested a decision-making impairment on the Gambling Task, in spite of otherwise intact cognitive functioning. This finding raises the possibility of disproportionate aging of the ventromedial prefrontal cortex in these individuals. Our finding has important societal and public policy implications (e.g., choosing medical care, allocating personal wealth), and may also help explain why many older individuals are targeted by and susceptible to fraudulent advertising.

Correlates of cognitive impairment among patients with heart failure: results of a multicenter survey

PURPOSE

Cognitive impairment is an exceedingly prevalent condition among patients with heart failure, independently associated with disability and mortality. However, the determinants of cognitive dysfunction associated with heart failure are still unclear. We assessed the correlates of cognitive impairment among patients with heart failure enrolled in a multicenter pharmacoepidemiology survey.

METHODS

The association with cognition of demographic characteristics, objective tests and measures, medications, and comorbid conditions was assessed in 1511 patients with heart failure who had been admitted to 81 hospitals throughout Italy. Cognitive impairment was defined by a Hodkinson Abbreviated Mental Test score < 7.

RESULTS

According to multivariate logistic regression modeling, age (per each decade: OR = 2.01; 95% confidence interval [CI] 1.72-2.35), the comorbidity score (OR 1.11; 95% CI 1.03-1.20), education (OR 0.88; 95% CI 0.84-0.2), low serum albumin (OR 1.78; 95% CI 1.35-2.34), sodium (OR 1.56; 95% CI 1.06-2.29), and potassium levels (OR 1.58; 95% CI 1.09-2.29), hyperglycemia (OR 1.33; 95% CI 1.02-1.73), anemia (OR 1.38; 95% CI 1.09-1.75), and systolic blood pressure levels > or = 130 mm Hg (OR 0.60; 95% CI 0.37-0.97) were independently associated with cognitive impairment, after adjusting for potential confounders. Among participants with abnormal laboratory findings on admission, restoration of normal glucose, potassium, and hemoglobin levels during hospital stay was associated with improved cognitive performance at discharge.

CONCLUSIONS

Cognitive impairment among patients with heart failure is associated with several comorbid conditions, some of which are potentially treatable. This highlights the key role of comprehensive approach to the assessment and treatment of patients with heart failure.

Use of angiotensin-converting enzyme inhibitors and variations in cognitive performance among patients with heart failure

AIMS

Cognitive dysfunction is a prevalent condition among patients with heart failure, and is independently associated with disability and mortality. Angiotensin-converting enzyme (ACE)-inhibitors might increase cerebral blood flow in subjects with heart failure. Our aim was to assess whether starting treatment with ACE-inhibitors might improve cognition in patients with heart failure.

METHODS AND RESULTS

Analyses involved 12 081 subjects, 1220 of whom had a verified diagnosis of heart failure, enrolled in a multi-centre pharmaco-epidemiology survey. None of these participants received ACE-inhibitors before hospitalization. Among participants with heart failure, cognitive performance improved in 30% of 446 participants who started ACE-inhibitors, but only in 22% of remaining patients (P=0.001). Among participants without heart failure, cognition improved in 19% of those receiving ACE-inhibitors, and in 18% of untreated patients (P=0.765). Use of ACE-inhibitors among patients with heart failure was associated with improving cognition (odds ratio=1.57; 95% CI 1.18-2.08) also in the multivariable regression modelling, independently of baseline or discharge blood pressure levels. The probability of improving cognitive performance was higher for dosages above the median values, as compared with lower doses (odds ratios=1.90 and 1.42; P for trend=0.001), and increased with duration of treatment (odds ratios for the lower, middle, and upper tertiles=1.25, 1.34, and 1.59; P for trend=0.007).

CONCLUSION

Treatment with ACE-inhibitors might selectively improve cognitive performance in patients with heart failure. However, up-titration of these agents might be required to yield the greatest benefit.

Internal Carotid Artery Occlusion Assessed at Pulsed Arterial Spin-labeling Perfusion MR Imaging at Multiple Delay Times

Magnetic resonance (MR) imaging with pulsed arterial spin labeling (ASL) was performed at six different inversion times in nine patients with internal carotid artery (ICA) occlusion and in 11 control subjects. The hospital's commission on scientific research on human subjects approved the study protocol, and all study subjects gave informed consent. Cerebral blood flow (CBF) in the middle cerebral artery territories was calculated from the combined signal intensities measured with ASL at the multiple inversion times. In the patients with ICA occlusion, mean CBF values were decreased in the gray matter of the hemisphere ipsilateral to the occlusion, as compared with values in the gray matter of the contralateral hemisphere (P < .05) and with values in the gray matter of the control subjects (P < .05). Quantification of CBF with ASL at multiple inversion times can compensate for the blood transit delays in patients with ICA occlusion.

Voxel-based morphometry of human brain with age and cerebrovascular risk factors

The objectives of this study were to evaluate the correlations of the volumes of the gray matter and white matter with age, and the correlations of the tissue probabilities of the gray matter and white matter with age and several cerebrovascular risk factors. We obtained magnetic resonance (MR) images of the brain and clinical information from 769 normal Japanese subjects. We processed the MR images automatically by correcting for inter-individual differences in brain size and shape, and by segmenting the MR images into the gray matter and white matter. Volumetry of the brain revealed a significant negative correlation between the gray matter volume and age, which was not observed between white matter volume and age. Voxel-based morphometry showed that age, systolic blood pressure, and alcohol drinking correlated with the regional tissue probabilities of the gray matter and white matter.

Factors associated with the development of vasospasm after planned surgical treatment of aneurysmal subarachnoid hemorrhage

OBJECT

The goal of this study was to determine factors associated with the development of symptomatic vasospasm among patients with aneurysmal subarachnoid hemorrhage (SAH) who participated in the randomized, double-blind, placebo-controlled trials of tirilazad between 1991 and 1997.

METHODS

Data obtained from 3567 patients entered into trials of tirilazad were analyzed using uni- and multivariate logistic regression to determine factors that predict the development of symptomatic vasospasm. Symptomatic vasospasm was defined by clinical criteria accompanied by laboratory- and radiologically determined exclusion of other causes of neurological deterioration. Transcranial Doppler ultrasonographic and/or angiographic confirmation was not required. In these patients, the aneurysms were scheduled to be treated surgically, and no patient undergoing endovascular treatment was included. A multivariate analysis showed that factors significantly associated with vasospasm were age 40 to 59 years, history of hypertension, worse neurological grade, thicker blood clot on the cranial computerized tomography (CT) scan obtained on hospital admission, larger aneurysm size, presence of intraventricular hemorrhage (IVH), prophylactic use of induced hypertension, and not participating in the first European tirilazad study.

CONCLUSIONS

Symptomatic vasospasm was associated with the amount of SAH on the CT scan, the presence of IVH, and the patient's neurological grade. The association with patient age may reflect alterations in vessel reactivity associated with age. A history of hypertension may render the brain more susceptible to symptoms from vasospasm. The explanation for the relationships with aneurysm size, use of prophylactic induced hypertension, and the particular study is unclear.

Neuroanatomical database of normal Japanese brains

To develop a high-resolution in vivo human neuroanatomy database for Japanese brains, a data set on 1547 normal subjects between the ages of 16 and 79 years has been collected. First, we determined individual reference brains of normal Japanese for each age and gender group. We found there exists cross-generational changes in brain shape, that is, the young generation has a shorter and wider brain than the older generation. Second, we determined the effect of aging on the volume of gray matter and white matter by voxel based morphometry. A significant negative correlation between the gray matter volume and age was observed. We assume that this kind of database is quite useful to investigators who are engaged in basic neuroscience, clinical diagnostics and evaluation of neuropsychiatric disorders in patients.

The effects of cognitive impairment on mortality among hospitalized patients with heart failure

PURPOSE

Cognitive impairment is a common, potentially reversible condition among older patients with heart failure. Because cerebral metabolic abnormalities have been associated with reduced survival in younger patients with advanced heart failure, we assessed the effect of cognitive impairment on the survival of older patients with heart failure.

METHODS

The association between cognitive dysfunction and in-hospital mortality was assessed in 1113 patients (mean [+/- SD] age, 78 +/- 9 years) who had been admitted for heart failure to 81 hospitals throughout Italy. One-year mortality was assessed in 968 patients with heart failure (age, 76 +/- 10 years) participating in the same study. Cognitive impairment was defined as a Hodkinson Abbreviated Mental Test score <7.

RESULTS

In-hospital death occurred in 65 (18%) of the 357 participants with cognitive impairment and in 26 (3%) of the 756 patients with normal cognition (P <0.0001). Out-of-hospital mortality was 27% (51/191) among patients with cognitive impairment and 15% (115/777) among other participants (P <0.0001). In multivariate Cox regression models, decreasing levels of cognitive functioning were associated with increasing in-hospital mortality; cognitive impairment was associated with an almost fivefold increase in mortality (relative risk = 4.9; 95% confidence interval: 2.9 to 8.3) after adjusting for several potential confounders.

CONCLUSION

Cognitive impairment is an independent prognostic marker in older patients with heart failure. Assessment of cognitive functioning, even by simple screening tests, should be part of the routine assessment of elderly patients with heart failure.

Cognitive deficits in patients with heart failure: a review of the literature

PURPOSE

Chronic heart failure (HF) and cognitive impairments (CI) are common problems in the elderly. Both are associated with increased mortality and disability, decreased quality of life, and increased health care costs. While these conditions may occur by chance in the same individual, there is increasing evidence that HF is independently associated with CI. The purpose of this article is to review and critique the literature addressing the prevalence, type, and severity of CI in HF patients, the clinical factors associated with CI, and the potential pathophysiology underlying the development of CI, and to recommend priority areas for future research.

RESULTS

Memory and attention deficits are the most frequently occurring CI in this patient population, followed by slowed motor response times and difficulties in problem solving. Prevalence rates range from 30% to 80% depending upon the age of the patients and the characteristics of the sample being studied. Most patients have mild impairments, although as many as one fourth may have moderate to severe CI. The relationship between left ventricular ejection fraction and cognition is inconsistent and may be nonlinear. The pathophysiology underlying the development of CI in HF patients may be related to both cerebral infarction and cerebral hypoperfusion either alone or in combination.

CONCLUSIONS

The current literature is limited by studies with sometimes small or nonrepresentative samples, few matched control studies, and lack of longitudinal data that could indicate the conditions that favor the development of CI over time. Future research needs to focus on (1) determining the types, frequency, and severity of impairments in cognitive functioning among a representative sample of HF patients, (2) explicating the pathological mechanisms and the clinical factors that underlie the development of cognitive deficits, and (3) identifying the ways CI influences quality of life. Interventions can then be developed to prevent or delay the occurrence of CI or to minimize their effect on patient self-management and quality of life.

Sleep-disordered breathing and stroke

Sleep-related breathing disorders are strongly associated with increased risk of stroke independent of known risk factors. The direction of causation favors sleep-disordered breathing leading to stroke rather than the other way around, although definitive proof of this awaits the results of prospective cohort studies. If causal, even a moderately elevated risk of stroke coupled with the high prevalence of sleep-disordered breathing could have significant public health implications. The relationship between sleep-disordered breathing and stroke risk factors is complex, and likely part of the risk for cerebrovascular events is because of higher cardiovascular risk factors in patients with increased RDI. The mechanisms underlying this increased risk of stroke are multi-factorial and include reduction in cerebral blood flow, altered cerebral autoregulation, impaired endothelial function, accelerated atherogenesis, thrombosis, and paradoxic embolism. Because of the effects of sleep-disordered breathing on vascular tone, hypertension is believed to be a major mechanism by which sleep-disordered breathing might influence risk of stroke. Because sleep-related breathing disorders are treatable patients with stroke/TIA should undergo investigation, with a thorough sleep history interview, physical examination, and polysomnography. Treatment of sleep apnea has been shown to improve quality of life, lower blood pressure, improve sleep quality, improve neurocognitive functioning, and decrease symptoms of excessive daytime sleepiness [98]. Further treatment trials are needed to determine whether treatment improves outcome after stroke and whether treatment may serve as secondary prophylaxis and modify the risk of recurrent stroke or death.

Relation between regional functional MRI activation and vascular reactivity to carbon dioxide during normal aging

Recent blood oxygenation level-dependent (BOLD) functional magnetic resonance imaging studies have shown a reduction of cerebral activation during aging, which may be associated with age-related changes of the cerebral vascular system. The authors used a global hypercapnic breath-holding challenge to define nonneuronal contributions to a significantly reduced activation in the primary sensorimotor cortex during finger tapping in a group of old (n = 6; mean age 65 years) compared with a group of young (n = 6; mean age 27 years) subjects. Within significantly activated voxels in both groups during finger tapping, the mean BOLD signal amplitudes were significantly smaller in the group of older subjects for both tasks. In those voxels showing significant activation only in young subjects during finger tapping, the response to hypercapnia was also greatly diminished in older subjects. The attenuated hypercapnic BOLD signal response in older subjects within this region suggests that age-dependent changes of the cerebral vasculature may alter the neuronal-vascular coupling. In older subjects, cerebral vessels may not react as effectively in response to a vasodilating stimulus, which will lead to differences in the number of voxels that pass a criterion threshold despite similar neuronal activation.

Surgery and outcome for aneurysmal subarachnoid hemorrhage in elderly patients

OBJECTIVE

The goal was to report treatment results of elderly patients (over 70 years) who underwent clipping of aneurysms after subarachnoid hemorrhage (SAH).

MATERIAL AND METHODS

From 1994 to 2000 41/284 (14%) patients older than 70 years were operated on aneurysmal SAH in our department. Localization of ruptured aneurysm was anterior communicating artery (n = 14), middle cerebral artery (n = 14), internal carotid artery (n = 6), anterior cerebral artery (n = 2), pericallosal artery (n = 1) and multiple in 4 patients. We used the Hunt and Hess classification for initial grading and the Glasgow Outcome Score at day 30 after surgery.

RESULTS

Patients with HH 1-3 had a low mortality (1/18, 6%), whereas 9 of 23 patients (39%) with HH 4-5 decreased within 30 days after surgery. Overall mortality was 24.5% (10/41) at 30 days after surgery. Most patients (n = 32) underwent early surgery (within 72 hours). Shunt dependent hydrocephalus developed in 15 patients (37%). The outcome was better in patients graded HH 1-3, in those without serious atherosclerotic changes in angiography, and in AcoA and ICA localization compared to MCA.

CONCLUSION

Advanced age does not preclude successful surgery for ruptured aneurysm. Most important factor for outcome was a good initial clinical status, though the majority of our patients presented with poor grades. Early surgical clipping and postoperative intensive care can attain a favorable outcome in a significant percentage of elderly patients.

Management of Cerebral Aneurysms in Elderly Patients

The number of elderly patients admitted with diagnosis of cerebral aneurysms is markedly increasing worldwide. Treatment in this group of patients is certainly more difficult than in the young subjects and not many reports deal with their management.

Many factors must be considered deciding if to pursue treatment. Patients admitted after bleeding (subarachnoid haemorrhage, SAH) have a different prognosis from young subjects and those harboring unruptured vascular malformations.

We have analyzed the literature on the basis of this distinction.

Cardiovascular consequences of sleep-related breathing disorders

Sleep-related breathing disorders (SRBDs) represent a spectrum of abnormalities that range from simple snoring to upper airway resistance syndrome to sleep apnea. The clinical presentation may include obesity, snoring, neuropsychological dysfunction, and daytime hypersomnolence and tiredness. The acute hemodynamic alterations of obstructive sleep apnea include systemic and pulmonary hypertension, increased right and left ventricular afterload, and increased cardiac output. Earlier reports attributed the coexistence of SRBDs with cardiovascular diseases to the shared risk factors such as age, sex, and obesity. However, recent epidemiologic data confirm an independent association between SRBDs and the different manifestations of cardiovascular diseases. Possible mechanisms may include a combination of intermittent hypoxia and hypercapnia, repeated arousals, sustained increase in sympathetic tone, reduced baroreflex sensitivity, increased platelet aggregation, and elevated plasma fibrinogen and homocysteine levels. The strength of the association, its pathogenesis, and the impact of treatment of SRBDs on the health outcome of patients with cardiovascular diseases are issues to be addressed in future studies.

Management outcome for ruptured anterior circulation aneurysms with a Hunt and Hess clinical grade of III in patients in the 9th decade of life

BACKGROUND

This study was conducted to define general guidelines for rational clinical decision-making with respect to patients older than 80 years who present with ruptured anterior circulation aneurysms and a Hunt and Hess clinical grade of III.

METHODS

The 29 consecutive patients enrolled in this study were treated at 4 participating centers between 1995 and 1998. All were 80 years or older on admission and met 7 eligibility criteria. The decision to treat surgically or non-surgically was made individually at each center. The outcome at discharge was assessed using the Glasgow Outcome Scale (GOS); the Barthel Score (BS) was used to determine the patients' quality of life after discharge.

RESULTS

Of 15 surgically treated patients, 4 died before discharge and 8 were discharged in poor condition. Of these, 7 died of unrelated causes within 2 years of the SAH and one is living in a nursing home. Three patients with middle cerebral artery (MCA) aneurysms made a good recovery; they are currently living at home. Of the 14 conservatively treated patients, 10 died during their hospital stay mainly because of rebleeding that occurred within 3 weeks of the subarachnoid hemorrhage (SAH). Three others who were discharged in poor condition died of systemic illness within 2 years. The remaining patient is living in a nursing home with a BS value of 0.

CONCLUSIONS

The outcomes for patients treated conservatively were catastrophic. Even in surgically treated patients, favorable outcomes were rare; the best results were achieved in surgically treated patients with MCA aneurysms.

Distinct pathways involved in sound recognition and localization: a human fMRI study

Evidence from psychophysical studies in normal and brain-damaged subjects suggests that auditory information relevant to recognition and localization are processed by distinct neuronal populations. We report here on anatomical segregation of these populations. Brain activation associated with performance in sound identification and localization was investigated in 18 normal subjects using fMRI. Three conditions were used: (i) comparison of spatial stimuli simulated with interaural time differences; (ii) identification of environmental sounds; and (iii) rest. Conditions (i) and (ii) required acknowledgment of predefined targets by pressing a button. After coregistering, images were normalized and smoothed. Activation patterns were analyzed using SPM99 for individual subjects and for the whole group. Sound recognition and localization activated, as compared to rest, inferior colliculus, medial geniculate body, Heschl gyrus, and parts of the temporal, parietal, and frontal convexity bilaterally. The activation pattern on the fronto-temporo-parietal convexity differed in the two conditions. Middle temporal gyrus and precuneus bilaterally and the posterior part of left inferior frontal gyrus were more activated by recognition than by localization. Lower part of inferior parietal lobule and posterior parts of middle and inferior frontal gyri were more activated, bilaterally, by localization than by recognition. Regions selectively activated by sound recognition, but not those selectively activated by localization, were significantly larger in women. Passive listening paradigm revealed segregated pathways on superior temporal gyrus and inferior parietal lobule. Thus, anatomically distinct networks are involved in sound recognition and sound localization.

Brain aging research at the close of the 20th century: from bench to bedside

Remarkable and continued growth in the field of brain aging research has been fueled by a confluence of factors. Developments in molecular biology, imaging, and genetics coupled with the imperative caused by the aging of the population has created fertile ground for improved understanding of the interaction between brain function and behavior. Aging changes in neurochemical systems may account for the spectrum of cognitive and behavioral states of successfully aged pen sons, but may also contribute to enhanced vulnerability to depressive or dementing illness. In particular, the refinement of in vivo imaging approaches to investigating the structure and function of the aging brain has provided the opportunity to strengthen our knowledge of the biological substrate of the aging brain and neuropsychiatrie disorders, and translate these into therapeutics.

Movement disorders and normal aging

As the population continues to age, it has become increasingly important for clinicians to recognize the clinical characteristics of normal aging. Impaired mobility is one of the most frequent effects of normal aging, and this necessitates a specific understanding of the effects of normal aging on the motor system. This article reviews the physiological basis and clinical manifestations of normal aging as related to movement disorders. The impact of normal aging on major hypokinetic and hyperkinetic movement disorders is also discussed.

Regional cerebral blood flow in normal individuals aged 40, 75 and 88 years studied by 99Tc(m)-d,l-HMPAO SPET

Age-related changes in cerebral blood flow (CBF) were examined with [99Tc(m)]-d,l-hexamethylpropylene amine oxime (HMPAO), using a single photon emission tomography (SPET) gamma camera system equipped with a high resolution collimator, in 33 normal individuals in three age groups: 40 years old (n = 11), 75 years old (n = 9) and 88 years old (n = 13). A standard activity of 1000 MBq [99Tc(m)]-d,l-HMPAO was administered. Regional CBF (rCBF) (relative to cerebellar counts) was quantified in 28 grey and white matter regions. The mean rCBF of all the regions was 0.80 (95% confidence interval [CI] 0.77-0.83) in 40 year olds, 0.77 (0.74-0.80) in 75 year olds and 0.76 (0.73-0.78) in 88 year olds. rCBF in the hippocampus, angular and cingular gyri, and frontal association and motor cortices was 5-10% lower in the 75 and 88 year olds than in the middle-aged subjects (P < 0.05). The annual reduction in rCBF was 0.10% between the ages of 40 and 75 years and 0.13% between the ages of 75 and 88 years. The reduction in rCBF in the hippocampus rose from 0.14% between the ages of 40 and 75 years to 0.33% between the ages of 75 and 88 years. The mean rCBF in all 33 individuals showed no sex-related differences.

Loss of presynaptic and postsynaptic structures is accompanied by compensatory increase in action potential-dependent synaptic input to layer V neocortical pyramidal neurons in aged rats

Reduction in both presynaptic and postsynaptic structures in the aging neocortex may significantly affect functional synaptic properties in this area. To directly address this issue, we combined whole-cell patch-clamp recording of spontaneously occurring postsynaptic currents (PSCs) with morphological analysis of layer V pyramidal neurons in the parietal cortex of young adult (1- to 2-month-old) and aged (28- to 37-month-old) BN x F344 F(1) hybrid rats. Analysis of spontaneous PSCs was used to contrast functional properties of basal synaptic input with structural alterations in the dendritic tree of pyramidal neurons and density of terminals in contact with these cells. We observed significant changes in a number of morphological parameters of pyramidal neurons in aged rats. These include smaller cell body size and fewer basal dendritic branches (but not of oblique dendrites and dendritic tufts) and spines. Ultrastructural analysis also revealed a lower density of presynaptic terminals per unit length of postsynaptic membrane of labeled pyramidal neurons in the aged brain. This reduction in both presynaptic and postsynaptic elements was paralleled by a significant decrease in frequency of tetrodotoxin-insensitive miniature (action potential-independent) PSCs (mPSCs). The frequency of excitatory and inhibitory mPSCs was reduced to the same extent. In contrast, no significant change was observed in the frequency of spontaneous PSCs recorded in absence of tetrodotoxin (sPSCs), indicating an increase in action potential-dependent (frequency(sPSCs) - frequency(mPSCs)) input to pyramidal neurons in the aged group. This functional compensation may explain the lack of drastic loss of spontaneous neuronal activity in normal aging.

Neuropharmacology and receptor studies in the elderly

Functional brain imaging has provided unique and exciting opportunities to strengthen our knowledge of the biologic substrate of the aging brain and neuropsychiatric disorders. Positron emission tomography (PET) is a particularly powerful tool for quantifying the neurobiologic correlates of cognition, mood, and behavior. Initial PET studies of aging, psychiatric disorders, and neurodegenerative disease focused primarily on generalized physiologic parameters such as cerebral blood flow and metabolism, and early neuroreceptor imaging studies relied on relatively nonselective markers. New, selective receptor radioligands now offer a previously inaccessible means to investigate the dynamic relationships among neurochemistry, aging, and psychopathology in vivo. This approach has substantial advantages over peripheral (platelet and cerebrospinal fluid) markers, neuroendocrine challenge studies, animal models, and postmortem receptor binding assays. Advances in tracer kinetic modeling, magnetic resonance imaging facilitated PET image analysis, radiochemistry techniques, instrumentation, and image processing have helped pave the way for increased emphasis on functional imaging studies of neuropsychiatric disorders. The capability to correct PET image data for the confounding effect of cerebral atrophy permits relationships among age-related brain changes and neurobiologic disease mechanisms to be more accurately examined in the elderly.

Measurement of cerebral blood flow volume by extracranial sonography

Measurement of global cerebral blood flow (CBF) using extracranial duplex sonography has been described, but normal values are still lacking. In 85 healthy adults (median age 43.4 years, range 20 to 80 years), CBF was determined by duplex sonographic examination of both internal carotid arteries and vertebral arteries. The mean global CBF was 630+/-97 mL/min. Global CBF declined with age; sex did not influence the total CBF. When measurements were repeated, the intraindividual variability was low. This noninvasive sonographic measurement of CBF is reproducible, and values correspond closely to those obtained with positron emission tomography and magnetic resonance imaging.

Sex differences in brain-behavior relationships between verbal episodic memory and resting regional cerebral blood flow

Women have better verbal memory, and higher rates of resting regional cerebral blood flow (rCBF). This study examined whether there are also sex differences in the relationship between verbal episodic memory and resting rCBF. Twenty eight healthy right-handed volunteers (14 male, 14 female) underwent a neuropsychological evaluation and a Positron Emission Tomography (PET) (15)O-water study. Immediate and delayed recall was measured on the logical memory subtest of the Wechsler Memory Scale - Revised (WMS-R), and on the California Verbal Learning Test (CVLT). Resting rCBF (ml/100 g/min) was calculated for four frontal, four temporal, and four limbic regions of interest (ROIs). Women had better immediate recall on both WMS-R and CVLT tasks. Sex differences in rCBF were found for temporal lobe regions. Women had greater bilateral blood flow in a mid-temporal brain region. There were also sex differences in rCBF correlations with performance. Women produced positive correlations with rCBF laterality in the temporal pole. Greater relative CBF in the left temporal pole was associated with better WMS-R immediate and delayed recall in women only. These results suggest that trait differences in temporal pole brain-behavior relationships may relate to sex differences in verbal episodic memory.

Effects of moderate caloric restriction on cortical microvascular density and local cerebral blood flow in aged rats

The present study was designed to assess the impact of moderate caloric restriction (60% of ad libitum fed animals) on cerebral vascular density and local cerebral blood flow. Vascular density was assessed in male Brown-Norway rats from 7-35 months of age using a cranial window technique. Arteriolar density, arteriole-arteriole anastomoses, and venular density decreased with age and these effects were attenuated by moderate caloric restriction. Analysis of local cerebral blood using [14C]iodoantipyrine indicated that basal blood flow decreased with age in CA1, CA3 and dentate gyrus of hippocampus; similar trends were evident in cingulate, retrosplenal, and motor cortex. Basal blood flow was increased in all brain regions of moderate caloric restricted old animals (compared to old ad libitum fed animals) and no differences were observed between ad libitum fed young and caloric restricted older animals. In response to a CO2 challenge to maximally dilate vessels, blood flow increased in young and old ad libitum fed animals, but a similar increase was not observed in caloric restricted old animals. We conclude that a decrease in cerebral vasculature is an important contributing factor in the reduction in blood flow with age. Nevertheless, vessels from young and old animals have the capacity to dilate in response to a CO2 challenge and, after CO2, no differences are observed between the two age-groups. These results are consistent with the hypothesis that aged animals fail to adequately regulate local cerebral blood flow in response to physiological stimuli. Moderate caloric restriction increases microvascular density and cerebral blood flow in aged animals but tissues exhibit little or no increase in blood flow in response to CO2 challenge. The cause of this deficient response may indicate that vessels are maximally dilated in aged calorically restricted animals or that they fail to exhibit normal regulatory control.

Alterations in insulin-like growth factor-1 gene and protein expression and type 1 insulin-like growth factor receptors in the brains of ageing rats

Ageing in mammals is characterized by a decline in plasma levels of insulin-like growth factor-1 that appears to contribute to both structural and functional changes in a number of tissues. Although insulin-like growth factor-1 has been shown to provide trophic support for neurons and administration of insulin-like growth factor-1 to ageing animals reverses some aspects of brain ageing, age-related changes in insulin-like growth factor-1 or type 1 insulin-like growth factor receptors in brain have not been well documented. In this series of studies, insulin-like growth factor-1 messenger RNA and protein concentrations, and type 1 insulin-like growth factor receptor levels were analysed in young (three to four- and 10-12-month-old), middle-aged (19-20-month-old) and old (29-32-month-old) Fisher 344 x Brown Norway rats. Localization of insulin-like growth factor-1 messenger RNA throughout the lifespan revealed that expression was greatest in arteries, arterioles, and arteriolar anastomoses with greater than 80% of these vessels producing insulin-like growth factor-1 messenger RNA. High levels of expression were also noted in the meninges. No age-related changes were detected by either in situ hybridization or quantitative dot blot analysis of cortical tissue. However, analysis of insulin-like growth factor-1 protein levels in cortex analysed after saline perfusion indicated a 36.5% decrease between 11 and 32 months-of-age (P<0.05). Similarly, analysis of type 1 insulin-like growth factor receptor messenger RNA revealed no changes with age but levels of type 1 insulin-like growth factor receptors indicated a substantial decrease with age (31% in hippocampus and 20.8 and 27.3% in cortical layers II/III and V/VI, respectively). Our results indicate that (i) vasculature and meninges are an important source of insulin-like growth factor-1 for the brain and that expression continues throughout life, (ii) there are no changes in insulin-like growth factor-1 gene expression with age but insulin-like growth factor-1 protein levels decrease suggesting that translational deficiencies or deficits in the transport of insulin-like growth factor-1 through the blood-brain barrier contribute to the decline in brain insulin-like growth factor-1 with age, and (iii) type 1 insulin-like growth factor receptor messenger RNA is unchanged with age but type 1 insulin-like growth factor receptors decrease in several brain regions. We conclude that significant perturbations occur in the insulin-like growth factor-1 axis with age. Since other studies suggest that i.c.v. administration of insulin-like growth factor-1 reverses functional and cognitive deficiencies with age, alterations within the insulin-like growth factor-1 axis may be an important contributing factor in brain ageing.

Ocular and regional cerebral blood flow in aging Fischer-344 rats

Vascular remodeling and changes in vascular responsiveness occur in the rat cerebrum with old age. This includes reductions in cerebral arteriolar numerical density, cross-sectional area, distensibility, the relative proportion of distensible elements in the cerebral arteriolar wall, and reduced endothelium-dependent relaxation. The purpose of this study was to test the hypothesis that old age results in an increase in vascular resistance and, correspondingly, a decrease in blood flow to ocular, regional cerebral, and spinal tissue in the rat. Blood flow was measured in the eye, olfactory bulb, left and right cerebrum, pituitary gland, midbrain, pons, cerebellum, medulla, and spinal cord of juvenile (2-mo-old, n = 6), adult (6-mo-old, n = 7), and aged (24-mo-old, n = 7) male Fischer-344 rats. Arterial pressure and blood flow were used to calculate vascular resistance. Vascular resistance in the eye of aged rats (6.03 +/- 1.08 mmHg . ml-1 . min . 100 g) was higher than that in juvenile (3.83 +/- 0.38 mmHg . ml-1 . min . 100 g) and adult rats (3.12 +/- 0.24 mmHg . ml-1 . min . 100 g). Similarly, resistance in the pons of older rats (2.24 +/- 0.55 mmHg . ml-1 . min . 100 g) was greater than in juvenile (0.66 +/- 0.06 mmHg .ml-1 . min . 100 g) and adult rats (0.80 +/- 0.11 mmHg . ml-1 . min . 100 g). In contrast, vascular resistance in the pituitary gland was lower in the aged rats (juvenile, 3.09 +/- 0.22; adult, 2.79 +/- 0.42; aged, 1.73 +/- 0.32 mmHg . ml-1 . min . 100 g, respectively). Vascular resistance was not different in other cerebral tissues or in the spinal cord in the aged rats. These data suggest that regional cerebral and spinal blood flow and vascular resistance remain largely unchanged in conscious aged rats at rest but that elevations in ocular vascular resistance and, correspondingly, decreases in ocular perfusion with advanced age could have serious adverse effects on visual function.

Sex-related differences in human cerebral hemodynamics

OBJECTIVES

To identify possible inter-hemispheric sex-related cerebral hemodynamic differences at rest, in healthy subjects by transcranial Doppler (TCD).

SUBJECTS AND METHODS

Mean flow velocity (MV) was recorded by TCD in 96 (48 males, 48 females) right-handed volunteers. Mean age was similar in males and females, distribution of age-groups by sex was similar, too.

RESULTS

Examining by sex MV values in each basal artery, left middle cerebral artery (MCA) showed a statistically significant difference (53.5+/-8.2 cm x s(-1) in males versus 58.5+/-10.4 cm x s(-1) in females, P=0.005, one-way ANOVA). Multiple regression models show a significant correlation between age and MV on each side, while sex correlates with MV on the left side.

CONCLUSION

A sex-dependent hemispheric difference in MV in the left MCA at rest (females>males) in the younger population subgroup was identified. These data support recent observations on anatomical differences between sexes, referring a proportionally larger Broca area in females compared to males.

Functional brain imaging and aging in schizophrenia

Patients with schizophrenia, even early in the course of illness, show some similarities in their brain-imaging findings to those in older normal controls: for example, ventricular enlargement and diminished functional activity in the frontal cortex. These findings suggest a possible similarity between the normal aging process and schizophrenia, or the possible existence in some schizophrenic patients of progressive processes that prematurely affect the brain in ways analogous to normal aging. In contrast to other brain regions, the basal ganglia in schizophrenia may show an atypical pattern of volumetric and metabolic change over time, possibly because of the effects of neuroleptic treatment. However, age and illness duration are highly correlated in our samples. Interpretation of imaging results is limited by the lack of studies in an adequate number of either first-break or older schizophrenic patients and the dearth of studies with longitudinal designs.

Brain microvascular changes in Alzheimer's disease and other dementias

Vasculopathy in Alzheimer's disease (AD) may represent an important pathogenetic factor of this disorder. In the present study, microvasculature was studied by immunohistochemistry using a monoclonal antibody against a vascular heparan sulfate proteoglycan. Vascular changes were consistently observed in AD and included decrease in vascular density, presence of atrophic and coiling vessels, and glomerular loop formations. The laminar and regional distribution of these vascular alterations was correlated with the presence of neurofibrillary tangles. However, vascular changes may also follow neuronal loss. Vascular density may be related to a decrease in brain metabolism. Furthermore, one of the main features of AD is the presence of amyloid deposits within brain parenchyma and blood vessel walls. It is not yet clear whether amyloid components are derived from the blood or the central nervous system. Because AD is clearly heterogeneous, based on clinical and genetic data, evidence for either a brain or peripheral origin is discussed. Microvasculature was also analyzed in other neurodegenerative disorders devoid of amyloid deposits including amyotrophic lateral sclerosis/parkinsonism-dementia complex of Guam and Pick's disease. In conclusion, if vasculopathy in neurodegenerative disorders is not directly involved in pathogenesis, it may act synergistically with other pathogenetic mechanisms including genetic and environmental factors. This aspect of pathology is particularly interesting in view of its accessibility to therapeutic interventions.

Hemodynamic consequences of deformed microvessels in the brain in Alzheimer's disease

The cause of sporadic Alzheimer's disease (AD) remains a mystery. Mounting clinical and experimental data, however, suggest that a cerebral hemodynamic role may affect neuronoglial metabolism. Light and electron microscopy have consistently revealed that the microvasculature in AD brains contains structurally deformed capillaries which create a distorted intraluminal conduit for blood flow. The cerebral capillary distortions can create "disturbed" rather than "laminar" blood flow. Chronically disturbed capillary blood flow will impair normal delivery of essential nutrients to brain neurons as well as impede catabolic outflow of CNS waste products. This condition will negatively affect cerebral metabolism, primarily because of impaired glucose delivery to neurons. Impaired glucose delivery to AD brain results in a patho-chemical cascade that will impair the Na+, K(+)-ATPase ion pump and affect the syntheses of ATP, acetylcholine, and other neurotransmitters. The outcome of this metabolic dysfunction can promote neurofibrillary tangle and senile plaque formation in AD brain.

Hemodynamically significant cerebral vasospasm and outcome after head injury: a prospective study

The authors prospectively investigated cerebral hemodynamic changes in 152 patients with head injuries to clarify the relationship between cerebral vasospasm and outcome. They also sought to determine the most clinically meaningful criteria for diagnosing cerebral vasospasm. Patients with varying degrees of moderate-to-severe head injury were monitored using transcranial Doppler (TCD) ultrasonography and intravenous 133Xe-cerebral blood flow (CBF) measurements. Outcome was determined at 6 months. Using TCD ultrasonography, mean flow velocities were determined for the middle cerebral artery (V(MCA), 149 patients) and basilar artery (V(BA), 126 patients). Recordings of the mean extracranial internal carotid artery velocity (V(EC-ICA)) were also performed to determine the hemispheric ratio (V(MCA)/V(EC-ICA), 147 patients). Cerebral blood flow measurements were obtained in 91 patients. Concurrent TCD and CBF data from 85 patients were used to calculate a "spasm index" (the V(MCA) or V(BA), respectively, divided by the hemispheric or global CBF). The authors investigated the clinical significance of elevated flow velocity, hemispheric ratio, and spasm index. Patients diagnosed as having MCA or BA vasospasm on the basis of TCD-derived criteria alone had a significantly worse outcome than patients without vasospasm. When CBF was considered, hemodynamically significant vasospasm, as defined by an elevated spasm index, was even more strongly associated with poor outcome. Stepwise logistic regression analysis confirmed that hemodynamically significant vasospasm was a significant predictor of poor outcome, independent of the effects of admission Glasgow Coma Scale score and age. On the basis of the results of this study, the authors suggest that the important factor impacting on outcome is not vasospasm per se, but hemodynamically significant vasospasm with low CBF. These findings show that vasospasm is a pathophysiologically important posttraumatic secondary insult, which is best diagnosed by the combined use of TCD and CBF measurements.

Decreases in cerebral microvasculature with age are associated with the decline in growth hormone and insulin-like growth factor 1

Several reports have demonstrated that cerebral blood flow decreases with age and may contribute to neurodegenerative changes found in aging animals and man. Because GH and insulin-like growth factor 1 (IGF-1) decrease with age and have an important role in vascular maintenance and remodeling, we hypothesized that the decrease in cerebral blood flow is associated with a rarefaction of cerebral blood vessels resulting from a decline in GH and IGF-1. Measurements of vascular density (number of vessels/cortical surface area) in both Brown-Norway and Fisher 344/Brown-Norway rats were made at 5, 13, and 29 months of age using chronic cranial window chambers that allowed viewing of the cortical surface and its corresponding vasculature. Correlations were made with plasma levels of IGF-1. In Brown-Norway rats, arteriolar density decreased from 15.53 +/- 1.08 to 9.49 +/- 0.62 endpoints/mm2 in 7- and 29-month-old animals, respectively (P < 0.05). A decline was observed also in arteriolar anastomoses [3.05 +/- 0.21 to 1.42 +/- 0.24 connections/mm2 in 7- and 29-month-old animals (P < 0.05)]. Venular density did not decrease with age. Similar changes were observed in Fisher 344/Brown-Norway rats. The number of cortical surface arterioles was correlated with plasma IGF-1 levels at the time of vascular mapping (r = 0.772, P < 0.05), and injection of bovine GH (0.25 mg/kg, s.c., twice daily for 35 days) to 30-month-old animals increased both plasma IGF-1 and the number of cortical arterioles. These data indicate that: 1) vascular density on the surface of the cortex decreases with age; 2) vascular density is correlated with plasma levels of IGF-1; and 3) injection of GH increases cortical vascular density in older animals. We conclude that GH and IGF-1 have an important role in the decline in vascular density with age and suggest that decreases in vascular density may have important implications for the age-related decline in cerebral blood flow and brain function.

Human biological decline and mortality rates

Intercepts on the x (age)-axis of 107 normalized declining human biological functions were determined and assembled in 3 histograms, being placed in increasing order within each decade (10 year period). The histograms were classed accordingly as they contained properties associated with dividing cells, sensory properties and non-dividing cells respectively. Their cumulants were determined, multiple regressions calculated and compared with current death-rates for women and men respectively, for 10 amongst the longest living populations in the World. An alternative verification based on risk theory led to an estimate of an optimal life expectancy of 96 years. The survival curve turns out to be of the form (See text: Formula) where the inner integral represents the cumulant dimension (t') and the outer one age (t"). The premises underlying this study are compatible with the notion of a probable life-span, rather than a fixed one.

Cerebral blood flow as a predictor of outcome following traumatic brain injury

As part of a prospective study of the cerebrovascular effects of head injury, 54 moderate and severely injured patients underwent 184 133Xe-cerebral blood flow (CBF) studies to determine the relationship between the period of maximum blood flow and outcome. The lowest blood flows were observed on the day of injury (Day 0) and the highest CBFs were documented on postinjury Days 1 to 5. Patients were divided into three groups based on CBF values obtained during this period of maximum flow: Group 1 (seven patients), CBF less than 33 ml/100 g/minute on all determinations; Group 2 (13 patients), CBF both less than and greater than or equal to 33 ml/100 g/minute; and Group 3 (34 patients), CBF greater than or equal to 33 ml/100 g/minute on all measurements. For Groups 1, 2, and 3, mean CBF during Days 1 to 5 postinjury was 25.7 +/- 4, 36.5 +/- 4.2, and 49.4 +/- 9.3 ml/100 g/minute, respectively, and PaCO2 at the time of the CBF study was 31.4 +/- 6, 32.7 +/- 2.9, and 33.4 +/- 4.7 mm Hg, respectively. There were significant differences across Groups 1, 2, and 3 regarding mean age, percentage of individuals younger than 35 years of age (42.9%, 23.1%, and 76.5%, respectively), incidence of patients requiring evacuation of intradural hematomas (57.1%, 38.5%, and 17.6%, respectively) and incidence of abnormal pupils (57.1%, 61.5%, and 32.4%, respectively). Favorable neurological outcome at 6 months postinjury in Groups 1, 2, and 3 was 0%, 46.2%, and 58.8%, respectively (p < 0.05). Further analysis of patients in Group 3 revealed that of 14 with poor outcomes, six had one or more episodes of hyperemia-associated intracranial hypertension (simultaneous CBF > 55 ml/100 g/minute and ICP > 20 mm Hg). These six patients were unique in having the highest CBFs for postinjury Days 1 to 5 (mean 59.8 ml/100 g/minute) and the most severe degree of intracranial hypertension and reduced cerebral perfusion pressure (p < 0.0001). These results indicate that a phasic elevation in CBF acutely after head injury is a necessary condition for achieving functional recovery. It is postulated that for the majority of patients, this rise in blood flow results from an increase in metabolic demands in the setting of intact vasoreactivity. In a minority of individuals, however, the constellation of supranormal CBF, severe intracranial hypertension, and poor outcome indicates a state of grossly impaired vasoreactivity with uncoupling between blood flow and metabolism.

Cerebral blood flow and temporal lobe epileptogenicity

Long-term surface cerebral blood flow (CBF) monitoring was performed to test the hypothesis that temporal lobe epileptogenicity is a function of epileptic cortical perfusion. Forty-three bitemporal 2-hour periictal CBF studies were performed in 13 patients. Homotopic regions of temporal cortex maintained interictal epileptic cortical hypoperfusion and nonepileptic normal cortical CBF. At 10 minutes preictus, a statistically significant, sustained increase in CBF was detected on the epileptic temporal lobe. Two minutes preictus, there was approximation of CBF in the epileptic and nonepileptic temporal lobes. Thereafter, electrocorticographic (ECoG) and clinical seizure onset occurred. The linear relationship between CBF in the two hemispheres (epileptic and nonepileptic) was the inverse of normal (y = -0.347x + 62.767, r = 0.470, df = 95, p < 0.05). The data indicated a direct linear correlation between epileptic cortical CBF and seizure interval (frequency-1), a clinical measure of epileptogenicity (r = 0.610, df = 49, p < 0.05). Epileptogenicity was also found to be a logarithmic function of the difference between nonepileptic and epileptic cortical perfusion (r = 0.564, df = 58, t = 5.20, p < 0.05). The results showed that progressive hypoperfusion of the epileptic focus correlated with a decreased seizure interval (increased epileptogenicity). Increased perfusion of the epileptic focus correlated with an increased seizure interval (decreased epileptogenicity). The fact that CBF alterations precede ECoG seizure activity suggests that vasomotor changes may produce electrical and clinical seizure onset.

Age and outcome after aneurysmal subarachnoid hemorrhage: why do older patients fare worse?

Advanced age is a recognized prognostic indicator of poor outcome after subarachnoid hemorrhage (SAH). The relationship of age to other prognostic factors and outcome was evaluated using data from the multicenter randomized trial of nicardipine in SAH conducted in 21 neurosurgical centers in North America. Among the 906 patients who were studied, five different age groups were considered: 40 years or less, 41 to 50, 51 to 60, 61 to 70, and more than 71 years. Twenty-three percent of the individuals enrolled were older than 60 years of age. Women outnumbered men in all age groups. Level of consciousness (p = 0.0002) and World Federation of Neurological Surgeons grade (p = 0.0001) at admission worsened with advancing age. Age was also related to the presence of a thick subarachnoid clot (p = 0.0001), intraventricular hemorrhage (p = 0.0003), and hydrocephalus (p = 0.0001) on an admission computerized tomography scan. The rebleeding rate increased from 4.5% in the youngest age group to 16.4% in patients more than 70 years of age (p = 0.002). As expected, preexisting medical conditions, such as diabetes (p = 0.028), hypertension (p = 0.0001), and pulmonary (p = 0.0084), myocardial (p = 0.0001), and cerebrovascular diseases (p = 0.0001), were positively associated with age. There were no age-related differences in the day of admission following SAH, timing of the surgery and/or location, and size (small vs. large) of the ruptured aneurysm. During the treatment period, the incidence of severe complications (that is, those complications considered life threatening by the reporting investigator) increased with advancing age, occurring in 28%, 33%, 36%, 40%, and 46% of the patients in each advancing age group, respectively (p = 0.0002). No differences were observed in the reported frequency of surgical complications. No age-related differences were found in the overall incidence of angiographic vasospasm; however, symptomatic vasospasm was more frequently reported in the older age groups (p = 0.01). Overall outcome, assessed using the Glasgow Outcome Scale at 3 months post-SAH, was poorer with advancing age (p < 0.001). Multivariate analysis of overall outcome, adjusting for the different prognostic factors, did not remove the age effect, which suggests that the aging brain has a less optimal response to the initial bleeding. Age as a risk factor is a continuum; however, there seems to be a significant increased risk of poor outcome after the age of 60 years.

Age dependence of total cerebral blood flow volume from childhood to adulthood

In a prospective study of the natural development of total cerebral blood flow volume (CBFV), the common, external and internal carotid and vertebral arteries were examined in 94 healthy children and adolescents between 3 and 18 years of age (sex and age evenly distributed) using a 7.0-MHz transducer of a computed sonography system. Intravascular flow volumes were calculated with the product of angle-corrected time-averaged flow velocity and the cross-sectional area of the vessel. CBFV was determined as the sum of flow volumes in the internal carotid and vertebral arteries of both sides. CBFV increased significantly between 3 and 6.5 years of age (from 687 +/- 85 to 896 +/- 110 ml/min; age correlation, p < or = 0.01) and declined thereafter (p < or = 0.001) to a constant level of approximately 700 ml/min at 15 years of age. There was no difference in CBFV between sexes. The proportion of bilateral vertebral artery flow volume in total CBFV decreased significantly between the ages of 3 and 18 years (p < or = 0.001). As the flow volumes of the external carotid arteries increased markedly from childhood to adulthood, flow volumes of the common carotid arteries were not representative of CBFV. Intrasession test-retest correlation of CBFV was high (r = 0.89, p < or = 0.0001). Reference data for the childhood years presented here and previously described results from healthy adults allow us to outline the natural evolution of CBFV in humans. The reliability of the method has already been demonstrated. Thus, it may now be introduced into clinical application.

Oxygen administration enhances memory formation in healthy young adults

Despite numerous studies indicating that transient cerebral oxygen depletion has a detrimental effect on cognition, surprisingly little research has examined the possibility of cognitive enhancement following elevated oxygen levels in healthy adults. Here, we present evidence demonstrating that oxygen administration improves memory formation. Inhalation of oxygen immediately prior to learning a word list resulted in a significant increase in mean number of words recalled 10 min later, compared to subjects who inhaled oxygen immediately prior to recall or to controls who underwent no intervention. In a second experiment, the learning-test interval was increased to 24 h and, again, only pre-learning (but not pre-test) oxygen administration resulted in significant memory facilitation. In experiment 3, inhalation of oxygen prior to learning was compared to inhalation of compressed air, oxygen (but not compressed air) resulted in a significant increase in word recall 24 h later. In no experiment did oxygen have a significant effect on any mood item measured. We interpret these data as indicating that increased availability of cerebral oxygen facilitates cognition, including memory consolidation. The implications for the psychopharmacology of cognitive enhancement are considered in the context of cholinergic systems and neural metabolism.

PET studies of cerebral glucose metabolism in conscious rhesus macaques

A growing body of evidence suggests that rhesus macaques may be a good model of human brain aging. We used positron emission tomography (PET) and 18F-fluorodeoxyglucose (FDG) to measure regional cerebral metabolic rates for glucose (rCMRglc) in young and aged rhesus macaques to determine if age-related decreases, such as those reported in humans, also occur in macaques. Whereas the aged animals had lower metabolic rates in every brain region studied, the largest differences were in left temporal cortex. The largest differences were also observed in left temporal cortex when relative rCMRglc values were used. Both rCMRglc and relative rCMRglc were marked by substantial individual variation within the aged group. This variation may parallel the variation observed in behavioral studies. Future studies that include both PET and behavioral measures should help determine if there is a relationship between age-related changes in rCMRglc and behavior.

Reduced temporal lobe glucose metabolism in aging

The results of a positron emission tomography study of regional cerebral metabolic rates of glucose are reported for 8 healthy old subjects (mean age, 66 yr; standard deviation [SD], 5) and 9 young subjects (mean age, 27 yr; SD, 4.6) using a high-resolution positron emission tomograph and the glucose metabolic tracer 18F-fluorodeoxyglucose. Older subjects showed significantly lower cerebral metabolic rates than did the young subjects, in anterior, middle, and posterior temporal neocortex and in mesial temporal cortex, with the largest differences occurring in anterior temporal cortex (temporal pole). The current findings may reflect either decreases in regional cerebral metabolic rates for glucose that occur with normal aging, or early indications of cognitive dysfunction that is associated with age-related disorders.