Cholinergic treatment of amnesia following basal forebrain lesion due to aneurysm rupture--an open-label pilot study

TREM2 alleviates long-term cognitive dysfunction after subarachnoid hemorrhage in mice by attenuating hippocampal neuroinflammation via PI3K/Akt signaling pathway

Subarachnoid hemorrhage (SAH) often leads to long-term cognitive deficits in patients, particularly due to injury to brain regions such as the hippocampus. This study aims to investigate the role of the triggering receptor expressed on myeloid cells 2 (TREM2) in mitigating hippocampal injury and associated cognitive impairments following SAH. To explore the protective effects of TREM2, we utilized the TREM2 agonist COG1410 to upregulate TREM2 expression and employed TREM2 knockout (KO) mice to verify the necessity of TREM2 for this protective role. The study further examined the involvement of the PI3K/Akt signaling pathway in TREM2-mediated neuroprotection. Our findings indicate that the upregulation of TREM2 significantly alleviated long-term cognitive deficits and promoted the recovery of hippocampal neural activity post-SAH. The neuroprotective effects were linked to reduced microglial activation and decreased secretion of inflammatory factors within the hippocampus. In contrast, TREM2 KO mice did not exhibit these protective effects. Furthermore, inhibition of the PI3K/Akt pathway also diminished these protective effects of TREM2 upregulation and worsened cognitive outcomes. In conclusion, TREM2 upregulation mitigates long-term cognitive dysfunction following SAH by attenuating hippocampal neuroinflammation via the PI3K/Akt signaling pathway. These findings suggest that TREM2 could be a potential therapeutic target for improving cognitive outcomes after SAH.

Neurocognitive Sequelae and Rehabilitation after Subarachnoid Hemorrhage: Optimizing Outcomes

Subarachnoid hemorrhage (SAH) is a medical emergency that requires immediate intervention. The etiology varies between cases; however, rupture of an intracranial aneurysm accounts for 80% of medical emergencies. Early intervention and treatment are essential to prevent long-term complications. Over the years, treatment of SAH has drastically improved, which is responsible for the rapid rise in SAH survivors. Post-SAH, a significant number of patients exhibit impairments in memory and executive function and report high rates of depression and anxiety that ultimately affect daily living, return to work, and quality of life. Given the rise in SAH survivors, rehabilitation post-SAH to optimize patient outcomes becomes crucial. The review addresses the current rehabilitative strategies to combat the neurocognitive and behavioral issues that may arise following SAH.

Association of Rebleeding and Delayed Cerebral Ischemia with Long-term Mortality Among 1-year Survivors After Aneurysmal Subarachnoid Hemorrhage

BACKGROUND AND OBJECTIVE

The potential impact of rebleeding and Delayed Cerebral Ischemia (DCI) on long-term survival in patients with aneurysmal subarachnoid hemorrhage (aSAH) remained unclear. This study aimed to investigate whether DCI and rebleeding increase the risk of long-term all-cause mortality in patients with aSAH who survived the follow-up period of one year.

METHODS

We retrospectively collected data on patients with atraumatic aSAH who were still alive 12 months after aSAH occurrence between December 2013 and June 2019 from the electronic health system. Patients were then classified by the occurrence of rebleeding or DCI during hospitalization. Death records were obtained from an administrative database, the Chinese Household Registration Administration System, until April 20, 2021. Multivariable Cox proportional hazards models were used to compare overall survival in different groups. Sensitivity analysis was performed with propensity-score matching (PSM).

RESULTS

A total of 2,607 patients were alive one year after aSAH. The crude annual death rate from any cause among patients who had rebleeding (7.2 per 100 person-years) and patients who had DCI (3.7 per 100 person-years) during hospitalization was higher than that of patients with neither event (2.1 per 100 person-years). Multivariate analysis showed that rebleeding is an independent risk factor for long-term mortality (adjusted hazard ratio (aHR), 2.37; 95% confidence interval (CI), 1.47- 3.81). DCI was an independent prognostic factor of poorer overall survival (aHR, 2.09; 95% CI, 1.54-2.84).

CONCLUSION

Amongst patients alive one year after aSAH, rebleeding and DCI during hospitalization were independently associated with higher rates of long-term mortality.

Postoperative Clipping Status after a Pterional versus Interhemispheric Approach for High-Positioned Anterior Communicating Artery Aneurysms

OBJECTIVE

When treating high-positioned anterior communicating artery (ACoA) aneurysms, pterional-transsylvian and interhemispheric approaches are both viable options, yet comparative studies of these two surgical approaches are rare. Accordingly, this retrospective study investigated the surgical results of both approaches.

METHODS

Twenty-four patients underwent a pterional approach (n=11) or interhemispheric approach (n=13), including a unilateral low anterior interhemispheric approach or bifrontal interhemispheric approach, for high-positioned ACoA aneurysms with an aneurysm dome height >15 mm and aneurysm neck height >10 mm both measured from the level of the anterior clinoid process. The clinical and radiological data were reviewed to investigate the surgical results and risk factors of incomplete clipping.

RESULTS

The pterional patient group showed a significantly higher incidence of incomplete clipping than the interhemispheric patient group (p=0.031). Four patients (36.4%) who underwent a pterional approach showed a postclipping aneurysm remnant, whereas all the patients who experienced an interhemispheric approach showed complete clipping. In one case, the aneurysm remnant was obliterated by coiling, while follow-up of the other three cases showed the remnants remained limited to the aneurysm base. A multivariate analysis revealed that a pterional approach for a large aneurysm with a diameter >8 mm presented a statistically significant risk factor for incomplete clipping.

CONCLUSION

For high-positioned ACoA aneurysms with a dome height >15 mm and neck height >10 mm above the level of the anterior clinoid process, a large aneurysm with a diameter >8 mm can be clipped more completely via an interhemispheric approach than via a pterional approach.

Aneurysmal subarachnoid hemorrhage: A pilot study for using longitudinal cognitive and neuropsychological testing for functional outcomes

OBJECTIVES

Patients with aneurysmal subarachnoid hemorrhage (aSAH) often sustain substantial cognitive and functional impairment. Traditional outcome measures have emphasized radiographic and gross clinical outcomes, but cognitive and functional outcomes are less frequently documented. This pilot study assessed the feasibility of administering longitudinal cognitive and neuropsychological testing and tracked patterns of functional improvement in aSAH patients.

PATIENTS AND METHODS

Standardized cognitive and neuropsychological testing were administered to a prospective cohort of aSAH patients admitted for treatment to our tertiary care center. Thirty consecutive aSAH patients (Hunt and Hess score 1-3) were enrolled over 23-months and baseline evaluations were completed within 24-h after admission. Patients were followed prospectively after treatment (coiling or clipping) at 1-, 3-, 6-, and 12-months. Functional outcome measures included the Montreal Cognitive Assessment, the Neuropsychiatric Inventory-Questionnaire, and the Functional Activities Questionnaire.

RESULTS

Of the 30 patients, 23 (77%) followed-up at 3-months, 21 (70%) at 6-months, and 19 (63%) at 12-months. Improvement from baseline to follow-up at 12-months was noted for general cognitive function (p = .004), memory (p = .025), and executive function (p = .039), with the greatest improvement occurring within 6-months. Daily function also improved mostly within 6-months (p = .022) while changes in neuropsychological disturbances were insignificant from baseline to follow-up at 12-months (p = .216).

CONCLUSION

Standardized cognitive and neuropsychological testing provides metrics for evaluating functional outcomes following treatment of aSAH. The addition of a brief battery of tests to routine clinical and radiographic evaluations is feasible. The main limitations are related to practice and referral patterns, and future studies are needed to evaluate the impact of treatment modalities on functional outcomes.

Cognitive Impairments After Clipping of Ruptured Anterior Circulation Aneurysms

BACKGROUND

The cognitive impairments after treatment of ruptured aneurysms have often been underestimated. This study sought to assess their prevalence and analyze various associated factors.

METHODS

Patients who were operated on for ruptured anterior circulation aneurysms and discharged with a Glasgow Outcome Scale score of 4-5 were studied at 3 months for various cognitive impairments. Continuous scales of memory (recent, remote, verbal, visual, and overall memory), verbal fluency (phonemic and category fluency), and others were studied in relation to various factors. Univariate and multivariate analyses were performed using SPSS version 21.

RESULTS

A total of 87 patients were included in our study. Phonemic fluency was the most affected, noted in 66% of patients. Although 56% had some memory-related impairments, 13 (15%) and 6 (7%) had moderate and severe deficits in recent memory and 19 (22%) and 12 (14%) had moderate and severe deficits in remote memory, respectively. Patients operated on for anterior cerebral artery (ACA) aneurysms had significantly greater impairments in recent (34% vs. 8%) and remote memory (43% vs. 28%) compared with the rest, both in univariate (P = 0.01 and 0.002, respectively) and multivariate analyses (P = 0.01 and 0.03, respectively). ACA-related aneurysms also had significantly greater independent impairments in phonemic fluency (P = 0.04), compared with others. The clinical grade had a significant independent impact only on remote memory (P = 0.01).

CONCLUSIONS

Cognitive impairments are frequent after treatment of ruptured anterior circulation aneurysms. Impairments in recent memory, remote memory, and phonemic fluency are significantly greater after treatment of ACA-related aneurysms, compared with others, independent of other factors.

Relation of gray-white matter ratio with long-term cognitive functions and quality of life in patients with mild to moderate aneurysmal subarachnoid hemorrhage: a prospective observational study

BACKGROUND

In the present study, we hypothesized that a low gray matter-white matter ratio (GWR) is associated with poor cognitive function and low quality of life in patients with mild to moderate (WFNS ≤3) aneurysmal subarachnoid hemorrhage (aSAH).

METHODS

All patients with aSAH who were admitted to the neurointensive care unit (Neuro ICU) and whose WFNS score was ≤ 3 were enrolled in the study. During the Neuro ICU follow-up period, the following variables were recorded: demographics, neurological status, comorbidities, time elapsed between onset of bleeding and Neuro ICU admission, treatment method, number of days with vasospasm symptoms (DVS) and vasopressor usage. One year after bleeding, all patients except those who could not answer the questionnaires appropriately were administered the MoCA and SF-36 tests, and brain magnetic resonance imaging and then volumetric brain analysis were performed.

RESULTS

Eighty-two patients completed the study. One year after aSAH, cognitive dysfunction and low quality of life were observed in 59.8% and 25.6% of patients, respectively. Among the variables obtained during Neuro ICU follow-up, DVS was found to be a major risk factor for cognitive dysfunction (OR: 3.9, 95% CI: 1.9-7.8; p < 0.001), poor quality of life (OR: 2.8, 95% CI: 1.4-5.3, p = 0.002) and a lower GWR value (p < 0.001, correlation coefficient = -0.410, R2 = 0.234). One year after aSAH, higher GWR values were associated with higher MoCA (R2 = 0.506 for males, R2 = 0.413 for females) and SF-36 (R2 = 0.270 for males, R2 = 0.364 for females) scores in both genders. Also, GWR ≤ 1.35 in males and GWR ≤1.33 in females indicated MoCApoor patients with over 80% specificity and sensitivity.

CONCLUSION

GWR has good correlation with the MoCA and SF-36 score, and a low GWR can indicate cognitive dysfunction. In this context, GWR can be used as an additional method to evaluate cognitive function and quality of life.

Cognitive Correlates of Basal Forebrain Atrophy and Associated Cortical Hypometabolism in Mild Cognitive Impairment

Degeneration of basal forebrain (BF) cholinergic nuclei is associated with cognitive decline, and this effect is believed to be mediated by neuronal dysfunction in the denervated cortical areas. MRI-based measurements of BF atrophy are increasingly being used as in vivo surrogate markers for cholinergic degeneration, but the functional implications of reductions in BF volume are not well understood. We used high-resolution MRI, fluorodeoxyglucose-positron emission tomography (PET), and neuropsychological test data of 132 subjects with mild cognitive impairment (MCI) and 177 cognitively normal controls to determine associations between BF atrophy, cortical hypometabolism, and cognitive deficits. BF atrophy in MCI correlated with both impaired memory function and attentional control deficits, whereas hippocampus volume was more specifically associated with memory deficits. BF atrophy was also associated with widespread cortical hypometabolism, and path analytic models indicated that hypometabolism in domain-specific cortical networks mediated the association between BF volume and cognitive dysfunction. The presence of cortical amyloid pathology, as assessed using AV45-PET, did not significantly interact with the observed associations. These data underline the potential of multimodal imaging markers to study structure-function-cognition relationships in the living human brain and provide important in vivo evidence for an involvement of the human BF in cortical activity and cognitive function.

Predicting return to work after subarachnoid hemorrhage using the Montreal Cognitive Assessment (MoCA)

BACKGROUND

Returning to work is a major issue for patients having had an aneurysmal subarachnoid hemorrhage (SAH). It is important, at an early stage, to identify the patients that are unlikely to return to work. The objective of this study was to assess the predictive value of the Montreal Cognitive Assessment (MoCA) at 6 months after ictus on return to work at 12 months.

METHODS

In this prospective study were 96 patients with SAH included in the acute phase. Cognitive functions were assessed at 6 months using the MoCA and return to work at 12 months. The predictive value of MoCA on return to work was analyzed using the area under the receiver operating characteristic curve as well as logistic regression.

RESULTS

Of those that had work before the SAH, 52 % were working at 12 months after the ictus. These patients had scored significantly better on MoCA at 6 months (p = 0.01). The area under the receiver operating characteristic curve was 0.75. By using a cut-off on MoCA of <27, 68 % of the patients could be correctly classified as returned/not returned to work. Adding data from the acute phase to the MoCA in a logistic regression model increased the percentage of patients correctly classified as returned/not returned to work by 2 %.

CONCLUSIONS

Returning to work is a major issue for SAH patients. It is important to identify factors that may interfere with a patient's ability to return to work, and address these issues appropriately. In our study, estimating cognitive functions at 6 months after SAH using the MoCA alone allowed us to predict return to work correctly in 68 % of the cases. We feel that this provides useful information in planning rehabilitation, but that other post-SAH symptoms have to be considered as well.

Endovascular perforation subarachnoid hemorrhage fails to cause Morris water maze deficits in the mouse

Cognitive dysfunction is the primary driver of poor long-term outcome in aneurysmal subarachnoid hemorrhage (SAH) survivors; modeling such deficits preclinically is thus key for mechanistic and translational investigation. Although rat SAH causes long-term deficits in learning and memory, it remains unknown whether similar deficits are seen in the mouse, a species particularly amenable to powerful, targeted genetic manipulation. We thus subjected mice to endovascular perforation SAH and assessed long-term cognitive outcome via the Morris water maze (MWM), the most commonly used metric for rodent neurocognition. No significant differences in MWM performance (by either of two protocols) were seen in SAH versus sham mice. Moreover, SAH caused negligible hippocampal CA1 injury. These results undercut the potential of commonly used methods (of SAH induction and assessment of long-term neurocognitive outcome) for use in targeted molecular studies of SAH-induced cognitive deficits in the mouse.

Current practice in neuropsychological outcome reporting after aneurysmal subarachnoid haemorrhage

BACKGROUND

Neuropsychological deficits (NPD) are common in patients with aneurysmal subarachnoid haemorrhage (aSAH). NPD are one of the major limiting factors for patients with an otherwise acceptable prognosis for sustained quality of life. There are only a few studies reporting outcome after aSAH, which used a standardized neuropsychological test battery as a primary or secondary outcome measure. Aim of this study was to determine the current practice of reporting NPD following aSAH in clinical studies.

METHODS

A MEDLINE analysis was performed using the search term "subarachnoid haemorrhage outcome". The latest 1,000 articles were screened. We recorded study design, number of patients, and the presence of neuropsychological outcome report. Additionally, the time of testing after aSAH, the neuropsychological tests administered, as well as the percentage of patients with NPD were analyzed.

RESULTS

A total of 324 publications between 2009 and 2012 were selected for further review. Of those, 21 studies (6.5%) reported neuropsychological outcome, in 2,001 of 346,666 patients (0.6%). The assessment of NPD differed broadly using both subjective and objective cognitive evaluation, and a large variety of tests were used.

CONCLUSION

Neuropsychological outcome is underreported, and there is great variety in assessment in currently published clinical articles on aSAH. Prospective randomized trials treating aSAH may benefit from implementing more comprehensive and standardized neuropsychological outcome measures. This approach might identify otherwise unnoticed treatment effects in future interventional studies of aSAH patients.

Amnesic disorders

Memory disturbances frequently occur after brain damage, but can be associated with psychiatric illnesses as well. Amnesia--the most severe form of memory impairment--has several variants, including anterograde and retrograde amnesia, material-specific and modality-specific amnesia, and transient global amnesia. We searched databases to obtain an overview of amnesia research from the past 5 years. Research into amnesia has increased exponentially, probably because of the availability of modern brain-imaging techniques. In line with the view that memory is not a unity but is organised into several systems, amnesia is described as a multifaceted disease with a frequently poor prognosis.

Injuries of the Cingulum and Fornix After Rupture of an Anterior Communicating Artery Aneurysm

BACKGROUND:

After rupture of an anterior communicating artery (ACoA) aneurysm, the anterior cingulum and the fornix can be vulnerable to injury. However, very little is known about this topic.

OBJECTIVE:

To investigate injuries of the cingulum and fornix in patients with an ACoA aneurysm rupture with diffusion tensor tractography.

METHODS:

Eleven consecutive patients with an ACoA aneurysm rupture and 11 age- and sex-matched normal control subjects were recruited. Diffusion tensor imaging was scanned at an average of 54.1 days (range, 29–97 days) after onset of ACoA aneurysm rupture.

RESULTS:

We found that 6 (54.5%) and 7 (63.6%) of 11 patients revealed no trajectory of the anterior cingulum and the fornical body on diffusion tensor tractography, respectively. In terms of diffusion tensor imaging parameters, we found that the fractional anisotropy value and tract volume of the cingulum and fornix were decreased (P &lt; .05) and that mean diffusivity values were increased (P &lt; .05), except for those of the left fornix, which showed no difference (P &gt; .05).

CONCLUSION:

We found injuries of the cingulum and fornix in patients with an ACoA aneurysm rupture. It is our belief that sustained memory impairment of patients with an ACoA aneurysm rupture might be related to injury of the cingulum and fornix. Therefore, we recommend evaluation of the cingulum and fornix with diffusion tensor tractography for patients with an ACoA aneurysm rupture.

The controlled generation of functional basal forebrain cholinergic neurons from human embryonic stem cells

An early substantial loss of basal forebrain cholinergic neurons (BFCN) is a constant feature of Alzheimer's disease and is associated with deficits in spatial learning and memory. The ability to selectively control the differentiation of human embryonic stem cells (hESCs) into BFCN would be a significant step toward a cell replacement therapy. We demonstrate here a method for the derivation of a predominantly pure population of BFCN from hESC cells using diffusible ligands present in the forebrain at developmentally relevant time periods. Overexpression of two relevant human transcription factors in hESC-derived neural progenitors also generates BFCN. These neurons express only those markers characteristic of BFCN, generate action potentials, and form functional cholinergic synapses in murine hippocampal slice cultures. siRNA-mediated knockdown of the transcription factors blocks BFCN generation by the diffusible ligands, clearly demonstrating the factors both necessary and sufficient for the controlled derivation of this neuronal population. The ability to selectively control the differentiation of hESCs into BFCN is a significant step both for understanding mechanisms regulating BFCN lineage commitment and for the development of both cell transplant-mediated therapeutic interventions for Alzheimer's disease and high-throughput screening for agents that promote BFCN survival.

A neural model of hippocampal-striatal interactions in associative learning and transfer generalization in various neurological and psychiatric patients

Building on our previous neurocomputational models of basal ganglia and hippocampal region function (and their modulation by dopamine and acetylcholine, respectively), we show here how an integration of these models can inform our understanding of the interaction between the basal ganglia and hippocampal region in associative learning and transfer generalization across various patient populations. As a common test bed for exploring interactions between these brain regions and neuromodulators, we focus on the acquired equivalence task, an associative learning paradigm in which stimuli that have been associated with the same outcome acquire a functional similarity such that subsequent generalization between these stimuli increases. This task has been used to test cognitive dysfunction in various patient populations with damages to the hippocampal region and basal ganglia, including studies of patients with Parkinson's disease (PD), schizophrenia, basal forebrain amnesia, and hippocampal atrophy. Simulation results show that damage to the hippocampal region-as in patients with hippocampal atrophy (HA), hypoxia, mild Alzheimer's (AD), or schizophrenia-leads to intact associative learning but impaired transfer generalization performance. Moreover, the model demonstrates how PD and anterior communicating artery (ACoA) aneurysm-two very different brain disorders that affect different neural mechanisms-can have similar effects on acquired equivalence performance. In particular, the model shows that simulating a loss of dopamine function in the basal ganglia module (as in PD) leads to slow acquisition learning but intact transfer generalization. Similarly, the model shows that simulating the loss of acetylcholine in the hippocampal region (as in ACoA aneurysm) also results in slower acquisition learning. We argue from this that changes in associative learning of stimulus-action pathways (in the basal ganglia) or changes in the learning of stimulus representations (in the hippocampal region) can have similar functional effects.

Errorless practice as a possible adjuvant to donepezil in Alzheimer's disease

Six individuals with probable Alzheimer's disease (AD) participated in a phase 1 study employing a repeated measures, parallel baseline design testing the hypothesis that error-free experience during word production practice combined with an acetyl cholinesterase inhibitor would improve confrontation naming ability. While acetyl cholinesterase inhibitors are safe and delay cognition decline associated with AD, improvement over baseline cognition is less evident; clinically significant cognitive deficits persist and progress. Both animal and clinical research strongly implicate acetylcholine in learning, a form of neuroplasticity. In clinical practice, however, people with AD are given cholinergic medications without concomitant systematic/targeted retraining. In this study six participants with probable AD and taking donepezil participated in targeted word production practice using an errorless learning strategy. Results showed that combining behavioral enrichment training and an acetyl cholinesterase inhibitor resulted in significant improvements in verbal confrontation naming of trained items for three of six participants. Differences in baseline dementia severity, living conditions, and medications may have influenced the training response. Detection of substantial treatment effects in 50% of subjects suggests further language treatment studies in AD in combination with an acetyl cholinesterase inhibitor are warranted and provide useful information on inclusion/exclusion criteria for use in subsequent studies.