Cyclophilin D deficiency rescues Aβ-impaired PKA/CREB signaling and alleviates synaptic degeneration

The coexistence of neuronal mitochondrial pathology and synaptic dysfunction is an early pathological feature of Alzheimer's disease (AD). Cyclophilin D (CypD), an integral part of mitochondrial permeability transition pore (mPTP), is involved in amyloid beta (Aβ)-instigated mitochondrial dysfunction. Blockade of CypD prevents Aβ-induced mitochondrial malfunction and the consequent cognitive impairments. Here, we showed the elimination of reactive oxygen species (ROS) by antioxidants probucol or superoxide dismutase (SOD)/catalase blocks Aβ-mediated inactivation of protein kinase A (PKA)/cAMP regulatory-element-binding (CREB) signal transduction pathway and loss of synapse, suggesting the detrimental effects of oxidative stress on neuronal PKA/CREB activity. Notably, neurons lacking CypD significantly attenuate Aβ-induced ROS. Consequently, CypD-deficient neurons are resistant to Aβ-disrupted PKA/CREB signaling by increased PKA activity, phosphorylation of PKA catalytic subunit (PKA C), and CREB. In parallel, lack of CypD protects neurons from Aβ-induced loss of synapses and synaptic dysfunction. Furthermore, compared to the mAPP mice, CypD-deficient mAPP mice reveal less inactivation of PKA-CREB activity and increased synaptic density, attenuate abnormalities in dendritic spine maturation, and improve spontaneous synaptic activity. These findings provide new insights into a mechanism in the crosstalk between the CypD-dependent mitochondrial oxidative stress and signaling cascade, leading to synaptic injury, functioning through the PKA/CREB signal transduction pathway.

Patient-specific metrics of invasiveness reveal significant prognostic benefit of resection in a predictable subset of gliomas

Object

Malignant gliomas are incurable, primary brain neoplasms noted for their potential to extensively invade brain parenchyma. Current methods of clinical imaging do not elucidate the full extent of brain invasion, making it difficult to predict which, if any, patients are likely to benefit from gross total resection. Our goal was to apply a mathematical modeling approach to estimate the overall tumor invasiveness on a patient-by-patient basis and determine whether gross total resection would improve survival in patients with relatively less invasive gliomas.

Methods

In 243 patients presenting with contrast-enhancing gliomas, estimates of the relative invasiveness of each patient's tumor, in terms of the ratio of net proliferation rate of the glioma cells to their net dispersal rate, were derived by applying a patient-specific mathematical model to routine pretreatment MR imaging. The effect of varying degrees of extent of resection on overall survival was assessed for cohorts of patients grouped by tumor invasiveness.

Results

We demonstrate that patients with more diffuse tumors showed no survival benefit (P = 0.532) from gross total resection over subtotal/biopsy, while those with nodular (less diffuse) tumors showed a significant benefit (P = 0.00142) with a striking median survival benefit of over eight months compared to sub-totally resected tumors in the same cohort (an 80% improvement in survival time for GTR only seen for nodular tumors).

Conclusions

These results suggest that our patient-specific, model-based estimates of tumor invasiveness have clinical utility in surgical decision making. Quantification of relative invasiveness assessed from routinely obtained pre-operative imaging provides a practical predictor of the benefit of gross total resection.

Length of red cell unit storage and risk for delirium after cardiac surgery

BACKGROUND

The time that red cell units are stored before transfusion may be associated with postoperative complications, although the evidence is conflicting. However, the association between the length of red cell unit storage and postoperative delirium has not been explored. We hypothesized that the length of storage of transfused red cell units would be associated with delirium after cardiac surgery.

METHODS

We conducted a case-control study in which patients undergoing coronary artery bypass, valve, or ascending aorta surgery with cardiopulmonary bypass at Johns Hopkins from 2005 to 2011 were eligible for inclusion. Patients were excluded if they did not receive red cell units, received >4 red cell units during hospitalization, received any transfusion after the first postoperative day, or received red cell units that were not exclusively stored for ≤14 days or >14 days. Eighty-seven patients met transfusion-related inclusion criteria and developed postoperative delirium. Controls who did not develop delirium were selected from the same source population of eligible patients and were matched 1:1 based on age (± 5 years), 2- to 2.5-year band of date of surgery, and surgical procedure. For each patient, we calculated the average storage duration of all transfused red cell units. The primary outcome was odds of delirium in patients who were transfused red cell units with exclusive storage duration >14 days compared with that of ≤14 days. Secondary outcomes were odds of delirium with each increasing day of average red cell unit storage duration. We used conditional multivariable regression to test our hypotheses.

RESULTS

In conditional multivariable analysis of 87 case-control pairs, there was no difference in the odds of patients developing delirium if they were transfused red cell units with an exclusive storage age >14 days compared with that ≤14 days (odds ratio [OR] 1.83; 95% confidence interval, 0.73-4.58, P = 0.20). Each additional day of average red cell unit storage beyond 14 days was associated with a 1.01- to 1.13-fold increase in the odds of postoperative delirium (OR, 1.07; P = 0.03). Each additional day of average storage beyond 21 days was associated with a 1.02- to 1.23-fold increase in the odds of postoperative delirium (OR, 1.12; P = 0.02).

CONCLUSIONS

Transfusion of red cell units that have been stored for >14 days is not associated with increased odds of delirium. However, each additional day of storage >14 or 21 days may be associated with increased odds of postoperative delirium in patients undergoing cardiac surgery. More research is needed to further characterize the association between delirium and storage duration of transfused red cell units.

Should ventriculoatrial shunting be the procedure of choice for normal-pressure hydrocephalus?

Object

Ventriculoatrial (VA) shunting is rarely used for patients with normal-pressure hydrocephalus (NPH), likely due to surgeon technical preference and case reports indicating cardiopulmonary complications. However, these complications have typically been limited to adults in whom VA shunts had been placed when they were children. Few studies have directly compared VA shunting to ventriculoperitoneal (VP) shunting in cases of NPH.

Methods

The authors retrospectively analyzed all NPH patients treated by a single surgeon at their center from January 2002 through December 2011. Thirty patients were treated with VA shunts (14 male) and 157 with VP shunts (86 male). The patients' mean age (± SD) at surgery was 73.7 ± 9.4 years for VA shunting and 76.0 ± 8.2 years for VP shunting; the median durations of follow-up were 42.0 months (IQR 19.2–63.6 months) and 34.2 months (IQR 15.8–67.5), respectively. Statistical analysis was performed using chi-square tests and Wilcoxon rank-sum tests.

Results

Perioperative and postoperative complications for VA and VP shunting cohorts, respectively, included distal revision (2.7% vs 6.6%, p = 0.45), proximal revision (2.7% vs 2.5%, p = 0.97), and postoperative seizure (2.7% vs 1.5%, p = 0.62). Shunt drainage–related subdural hematomas/hygromas developed in 8.1%/27.0% of VA shunt–treated patients versus 6.6%/26.4% of VP shunt–treated patients (p = 0.76/0.98) and were nearly always successfully managed with programmable-valve adjustment. Symptomatic intracerebral hemorrhage (1.5%) and shunt infection (2.0%) were only observed in those who underwent VP shunting. Of note, no cardiovascular complications were observed in any patient, and there were no cases of distal occlusion of the VA shunt.

Conclusions

The authors found no significant differences in complication rates between VA and VP shunting, and VA shunting was not associated with any cardiopulmonary complications. Thus, in the authors' experience, VA shunting is at least as safe as VP shunting for treating NPH.

Direct, intraoperative observation of ~0.1 Hz hemodynamic oscillations in awake human cortex: implications for fMRI

An almost sinusoidal, large amplitude ~0.1 Hz oscillation in cortical hemodynamics has been repeatedly observed in species ranging from mice to humans. However, the occurrence of 'slow sinusoidal hemodynamic oscillations' (SSHOs) in human functional magnetic resonance imaging (fMRI) studies is rarely noted or considered. As a result, little investigation into the cause of SSHOs has been undertaken, and their potential to confound fMRI analysis, as well as their possible value as a functional biomarker has been largely overlooked. Here, we report direct observation of large-amplitude, sinusoidal ~0.1 Hz hemodynamic oscillations in the cortex of an awake human undergoing surgical resection of a brain tumor. Intraoperative multispectral optical intrinsic signal imaging (MS-OISI) revealed that SSHOs were spatially localized to distinct regions of the cortex, exhibited wave-like propagation, and involved oscillations in the diameter of specific pial arterioles, indicating that the effect was not the result of systemic blood pressure oscillations. fMRI data collected from the same subject 4 days prior to surgery demonstrates that ~0.1 Hz oscillations in the BOLD signal can be detected around the same region. Intraoperative optical imaging data from a patient undergoing epilepsy surgery, in whom sinusoidal oscillations were not observed, is shown for comparison. This direct observation of the '0.1 Hz wave' in the awake human brain, using both intraoperative imaging and pre-operative fMRI, confirms that SSHOs occur in the human brain, and can be detected by fMRI. We discuss the possible physiological basis of this oscillation and its potential link to brain pathologies, highlighting its relevance to resting-state fMRI and its potential as a novel target for functional diagnosis and delineation of neurological disease.

Abstract W P156: Perioperative Low Arterial Oxygenation is Associated With Increased Risk of Stroke After Cardiac Surgery

Background: Postoperative stroke occurs in up to 5% of cardiac surgery patients, contributing significantly to mortality and morbidity. Patient characteristics as well as intraoperative factors have been associated with a higher risk of stroke. We hypothesized that poor systemic blood oxygenation in the perioperative period is associated with increased risk of stroke following cardiac surgery.

Methods: This was a case-control study of 311 adult patients who underwent cardiac surgical procedures at a single center from 2003-6. Patients having a postoperative stroke were matched 1:2 with controls. Minimum and average pO2 values, as measured from arterial blood gas values during and up to 24 hours after the start of surgery, were recorded and evaluated as continuous and categorical (in quartiles) predictors. Conditional logistic regression models adjusted for hypertension, diabetes, hyperlipidemia, cardiopulmonary bypass time, and prior stroke were used to evaluate associations between minimum and average pO2, each, and stroke status.

Results: Lower nadir pO2 values were significantly associated with postoperative stroke. Per 10 mm Hg decline in nadir pO2, odds of stroke increased nearly 25% (OR 1.23, 95% CI 1.09-1.39). Nonlinear models of oxygen levels predicting stroke were explored (figure) but results remained similar; the linear model had the best statistical fit. Each equivalent decrease in mean pO2 was associated with smaller but significantly increased odds of stroke (OR 1.08, 95% CI 1.01-1.15). Having a nadir pO2 value in the lowest vs highest quartile was associated with 3.3-fold increased odds of stroke (95% CI 1.51-7.23).

Conclusion: Odds of stroke after cardiac surgery is significantly increased in patients with a low minimum or average pO2 within 24 hours of surgery. This relationship is independent of other potential confounders of operative outcome.

Ictal high frequency oscillations distinguish two types of seizure territories in humans

High frequency oscillations have been proposed as a clinically useful biomarker of seizure generating sites. We used a unique set of human microelectrode array recordings (four patients, 10 seizures), in which propagating seizure wavefronts could be readily identified, to investigate the basis of ictal high frequency activity at the cortical (subdural) surface. Sustained, repetitive transient increases in high gamma (80-150 Hz) amplitude, phase-locked to the low-frequency (1-25 Hz) ictal rhythm, correlated with strong multi-unit firing bursts synchronized across the core territory of the seizure. These repetitive high frequency oscillations were seen in recordings from subdural electrodes adjacent to the microelectrode array several seconds after seizure onset, following ictal wavefront passage. Conversely, microelectrode recordings demonstrating only low-level, heterogeneous neural firing correlated with a lack of high frequency oscillations in adjacent subdural recording sites, despite the presence of a strong low-frequency signature. Previously, we reported that this pattern indicates a failure of the seizure to invade the area, because of a feedforward inhibitory veto mechanism. Because multi-unit firing rate and high gamma amplitude are closely related, high frequency oscillations can be used as a surrogate marker to distinguish the core seizure territory from the surrounding penumbra. We developed an efficient measure to detect delayed-onset, sustained ictal high frequency oscillations based on cross-frequency coupling between high gamma amplitude and the low-frequency (1-25 Hz) ictal rhythm. When applied to the broader subdural recording, this measure consistently predicted the timing or failure of ictal invasion, and revealed a surprisingly small and slowly spreading seizure core surrounded by a far larger penumbral territory. Our findings thus establish an underlying neural mechanism for delayed-onset, sustained ictal high frequency oscillations, and provide a practical, efficient method for using them to identify the small ictal core regions. Our observations suggest that it may be possible to reduce substantially the extent of cortical resections in epilepsy surgery procedures without compromising seizure control.

Unchanged safety outcomes in deep brain stimulation surgery for Parkinson disease despite a decentralization of care

OBJECT

Early work on deep brain stimulation (DBS) surgery, when procedures were mostly carried out in a small number of high-volume centers, demonstrated a relationship between surgical volume and procedural safety. However, over the past decade, DBS has become more widely available in the community rather than solely at academic medical centers. The authors examined the Nationwide Inpatient Sample (NIS) to study the safety of DBS surgery for Parkinson disease (PD) in association with this change in practice patterns.

METHODS

The NIS is a stratified sample of 20% of all patient discharges from nonfederal hospitals in the United States. The authors identified patients with a primary diagnosis of PD (332.0) and a primary procedure code for implantation/replacement of intracranial neurostimulator leads (02.93) who underwent surgery between 2002 and 2009. They analyzed outcomes using univariate and hierarchical, logistic regression analyses.

RESULTS

The total number of DBS cases remained stable from 2002 through 2009. Despite older and sicker patients undergoing DBS, procedural safety (rates of non-home discharges, complications) remained stable. Patients at low-volume hospitals were virtually indistinguishable from those at high-volume hospitals, except that patients at low-volume hospitals had slightly higher comorbidity scores (0.90 vs 0.75, p < 0.01). Complications, non-home discharges, length of hospital stay, and mortality rates did not significantly differ between low- and high-volume hospitals when accounting for hospital-related variables (caseload, teaching status, location).

CONCLUSIONS

Prior investigations have demonstrated a robust volume-outcome relationship for a variety of surgical procedures. However, the present study supports safety of DBS at smaller-volume centers. Prospective studies are required to determine whether low-volume centers and higher-volume centers have similar DBS efficacy, a critical factor in determining whether DBS is comparable between centers.

Salomón Hakim and the discovery of normal-pressure hydrocephalus

INTRODUCTION

Normal-pressure hydrocephalus (NPH) is a chronic neurological disorder characterized by enlarged ventricles and a triad of clinical symptoms affecting gait, cognition, and urinary continence. Salomón Hakim first identified the syndrome in 1957 at the Hospital San Juan de Dios in Bogotá, Colombia. Even after decades of international focus and thousands of publications on his disorder, Hakim's story remains largely untold.

METHODS

In this historical review, we explore the discovery of NPH through a series of personal interviews with Professor Hakim and his family, discussions with former colleagues, and review of the relevant medical literature.

RESULTS

Professor Hakim first published his thesis in 1964 and 6 case reports of NPH in The New England Journal of Medicine and the Journal of the Neurological Sciences in 1965. Hakim rose to the forefront of academic medicine as he described a newfound ability to reverse symptoms of "neurodegeneration" that had long been considered irreversible.

CONCLUSIONS

As we learn more about NPH, the fascinating story of Professor Hakim, the father of NPH, is of both historical relevance and current interest.

Inferior Short-term Safety Profile of Endoscopic Third Ventriculostomy Compared With Ventriculoperitoneal Shunt Placement for Idiopathic Normal-Pressure Hydrocephalus

BACKGROUND:

In small series, endoscopic third ventriculostomy (ETV) has been shown to potentially have efficacy similar to that of ventriculoperitoneal shunting (VPS) for idiopathic normal-pressure hydrocephalus (iNPH). Therefore, some clinicians have advocated for ETV to avoid the potential long-term complications associated with VPS. Complication rates for these procedures vary widely based on limited small series data.

OBJECTIVE:

We used a nationwide database that provides a comprehensive investigation of the perioperative safety of ETV for iNPH compared with VPS.

METHODS:

We identified discharges with the primary diagnosis of iNPH (International Classification of Diseases, Ninth Revision code 331.5 [ICD-9]) with ICD-9 primary procedure codes for VPS (02.34) and ETV (02.2) from 2007 to 2010. We analyzed short-term safety outcomes using univariate and hierarchical logistic regression analyses.

RESULTS:

There were a total of 652 discharges for ETV for iNPH and 12 845 discharges for VPS for iNPH over the study period. ETV was associated with a significantly higher mortality (3.2% vs 0.5%) and short-term complication (17.9% vs 11.8%) rates than VPS despite similar mean modified comorbidity scores. On multivariate analysis, ETV alone predicted increased mortality and increased length of stay when adjusted for other patient and hospital factors.

CONCLUSION:

This is the first study that robustly assesses the perioperative complications and safety outcomes of ETV for iNPH. Compared with VPS, ETV is associated with higher perioperative mortality and complication rates. This consideration is important to weigh against the potential benefit of ETV: avoiding long-term shunt dependence. Prospective, randomized studies are needed.

Mechanisms underlying selective neuronal tracking of attended speech at a "cocktail party"

The ability to focus on and understand one talker in a noisy social environment is a critical social-cognitive capacity, whose underlying neuronal mechanisms are unclear. We investigated the manner in which speech streams are represented in brain activity and the way that selective attention governs the brain's representation of speech using a "Cocktail Party" paradigm, coupled with direct recordings from the cortical surface in surgical epilepsy patients. We find that brain activity dynamically tracks speech streams using both low-frequency phase and high-frequency amplitude fluctuations and that optimal encoding likely combines the two. In and near low-level auditory cortices, attention "modulates" the representation by enhancing cortical tracking of attended speech streams, but ignored speech remains represented. In higher-order regions, the representation appears to become more "selective," in that there is no detectable tracking of ignored speech. This selectivity itself seems to sharpen as a sentence unfolds.

Exemplar selectivity reflects perceptual similarities in the human fusiform cortex

While brain imaging studies emphasized the category selectivity of face-related areas, the underlying mechanisms of our remarkable ability to discriminate between different faces are less understood. Here, we recorded intracranial local field potentials from face-related areas in patients presented with images of faces and objects. A highly significant exemplar tuning within the category of faces was observed in high-Gamma (80-150 Hz) responses. The robustness of this effect was supported by single-trial decoding of face exemplars using a minimal (n = 5) training set. Importantly, exemplar tuning reflected the psychophysical distance between faces but not their low-level features. Our results reveal a neuronal substrate for the establishment of perceptual distance among faces in the human brain. They further imply that face neurons are anatomically grouped according to well-defined functional principles, such as perceptual similarity.

Cyclophilin D deficiency rescues axonal mitochondrial transport in Alzheimer's neurons

Normal axonal mitochondrial transport and function is essential for the maintenance of synaptic function. Abnormal mitochondrial motility and mitochondrial dysfunction within axons are critical for amyloid β (Aβ)-induced synaptic stress and the loss of synapses relevant to the pathogenesis of Alzheimer's disease (AD). However, the mechanisms controlling axonal mitochondrial function and transport alterations in AD remain elusive. Here, we report an unexplored role of cyclophilin D (CypD)-dependent mitochondrial permeability transition pore (mPTP) in Aβ-impaired axonal mitochondrial trafficking. Depletion of CypD significantly protects axonal mitochondrial motility and dynamics from Aβ toxicity as shown by increased axonal mitochondrial density and distribution and improved bidirectional transport of axonal mitochondria. Notably, blockade of mPTP by genetic deletion of CypD suppresses Aβ-mediated activation of the p38 mitogen-activated protein kinase signaling pathway, reverses axonal mitochondrial abnormalities, improves synaptic function, and attenuates loss of synapse, suggesting a role of CypD-dependent signaling in Aβ-induced alterations in axonal mitochondrial trafficking. The potential mechanisms of the protective effects of lacking CypD on Aβ-induced abnormal mitochondrial transport in axon are increased axonal calcium buffer capability, diminished reactive oxygen species (ROS), and suppressing downstream signal transduction P38 activation. These findings provide new insights into CypD-dependent mitochondrial mPTP and signaling on mitochondrial trafficking in axons and synaptic degeneration in an environment enriched for Aβ.

The role of head computed tomography imaging in the evaluation of postoperative neurologic deficits in cardiac surgery patients

BACKGROUND

Computed tomography (CT) scans of the head without contrast are routinely obtained to evaluate neurologic deficits after cardiac surgery, but their utility is unknown. We evaluated our experience with this imaging modality to determine its value.

METHODS

We retrospectively identified cardiac surgery patients with postoperative neurologic deficits occurring during the first week after surgery between January 2000 and December 2012. Stroke was defined by neurologist's determination, whereas a nonfocal deficit (NFD) was defined by the presence of seizure, delirium, or cognitive impairment. We defined early noncontrast head CT as occurring within 7 days of surgery. Outcomes included positive findings on CT, in-hospital mortality, and length of stay. Multivariate logistic regression identified predictors of positive findings on head CT.

RESULTS

Within the population of 11,070 postoperative patients, 451 had early noncontrast head CT scans (4%). Two hundred two (44.7%) were associated with stroke, and 249 (55.2%) were associated with NFD. Among stroke patients, 40 of 202 (20%) showed acute infarction, 17 of 202 (8%) showed subacute infarction, and 5 of 202 (2%) showed hemorrhage. Among NFD patients, 1 of 248 (0.4%) showed acute infarction, 4 of 248 (1.6%) showed subacute infarction, and 1 of 248 (0.4%) showed hemorrhage. There was no difference in in-hospital mortality (stroke, 42 of 201 [21%] versus NFD, 41 of 248 [16%]; p = 0.2) or length of stay (stroke, 24 d versus NFD, 22 d; p = 0.5). On multivariable logistic regression, only focal deficits and aortic procedures predicted a positive finding on CT scan.

CONCLUSIONS

This study reviewed the utility of early postoperative noncontrast head CT in cardiac surgery patients. With focal neurologic deficits, this imaging modality was positive for approximately one third of patients, but rarely positive for NFD. Its use in this setting has limited utility.

The mTOR pathway is activated in glial cells in mesial temporal sclerosis

Mammalian target of rapamycin (mTOR) is a key protein kinase that regulates basic cellular processes, including development and growth. Mutations in mTOR cause tuberous sclerosis complex (TSC), a condition that is characterized by developmental brain malformations (cortical tubers) and epilepsy. Although considerable insight has been gained recently into the pathologic dysfunction of mTOR in tubers in TSC-related epilepsy, data on the mTOR cascade in mesial temporal lobe epilepsy (MTLE) are lacking. Immunohistochemical investigation with confocal microscopy was performed to evaluate mTOR cascade and to correlate its activity with cellular alterations observed in surgically resected samples of human neocortex and hippocampus in MTLE. We compared results in human tissue to findings in the rat pilocarpine model of sclerotic MTLE. In nonsclerotic and control hippocampus, many neurons in the CA1 subfield expressed high levels of phospho-S6 (p-S6), a reliable marker of mTOR activation. In nonsclerotic and control hippocampus, as well as in magnetic resonance imaging (MRI) normal human neocortex, protoplasmic astrocytes did not express p-S6. In contrast, in sclerotic hippocampus, prominent p-S6 immunostaining was observed mainly in astrocytes and microglia located in the areas of neuronal loss and astrogliosis, whereas neurons in preserved areas of CA1 expressed significantly lower levels of p-S6 immunopositivity than neurons in nonsclerotic or control CA1 subfields. In surgically resected neocortex with chronic astroglial scar tissue, only microglia revealed moderate p-S6 immunoreactivity. Different from human sclerotic epileptic hippocampus, astrogliosis in the chronic rat pilocarpine model of epilepsy was not characterized by glial cells with mTOR activation. The mTOR cascade is activated in astroglial cells in sclerotic MTLE, but not in astrocytes in chronic neocortical scarring or in the pilocarpine model of MTLE. These findings suggest that the astroglial "scar" in sclerotic MTLE has active, ongoing cellular changes. Targeting mTOR in MTLE may provide new pathways for the medical therapy of epilepsy.

Motor deficits correlate with resting state motor network connectivity in patients with brain tumours

While a tumour in or abutting primary motor cortex leads to motor weakness, how tumours elsewhere in the frontal or parietal lobes affect functional connectivity in a weak patient is less clear. We hypothesized that diminished functional connectivity in a distributed network of motor centres would correlate with motor weakness in subjects with brain masses. Furthermore, we hypothesized that interhemispheric connections would be most vulnerable to subtle disruptions in functional connectivity. We used task-free functional magnetic resonance imaging connectivity to probe motor networks in control subjects and patients with brain tumours (n = 22). Using a control dataset, we developed a method for automated detection of key nodes in the motor network, including the primary motor cortex, supplementary motor area, premotor area and superior parietal lobule, based on the anatomic location of the hand-motor knob in the primary motor cortex. We then calculated functional connectivity between motor network nodes in control subjects, as well as patients with and without brain masses. We used this information to construct weighted, undirected graphs, which were then compared to variables of interest, including performance on a motor task, the grooved pegboard. Strong connectivity was observed within the identified motor networks between all nodes bilaterally, and especially between the primary motor cortex and supplementary motor area. Reduced connectivity was observed in subjects with motor weakness versus subjects with normal strength (P < 0.001). This difference was driven mostly by decreases in interhemispheric connectivity between the primary motor cortices (P < 0.05) and between the left primary motor cortex and the right premotor area (P < 0.05), as well as other premotor area connections. In the subjects without motor weakness, however, performance on the grooved pegboard did not relate to interhemispheric connectivity, but rather was inversely correlated with connectivity between the left premotor area and left supplementary motor area, for both the left and the right hands (P < 0.01). Finally, two subjects who experienced severe weakness following surgery for their brain tumours were followed longitudinally, and the subject who recovered showed reconstitution of her motor network at follow-up. The subject who was persistently weak did not reconstitute his motor network. Motor weakness in subjects with brain tumours that do not involve primary motor structures is associated with decreased connectivity within motor functional networks, particularly interhemispheric connections. Motor networks become weaker as the subjects become weaker, and may become strong again during motor recovery.

Pre-operative intracranial meningioma embolization

Pre-operative embolization is a routinely utilized therapeutic adjunct to the resection of hypervascular lesions of the head and neck. In particular, pre-operative cerebral angiography and tumor embolization has become standard practice at many centers in the management of select intracranial meningiomas. However, controversy remains regarding its specific indications and clinical utility. In this article, we examine the principles of meningioma embolization, emphasizing the indications, risks and benefits associated with its use in the pre-operative setting.

Clinical impact of updated diagnostic and research criteria for Alzheimer's disease

Almost 30 years ago, the National Institute of Neurological and Communicative Disorders and Stroke and the Alzheimer's Disease and Related Disorders Association (more commonly known as the Alzheimer's Association) developed the original clinical diagnostic criteria for Alzheimer's disease (AD). Recently, the National Institute on Aging and the Alzheimer's Association released updated research and diagnostic criteria for AD. The new criteria establish that AD exists on a continuum and is comprised of not only dementia but also a preclinical phase and a phase of mild cognitive impairment due to AD. The new criteria also describe advancements in biomarker evidence, which is still being researched and is not yet ready for clinical settings. Additionally, the American Psychiatric Association is currently revising the Diagnostic and Statistical Manual of Mental Disorders, which will include updated diagnostic criteria for AD and other neurocognitive disorders.

Epidermoid tumors of the temporal lobe as epileptogenic foci

Intracerebral epidermoid tumors of the temporal lobe are exceedingly rare. The vast majority of these slow-growing tumors remain clinically silent while only a select few are associated with overt symptomatology. We report two patients with epidermoid tumors whose unique location in the temporal lobe resulted in secondarily generalized seizures. Our first patient, a 19-year-old female, presented with a secondarily generalized tonic-clonic seizure and MRI revealed a superior temporal lobe lesion that was subsequently treated with an awake craniotomy and gross total resection. Our second patient was a 71-year-old male with a recent seizure history and known left temporal lobe lesion. The patient underwent craniotomy for gross total resection of the mass. In these two patients, we found that MRI proved diagnostic and surgical resection was curative. Our clinical experience and review of the literature indicate that gross total resection of these lesions confers control of localization-related epilepsy.

Intraoperative hemoglobin levels and transfusion independently predict stroke after cardiac operations

BACKGROUND

Anemia has been associated with adverse cerebrovascular outcomes, particularly after cardiac operations. This study was conducted to determine if hemoglobin levels during and after cardiopulmonary bypass (CPB) predict postoperative stroke in cardiac surgical patients, independent of transfusion requirements.

METHODS

Individuals who had sustained a clinical postoperative stroke (cases) were matched 1:2 with controls by age, sex, surgical procedure, and year of operation. In 617 patients, conditional logistic regression was performed to analyze associations between hemoglobin levels before and after CPB, and stroke.

RESULTS

After adjustment for potentially confounding vascular risk factors, lower hemoglobin after CPB was associated with a higher risk of stroke, even after adjustment for the amount of packed red blood cells transfused (adjusted odds ratio, 1.28; 95% confidence interval, 1.00 to 1.64, per point of lower hemoglobin level; adjusted odds ratio for stroke per higher quartile of packed red blood cells transfused in this model, 1.37; 95% confidence interval, 1.02 to 1.83). Similar associations were not found for hemoglobin concentrations preoperatively nor change in hemoglobin from before to after CPB. A post-CPB hemoglobin level below the median was associated with 37% increased odds of a postoperative stroke occurring (p = 0.02).

CONCLUSIONS

Lower postoperative hemoglobin levels and higher intraoperative transfusion requirements are each independently associated with a higher risk of stroke. Reduced cerebral oxygen delivery due to anemia may contribute to cerebral injury after coronary artery bypass grafting.

The diagnosis of dementia due to Alzheimer's disease: recommendations from the National Institute on Aging-Alzheimer's Association workgroups on diagnostic guidelines for Alzheimer's disease

The National Institute on Aging and the Alzheimer's Association charged a workgroup with the task of revising the 1984 criteria for Alzheimer's disease (AD) dementia. The workgroup sought to ensure that the revised criteria would be flexible enough to be used by both general healthcare providers without access to neuropsychological testing, advanced imaging, and cerebrospinal fluid measures, and specialized investigators involved in research or in clinical trial studies who would have these tools available. We present criteria for all-cause dementia and for AD dementia. We retained the general framework of probable AD dementia from the 1984 criteria. On the basis of the past 27 years of experience, we made several changes in the clinical criteria for the diagnosis. We also retained the term possible AD dementia, but redefined it in a manner more focused than before. Biomarker evidence was also integrated into the diagnostic formulations for probable and possible AD dementia for use in research settings. The core clinical criteria for AD dementia will continue to be the cornerstone of the diagnosis in clinical practice, but biomarker evidence is expected to enhance the pathophysiological specificity of the diagnosis of AD dementia. Much work lies ahead for validating the biomarker diagnosis of AD dementia.

Introduction to the recommendations from the National Institute on Aging-Alzheimer's Association workgroups on diagnostic guidelines for Alzheimer's disease

BACKGROUND

Criteria for the clinical diagnosis of Alzheimer's disease (AD) were established in 1984. A broad consensus now exists that these criteria should be revised to incorporate state-of-the-art scientific knowledge.

METHODS

The National Institute on Aging (NIA) and the Alzheimer's Association sponsored a series of advisory round table meetings in 2009 whose purpose was to establish a process for revising diagnostic and research criteria for AD. The recommendation from these advisory meetings was that three separate work groups should be formed with each assigned the task of formulating diagnostic criteria for one phase of the disease: the dementia phase; the symptomatic, pre-dementia phase; and the asymptomatic, preclinical phase of AD.

RESULTS

Two notable differences from the AD criteria published in 1984 are incorporation of biomarkers of the underlying disease state and formalization of different stages of disease in the diagnostic criteria. There was a broad consensus within all three workgroups that much additional work is needed to validate the application of biomarkers for diagnostic purposes. In the revised NIA-Alzheimer's Association criteria, a semantic and conceptual distinction is made between AD pathophysiological processes and clinically observable syndromes that result, whereas this distinction was blurred in the 1984 criteria.

CONCLUSIONS

The new criteria for AD are presented in three documents. The core clinical criteria of the recommendations regarding AD dementia and MCI due to AD are intended to guide diagnosis in the clinical setting. However, the recommendations of the preclinical AD workgroup are intended purely for research purposes.

Association between hypotension, low ejection fraction and cognitive performance in cardiac patients

BACKGROUND AND PURPOSE

Impaired cardiac function can adversely affect the brain via decreased perfusion. The purpose of this study was to determine if cardiac ejection fraction (EF) is associated with cognitive performance, and whether this is modified by low blood pressure.

METHODS

Neuropsychological testing evaluating multiple cognitive domains, measurement of mean arterial pressure (MAP), and measurement of EF were performed in 234 individuals with coronary artery disease. The association between level of EF and performance within each cognitive domain was explored, as was the interaction between low MAP and EF.

RESULTS

Adjusted global cognitive performance, as well as performance in visuoconstruction and motor speed, was significantly directly associated with cardiac EF. This relationship was not entirely linear, with a steeper association between EF and cognition at lower levels of EF than at higher levels. Patients with low EF and low MAP at the time of testing had worse cognitive performance than either of these alone, particularly for the global and motor speed cognitive scores.

CONCLUSIONS

Low EF may be associated with worse cognitive performance, particularly among individuals with low MAP and for cognitive domains typically associated with vascular cognitive impairment. Further care should be paid to hypotension in the setting of heart failure, as this may exacerbate cerebral hypoperfusion.

Does cortical mapping protect naming if surgery includes hippocampal resection?

OBJECTIVE

Preresection electrical stimulation mapping is frequently used to identify cortical sites critical for visual object naming. These sites are typically spared from surgical resection with the goal of preserving postoperative language. Recent studies, however, suggest a potential role of the hippocampus in naming, although this is inconsistent with neurocognitive models of language and memory. We sought to determine whether preservation of visual naming sites identified via cortical stimulation mapping protects against naming decline when resection includes the hippocampal region.

METHODS

We assessed postoperative changes in visual naming in 33 patients, 14 who underwent left temporal resection including hippocampal removal and 19 who had left temporal resection without hippocampal removal. All patients had preresection cortical language mapping. Visual object naming sites identified via electrical stimulation were always preserved.

RESULTS

Patients without hippocampal resection showed no significant naming decline, suggesting a clinical benefit from cortical mapping. In contrast, patients who had hippocampal resection exhibited significant postoperative naming decline, despite preresection mapping and preservation of all visual naming sites (p < or = 0.02). These group effects were also evident in individual patients (p = 0.02). More detailed, post hoc examination of patients who had hippocampal resection revealed that overall, patients who declined were those with a preoperative, structurally intact hippocampus, whereas patients with preoperative hippocampal sclerosis did not exhibit significant decline.

INTERPRETATION

Despite cortical language mapping with preservation of visual naming sites from resection, removal of an intact dominant hippocampus will likely result in visual naming decline postoperatively.

Delirium after coronary artery bypass graft surgery and late mortality

OBJECTIVE

Delirium is common after cardiac surgery, although under-recognized, and its long-term consequences are likely underestimated. The primary goal of this study was to determine whether patients with delirium after coronary artery bypass graft (CABG) surgery have higher long-term out-of-hospital mortality when compared with CABG patients without delirium.

METHODS

We studied 5,034 consecutive patients undergoing CABG surgery at a single institution from 1997 to 2007. Presence or absence of neurologic complications, including delirium, was assessed prospectively. Survival analysis was performed to determine the role of delirium in the hazard of death, including a propensity score to adjust for potential confounders. These analyses were repeated to determine the association between postoperative stroke and long-term mortality.

RESULTS

Individuals with delirium had an increased hazard of death (adjusted hazard ratio [HR], 1.65; 95% confidence interval [CI], 1.38-1.97) up to 10 years postoperatively, after adjustment for perioperative and vascular risk factors. Patients with postoperative stroke had a HR of 2.34 (95% CI, 1.87-2.92). The effect of delirium on subsequent mortality was the strongest among those without a prior stroke (HR 1.83 vs HR 1.11 [with a prior stroke] [p-interaction = 0.02]) or who were younger (HR 2.42 [<65 years old] vs HR 1.49 [>/=65 years old] [p-interaction = 0.04]).

INTERPRETATION

Delirium after cardiac surgery is a strong independent predictor of mortality up to 10 years postoperatively, especially in younger individuals and in those without prior stroke. Future studies are needed to determine the impact of delirium prevention and/or treatment in long-term patient mortality.

Hippocampal removal affects visual but not auditory naming

OBJECTIVE

Dominant, left anteromedial temporal lobe resection (AMTLR) for seizure control carries risks to verbal episodic memory and visual object naming. Consistent with traditional thinking, verbal memory decline is considered a consequence of hippocampal removal and naming decline has been attributed to lateral temporal resection. Interestingly, recent findings suggest a potential relation between visual naming and hippocampal integrity, which is consistent with studies that link the hippocampus with higher level visual processing. Historically, naming has been evaluated using visual object naming tasks; however, naming can also be assessed using auditory verbal descriptions. Recent cortical stimulation studies have shown a neuroanatomic distinction between visual naming and auditory description naming. We speculated that unlike visual naming, the hippocampus is not involved in auditory naming, and hypothesized that left AMTLR would not result in auditory naming decline, despite visual naming and verbal memory decline.

METHODS

In this cohort study, we tested auditory naming, visual naming, and verbal memory in 25 left medial temporal lobe epilepsy (MTLE) and 20 right MTLE patients pre-AMTLR and 1 year post-AMTLR.

RESULTS

Left AMTLR patients declined in visual naming and verbal memory, with no decline in auditory naming. Right AMTLR patients exhibited no decline.

CONCLUSIONS

Results suggest that left anteromedial temporal lobe resection presents a greater risk to visual naming than auditory naming in patients with left medial temporal lobe epilepsy.

Statin use and neurologic morbidity after coronary artery bypass grafting: A cohort study

BACKGROUND

Statin use before surgery has been associated with reduced morbidity and mortality after vascular surgery. The effect of preoperative statin use on stroke and encephalopathy after coronary artery bypass grafting (CABG) is unclear.

METHODS

A post hoc analysis was undertaken of a prospectively collected cohort of isolated CABG patients over a 10-year period at a single institution. Primary outcomes were stroke and encephalopathy. Univariable analyses identified risk factors for statin use, which were applied to a propensity score model using logistic regression and patients were divided into quintiles of propensity for statin use. Controlling for propensity score quintile, the odds ratio (OR) of combined stroke and encephalopathy (primary endpoint), cardiovascular mortality, myocardial infarction, and length of stay were compared between statin users and nonusers.

RESULTS

There were 5,121 CABG patients, of whom 2,788 (54%) were taking statin medications preoperatively. Stroke occurred in 166 (3.2%) and encephalopathy in 438 (8.6%), contributing to 604 patients (11.8%) who met the primary endpoint. The unadjusted OR of stroke/encephalopathy in statin users was 1.053 (95% confidence interval [CI] 0.888-1.248, p = 0.582). Adjustment based on propensity score resulted in balance of stroke risk factors among quintiles. The propensity score-adjusted OR of stroke/encephalopathy in statin users was 0.958 (95% CI 0.784-1.170, p = 0.674). There were no significant differences in cardiovascular mortality, myocardial infarction, or length of stay between statin users and otherwise similar nonusers.

CONCLUSIONS

In this large data cohort study, preoperative statin use was not associated with a decreased incidence of stroke and encephalopathy after coronary artery bypass grafting.

Do management strategies for coronary artery disease influence 6-year cognitive outcomes?

BACKGROUND

Previous uncontrolled studies have suggested that there is late cognitive decline after coronary artery bypass grafting that may be attributable to use of the cardiopulmonary bypass pump.

METHODS

In this prospective, nonrandomized, longitudinal study, we compared cognitive outcomes after on-pump coronary artery bypass surgery (n = 152) with off-pump bypass surgery patients (n = 75); nonsurgical cardiac comparison subjects (n = 99); and 69 heart-healthy comparison (HHC) subjects. The primary outcome measure was change from baseline to 72 months in the following cognitive domains: verbal memory, visual memory, visuoconstruction, language, motor speed, psychomotor speed, attention, executive function, and a composite global score.

RESULTS

There were no consistent differences in 72-month cognitive outcomes among the three groups with coronary artery disease (CAD). The CAD groups had lower baseline performance, and a greater degree of decline compared with HHC. The degree of change was small, with none of the groups having more than 0.5 SD decline. None of the groups was substantially worse at 72 months compared with baseline.

CONCLUSIONS

Compared with subjects with no vascular disease risk factors, the CAD patients had lower baseline cognitive performance and greater degrees of decline over 72 months, suggesting that in these patients, vascular disease may have an impact on cognitive performance. We found no significant differences in the long-term cognitive outcomes among patients with various CAD therapies, indicating that management strategy for CAD is not an important determinant of long-term cognitive outcomes.