Direct Intracranial Injection of AAVrh8 Encoding Monkey β-N-Acetylhexosaminidase Causes Neurotoxicity in the Primate Brain

GM2 gangliosidoses, including Tay-Sachs disease and Sandhoff disease, are lysosomal storage disorders caused by deficiencies in β-N-acetylhexosaminidase (Hex). Patients are afflicted primarily with progressive central nervous system (CNS) dysfunction. Studies in mice, cats, and sheep have indicated safety and widespread distribution of Hex in the CNS after intracranial vector infusion of AAVrh8 vectors encoding species-specific Hex α- or β-subunits at a 1:1 ratio. Here, a safety study was conducted in cynomolgus macaques (cm), modeling previous animal studies, with bilateral infusion in the thalamus as well as in left lateral ventricle of AAVrh8 vectors encoding cm Hex α- and β-subunits. Three doses (3.2 × 10¹² vg [n = 3]; 3.2 × 10¹¹ vg [n = 2]; or 1.1 × 10¹¹ vg [n = 2]) were tested, with controls infused with vehicle (n = 1) or transgene empty AAVrh8 vector at the highest dose (n = 2). Most monkeys receiving AAVrh8-cmHexα/β developed dyskinesias, ataxia, and loss of dexterity, with higher dose animals eventually becoming apathetic. Time to onset of symptoms was dose dependent, with the highest-dose cohort producing symptoms within a month of infusion. One monkey in the lowest-dose cohort was behaviorally asymptomatic but had magnetic resonance imaging abnormalities in the thalami. Histopathology was similar in all monkeys injected with AAVrh8-cmHexα/β, showing severe white and gray matter necrosis along the injection track, reactive vasculature, and the presence of neurons with granular eosinophilic material. Lesions were minimal to absent in both control cohorts. Despite cellular loss, a dramatic increase in Hex activity was measured in the thalamus, and none of the animals presented with antibody titers against Hex. The high overexpression of Hex protein is likely to blame for this negative outcome, and this study demonstrates the variations in safety profiles of AAVrh8-Hexα/β intracranial injection among different species, despite encoding for self-proteins.

A Phase II Study of Fornix Deep Brain Stimulation in Mild Alzheimer's Disease

BACKGROUND

Deep brain stimulation (DBS) is used to modulate the activity of dysfunctional brain circuits. The safety and efficacy of DBS in dementia is unknown.

OBJECTIVE

To assess DBS of memory circuits as a treatment for patients with mild Alzheimer's disease (AD).

METHODS

We evaluated active "on" versus sham "off" bilateral DBS directed at the fornix-a major fiber bundle in the brain's memory circuit-in a randomized, double-blind trial (ClinicalTrials.gov NCT01608061) in 42 patients with mild AD. We measured cognitive function and cerebral glucose metabolism up to 12 months post-implantation.

RESULTS

Surgery and electrical stimulation were safe and well tolerated. There were no significant differences in the primary cognitive outcomes (ADAS-Cog 13, CDR-SB) in the "on" versus "off" stimulation group at 12 months for the whole cohort. Patients receiving stimulation showed increased metabolism at 6 months but this was not significant at 12 months. On post-hoc analysis, there was a significant interaction between age and treatment outcome: in contrast to patients <65 years old (n = 12) whose results trended toward being worse with DBS ON versus OFF, in patients≥65 (n = 30) DBS-f ON treatment was associated with a trend toward both benefit on clinical outcomes and a greater increase in cerebral glucose metabolism.

CONCLUSION

DBS for AD was safe and associated with increased cerebral glucose metabolism. There were no differences in cognitive outcomes for participants as a whole, but participants aged≥65 years may have derived benefit while there was possible worsening in patients below age 65 years with stimulation.

Computational modeling to improve treatments for essential tremor

Essential tremor (ET) is a neurological disorder of unknown etiology that is typically characterized by an involuntary periodic movement of the upper limbs. No longer considered monosymptomatic, ET patients often have additional motor and even cognitive impairments. Although there are several pharmacological treatments, no drugs have been developed specifically for ET [1], and 30-70% of patients are medication-refractory [2]. A subset of medication-refractory patients may benefit from electrical deep brain stimulation (DBS) of the ventral intermediate nucleus of the thalamus (VIM), which receives cerebellar inputs. Abnormal cerebellar input to VIM is presumed to be a major contributor to tremor symptoms, which is alleviated by DBS. Computational modeling of the effects of DBS in VIM has been a powerful tool to design DBS protocols to reduce tremor activity. However, far less is known about how these therapies affect non-tremor symptoms, and more experimental and computational modeling work is required to address these growing considerations. Models capable of addressing multiple facets of ET will lead to novel, more efficient treatment.

Bilateral deep brain stimulation of the fornix for Alzheimer's disease: surgical safety in the ADvance trial

OBJECT This report describes the stereotactic technique, hospitalization, and 90-day perioperative safety of bilateral deep brain stimulation (DBS) of the fornix in patients who underwent DBS for the treatment of mild, probable Alzheimer's disease (AD). METHODS The ADvance Trial is a multicenter, 12-month, double-blind, randomized, controlled feasibility study being conducted to evaluate the safety, efficacy, and tolerability of DBS of the fornix in patients with mild, probable AD. Intraoperative and perioperative data were collected prospectively. All patients underwent postoperative MRI. Stereotactic analyses were performed in a blinded fashion by a single surgeon. Adverse events (AEs) were reported to an independent clinical events committee and adjudicated to determine the relationship between the AE and the study procedure. RESULTS Between June 6, 2012, and April 28, 2014, a total of 42 patients with mild, probable AD were treated with bilateral fornix DBS (mean age 68.2 ± 7.8 years; range 48.0-79.7 years; 23 men and 19 women). The mean planned target coordinates were x = 5.2 ± 1.0 mm (range 3.0-7.9 mm), y = 9.6 ± 0.9 mm (range 8.0-11.6 mm), z = -7.5 ± 1.2 mm (range -5.4 to -10.0 mm), and the mean postoperative stereotactic radial error on MRI was 1.5 ± 1.0 mm (range 0.2-4.0 mm). The mean length of hospitalization was 1.4 ± 0.8 days. Twenty-six (61.9%) patients experienced 64 AEs related to the study procedure, of which 7 were serious AEs experienced by 5 patients (11.9%). Four (9.5%) patients required return to surgery: 2 patients for explantation due to infection, 1 patient for lead repositioning, and 1 patient for chronic subdural hematoma. No patients experienced neurological deficits as a result of the study, and no deaths were reported. CONCLUSIONS Accurate targeting of DBS to the fornix without direct injury to it is feasible across surgeons and treatment centers. At 90 days after surgery, bilateral fornix DBS was well tolerated by patients with mild, probable AD. Clinical trial registration no.: NCT01608061 ( clinicaltrials.gov ).

Estimating a dynamic state to relate neural spiking activity to behavioral signals during cognitive tasks

An important question in neuroscience is understanding the relationship between high-dimensional electrophysiological data and complex, dynamic behavioral data. One general strategy to address this problem is to define a low-dimensional representation of essential cognitive features describing this relationship. Here we describe a general state-space method to model and fit a low-dimensional cognitive state process that allows us to relate behavioral outcomes of various tasks to simultaneously recorded neural activity across multiple brain areas. In particular, we apply this model to data recorded in the lateral prefrontal cortex (PFC) and caudate nucleus of non-human primates as they perform learning and adaptation in a rule-switching task. First, we define a model for a cognitive state process related to learning, and estimate the progression of this learning state through the experiments. Next, we formulate a point process generalized linear model to relate the spiking activity of each PFC and caudate neuron to the stimated learning state. Then, we compute the posterior densities of the cognitive state using a recursive Bayesian decoding algorithm. We demonstrate that accurate decoding of a learning state is possible with a simple point process model of population spiking. Our analyses also allow us to compare decoding accuracy across neural populations in the PFC and caudate nucleus.

Penetrating brain injury after suicide attempt with speargun: case study and review of literature

Penetrating cranial injury by mechanisms other than gunshots are exceedingly rare, and so strategies and guidelines for the management of PBI are largely informed by data from higher-velocity penetrating injuries. Here, we present a case of penetrating brain injury by the low-velocity mechanism of a harpoon from an underwater fishing speargun in an attempted suicide by a 56-year-old Caucasian male. The case raised a number of interesting points in management of low-velocity penetrating brain injury (LVPBI), including benefit in delaying foreign body removal to allow for tamponade; the importance of history-taking in establishing the social/legal significance of the events surrounding the injury; the use of cerebral angiogram in all cases of PBI; advantages of using dual-energy CT to reduce artifact when available; and antibiotic prophylaxis in the context of idiosyncratic histories of usage of penetrating objects before coming in contact with the intracranial environment. We present here the management of the case in full along with an extended discussion and review of existing literature regarding key points in management of LVPBI vs. higher-velocity forms of intracranial injury.

Comprehensive assessment of isolated traumatic subarachnoid hemorrhage

Recent studies have shown that isolated traumatic subarachnoid hemorrhage (tSAH) in the setting of a high Glasgow Coma Scale (GCS) score (13-15) is a relatively less severe finding not likely to require operative neurosurgical intervention. This study sought to provide a more comprehensive assessment of isolated tSAH among patients with any GCS score, and to expand the analysis to examine the potential need for aggressive medical, endovascular, or open surgical interventions in these patients. By undertaking a retrospective review of all patients admitted to our trauma center from 2003-2012, we identified 661 patients with isolated tSAH. Only four patients (0.61%) underwent any sort of aggressive neurosurgical, medical, or endovascular intervention, regardless of GCS score. Most tSAH patients without additional systemic injury were discharged home (68%), including 53% of patients with a GCS score of 3-8. However, older patients were more likely to be discharged to a rehabilitation facility (p<0.01). There were six (1.7%) in-hospital deaths, and five patients of these patients were older than 80 years old. We conclude that isolated tSAH, regardless of admission GCS score, is a less severe intracranial injury that is highly unlikely to require aggressive operative, medical, or endovascular intervention, and is unlikely to be associated with major neurologic morbidity or mortality, except perhaps in elderly patients. Based upon our findings, we argue that impaired consciousness in the setting of isolated tSAH should strongly compel a consideration of non-traumatic factors in the etiology of the altered neurological status.

Predictors of cranioplasty complications in stroke and trauma patients

Object

Decompressive craniectomy mandates subsequent cranioplasty. Complications of cranioplasty may be independent of the initial craniectomy, or they may be contingent upon the craniectomy. Authors of this study aimed to identify surgery- and patient-specific risk factors related to the development of surgical site infection and other complications following cranioplasty.

Methods

A consecutive cohort of patients of all ages and both sexes who had undergone cranioplasty following craniectomy for stroke or trauma at a single institution in the period from May 2004 to May 2012 was retrospectively established. Patients who had undergone craniectomy for infectious lesions or neoplasia were excluded. A logistic regression analysis was performed to model and predict determinants related to infection following cranioplasty.

Results

Two hundred thirty-nine patients met the study criteria. The overall rate of complication following cranioplasty was 23.85% (57 patients). Complications included, predominantly, surgical site infection, hydrocephalus, and new-onset seizures. Logistic regression analysis identified previous reoperation (OR 3.25, 95% CI 1.30–8.11, p = 0.01) and therapeutic indication for stroke (OR 2.45, 95% CI 1.11–5.39, p = 0.03) as significantly associated with the development of cranioplasty infection. Patient age, location of cranioplasty, presence of an intracranial device, bone flap preservation method, cranioplasty material, booking method, and time interval > 90 days between initial craniectomy and cranioplasty were not predictive of the development of cranioplasty infection.

Conclusions

Cranioplasty complications are common. Cranioplasty infection rates are predicted by reoperation following craniectomy and therapeutic indication (stroke). These variables may be associated with patient-centered risk factors that increase cranioplasty infection risk.

Action initiation in the human dorsal anterior cingulate cortex

The dorsal anterior cingulate cortex (dACC) has previously been implicated in processes that influence action initiation. In humans however, there has been little direct evidence connecting dACC to the temporal onset of actions. We studied reactive behavior in patients undergoing therapeutic bilateral cingulotomy to determine the immediate effects of dACC ablation on action initiation. In a simple reaction task, three patients were instructed to respond to a specific visual cue with the movement of a joystick. Within minutes of dACC ablation, the frequency of false starts increased, where movements occurred prior to presentation of the visual cue. In a decision making task with three separate patients, the ablation effect on action initiation persisted even when action selection was intact. These findings suggest that human dACC influences action initiation, apart from its role in action selection.

High-performance execution of psychophysical tasks with complex visual stimuli in MATLAB

Behavioral, psychological, and physiological experiments often require the ability to present sensory stimuli, monitor and record subjects' responses, interface with a wide range of devices, and precisely control the timing of events within a behavioral task. Here, we describe our recent progress developing an accessible and full-featured software system for controlling such studies using the MATLAB environment. Compared with earlier reports on this software, key new features have been implemented to allow the presentation of more complex visual stimuli, increase temporal precision, and enhance user interaction. These features greatly improve the performance of the system and broaden its applicability to a wider range of possible experiments. This report describes these new features and improvements, current limitations, and quantifies the performance of the system in a real-world experimental setting.

Bilateral hemicraniectomy in non-penetrating traumatic brain injury

Traumatic brain injury is a heterogeneous entity that encompasses both surgical and non-surgical conditions. Surgery may be indicated with traumatic lesions such as hemorrhage, fractures, or malignant cerebral edema. However, the neurological exam may be clouded by the effects of medications administered in the field, systemic injuries, and inaccuracies in hyperacute prognostication. Typically, neurological injury is considered irreversible if diffuse loss of grey/white matter differentiation or if brainstem hemorrhage (Duret hemorrhage) exists. We aim to characterize a cohort of patients undergoing bilateral hemicraniectomy for severe traumatic brain injury. A retrospective consecutive cohort of adult patients undergoing craniectomy for trauma was established between the dates of January 2008 and November 2011. The primary outcome of the study was in-hospital mortality. Secondary outcomes were ICU length of stay, surgical complications, and Glasgow Outcome Score at most recent follow-up. During the study period, 210 patients undergoing craniectomy for traumatic mass-occupying lesion (epidural hematoma, subdural hematoma, or parenchymal contusion) were analyzed. Of those, 9 met study criteria. In-hospital mortality was 67% (6 of 9 patients). The average ICU length of stay was 12 days. The GOS score was 3 in surviving patients. Bilateral hemicraniectomy is a heroic intervention for patients with severe TBI, but can be a life-saving procedure.

The use of intra-operative blood gas analysis in the investigation of suspected iatrogenic vascular injury

BACKGROUND

Iatrogenic injury to the vertebral artery during posterior cervical fusion is a rare and potentially disastrous complication. Differentiating arterial from brisk venous bleeding would be ideal to assist in the intra-operative management. Definitive angiography is typically not feasible during most routine spine surgery.

CASE DESCRIPTION

We describe the case of a patient undergoing an occipitocervical fusion, where brisk bleeding was encountered during dissection of the CB lateral mass. While the dissection was thought to be superficial to critical structures, the nature of the hemorrhage could not be definitely determined by visual inspection by two senior surgeons. The hemorrhage did not readily cease with standard maneuvers such as, the application of various hemostatic agents. Simultaneous blood gas analysis was performed on samples obtained from the patient's radial artery and from the hemorrhage in the operative bed. Comparative analysis concluded that the bleeding encountered in the surgical field was venous in nature.

CONCLUSION

Blood gas analysis can be a useful adjunct in determining the nature of hemorrhage from vascular structures in spine surgery when visual inspection is indeterminate.

Craniectomy for malignant cerebral infarction: prevalence and outcomes in US hospitals

Object

Randomized trials have demonstrated the efficacy of craniectomy for the treatment of malignant cerebral edema following ischemic stroke. We sought to determine the prevalence and outcomes related to this by using a national database.

Methods

Patient discharges with ischemic stroke as the primary diagnosis undergoing craniectomy were queried from the US Nationwide Inpatient Sample from 1999 to 2008. A subpopulation of patients was identified that underwent thrombolysis. Two primary end points were examined: in-hospital mortality and discharge to home/routine care. To facilitate interpretations, adjusted prevalence was calculated from the overall prevalence and two age-specific logistic regression models. The predictive margin was then generated using a multivariate logistic regression model to estimate the probability of in-hospital mortality after adjustment for admission type, admission source, length of stay, total hospital charges, chronic comorbidities, and medical complications.

Results

After excluding 71,996 patients with the diagnosis of intracranial hemorrhage and posterior intracranial circulation occlusion, we identified 4,248,955 adult hospitalizations with ischemic stroke as a primary diagnosis. The estimated rates of hospitalizations in craniectomy per 10,000 hospitalizations with ischemic stroke increased from 3.9 in 1999–2000 to 14.46 in 2007–2008 (p for linear trend<0.001). Patients 60+ years of age had in-hospital mortality of 44% while the 18–59 year old group was found to be 24%(p = 0.14). Outcomes were comparable if recombinant tissue plasminogen activator had been administered.

Conclusions

Craniectomy is being increasingly performed for malignant cerebral edema following large territory cerebral ischemia. We suspect that the increase in the annual incidence of DC for malignant cerebral edema is directly related to the expanding collection of evidence in randomized trials that the operation is efficacious when performed in the correct patient population. In hospital mortality is high for all patients undergoing this procedure.

Temporal bone chondroblastoma with secondary aneurysmal bone cyst presenting as an intracranial mass with clinical seizure activity

Chondroblastomas are rare tumors that characteristically arise from the epiphyseal cartilage of long bones of the immature skeleton. Intracranial involvement is uncommon, though the squamous portion of the temporal bone is preferentially affected due to its cartilaginous origin. Patients with temporal bone chondroblastomas classically present with otologic symptoms, while primary neurological complaints are rare. In this report, we describe a 33 year-old man with a chondroblastoma of the temporal bone and an associated aneurysmal bone cyst constituting a large intracranial mass lesion who presented with new-onset seizure activity. We review issues relevant to the pathology and treatment of these lesions.

Operative management of brainstem cavernous malformations

Brainstem cavernous malformations (CMs) are complex lesions associated with hemorrhage and neurological deficit. In this review, the authors describe the anatomical nuances relating to the operative techniques for these challenging lesions. The resection of brainstem CMs in properly selected patients has been demonstrated to reduce the risk of rehemorrhage and can be achieved relatively safely in experienced hands.

Risk factors for hemorrhage during microelectrode-guided deep brain stimulation and the introduction of an improved microelectrode design

OBJECTIVE

Hemorrhage is an infrequent but potentially devastating complication of deep brain stimulation (DBS) surgery. We examined the factors associated with hemorrhage after DBS surgery and evaluated a modified microelectrode design that may improve the safety of this procedure.

METHODS

All microelectrode-guided DBS procedures performed at our institution between January 2000 and March 2008 were included in this study. A new microelectrode design with decreased diameter was introduced in May 2004, and data from the 2 types of electrodes were compared.

RESULTS

We examined 246 microelectrode-guided lead implantations in 130 patients. Postoperative imaging revealed 7 hemorrhages (2.8%). Five of the 7 (2.0%) resulted in focal neurological deficits, all of which resolved within 1 month with the exception of 1 patient lost to follow-up. The new microelectrode design significantly decreased the number of hemorrhages (P = 0.04). A surgical trajectory traversing the ventricle also contributed significantly to the overall hemorrhage rate (P = 0.02) and specifically to the intraventricular hemorrhage rate (P = 0.01). In addition, the new microelectrode design significantly decreased the rate of intraventricular hemorrhage, given a ventricular penetration (P = 0.01). The mean age of patients with hemorrhage was significantly higher than that of patients without hemorrhage (P = 0.02). Hypertension, sex, and number of microelectrodes passed did not significantly contribute to hemorrhage rates in our population.

CONCLUSION

The rate of complications after DBS surgery is not uniformly distributed across all cases. In particular, the rates of hemorrhage were increased in older patients. Importantly, transventricular electrode trajectories appeared to increase the risk of hemorrhage. A new microelectrode design minimizing the volume of brain parenchyma penetrated during microelectrode recording leads to decreased rates of hemorrhage, particularly if the ventricles are breached.

A flexible software tool for temporally-precise behavioral control in Matlab

Systems and cognitive neuroscience depend on carefully designed and precisely implemented behavioral tasks to elicit the neural phenomena of interest. To facilitate this process, we have developed a software system that allows for the straightforward coding and temporally-reliable execution of these tasks in Matlab. We find that, in most cases, millisecond accuracy is attainable, and those instances in which it is not are usually related to predictable, programmed events. In this report, we describe the design of our system, benchmark its performance in a real-world setting, and describe some key features.

A neural circuit model of flexible sensorimotor mapping: learning and forgetting on multiple timescales

Volitional behavior relies on the brain's ability to remap sensory flow to motor programs whenever demanded by a changed behavioral context. To investigate the circuit basis of such flexible behavior, we have developed a biophysically based decision-making network model of spiking neurons for arbitrary sensorimotor mapping. The model quantitatively reproduces behavioral and prefrontal single-cell data from an experiment in which monkeys learn visuomotor associations that are reversed unpredictably from time to time. We show that when synaptic modifications occur on multiple timescales, the model behavior becomes flexible only when needed: slow components of learning usually dominate the decision process. However, if behavioral contexts change frequently enough, fast components of plasticity take over, and the behavior exhibits a quick forget-and-learn pattern. This model prediction is confirmed by monkey data. Therefore, our work reveals a scenario for conditional associative learning that is distinct from instant switching between sets of well-established sensorimotor associations.

Task-specific neural activity in the primate prefrontal cortex

Real-world behavior is typically more complicated than a one-to-one mapping between a stimulus and response; the same stimulus can lead to different behaviors depending on the situation, or the same behavior may be cued by different stimuli. In such cases, knowledge of the formal demands of the task at hand is required. We found that in monkeys trained to alternate between three tasks, the activity of many neurons in the prefrontal cortex was task dependent. This included changes in overall firing rate, in firing-rate profiles (shape of responses over time), and in stimulus and response selectivity. These findings support the hypothesis that a major prefrontal function is the acquisition and implementation of task context and the "rules" used to guide behavior.

Memory fields of neurons in the primate prefrontal cortex

Many prefrontal (PF) neurons convey information about both an object's identity (what) and its location (where). To explore how they represent conjunctions of what and where, we explored the receptive fields of their mnemonic activity (i.e., their "memory fields") by requiring monkeys to remember both an object and its location at many positions throughout a wide portion of central vision. Many PF neurons conveyed object information and had highly localized memory fields that emphasized the contralateral, but not necessarily foveal, visual field. These results indicate that PF neurons can simultaneously convey precise location and object information and thus may play a role in constructing a unified representation of a visual scene.

Neural activity in the primate prefrontal cortex during associative learning

The prefrontal (PF) cortex has been implicated in the remarkable ability of primates to form and rearrange arbitrary associations rapidly. This ability was studied in two monkeys, using a task that required them to learn to make specific saccades in response to particular cues and then repeatedly reverse these responses. We found that the activity of individual PF neurons represented both the cues and the associated responses, perhaps providing a neural substrate for their association. Furthermore, during learning, neural activity conveyed the direction of the animals' impending responses progressively earlier within each successive trial. The final level of activity just before the response, however, was unaffected by learning. These results suggest a role for the PF cortex in learning arbitrary cue-response associations, an ability critical for complex behavior.

Selective representation of relevant information by neurons in the primate prefrontal cortex

The severe limitation of the capacity of working memory, the ability to store temporarily and manipulate information, necessitates mechanisms that restrict access to it. Here we report tests to discover whether the activity of neurons in the prefrontal (PF) cortex, the putative neural correlate of working memory, might reflect these mechanisms and preferentially represent behaviourally relevant information. Monkeys performed a 'delayed-matching-to-sample' task with an array of three objects. Only one of the objects in the array was relevant for task performance and the monkeys needed to find that object (the target) and remember its location. For many PF neurons, activity to physically identical arrays varied with the target location; the location of the non-target objects had little or no influence on activity. Information about the target location was present in activity as early as 140ms after array onset. Also, information about which object was the target was reflected in the sustained activity of many PF neurons. These results suggest that the prefrontal cortex is involved in selecting and maintaining behaviourally relevant information.