Neuroanatomy of a neurobehavioral disturbance in the left anterior thalamic infarction

NODDI Identifies Cognitive Associations with In Vivo Microstructural Changes in Remote Cortical Regions and Thalamocortical Pathways in Thalamic Stroke

The roles of cerebral structures distal to isolated thalamic infarcts in cognitive deficits remain unclear. We aimed to identify the in vivo microstructural characteristics of remote gray matter (GM) and thalamic pathways and elucidate their roles across cognitive domains. Patients with isolated ischemic thalamic stroke and healthy controls underwent neuropsychological assessment and magnetic resonance imaging. Neurite orientation dispersion and density imaging (NODDI) was modeled to derive the intracellular volume fraction (VFic) and orientation dispersion index. Fiber density (FD) was determined by constrained spherical deconvolution, and tensor-derived fractional anisotropy (FA) was calculated. Voxel-wise GM analysis and thalamic pathway tractography were performed. Twenty-six patients and 26 healthy controls were included. Patients exhibited reduced VFic in remote GM regions, including ipsilesional insular and temporal subregions. The microstructural metrics VFic, FD, and FA within ipsilesional thalamic pathways decreased (false discovery rate [FDR]-p < 0.05). Noteworthy associations emerged as VFic within insular cortices (ρ = -0.791 to -0.630; FDR-p < 0.05) and FD in tracts connecting the thalamus and insula (ρ = 0.830 to 0.971; FDR-p < 0.001) were closely associated with executive function. The VFic in Brodmann area 52 (ρ = -0.839; FDR-p = 0.005) and FA within its thalamic pathway (ρ = -0.799; FDR-p = 0.003) correlated with total auditory memory scores. In conclusion, NODDI revealed neurite loss in remote normal-appearing GM regions and ipsilesional thalamic pathways in thalamic stroke. Reduced cortical dendritic density and axonal density of thalamocortical tracts in specific subregions were associated with improved cognitive functions. Subacute microstructural alterations beyond focal thalamic infarcts might reflect beneficial remodeling indicating post-stroke plasticity.

Plasticity of cortico-striatal neurons of the caudal anterior cingulate cortex during experimental neuropathic pain

Maladaptive neuronal plasticity is a main mechanism for the development and maintenance of pathological pain. Affective, motivational and cognitive deficits that are comorbid with pain involve cellular and synaptic modifications in the anterior cingulate cortex (ACC), a major brain mediator of pain perception. Here we use a model of neuropathic pain (NP) in male mice and ex-vivo electrophysiology to investigate whether layer 5 caudal ACC (cACC) neurons projecting to the dorsomedial striatum (DMS), a critical region for motivational regulation of behavior, are involved in aberrant neuronal plasticity. We found that while the intrinsic excitability of cortico-striatal cACC neurons (cACC-CS) was preserved in NP animals, excitatory postsynaptic potentials (EPSP) induced after stimulation of distal inputs were enlarged. The highest synaptic responses were evident both after single stimuli and in each of the EPSP that compose responses to trains of stimuli, and were accompanied by increased synaptically-driven action potentials. EPSP temporal summation was intact in ACC-CS neurons from NP mice, suggesting that the plastic changes were not due to alterations in dendritic integration but rather through synaptic mechanisms. These results demonstrate for the first time that NP affects cACC neurons that project to the DMS and reinforce the notion that maladaptive plasticity of the cortico-striatal pathway may be a key factor in sustaining pathological pain.

Abnormal brain network community structure related to psychological stress in schizophrenia

Recent functional imaging studies in schizophrenia consistently report a disruption of brain connectivity. However, most of these studies analyze the brain connectivity during resting state. Since psychological stress is a major factor for the emergence of psychotic symptoms, we sought to characterize the brain connectivity reconfiguration induced by stress in schizophrenia. We tested the hypothesis that an alteration of the brain's integration-segregation dynamic could be the result of patients with schizophrenia facing psychological stress. To this end, we studied the modular organization and the reconfiguration of networks induced by a stress paradigm in forty subjects (twenty patients and twenty controls), thus analyzing the dynamics of the brain in terms of integration and segregation processes by using 3T-fMRI. Patients with schizophrenia did not show statistically significant differences during the control task compared with controls, but they showed an abnormal community structure during stress condition and an under-connected reconfiguration network with a reduction of hub nodes, suggesting a deficit of integration dynamic with a greater compromise of the right hemisphere. These results provide evidence that schizophrenia has a normal response to undemanding stimuli but shows a disruption of brain functional connectivity between key regions involved in stress response, potentially leading to altered functional brain dynamics by reducing integration capacity and showing deficits recruiting right hemisphere regions. This could in turn underlie the hyper-sensitivity to stress characteristic of schizophrenia.

Dual-Phase 18F-Florbetaben PET/CT: Unsuspected Thalamic Infarction Mimicking Alzheimer Disease

ABSTRACT

Dual-phase amyloid PET is considered a useful protocol to study patients with cognitive impairment. Early-phase 18F-florbetaben PET/CT has been proposed as a surrogate of 18F-FDG PET/CT providing information related to regional brain perfusion. We report the case of a 61-year-old woman referred to the cognitive impairment unit for study, preliminary diagnosed as probable Alzheimer disease. The dual-phase 18F-florbetaben PET/CT was shown as the main finding, no uptake in the left anterior thalamus. Memory and language symptoms have been described as primary clinical features of anterior thalamic infarctions that could be confused with the main manifestations of Alzheimer disease.

Premammillary artery infarction after microsurgical clipping of unruptured posterior communicating artery aneurysm: risk factors and surgical and anatomical considerations

Posterior communicating artery (PCoA) aneurysm is common and sometimes requires microsurgery; however, as data on premammillary artery (PMA) infarction after clipping is scarce, we retrospectively reviewed cases of post-clipping PMA infarction to analyze incidence, independent risk factors of infarction, and anatomical considerations. Data from 569 consecutive patients who underwent microsurgical clipping for unruptured PCoA aneurysm between January 2008 and December 2020 were included. Patients were categorized into the normal or the PMA infarction group. Statistical analyses and comparisons between the two groups were used to determine the influence of various factors. The normal group included 515 patients while the PMA infarction group had 31. The mean length of hospital stay was significantly longer in the PMA infarction group (10.3 ± 9.1 days) than in the normal group (6.5 ± 6.4 days; p < 0.0001). The distribution of Glasgow Outcome Scale at discharge was significantly different between the two groups (p ≤ 0.0001) but was not so at 6 months after discharge (p = 0.0568). Multivariate logistic regression analysis identified aneurysm size (odds ratio [OR], 1.194; 95% confidence interval [CI], 1.08-1.32; p = 0.0005) and medial direction of aneurysm (OR, 4.615; 95% CI, 1.224-17.406; p = 0.0239) as independent risk factors of post-clipping PMA infarction. Surgeons must beware of PMA infarction after clipping of large aneurysms that are medial in direction. Intraoperative verification of the patency of the PCoA and the PMA from various angles using various intraoperative methods can reduce morbidity due to PMA infarction.

Thalamic Aphasia: a Review

PURPOSE OF REVIEW

Thalamic aphasia is a rare language disorder resulting from lesions to the thalamus. While most patients exhibit mild symptoms with a predominance of lexical-semantic difficulties, variations in phenotype have been described. Overall, the exact mechanisms of thalamic aphasia await empirical research. The article reviews recent findings regarding phenotypes and possible underlying mechanisms of thalamic aphasia.

RECENT FINDINGS

Variations in phenotype of thalamic aphasia may be related to different lesion locations. Overall, the thalamus' role in language is thought to be due to its involvement in cortico-thalamic language networks with lesioning of certain nuclei resulting in the diachisis of otherwise interconnected areas. Its possible monitoring function in such a network might be due to its different cellular firing modes. However, no specific evidence has been collected to date. While recent findings show a more distinct understanding of thalamic aphasia phenotypes and possible underlying mechanisms, further research is needed. Additionally, as standard language testing might oftentimes not pick up on its subtle symptoms, thalamic aphasia might be underdiagnosed.

Subcortical Aphasia

PURPOSE OF REVIEW

Subcortical structures have long been thought to play a role in language processing. Increasingly spirited debates on language studies, arising from as early as the nineteenth century, grew remarkably sophisticated as the years pass. In the context of non-thalamic aphasia, a few theoretical frameworks have been laid out. The disconnection hypothesis postulates that basal ganglia insults result in aphasia due to a rupture of connectivity between Broca and Wernicke's areas. A second viewpoint conjectures that the basal ganglia would more directly partake in language processing, and a third stream proclaims that aphasia would stem from cortical deafferentation. On the other hand, thalamic aphasia is more predominantly deemed as a resultant of diaschisis. This article reviews the above topics with recent findings on deep brain stimulation, neurophysiology, and aphasiology.

RECENT FINDINGS

The more recent approach conceptualizes non-thalamic aphasias as the offspring of unpredictable cortical hypoperfusion. Regarding the thalamus, there is mounting evidence now pointing to leading contributions of the pulvinar/lateral posterior nucleus and the anterior/ventral anterior thalamus to language disturbances. While the former appears to relate to lexical-semantic indiscrimination, the latter seems to bring about a severe breakdown in word selection and/or spontaneous top-down lexical-semantic operations. The characterization of subcortical aphasias and the role of the basal ganglia and thalamus in language processing continues to pose a challenge. Neuroimaging studies have pointed a path forward, and we believe that more recent methods such as tractography and connectivity studies will significantly expand our knowledge in this particular area of aphasiology.

Bridging large-scale cortical networks: Integrative and function-specific hubs in the thalamus

The thalamus is critical for the brain's integrative hub functions; however, the localization and characterization of the different thalamic hubs remain unclear. Using a voxel-level network measure called functional connectivity overlap ratio (FCOR), we examined the thalamus' association with large-scale resting-state networks (RSNs) to elucidate its connector hub roles. Connections to the core-neurocognitive networks were localized in the anterior and medial parts, such as the anteroventral and mediodorsal nuclei areas. Regions functionally connected to the sensorimotor network were distinctively located around the lateral pulvinar nucleus but to a limited extent. Prominent connector hubs include the anteroventral, ventral lateral, and mediodorsal nuclei with functional connections to multiple RSNs. These findings suggest that the thalamus, with extensive connections to most of the RSNs, is well placed as a critical integrative functional hub and could play an important role for functional integration facilitating brain functions associated with primary processing and higher cognition.

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Multiple large-scale cortical networks converged in the thalamus

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Neurocognitive associated hub existed in the anterior and medial region

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Control-processing hub localized in the intermediate thalamus

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Sensorimotor network was located around the lateral pulvinar nucleus

[Non-aphasic misnaming: a case report and literature review]

A 71-year-old, right-handed woman was admitted to our hospital due to a sudden difficulty with conversation. On admission, she was alert, but had a euphoric mood, disorientation, and a disturbance of recent memory. Her speech was fluent. Her repetition and auditory word cognition were excellent, but she had a slight difficulty with naming visual objects. She frequently showed word-finding difficulty and irrelevant paraphasia during free conversation and a word fluency task. Her irrelevant paraphasia was observed more frequently when she was asked to explain her outbreak of anger at the hospital, i.e., it was situation-dependent. She also had anosognosia. MRI showed an infarct in the territory of the left tuberothalamic artery. Single-photon emission computed tomography revealed low-uptake lesions in the left thalamus and orbital frontal, medial frontal, and medial temporal lobes. The patient was diagnosed with non-aphasic misnaming. The clinical characteristics of patients with non-aphasic misnaming in the literature were reviewed. All of the patients with non-aphasic misnaming had word-finding difficulty and irrelevant paraphasia. Additionally, they had either emotional disturbance or anosognosia.

Assessment of Memory among Traumatic Brain Injury Patients during Follow-Up at a Tertiary Health Care Facility in Rural Setting

Background Head injury is an important public health problem nowadays. Traumatic brain injury (TBI) results from external force that leads to damage to brain tissue. Main causes of TBI are motor vehicle collisions and fall from height. One of the primary symptoms after TBI is impaired word retrieval. Therefore, this study was undertaken to assess memory impairment in TBI patients following treatment to asses a residual memory status to declare them apt for official works if improved enough.

Objectives The purpose of this study was to assess memory impairment in TBI patients to assess the residual memory status following treatment.

Materials and Methods The study was conducted in Outpatient Department (OPD) of Neurosurgery, Uttar Pradesh University of Medical Sciences, Saifai, Etawah, Uttar Pradesh. The TBI patients were assessed by predesigned memory assessment questionnaire during their follow-up following discharge from hospital.

Results A total of 65 patients with TBI were assessed, of which 21 (32.3%) cases had frontal lobe injuries with 9 of 21 having memory loss (42.9% cases). The temporoparietal lobe was affected in 10 (15.4%) cases out of which 5 developed memory loss, that is, 50% cases. The multiple lobes were involved in 24 (36.9%) cases, out of which memory impairment occurred in 9 cases, that is, 37.5%. Four of total five cases (80%) of diffuse axonal injury had memory loss. Further, 16.9% (n = 11) TBI patients were unable to perform digit span test (immediate memory test), 44.6% (n = 29) cases could not perform three-word recall at 5 minutes (short-term memory test), and 15.4% (n = 10) cases could not perform (long-term memory test).

Conclusion The study showed that memory assessment is required in TBI patients for instituting proper rehabilitation measures and to allow them for sensitive memory-related work following discharge from hospital.

Functional connectivity of the retrosplenial cortex in rats with ischemic stroke is improved by electroacupuncture

BACKGROUND

The aim of this study was to investigate the central mechanism underlying the putative beneficial effects of electroacupuncture (EA) on learning and memory ability of rats with ischemic stroke-induced cognitive deficits by resting-state functional magnetic resonance imaging (fMRI).

METHODS

A rat model of middle cerebral artery occlusion (MCAO)-induced cognitive deficit (MICD) was established. Rats were randomly assigned into a sham-operated control group (SC group, n = 12), untreated MICD model group (MICD group, n = 12), and MICD group receiving EA treatment at GV20 and GV24 (MICD + EA group, n = 12).

RESULTS

Compared to the MICD group, rats in the MICD + EA group receiving EA at GV20 and GV24 exhibited significantly shortened escape latency times and crossed the position of the platform a significantly increased number of times during the Morris water maze test on the 14th day after EA, which suggested EA could significantly improve spatial learning and memory ability. Furthermore, compared to the MICD group, functional connectivity of the left retrosplenial cortex (RSC) with the left hippocampus, left RSC, right RSC, left cingulate gyrus, right cingulate gyrus, right tegmentum of midbrain, and right visual cortex was increased in the MICD + EA group; the MICD group showed decreased functional connectivity of the left RSC with the left hippocampus, right hippocampus, left RSC, right RSC, right amygdaloid body, left visual cortex, and right visual cortex.

CONCLUSION

These findings suggest that EA at GV20 and GV24 might improve the learning and memory ability of MICD rats by increasing the functional connectivity between the RSC and hippocampus, cingulate gyrus and midbrain, which is encouraging for the potential treatment for cognitive impairment secondary to ischemia stroke.

Fluency and rule breaking behaviour in the frontal cortex

Design (DF) and phonemic fluency tests (FAS; D-KEFS, 2001) are commonly used to investigate voluntary generation. Despite this, several important issues remain poorly investigated. In a sizeable sample of patients with focal left or right frontal lesion we established that voluntary generation performance cannot be accounted for by fluid intelligence. For DF we found patients performed significantly worse than healthy controls (HC) only on the switch condition. However, no significant difference between left and right frontal patients was found. In contrast, left frontal patients were significantly impaired when compared with HC and right frontal patients on FAS. These lateralization findings were complemented, for the first time, by three neuroimaging; investigations. A traditional frontal subgrouping method found significant differences on FAS between patients with or without Left Inferior Frontal Gyrus lesions involving BA 44 and/or 45. Parcel Based Lesion Symptom Mapping (PLSM) found lower scores on FAS were significantly associated with damage to posterior Left Middle Frontal Gyrus. An increase in rule break errors, so far only anecdotally reported, was associated with damage to the left dorsal anterior cingulate and left body of the corpus callosum, supporting the idea that conflict resolution and monitoring impairments may play a role. Tractwise statistical analysis (TSA) revealed that patients with disconnection; in the left anterior thalamic projections, frontal aslant tract, frontal; orbitopolar tract, pons, superior longitudinal fasciculus I and II performed significantly worse than patients without disconnection in these tracts on FAS. In contrast, PLSM and TSA analyses did not reveal any significant relationship between lesion location and performance on the DF switch condition. Overall, these findings suggest DF may have limited utility as a tool in detecting lateralized frontal executive dysfunction, whereas FAS and rule break behavior appears to be linked to a set of well localized left frontal grey matter regions and white matter tracts.

Characteristics and correlates of poststroke depression: An Indian study

BACKGROUND

Post stroke depression adversely affects long term outcome of stroke and increases mortality risk. Few studies have looked into the comprehensive picture of post stroke depression in past.

AIM

The current study aimed to look into the phenomenology, characteristic features and various correlates of post stroke depression.

METHOD

142 consecutive stroke patients aged 60 years or above, fulfilling the inclusion criteria were assessed. Sociodemographic and clinical data were gathered using a specially designed pro-forma. Depression, apathy and psychosis were assessed by Post stroke depression rating scale, Apathy Evaluation Scale, and Brief Psychiatric Rating Scale respectively. Groups (with or without major depression) were compared using Mann-Whitney U, chi square or Fisher's exact test. One way ANOVA was conducted to see the relations of lesion location and laterality with various clinical parameters. Kaplan-Meier survival analysis was done to see the time to develop depression. The effect sizes were reported as r and partial eta squared.

RESULTS

Guilt was significantly higher (p<.05) with lesions in parietal lobe and remaining of middle cerebral artery territory. Catastrophic reaction (p<.05) and emotional dyscontrol (p<.05) were higher for diffuse lesions, periventricular lesions and lesions in frontal/occipital lobe. BPRS score, but not apathy, had a significant positive correlation with depression (Pearson's r=.692). Mean time to develop depression after stroke was 28.34 (95% CI 22.37 to 34.31) months.

CONCLUSIONS

Post stroke depression consists of various clinically important sub-components whose occurrence varies with different lesion locations. Post stroke depression is discriminable from apathy but is related to psychosis.

Association between NRGN gene polymorphism and resting-state hippocampal functional connectivity in schizophrenia

BACKGROUND

Based on genome-wide association studies, a single-nucleotide polymorphism in the NRGN gene (rs12807809) is considered associated with schizophrenia (SZ). Moreover, hippocampal dysfunction is associated with rs12807809. In addition, converging evidence suggests that hippocampal dysfunction is involved in SZ pathophysiology. However, the association among rs12807809, hippocampal dysfunction and SZ pathophysiology is unknown. Therefore, this study investigated the association between rs12807809 and hippocampal functional connectivity at rest in SZ.

METHODS

In total, 158 participants were studied, including a C-carrier group carrying the non-risk C allele (29 SZ patients and 46 healthy controls) and a TT homozygous group carrying the risk T allele (30 SZ patients and 53 healthy controls). All participants were scanned using resting-state functional magnetic resonance imaging. Hippocampal functional connectivity was computed and compared among the 4 groups.

RESULTS

Significant main effects of diagnosis were observed in the functional connectivity between the hippocampus and bilateral fusiform gyrus, bilateral lingual gyrus, left inferior temporal gyrus, left caudate nucleus, bilateral thalamus and bilateral anterior cingulate gyri. In contrast, no significant main effect of genotype was found. In addition, a significant genotype by diagnosis interaction in the functional connectivity between the hippocampus and left anterior cingulate gyrus, as well as bilateral middle cingulate gyri, was observed, with TT homozygotes with SZ showing less functional connectivity than C-carriers with SZ and healthy control TT homozygotes.

CONCLUSIONS

These findings are the first to suggest an association between rs12807809 and abnormal Papez circuit function in patients with SZ. This study also implicates NRGN variation and abnormal Papez circuit function in SZ pathophysiology.

Resting-state thalamic dysconnectivity in schizophrenia and relationships with symptoms

BACKGROUND

Schizophrenia (SZ) is a severe neuropsychiatric disorder associated with disrupted connectivity within the thalamic-cortico-cerebellar network. Resting-state functional connectivity studies have reported thalamic hypoconnectivity with the cerebellum and prefrontal cortex as well as thalamic hyperconnectivity with sensory cortical regions in SZ patients compared with healthy comparison participants (HCs). However, fundamental questions remain regarding the clinical significance of these connectivity abnormalities.

METHOD

Resting state seed-based functional connectivity was used to investigate thalamus to whole brain connectivity using multi-site data including 183 SZ patients and 178 matched HCs. Statistical significance was based on a voxel-level FWE-corrected height threshold of p < 0.001. The relationships between positive and negative symptoms of SZ and regions of the brain demonstrating group differences in thalamic connectivity were examined.

RESULTS

HC and SZ participants both demonstrated widespread positive connectivity between the thalamus and cortical regions. Compared with HCs, SZ patients had reduced thalamic connectivity with bilateral cerebellum and anterior cingulate cortex. In contrast, SZ patients had greater thalamic connectivity with multiple sensory-motor regions, including bilateral pre- and post-central gyrus, middle/inferior occipital gyrus, and middle/superior temporal gyrus. Thalamus to middle temporal gyrus connectivity was positively correlated with hallucinations and delusions, while thalamus to cerebellar connectivity was negatively correlated with delusions and bizarre behavior.

CONCLUSIONS

Thalamic hyperconnectivity with sensory regions and hypoconnectivity with cerebellar regions in combination with their relationship to clinical features of SZ suggest that thalamic dysconnectivity may be a core neurobiological feature of SZ that underpins positive symptoms.

The anatomy of apathy: A neurocognitive framework for amotivated behaviour

Apathy is a debilitating syndrome associated with many neurological disorders, including several common neurodegenerative diseases such as Parkinson's disease and Alzheimer's disease, and focal lesion syndromes such as stroke. Here, we review neuroimaging studies to identify anatomical correlates of apathy, across brain disorders. Our analysis reveals that apathy is strongly associated with disruption particularly of dorsal anterior cingulate cortex (dACC), ventral striatum (VS) and connected brain regions. Remarkably, these changes are consistent across clinical disorders and imaging modalities. Review of the neuroimaging findings allows us to develop a neurocognitive framework to consider potential mechanisms underlying apathy. According to this perspective, an interconnected group of brain regions - with dACC and VS at its core - plays a crucial role in normal motivated behaviour. Specifically we argue that motivated behaviour requires a willingness to work, to keep working, and to learn what is worth working for. We propose that deficits in any one or more of these processes can lead to the clinical syndrome of apathy, and outline specific approaches to test this hypothesis. A richer neurobiological understanding of the mechanisms underlying apathy should ultimately facilitate development of effective therapies for this disabling condition.

Hypothalamic relapse of a cardiac large B-cell lymphoma presenting with memory loss, confabulation, alexia-agraphia, apathy, hypersomnia, appetite disturbances and diabetes insipidus

A 37-year-old Hispanic man with a right atrial intracardiac mass diagnosed as diffuse large B-cell lymphoma (DLBCL) was successfully treated with surgery and chemotherapy. During 4 years, several total-body positron emission tomography and MRI scans showed no extracardiac lymphoma. On year 5 after the cardiac surgery, patient presented with sleepiness, hyperphagia, memory loss, confabulation, dementia and diabetes insipidus. Brain MRI showed a single hypothalamic recurrence of the original lymphoma that responded to high-dose methotrexate treatment. Correction of diabetes insipidus improved alertness but amnesia and cognitive deficits persisted, including incapacity to read and write. This case illustrates two unusual locations of DLBCL: primary cardiac lymphoma and hypothalamus. We emphasise the importance of third ventricle tumours as causing amnesia, confabulation, behavioural changes, alexia-agraphia, endocrine disorders and alterations of the circadian rhythm of wakefulness-sleep secondary to lesions of specific hypothalamic nuclei and disruption of hypothalamic-thalamic circuits.

Electroacupuncture Ameliorates Cognitive Impairment and Spontaneous Low-Frequency Brain Activity in Rats with Ischemic Stroke

BACKGROUND

To evaluate whether electroacupuncture (EA) at Baihui (DU20) and Shenting (DU24) acupoints could improve cognitive function and enhance spontaneous low-frequency brain activity in rats with ischemic stroke.

METHODS

Total 36 rats were randomly divided into 3 groups-the sham surgery (Sham) group, the middle cerebral artery occlusion induced cognitive deficit (MICD) group, and the MICD with EA (MICD + EA) treatment group. The rats in MICD + EA group received EA treatment at DU20 and DU24 acupoints for 14 consecutive days after the surgery. The Morris water maze test was performed to assess the spatial learning and memory ability of the rats. Magnetic resonance imaging (MRI) was used to investigate the infarction volume and spontaneous low-frequency brain activity of each group.

RESULTS

After EA for 14 days, the learning and memory ability of the MICD rats was improved, and the brain infarction volume was reduced. Furthermore, basing on the fMRI amplitude of low-frequency fluctuation (ALFF) analysis, the decreased ALFF of the MICD rats was found in auditory cortex, cingulate gyrus, lateral nucleus group of dorsal thalamus, hippocampus, motor cortex, prelimbic cortex, retrosplenial cortex, and sensory cortex compared with the rats in sham group. However, these suppressive regions were notably attenuated after EA treatment.

CONCLUSIONS

Our results suggested that EA at DU20 and DU24 acupoints could ameliorate cognitive impairment in rats with ischemic stroke, and the protective effect of EA may attribute to reactivating the cognition-related brain regions, such as hippocampus, retrosplenial cortex, cingulate gyrus, prelimbic cortex, and sensory cortex.

Correlation of Longitudinal Gray Matter Volume Changes and Motor Recovery in Patients After Pontine Infarction

The mechanisms of motor functional recovery after pontine infarction (PI) remain unclear. Here, we assessed longitudinal changes in gray matter volume (GMV) and examined the relationship between GMV and clinical outcome. Fifteen patients with unilateral PI underwent magnetic resonance imaging and neurological exams five times during a period of 6 months. Another 15 healthy participants were enrolled as the normal control (NC) group and were examined with the same protocol. The MR exam included routine protocol and a 3D T1-weighted magnetization-prepared rapid acquisition gradient echo scan. Changes in GMV were assessed using voxel-based morphometry. Furthermore, the correlations between GMV changes in regions of interest and clinical scores were assessed. Compared with NCs, the decreased GMVs in the contralateral uvula of cerebellum and the ipsilateral tuber of cerebellum were detected at third month after stroke onset. At the sixth month after stroke onset, the decreased GMVs were detected in the contralateral culmen of cerebellum, putamen, as well as in the ipsilateral tuber/tonsil of cerebellum. Compared with NC, the PI group exhibited significant increases in GMV at each follow-up time point relative to stroke onset. Specifically, the significant GMV increase was found in the ipsilateral middle frontal gyrus and ventral anterior nucleus of thalamus at second week after stroke onset. At first month after stroke onset, the increased GMVs in the ipsilateral middle temporal gyrus were detected. The significant GMV increase in the ipsilateral mediodorsal thalamus was noted at third month after stroke onset. At the end of sixth month after stroke onset, the GMV increase was found in the ipsilateral mediodorsal thalamus, superior frontal gyrus, and the contralateral precuneus. Across five times during a period of 6-month, a negative correlation was observed between mean GMV in the contralateral uvula, culmen, putamen, and ipsilateral tuber/tonsil and mean Fugl-Meyer (FM) score. However, mean GMV in the ipsilateral mediodorsal thalamus was positively correlated with mean FM score. Our findings suggest that structural reorganization of the ipsilateral mediodorsal thalamus might contribute to motor functional recovery after PI.

The association between vertebrobasilar insufficiency and the risk of dementia: a nationwide register-based retrospective cohort study in Taiwan

OBJECTIVES

Neurodegenerative disorders are reportedly characterised by decreased regional cerebral blood flow. However, the association between vertebrobasilar insufficiency (VBI) and dementia remains unclear. In this nationwide, population-based, retrospective cohort study, we explored the potential association between VBI and dementia.

DESIGN

Nationwide population-based cohort study.

SETTING

Patients with VBI were newly diagnosed between 2000 and 2005 from the Taiwan National Health Insurance Research Database.

PARTICIPANTS

We included 3642 subjects as the VBI group. The control cohort included 14 568 randomly selected age-matched and sex-matched VBI-free individuals.

OUTCOME MEASURES

All subjects were followed until the diagnosis of dementia, death or the end of 2010. Patients with VBI, dementia (viz, vascular and non-vascular, including Alzheimer's) subtypes and other confounding factors were identified according to the International Classification of Diseases Clinical Modification Codes. Cox proportional hazards regression analysis was employed to examine adjusted HRs after adjusting for confounding factors.

RESULTS

Patients with VBI had a 1.807-fold (95% CI 1.643 to 1.988, p<0.001) higher risk to develop all-cause dementia than individuals without VBI. The risk was significantly higher in the VBI group than in the non-VBI group regardless of age (<65 years: HR: 2.997, 95% CI 1.451 to 6.454, p<0.001; ≥65 years: HR: 1.752, 95% CI 1.584 to 1.937, p<0.001). The VBI group had a higher risk of all-cause dementia than the non-VBI group regardless of sex and follow-up time intervals (<1 year, 1-2 years and≥2 years).

CONCLUSION

Patients with VBI appear to have an increased risk of developing dementia. Further research is needed to investigate the underlying pathophysiology.

James Wenceslaus Papez, His Circuit, and Emotion

James Papez worked on the anatomical substrates of emotion and described a circuit, mainly composed of the hippocampus, thalamus and cingulum, and published his observations in 1937. However, such an idea existed before him, as evidenced by the rudimentary indications from Paul Broca, and Paul MacLean added some other structures like, septum, amygdala, and hypothalamus in its ambit and called it the limbic system. Paul Ivan Yakovlev, proposed a circuit which also referred to orbitofrontal, insular, anterior temporal lobe, and other nuclei of thalamus. Further works hinted at cerebellar projections into this system and the clinical picture of aggression, arousal and positive feeding responses with stimulation of cerebellar nuclei, attests its possible role. Finally, the work of Heinrich Klüver and Paul Bucy of the United States of America on ablating the temporal lobes and amygdala and the resultant behaviour of the animals, almost incontrovertibly adduced evidence for the operation of a neural circuitry in the genesis of emotion. Additionally, Papez circuit may also be concerned with memory and damage to its various components in Parkinson's disease, Alzheimer's disease, Korsakoff's syndrome, semantic dementia, and global amnesia, where cognitive disturbance is almost universal, lends credence to its putative role.

Neural injury of the Papez circuit following hypoxic-ischemic brain injury: A case report

INTRODUCTION

Hypoxic-ischemic brain injury (HI-BI), a result of oxygen deprivation of the brain, is accompanied by memory impairment. In this study, we report on a patient with neural injury of the Papez circuit following HI-BI, demonstrated by diffusion tensor tractography (DTT).

CLINICAL FINDINGS/PATIENT CONCERNS

A 48-year-old male patient suffered spontaneous cardiopulmonary arrest and underwent cardiopulmonary resuscitation for approximately 20 minutes with the concomitant oxygen deprivation leading to HI-BI. The patient showed severe memory impairment at 10 weeks after onset: a Mini-Mental State Examination score of 11 (full score: 30, cut-off score < 24), and examination using the memory function test was not possible due to severe cognitive deficit.

OUTCOMES

On 10-week DTT, discontinuation of the fornical column was observed in both hemispheres and thinning of the thalamocingulate tract was observed in the right hemisphere and nonreconstruction in the left hemisphere.

CONCLUSION

Using DTT, neural injury of the Papez circuit was demonstrated in a patient with memory impairment following HI-BI. These results suggest that analysis of the Papez circuit using DTT could provide beneficial information by detecting injury of the Papez circuit that cannot be detected on conventional brain MRI in patients with HI-BI.

Dural arteriovenous fistula-induced thalamic dementia: report of 4 cases

Nonhemorrhagic neurological deficits are underrecognized symptoms of intracranial dural arteriovenous fistulas (dAVFs) having cortical venous drainage. These symptoms are the consequence of cortical venous hypertension and portend a clinical course with increased risk of neurological morbidity and mortality. One rarely documented and easily misinterpreted type of nonhemorrhagic neurological deficit is progressive dementia, which can result from venous hypertension in the cortex or in bilateral thalami. The latter, which is due to dAVF drainage into the deep venous system, is the less common of these 2 dementia syndromes. Herein, the authors report 4 cases of dAVF with venous drainage into the vein of Galen causing bithalamic edema and rapidly progressive dementia. Two patients were treated successfully with endovascular embolization, and the other 2 patients were treated successfully with endovascular embolization followed by surgery. The radiographic abnormalities and presenting symptoms rapidly resolved after dAVF obliteration in all 4 cases. Detailed descriptions of these 4 cases are presented along with a critical review of 15 previously reported cases. In our analysis of these 19 published cases, the following were emphasized: 1) the clinical and radiographic differences between dAVF-induced thalamic versus cortical dementia syndromes; 2) the differential diagnosis and necessary radiographic workup for patients presenting with a rapidly progressive thalamic dementia syndrome; 3) the frequency at which delays in diagnosis occurred and potentially dangerous and avoidable diagnostic procedures were used; and 4) the rapidity and completeness of symptom resolution following dAVF treatment.

The papez circuit in first-episode, treatment-naive adults with major depressive disorder: combined atlas-based tract-specific quantification analysis and voxel-based analysis

Previous findings suggest that the Papez Circuit may have a role in major depressive disorders. We used atlas-based tract-specific quantification analysis and voxel-based analysis to examine the integrity of white matter tracts involved in mood regulation (including tracts in the Papez Circuit). Diffusion tensor imaging acquired from 35 first-episode, treatment-naive adults with major depressive disorders and 34 healthy adult controls were compared. Our statistical approach compared structural integrity of 11 major white matter tracts between the major depressive disorder and adult controls, as well as illness duration influence in patients. Fractional anisotropy was decreased in the hippocampal cingulum and in the anterior thalamic radiation according to both analytical approaches, all of which were important tracts included in the Papez Circuit. Our results support the role of the Papez Circuit in major depressive disorders with the minimal probability of false positive due to similar findings in both analyses that have complementary advantages. Dysfunction of the Papez Circuit may be a potential marker for studying the pathogenesis of major depressive disorders.

Major Cognitive Changes and Micrographia following Globus Pallidus Infarct

Importance. Globus pallidus (GP) lesions are well known to cause motor deficits but are less commonly—and perhaps not conclusively—associated with cognitive problems. Observations. We present a 45-year-old male with no significant neurological or psychological problems who after suffering a GP infarct was subsequently found to have substantial cognitive problems and micrographia. Formal neuropsychological testing was not possible due to lack of patient follow-up. Conclusions and Relevance. Despite the conflicting literature on the association of GP lesions and cognitive deficits, our patient demonstrated significant neuropsychological changes following his stroke. In addition, evidence of micrographia likely adds to the literature on the localization of this finding. Our case thus suggests that neuropsychological testing may be beneficial after GP strokes.

The circuitry of abulia: insights from functional connectivity MRI

Background

Functional imaging and lesion studies have associated willed behavior with the anterior cingulate cortex (ACC). Abulia is a syndrome characterized by apathy and deficiency of motivated behavior. Abulia is most frequently associated with ACC damage, but also occurs following damage to subcortical nuclei (striatum, globus pallidus, thalamic nuclei). We present resting state functional connectivity MRI (fcMRI) data from an individual who suffered a stroke leading to abulia. We hypothesized that, although structural imaging revealed no damage to the patient's ACC, fcMRI would uncover aberrant function in this region and in the relevant cortical networks.

Methods

Resting state correlations in the patient's gray matter were compared to those of age-matched controls. Using a novel method to identify abnormal patterns of functional connectivity in single subjects, we identified areas and networks with aberrant connectivity.

Results

Networks associated with memory (default mode network) and executive function (cingulo-opercular network) were abnormal. The patient's anterior cingulate was among the areas showing aberrant functional connectivity. In a rescan 3 years later, deficits remained stable and fcMRI findings were replicated.

Conclusions

These findings suggest that the aberrant functional connectivity mapping approach described may be useful for linking stroke symptoms to disrupted network connectivity.

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A method for single subject functional connectivity analysis is proposed.

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In a case study, resting state fcMRI identifies reproducible disruption that corresponds to clinical deficit.

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Damage to the anterior thalamus results in disrupted functional connectivity in the cingulate cortex.

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Abulia without frontal lesion shows disrupted functional connectivity in the cingulo-opercular and default mode networks.

Accelerated forgetting of contextual details due to focal medio-dorsal thalamic lesion

Effects of thalamic nuclei damage and related white matter tracts on memory performance are still debated. This is particularly evident for the medio-dorsal thalamus which has been less clear in predicting amnesia than anterior thalamus changes. The current study addresses this issue by assessing 7 thalamic stroke patients with consistent unilateral lesions focal to the left medio-dorsal nuclei for immediate and delayed memory performance on standard visual and verbal tests of anterograde memory, and over the long-term (>24 h) on an object-location associative memory task. Thalamic patients showed selective impairment to delayed recall, but intact recognition memory. Patients also showed accelerated forgetting of contextual details after a 24 h delay, compared to controls. Importantly, the mammillothalamic tract was intact in all patients, which suggests a role for the medio-dorsal nuclei in recall and early consolidation memory processes.

Immediate effects of deep brain stimulation of anterior thalamic nuclei on executive functions and emotion-attention interaction in humans

Background

Deep brain stimulation (DBS) of anterior thalamic nuclei (ANT) is a novel promising therapeutic method for treating refractory epilepsy. Despite reports of subjective memory impairments and mood disturbances in patients with ANT-DBS, little is known of its effects on cognitive and affective processes.

Hypothesis

The anterior thalamus has connections to prefrontal and limbic networks important for cognitive control and emotional reactivity. More specifically, anterior cingulate cortex (ACC), linked with ANT, has been assigned roles related to response inhibition and attention allocation to threat. Thus, we hypothesized ANT-DBS to influence executive functions, particularly response inhibition, and modulate emotional reactivity to threat.

Method

Twelve patients having undergone ANT-DBS for intractable epilepsy participated in the study. Patients performed a computer-based executive reaction time (RT) test—that is, a go/ no-go visual discrimination task with threat-related emotional distractors and rule switching, while the DBS was switched ON (5/5 mA constant current) and OFF every few minutes.

Results

ANT-DBS increased the amount of commission errors—that is, errors where subjects failed to withhold from responding. Furthermore, ANT-DBS slowed RTs in context of threat-related distractors. When stimulation was turned off, threat-related distractors had no distinct effect on RTs.

Conclusion

We found immediate objective effects of ANT-DBS on human cognitive control and emotion-attention interaction. We suggest that ANT-DBS compromised response inhibition and enhanced attention allocation to threat due to altered functioning of neural networks that involve the DBS-target, ANT, and the regions connected to it such as ACC. The results highlight the need to consider affective and cognitive side-effects in addition to the therapeutic effect when adjusting stimulation parameters. Furthermore, this study introduces a novel window into cognitive and affective processes by modulating the associative and limbic networks with direct stimulation of key nodes in the thalamus.

Multiple thalamo-cortical disconnections in anterior thalamic infarction: implications for thalamic mechanisms of memory and language

Amnesia and linguistic deficits that are associated with thalamic damage have attracted the attention of researchers interested in identifying the neural networks involved in memory and language. The Papez circuit, which is composed of the hippocampus, mammillary body and anterior thalamic nuclei, was first proposed to be critical for memory. However, subsequently, the roles of the neural circuit consisting of the rhinal/parahippocampal cortices and the mediodorsal thalamic nuclei became evident. The ventral lateral nuclei or its adjacent structures have been found to be involved in semantic processing, but the specific neural circuits dedicated to language functions have not been identified. Anterior thalamic infarcts, which affect very circumscribed regions of the ventral anterior portion of the thalamus, often cause paradoxically prominent memory and language deficits. We conducted tractography analyses in 6 patients with left anterior thalamic infarcts to identify neural connections or circuits in which disruptions are associated with memory and language deficits in this condition. The current study demonstrated that the mammillothalamic tract, which connects the mammillary body with the anterior thalamic nuclei, and the anterior and inferior thalamic peduncles, which contain neural fibers that extend from several thalamic nuclei to the anterior temporal, medial temporal and frontal cortices, are disrupted in anterior thalamic infarction. These extensive thalamo-cortical disconnections appear to be due to the dissection of the neural fibers that penetrate the ventral anterior nucleus of the thalamus. Our results suggest the following: (1) amnesia that is associated with anterior thalamic infarction is best interpreted in the context of dual/multiple-system theories of memory/amnesia that posit that multiple neural circuits connecting the anterior and mediodorsal thalamic nuclei with the hippocampus and rhinal/parahippocampal cortices work in concert to support memory function; and (2) the semantic deficits observed in this syndrome may be associated with thalamo-anterior temporal and thalamo-lateral frontal disconnections.

Subcortical volumetric reductions in adult Niemann-Pick disease type C: a cross-sectional study

BACKGROUND AND PURPOSE

Voxel-based analysis has suggested that deep gray matter rather than cortical regions is initially affected in adult Niemann-Pick type C. We sought to examine a range of deep gray matter structures in adults with NPC and relate these to clinical variables.

MATERIALS AND METHODS

Ten adult patients with NPC (18-49 years of age) were compared with 27 age- and sex-matched controls, and subcortical structures were automatically segmented from normalized T1-weighted MR images. Absolute volumes (in cubic millimeters) were generated for a range of deep gray matter structures and were compared between groups and correlated with illness variables.

RESULTS

Most structures were smaller in patients with NPC compared with controls. The thalamus, hippocampus, and striatum showed the greatest and most significant reductions, and left hippocampal volume correlated with symptom score and cognition. Vertex analysis of the thalamus, hippocampus, and caudate implicated regions involved in memory, executive function, and motor control.

CONCLUSIONS

Thalamic and hippocampal reductions may underpin the memory and executive deficits seen in adult NPC. Volume losses in other subcortical regions may also be involved in the characteristic range of motor, psychiatric, and cognitive deficits seen in the disease.

Nuclear medicine in cerebrovascular disease

Stroke and cerebrovascular diseases are major causes of mortality, morbidity, and disability. Nuclear Medicine, primarily via tomographic methods, has made significant contributions to the understanding of the hemodynamic and metabolic consequences of cerebrovascular diseases. In this review, the findings in acute, subacute, and chronic cerebrovascular diseases are described. Many of the pathophysiologic processes and consequences that follow stroke, including completed infarct core, adjacent penumbra, and diaschisis, have been investigated with Nuclear Medicine, and stroke outcome may be related to these phenomena. Additional topics included in this review are cerebrovascular reserve tests and multi-infarct dementia. Finally, Nuclear Medicine investigations of stroke recovery and cerebral plasticity appear to indicate that enhanced activity of preexisting networks, rather than substitution of function, represents the most important mechanism of improvement in chronic stroke rehabilitation.

Diagnosis of vascular cognitive impairment and its main categories

OBJECTIVE

A review of current criteria for the diagnosis of categories related with vascular cognitive impairment, in particular the nomenclature, diagnostic criteria, and differential clinical-radiological findings.

DEVELOPMENT

The criteria for the diagnosis of vascular cognitive impairment have evolved, but available criteria were designed basically for differentiating between vascular dementia and dementia due to Alzheimer disease, and for research purposes. Nevertheless, in clinical practice precise elements are required for: 1) Clinical diagnosis of dementia and mild cognitive impairment; 2) Clinical and neuroimaging criteria for identification of the various cerebrovascular lesions associated with cognitive dysfunction, and 3) A formulation of the aetiogenic-pathogenic relationship between cognitive impairment and cerebrovascular lesions. For this reason, a review was carried out on the diagnostic elements of vascular cognitive impairment categories, classification, and their most relevant characteristics. It highlights the characteristic for the diagnosis of multi-infarction dementia, strategic single infarct dementia, small vessel disease with dementia, mixed dementia, and vascular mild cognitive impairment.

CONCLUSIONS

Standardisation is required, by a multidisciplinary expert team, as regards nomenclature and criteria for the diagnosis of the full spectrum associated with vascular cognitive impairment and especially for vascular dementia and its categories.