Chronic cognitive impairment following laterothalamic infarcts: a study of 9 cases

Long-Term Functional Outcome in Patients With Isolated Thalamic Stroke: The KOSCO Study

BACKGROUND

Information on the long-term prognosis in patients with isolated thalamic stroke is sparse. We report the functional outcomes of patients with thalamic stroke up to 24 months from the KOSCO (Korean Stroke Cohort for Functioning and Rehabilitation) study.

METHODS AND RESULTS

Isolated thalamic stroke was defined as the presence of lesions solely in the thalamus, excluding cases with lesions in other brain parenchyma areas apart from the thalamus, as identified by brain magnetic resonance imaging or computed tomography scans. The Fugl-Meyer Assessment, the Functional Ambulatory Category, the Korean Mini-Mental State Examination, the American Speech-Language-Hearing Association National Outcome Measurement System Swallowing Scale, and the short version of the Korean Frenchay Aphasia Screening Test were used to assess physical impairment. The Functional Independence Measure and modified Rankin Scale were used to assess functional outcomes. All measurements were conducted up to 24 months poststroke. A total of 297 patients were included, consisting of 235 with ischemic and 62 with hemorrhagic stroke. Except for the Functional Ambulatory Category and Functional Independence Measure, all physical impairments showed significant improvement up to 3 months poststroke (P<0.001) and reached a plateau. The Functional Ambulatory Category and Functional Independence Measure scores continued to improve up to 12 months poststroke (P<0.05) and reached a plateau. At 7 days poststroke, 47.5% of patients had no disability (modified Rankin Scale score<2), whereas at 24 months poststroke, 76.4% of patients had no significant disability.

CONCLUSIONS

Patients showed rapid recovery from physical impairment up to 3 months poststroke, with additional improvements in ambulatory function and independence observed up to 12 months poststroke. Additionally, relatively favorable long-term functional prognosis at 24 months after onset was demonstrated. These results could provide insights into the proper management regarding functional outcomes of patients with isolated thalamic stroke.

Characterization of Macular Structural and Microvascular Changes in Thalamic Infarction Patients: A Swept-Source Optical Coherence Tomography-Angiography Study

Background: The retina and brain share similar neuronal and microvascular features. We aimed to investigate the retinal thickness and microvasculature in patients with thalamic infarcts compared with control participants. Material and methods: Swept-source optical coherence tomography (SS-OCT) was used to image the macular thickness (retinal nerve fiber layer, RNFL; ganglion cell-inner plexiform layer, GCIP), while OCT angiography was used to image the microvasculature (superficial vascular plexus, SVP; intermediate capillary plexus, ICP; deep capillary plexus, DCP). Inbuilt software was used to measure the macular thickness (µm) and microvascular density (%). Lesion volumes were quantitively assessed based on structural magnetic resonance images. Results: A total of 35 patients with unilateral thalamic infarction and 31 age−sex-matched controls were enrolled. Compared with control participants, thalamic infarction patients showed a significantly thinner thickness of RNFL (p < 0.01) and GCIP (p = 0.02), and a lower density of SVP (p = 0.001) and ICP (p = 0.022). In the group of patients, ipsilateral eyes showed significant reductions in SVP (p = 0.033), RNFL (p = 0.01) and GCIP (p = 0.043). When divided into three groups based on disease duration (<1 month, 1−6 months, and >6 months), no significant differences were found among these groups. After adjusting for confounders, SVP, ICP, DCP, RNFL, and GCIP were significantly correlated with lesion volume in patients. Conclusions: Thalamic infarction patients showed significant macular structure and microvasculature changes. Lesion size was significantly correlated with these alterations. These findings may be useful for further research into the clinical utility of retinal imaging in stroke patients, especially those with damage to the visual pathway.

Evolution of Neuropsychological Deficits in First-Ever Isolated Ischemic Thalamic Stroke and Their Association With Stroke Topography: A Case-Control Study

The thalamus plays an essential role in cognition. Cognitive deficits have to date mostly been studied retrospectively in chronic thalamic stroke in small cohorts. Studies prospectively evaluating the evolution of cognitive deficits and their association with thalamic stroke topography are lacking. This knowledge is relevant for targeted patient diagnostics and rehabilitation.

Thalamocortical connectivity in electroconvulsive therapy for major depressive disorder

BACKGROUND

Electroconvulsive therapy (ECT) can lead to rapid and effective responses in major depressive disorder (MDD). However, the precise neural mechanisms of ECT for MDD are still unclear. Previous work has confirmed that thalamocortical circuits play an important role in emotion and cognition. However, the relationship between mechanisms of ECT for MDD and thalamocortical connectivity has not yet been investigated.

METHOD

Thalamocortical functional connectivity analysis was performed on resting-state functional magnetic resonance imaging (fMRI) data collected from 28 MDD patients both pre- and post-ECT treatment, as well as 20 healthy controls. The cortex was parceled into six regions of interest (ROIs), which were used as seeds to assess the functional connectivity between the cortex and each voxel in the thalamus. Then, functional connectivity between the identified thalamic subregions and the rest of the brain was quantified to better localize thalamocortical connectivity related to ECT. Structural connectivity among the functionally abnormal regions was also determined using probabilistic tractography from diffusion tensor imaging (DTI) data.

RESULTS

There was decreased parietal cortex-left pulvinar and left pulvinar-bilateral precuneus functional connectivity in post-ECT MDD patients, compared to pre-ECT MDD patients. Furthermore, functional connectivity strength of parietal cortex-left pulvinar and left pulvinar-bilateral precuneus was negative correlation with verbal fluency test scores in post-ECT MDD patients. No significant change was found in structural connectivity analysis.

LIMITATIONS

The sample size of our study was not large.

CONCLUSION

Our findings implicate that the specific abnormalities in thalamocortical circuit may be associated with cognitive impairment induced by ECT.

Presence of White Matter Lesions Associated with Diabetes-Associated Cognitive Decline in Male Rat Models of Pre-Type 2 Diabetes

BACKGROUND The aim of this study was to determine the association between white matter lesions (WML) and diabetes-associated cognitive decline (DACD) in rat models of type 2 diabetes (T2DM). MATERIAL AND METHODS Sixty Sprague-Dawley male rats were divided into 4 groups: control, control+metformin, T2DM, and T2DM+metformin groups. The T2DM groups were fed a diet high in fat and glucose to induce impaired glucose tolerance (IGT) and then were injected with streptozotocin to induce T2DM. The Morris water maze test was used to evaluate cognitive function. Brain diffusion tensor imaging scans were performed for WML. The expression of myelin basic protein (MBP), oligodendrocyte transcription factor 1 (OLIG1), and OLIG2 (markers of brain damage and repair) was determined using immunofluorescence. After IGT, the fractional anisotropy (FA) values of the right thalamus area were significantly lower in both T2DM groups compared with controls. RESULTS Eight weeks after streptozotocin injection, the FA values of the thalamus were lower in the T2DM (bilateral thalamus) group and T2DM+metformin (left thalamus) group than in controls, while the FA values in the left thalamus area were lower in the T2DM+metformin group than in the control and control+metformin groups. The maze escape latency was longer and the number of rats passing through the platform was smaller in the T2DM and T2DM+metformin groups than in the control group. MBP levels were lower and OLIG1 and OLIG2 levels were higher in both T2DM groups than in controls. CONCLUSIONS WML is associated with DACD and appears before the onset of T2DM and signs of DACD and plays a role in diabetes-associated cognitive decline. Metformin reduces WMLs but does not rescue cognitive dysfunction.

Verbal Fluency Is Affected by Altered Brain Lateralization in Adults Who Were Born Very Preterm

Language difficulties have been reported in children and adolescents who were born very preterm (<32 weeks’ gestation) and associated with an atypical lateralization of language processing, i.e., increased right-hemispheric engagement. This study used functional magnetic resonance imaging (fMRI) and spherical deconvolution tractography to study the hemodynamic responses associated with verbal fluency processing (easy and hard letter trials) and verbal fluency-related white matter fiber tracts in 64 very preterm born adults and 36 adult controls (mean age: 30 years). Tractography of the arcuate fasciculus (AF) and frontal aslant tract (FAT) was performed. Tracts were quantified in terms of mean volume, hindrance modulated orientational anisotropy, and lateralization, assessed using a laterality index (LI) to indicate hemispheric dominance. During verbal fluency fMRI, very preterm participants displayed decreased hemodynamic response suppression in both the Easy > Rest and Hard > Rest conditions, compared to controls, in superior temporal gyrus (STG), insula, thalamus, and sensorimotor cortex, particularly in the right hemisphere. At the whole-group level, decreased hemodynamic response suppression in the right sensorimotor cortex was associated with worse on-line performance on the hard letter trials. Increased left-laterality in the AF was present alongside increased right hemispheric hemodynamic response suppression in controls. When only right-handed participants were considered, decreased hemodynamic response suppression in the right STG during hard letter trials was related to weaker left and right FAT white matter integrity in the preterm group only. These results show that verbal fluency is affected by altered functional lateralization in adults who were born very preterm.

Relationship between hippocampal subfield volumes and memory deficits in patients with thalamus infarction

Clinical studies have shown that thalamus infarction (TI) affects memory function. The thalamic nucleus is directly or indirectly connected to the hippocampal system in animal models. However, this connection has not been investigated using structural magnetic resonance imaging (MRI) in humans. From the pathological perspective, TI patients may serve as valid models for revealing the interaction between the thalamus and hippocampus in memory function. In this study, we aim to assess different hippocampal subfield volumes in TI patients and control subjects using MRI and test their associations with memory function. A total of 37 TI patients (TI group), 38 matched healthy control subjects (HC group), and 22 control patients with other stroke location (SC group) underwent 3.0-T MRI scans and clinical memory examinations. Hippocampal subfield volumes were measured and compared by using FreeSurfer software. We examined the correlation between hippocampal subfield volumes and memory scores. Smaller ipsilesional presubiculum and subiculum volumes were observed, and former was related to graphics recall in both left and right TI patients. The left subiculum volume was correlated with short-delayed recall in left TI patients. The right presubiculum volume was correlated with short- and long-delayed recall in right TI patients. TI was found to result in hippocampal abnormality and memory deficits, and its neural mechanisms might be related with and interaction between the thalamus and hippocampus.

Multiple variant type thalamic infarcts: pure and combined types

BACKGROUND AND PURPOSE

Variant topographic patterns of thalamic infarction with distinct manifestations have been classified into three territories: anteromedian, central, and posterolateral. The purpose of this study was to determine clinical, etiological, and radiological features of multiple variant thalamic infarcts.

METHODS

We reviewed 8400 patients with a first clinical stroke included in the Ege Stroke Registry between 2000 and 2013. Among 80 patients with an acute multiple thalamic infarcts confirmed by MRI, we selected all patients with lesions outside the classical territories and studied their clinical, etiological, and radiological features.

RESULTS

Among 8400 patients with first-ever stroke in our registry, 21 patients (26% of all multiple thalamic infarcts) showed infarction outside the classical territories, allowing us to delineate three variant distributions; (i) unilateral multiple variant infarcts [seven patients (9%) in the anteromedian, central, and posterolateral territories] presented with predominantly decreased vigilance (66% with right lesions, 75% with left lesions), cognitive impairment including amnesia (71%), aphasia (57%) in left-sided or bilateral lesions, and executive dysfunction (43%). The most frequent stroke mechanism was cardioembolism (43%). (ii) Bilateral multiple variant infarcts [five patients (6%)], with lesions on the variant territories of the thalamus, resulting in a variety of neurological and neuropsychological signs, consciousness disturbances (80%), sensory-motor deficits (80%). Cardioembolism (60%) was the most frequent etiology. (iii) Combined multiple variant and classical infarcts [nine patients (11%)], characterized by hemihypesthesia (89%) as the most frequent manifestation, followed by hemiataxia (78%), and cognitive deficits. Cardioembolism (56%) and large-artery disease of the vertebrobasilar system (33%) were the main stroke mechanisms.

CONCLUSIONS

We described multiple variant topographic patterns of thalamic infarction with distinct manifestations and etiologies. We thought that multiple variant infarcts are the result of variation in thalamic arterial supply or reflect a source of embolism.

Social cognitive and neurocognitive deficits in inpatients with unilateral thalamic lesions - pilot study

BACKGROUND

The essential role of the thalamus in neurocognitive processes has been well documented. In contrast, relatively little is known about its involvement in social cognitive processes such as recognition of emotion, mentalizing, or empathy.

THE AIM OF THE STUDY

This study was designed to compare the performance of eight patients (five males, three females, mean age ± SD: 63.7±7.9 years) at early stage of unilateral thalamic lesions and eleven healthy controls (six males, five females, 49.6±12.2 years) in neurocognitive tests (CogState Battery: Groton Maze Learning Test, GML; Groton Maze Learning Test-Delayed Recall, GML-DR; Detection Task, DT; Identification Task, IT; One Card Learning Task, OCLT; One Back Task, OBT; Two Back Task, TBT; Set-Shifting Task, S-ST) and other well-known tests (Benton Visual Retention Test, BVRT; California Verbal Learning Test, CVLT; The Rey-Osterrieth Complex Figure Test, ROCF; Trail Making Test, TMT part A and B; Color - Word Stroop Task, CWST; Verbal Fluency Test, VFT), and social cognitive tasks (The Penn Emotion Recognition Test, ER40; Penn Emotion Discrimination Task, EmoDiff40; The Penn Emotional Acuity Test, PEAT40; Reading the Mind in the Eyes Test, revised version II; Toronto Alexithymia Scale, TAS-20).

METHODS

Thalamic-damaged subjects were included if they experienced a single-episode ischemic stroke localized in right or left thalamus. The patients were examined at 3 weeks after the stroke onset. All were right handed. In addition, the following clinical scales were used: the Mini-Mental State Examination (MMSE), Spielberger State-Trait Anxiety Inventory (STAI), Beck Depression Inventory (BDI II). An inclusion criteria was a minimum score of 23/30 in MMSE.

RESULTS

Compared with the healthy controls, patients revealed significantly lower scores in CVLT, GML-DR, and VFT. Furthermore, compared to healthy controls, patients showed significantly delayed recognition of "happiness" in EmoDiff40 and significantly worse performance on Reading the Mind in the Eyes Test, revised version II. Neuropsychological assessment demonstrated some statistically significant deficits in learning and remembering both verbal and visual material, long-term information storing, problem solving, and executive functions such as verbal fluency.

CONCLUSION

Patients at early stage of unilateral thalamic stroke showed both neurocognitive and social cognitive deficits. Further research is needed to increase understanding about diagnosis, early treatment, and prognosis of patients with thalamic lesions.

Verbal fluency in essential tremor patients: the effects of deep brain stimulation

OBJECTIVE

To assess the effects of different frequencies of thalamic Deep-Brain-Stimulation (DBS) on cognitive performance of patients suffering from Essential Tremor (ET).

METHODS

In 17 ET-patients with thalamic-DBS, Tremor-Rating-Scale (TRS), standardized phonemic and semantic verbal fluency (VF), Stroop-Color-Word-Test and Digit-span-test were investigated in three randomized stimulation-settings: i) high-frequency stimulation (HFS), ii) low-frequency stimulation (LFS) and iii) OFF-stimulation (DBS-OFF). Paired-samples t-test for TRS and one-way repeated measures analysis of variance for cognitive performance were calculated.

RESULTS

Tremor was reduced during HFS (MeanTRS-HFS = 12.9 ± 9.6) compared to DBS-OFF (MeanTRS-OFF = 44.4 ± 19.8, P < .001) and to LFS (MeanTRS-10 Hz = 50.0 ± 24.2; P < .001). While performance of Stroop-task and digit-span remained unaffected by stimulation-settings (P > .05), phonemic and semantic VF differed significantly between the three conditions (FPvf = 5.28, FSvf = 3.41, both P < .05). Post-hoc comparisons revealed significant differences for both phonemic and semantic VF between LFS (MeanPvf-10 Hz = 54.6 ± 9.2, MeanSvf-10 Hz = 56.4 ± 7.9) and HFS (MeanPvf-ON = 48.3 ± 11.4, MeanSvf-ON = 51.1 ± 11.0, both P < .05), while DBS-OFF (MeanPvf-OFF = 51.2 ± 9.3, MeanSvf-OFF = 53.6 ± 12.9) and HFS and DBS-OFF and LFS did not differ significantly (P > .05).

CONCLUSIONS

HFS compared to LFS or DBS-OFF significantly reduced tremor but simultaneously worsened VF while working memory and cognitive inhibition remained unaffected. In contrast, LFS enhanced VF but did not ameliorate tremor. The data emphasize the relevance of thalamocortical loops for verbal fluency but also suggest that more sophisticated DBS-regimes in ET may improve both motor and cognitive performance.

Trail making test B and brain perfusion imaging in mild cognitive impairment and mild Alzheimer's disease

The trail making test (TMT) has long been used to investigate deficits in cognitive processing speed and executive function in humans. However, there are few studies that elucidate the neural substrates of the TMT. The aim of the present study was to identify the brain regional perfusion patterns associated with performance on TMT part B (TMT-B) in patients with amnestic mild cognitive impairment (aMCI) or mild Alzheimer's disease (AD). Twenty-one patients with good TMT-B scores and 21 age- and sex-matched patients with poor TMT-B scores were selected. All 42 subjects underwent brain single photon emission computed tomography (SPECT), and the SPECT images were analyzed by statistical parametric mapping. No significant differences between good- and poor-scoring groups were found with respect to years of education, Addenbrooke's Cognitive Examination scores, and scores on TMT-A. Compared to patients with good scores on TMT-B, patients with poor scores showed significant hypoperfusion in the bilateral anterior cingulate extending to the posterior region on the right side, bilateral caudate nucleus and putamen, and bilateral thalamus. Analysis of 63 AD or aMCI subjects revealed significant correlation a between regional cerebral blood flow in the right cingulate cortex and TMT-B scores. Our results suggest that functional activity of the anterior cingulate, striatum and thalamus is closely related to performance time on TMT-B. The performance time on the TMT-B score might be a promising index of dysfunction of the anterior cingulate, striatum, and thalamus among patients with aMCI or mild AD.

Atypical pulvinar-cortical pathways during sustained attention performance in children with attention-deficit/hyperactivity disorder

OBJECTIVE

The neurobiological basis of inattentiveness, a core feature of attention-deficit/hyperactivity disorder (ADHD), is not yet well understood. Structural abnormalities in thalamus, especially the pulvinar nuclei, have recently been reported in ADHD. Pulvinar nuclei maintain reciprocal connections with cortical/subcortical areas, and play a central coordinating role during visual attention processing. The objective of this study was to test the hypothesis that children and young adolescents with ADHD would show atypical pulvinar-cortical functional pathways during sustained attention performance, and that these functional abnormalities would be associated with the inattentive symptoms of the disorder.

METHOD

Visual attention task-based functional magnetic resonance imaging (fMRI) data from 22 children and young adolescents with ADHD and 22 demographically matched, normal control subjects were analyzed. Cortical activation maps and temporal correlations of activity patterns between pulvinar nuclei and the remainder of brain were constructed for each participant. Correlations between activation magnitude of pulvinar and diagnostic measures were calculated in subjects with ADHD.

RESULTS

Compared to controls, subjects with ADHD showed significantly reduced pulvinar activations bilaterally, significantly decreased functional connectivity between bilateral pulvinar and right prefrontal regions, and significantly increased connectivity between the right pulvinar and bilateral occipital regions. In addition, the activation magnitude in the left pulvinar was negatively correlated with the DSM-IV inattentive index in ADHD group.

CONCLUSIONS

Allied with previous evidence of structural abnormalities in pulvinar, the current data suggest that inappropriate development of pulvinar may lead to disrupted functional circuits for visual attention processing, and that these disruptions contribute significantly to the pathophysiological mechanisms of the inattentiveness symptoms in ADHD.

The effects of cerebral white matter changes on cardiovascular responses to cognitive and physical activity in a stroke population

Autonomic nervous system (ANS) control may be disrupted by cerebrovascular disease. We investigated the relationship between alterations in white matter integrity and regulation of the ANS in 23 participants who sustained a stroke within 5 years. These participants underwent diffusion tensor imaging, and fractional anisotropy values were calculated (DTI-FA) for each hemisphere and lobe. Cognitive and physical exertion tasks were performed while recording an electrocardiogram. Respiratory sinus arrhythmia (RSA) decreased more during a verbal fluency task with lower left hemisphere DTI-FA. Further, the physical stressor yielded decreases in RSA with lower frontal DTI-FA and higher temporal lobe DTI-FA, p < .05 (perhaps a release effect on the central autonomic network). Decrements in ANS regulation may have functional consequences that alter behavior, as well as potentially increasing the risk for further vascular disease.

Predicting Compliance With Treatment Following Stroke: A New Model of Adherence Following Rehabilitation

Background and purpose: Adherence to medication is fundamental to optimal health recovery yet compliance to medication rates are lower than 50% in most studies. This study aimed to investigate the correlates of adherence in stroke patients. Method: Twenty-six stroke patients and 29 amputee patients who had completed a rehabilitation program at Melbourne Rehabilitation Centre were investigated. Medical adherence was determined from computed adherence metrics based on pill counts and subjective reports of patient knowledge of medication use. Model components that were believed to contribute to poor adherence, included emotional and cognitive dysfunction, beliefs about medication, and social support. These factors were assessed by patient and partner self-rating questionnaires. Results: Stroke patients showed a lower level of adherence compared to amputee patients. Cognitive and emotional dysfunction, beliefs about medication, and the level of care were significantly associated with low adherence to medicine regimes in stroke patients. Level of cognitive impairment and emotional impairment were significantly associated with low adherence to medicines in amputee patients. Emotional dysfunction was the best predictor of poor adherence in both patient groups. Conclusion: The findings are in keeping with past adherence studies with other patient groups and support the position that emotional, cognitive, and social factors are important factors in adherence. The specific nonadherence profile for this brain-damaged group is modeled and the application for outpatients following rehabilitation is discussed.

Cognitive, affective and behavioural disturbances following vascular thalamic lesions: a review

During the last decades, many studies have shown that the thalamus is crucially involved in language and cognition. We critically reviewed a study corpus of 465 patients with vascular thalamic lesions published in the literature since 1980. 42 out of 465 (9%) cases with isolated thalamic lesions allowed further neurocognitive analysis. On the neurolinguistic level, fluent output (=31/33; 93.9%), normal to mild impairment of repetition (=33/35; 94.3%), mild dysarthria (=8/9; 88.9%) and normal to mild impairment of auditory comprehension (=27/34; 79.4%) were most commonly found in the group of patients with left and bilateral thalamic lesions. The taxonomic label of thalamic aphasia applied to the majority of the patients with left thalamic damage (=7/11; 63.6%) and to one patient with bithalamic lesions (=1/1). On the neuropsychological level, almost 90% of the left thalamic and bithalamic patient group presented with amnestic problems, executive dysfunctions and behaviour and/or mood alterations. In addition, two thirds (2/3) of the patients with bilateral thalamic damage presented with a typical cluster of neurocognitive disturbances consisting of constructional apraxia, anosognosia, desorientation, global intellectual dysfunctioning, amnesia, and executive dysfunctions associated with behaviour and/or mood alterations. Our study supports the long-standing view of a 'lateralised linguistic thalamus' but restates the issue of a 'lateralised cognitive thalamus'. In addition, critical analysis of the available literature supports the view that aphasia following left or bithalamic damage constitutes a prototypical linguistic syndrome.

Enlargement of thalamic nuclei in Tourette syndrome

CONTEXT

The basal ganglia and thalamus together connect in parallel closed-loop circuits with the cortex. Previous imaging studies have shown modifications of the basal ganglia and cortical targets in individuals with Tourette syndrome (TS), but less is known regarding the role of the thalamus in TS pathogenesis.

OBJECTIVE

To study the morphological features of the thalamus in children and adults with TS.

DESIGN

A cross-sectional, case-control study using anatomical magnetic resonance imaging.

SETTING

University research center.

PARTICIPANTS

The 283 participants included 149 with TS and 134 normal control individuals aged 6 to 63 years.

MAIN OUTCOME MEASURES

Conventional volumes and measures of surface morphology of the thalamus.

RESULTS

Analyses of conventional volumes and surface morphology were consistent in demonstrating an enlargement in TS-affected thalami. Overall volumes were 5% larger in the group composed of children and adults with TS. Statistical maps of surface contour demonstrated enlargement over the lateral thalamus. Post hoc testing indicated that differences in IQ, comorbid illnesses, and medication use did not account for these findings.

CONCLUSIONS

Morphological abnormalities in the thalamus, together with the disturbances reported in the sensorimotor cortex, striatum, and globus pallidus, support the hypothesis of a circuitwide disorder within motor pathways in TS. The connectivity and function of the numerous and diverse thalamic nuclei within cortical-subcortical circuits constitute an anatomical crossroad wherein enlargement of motor nuclei may represent activity-dependent hypertrophy within this component of cortical-subcortical motor circuits, or an adaptive response within a larger putative compensatory system that could thereby directly modulate activity in motor circuits to attenuate the severity of tics.

Extrahippocampal integrity in temporal lobe epilepsy and cognition: thalamus and executive functioning

Chronic temporal lobe epilepsy (TLE) is characterized by the presence of extra-hippocampal brain abnormality and cognitive impairment in both memory and nonmemory domains. However, the link between structural integrity and cognition has not frequently been studied. Forty-six patients with TLE and 61 age-matched controls were studied to determine the predictive relationship between baseline thalamic volume and performance on measures of executive functioning evaluated 4 years later. As expected, the TLE group had lower baseline thalamic volumes than controls and also performed more poorly on measures of executive functioning. Total thalamic volume significantly predicted subsequent performance on all three measures of executive functioning. These findings were maintained when both hippocampal volume and frontal lobe volume were taken into account. These findings add to a growing literature demonstrating a link between extra-hippocampal volume abnormalities and cognitive functioning in TLE.

Thalamic pathology in schizophrenia

The thalamus plays a critical role in the coordination of information as it passes from region to region within the brain. A disruption of that information flow may give rise to some of the cardinal symptoms of schizophrenia. In support of this hypothesis, schizophrenia-like syndromes emerge when illnesses, such as stroke, selectively damage the thalamus while sparing the rest of the brain. Evidence from many sources has implicated thalamic dysfunction in schizophrenia. In postmortem studies, several subregions of the thalamus, including the mediodorsal nucleus and the pulvinar, have been shown to have fewer neurons in schizophrenia. Neurochemical disturbances are also seen, with changes in both the glutamate and dopamine systems; thalamic glutamate receptor expression is altered in schizophrenia, and dopamine appears to be elevated in thalamic subregions, while evidence exists of an imbalance between dopamine and other neurotransmitters. In vivo studies using magnetic resonance imaging have demonstrated smaller thalamic volumes in schizophrenia, as well as shape deformations suggesting changes in those thalamic regions that are most densely connected to the portions of the brain responsible for executive function and sensory integration. These changes seem to be correlated with clinical symptoms. The thalamus is a starting point for several parallel, overlapping networks that extend from thalamic nuclei to the cortex. Evidence is emerging that changes in the thalamic nodes of these networks are echoed by changes at other points along the chain; this suggests that schizophrenia might be a disease of disrupted thalamocortical neural networks. This model distributes the pathology throughout the network, but also concentrates attention on the thalamus as a critical structure, especially because of its role in coordinating the flow of information within and between neural networks.

Glucose metabolism and PIB binding in carriers of a His163Tyr presenilin 1 mutation

Six young related pre-symptomatic carriers of a His163Tyr mutation in the presenilin 1 gene who will develop early onset familial Alzheimer's disease (eoFAD), and a control group of 23 non-carriers underwent (18)F-fluorodeoxyglucose positron emission tomography (FDG PET). The mutation carriers were followed-up after 2 years. Multivariate analysis showed clear separation of carriers from non-carriers on both occasions, with the right thalamus being the region contributing most to group differentiation. Statistical parametric mapping (SPM) revealed in the carriers non-significantly lower thalamic cerebral glucose metabolism (CMRglc) at baseline and significantly decreased CMRglc in the right thalamus at follow-up. One mutation carrier was followed-up with FDG PET 10 years after baseline and showed reductions in cognition and CMRglc in the posterior cingulate and the frontal cortex. This subject was diagnosed with AD 1 year later and assessed with an additional FDG as well as an (11)C-PIB PET scan 12 years after baseline. Global cortical CMRglc and cognition were distinctly decreased. PIB binding was comparable with sporadic AD patterns but showing slightly higher striatal levels.

Injury and recovery in the developing brain: evidence from functional MRI studies of prematurely born children

Functional MRI (fMRI) might provide important insights into emerging data that suggest that recovery from injury can occur in the brains of children born prematurely. Strategies employing auditory stimulation demonstrate blood-oxygen-level-dependent (BOLD) activation in preterm infants as young as 33 weeks' gestational age, and reliable BOLD signal in response to visual stimulation occurs at term-equivalent age. Strategies based on fMRI are particularly suited to the study of language and memory, and emerging data are likely to provide insights into perplexing reports that have demonstrated improving cognitive scores but persistent volumetric and microstructural changes in frontotemporal language systems in the prematurely born. Even when sex, gestational age and early medical and environmental interventions are taken into account, fMRI data from several investigators suggest the engagement of alternative neural networks for language and memory in the developing preterm brain.

Cognitive Disorders in Acute Stroke: Prevalence and Clinical Determinants

BACKGROUND

Although cognitive impairment early after stroke is a powerful predictor of long-term functional dependence and dementia, little is known about the characteristics and determinants of cognitive dysfunction in acute stroke.

METHODS

We administered a neuropsychological examination covering 7 cognitive domains to 190 patients within 3 weeks after a first stroke. We also assembled lesion characteristics, clinical factors at admission, demographic characteristics and vascular risk factors. Multivariate logistic regression adjusted for age, gender and education was performed to examine determinants of acute cognitive impairment.

RESULTS

Overall, 74% of patients with a cortical stroke, 46% with a subcortical stroke and 43% with an infratentorial stroke demonstrated acute cognitive impairment. Disorders in executive functioning (39%) and visual perception/construction (38%) were the most common. The prevalence and severity of deficits in executive functioning, language, verbal memory and abstract reasoning was more pronounced following left compared to right cortical stroke (all p < 0.05). Intracerebral haemorrhage (OR = 5.6; 95% CI = 1.2-25.4) and cortical involvement of the stroke (OR = 3.6; 95%, CI = 1.3-9.9) were independent determinants of acute cognitive impairment, whereas premorbid moderate alcohol consumption exerted a protective effect (OR = 0.4; 95% CI = 0.1-1.1).

CONCLUSIONS

Cognitive impairment is common in the first weeks after stroke, with executive and perceptual disorders being the most frequent. Intracerebral haemorrhage, cortical involvement of the lesion and premorbid moderate alcohol consumption are independently associated with acute cognitive impairment.

I. Longitudinal changes in aging brain function

Changes in brain activity over time were evaluated in a group of older adults in the Baltimore Longitudinal Study of Aging who maintained good physical and cognitive health. Participants underwent PET scans during rest and delayed verbal and figural recognition memory performance at year 1 baseline and at year 9. While memory performance remained stable over the 8 years, longitudinal changes in regional cerebral blood flow were observed within each scan condition. Further analyses revealed distinctive patterns of change related specifically to verbal or figural recognition, as well as longitudinal changes common to all scan conditions. These findings demonstrate that the older brain undergoes functional reorganization with increasing age in healthy, cognitively stable individuals. In view of the stable memory performance, the task-dependent results suggest that age-related changes in brain activity help maintain cognitive function with advancing age.

Correlations of thalamic reductions with verbal fluency impairment in those born prematurely

Prematurity is associated with reduced brain volume, and the thalamus is among the structures most affected. We used a voxel-based morphometry analysis of gray matter to map regional atrophy in the thalamus in a sample of 30 adolescents with antecedents of very preterm birth. The preterm sample was compared with 30 controls matched by age, sex, handedness and sociocultural status. Individuals with very preterm birth differed from controls in several thalamic nuclei, and semantic and phonetic fluency showed different correlation patterns with brain volume. Semantic fluency achieved significant correlations with more thalamic nuclei than phonetic fluency. These results agree with functional magnetic resonance imaging studies showing that semantic fluency involves more cerebral regions than phonetic fluency.

Vascular cognitive impairment

Vascular cognitive impairment encompasses a spectrum of clinically defined syndromes ranging from vascular cognitive impairment-no dementia, to vascular dementia. The underlying cerebrovascular pathology includes both overt infarction as well as rarefaction of gray and white matter. Alzheimer's pathology may coexist with vascular pathology. Diagnosis rests on identifying acquired cognitive impairment in the setting of documented cerebrovascular disease, based on clinical presentation and neuroimaging; MRI is more sensitive than CT. The course can be stepwise or gradually progressive. The clinical picture is typically dominated by deficits in executive function rather than the short-term memory deficit typical of Alzheimer's disease. No specific therapies exist, but treatment with anticholinesterase agents and N-methyl-d-aspartate antagonists may result in clinical improvement. Prevention remains paramount, with early recognition of populations at risk and early and aggressive management of risk factors, including hypertension, dyslipidemia, diabetes, and tobacco use as well as antithrombotic therapy, in appropriate populations.

Alterações cognitivas, comunicativas e emocionais após lesão hemisférica direita: em busca de uma caracterização da Síndrome do Hemisfério Direito

O conjunto de sinais e sintomas observados após um acometimento neurológico no hemisfério direito pode ser denominado de Síndrome do Hemisfério Direito &– SHD. Esse ensaio teórico tem por objetivo apresentar uma caracterização desse quadro neuropsicológico. A SHD é, então, caracterizada por déficits nas funções cognitivas atenção, percepção, memória, praxias e funções executivas, com a presença de anosognosia, heminegligência sensorial, prosopagnosia, alterações de memória visuo-espacial e de trabalho, dispraxia construtiva e disfunção executiva. Quanto às habilidades comunicativas, a SHD engloba alterações nos componentes discursivo, pragmático-inferencial, léxico-semântico e prosódico. Os déficits de processamento emocional incluem dificuldades de compreensão e produção de emoções a partir de expressões faciais ou emissões vocais e alterações neuropsiquiátricas. Há, no entanto, uma heterogeneidade na sua manifestação. Tendo em vista essa variabilidade de sinais e sintomas, mais estudos de caso e de grupo com indivíduos lesados de hemisfério direito devem ser conduzidos para um melhor entendimento da SHD.

Changes in artistic style after minor posterior stroke

BACKGROUND

Two professional painters experienced significant changes in their art as the main consequence of minor stroke located in the left occipital lobe or thalamus.

METHODS

The features of this artistic conversion were analysed on the basis of extensive neurological, neuropsychological, and psychiatric evaluations.

RESULTS

Both painters, initially unaware of the artistic changes, exhibited mild signs of executive dysfunction, but no general cognitive decline. The first painter, who showed mild visual-perceptive difficulties (dyschromatopsia and scotoma in his right upper visual field after left occipital stroke), together with increased anxiety and difficulty in emotional control, switched to a more stylised and symbolic art. The second painter, who also presented features of emotionalism related to his left latero-thalamic stroke, switched from an impressionist style to a more joyous and geometric, but more simplistic, abstract art.

CONCLUSIONS

These findings show that mild cognitive and affective modifications due to focal posterior brain lesions can have significant repercussions on artistic expression.

Anteromedian, central, and posterolateral infarcts of the thalamus: three variant types

BACKGROUND AND PURPOSE

Thalamic infarcts have traditionally been classified into 4 territories: anterior, paramedian, inferolateral, and posterior. The purpose of this study was to review this classical versus variant distribution in patients with thalamic stroke.

METHODS

We reviewed all patients with a first clinical stroke included in the Lausanne Stroke Registry between 1990 and 2002. Among 71 patients with an acute stroke isolated to the thalamus confirmed by MRI, we selected all patients with lesions outside the classical territories and studied their clinical, etiological, and radiological features.

RESULTS

A total of 21 patients (30% of all thalamic stroke patients) showed infarction outside the classical territories, allowing us to delineate 3 variant distributions: (1) Anteromedian territory (9 patients [13%]) involving anterior and paramedian territories, with predominantly cognitive impairment, including executive dysfunction, anterograde amnesia, and aphasia in left-sided or bilateral lesions. The most frequent stroke mechanism was cardiac embolism. (2) Central territory (4 patients [6%]), with lesions on the central part of the thalamus, resulting in a variety of neurological and neuropsychological signs, reflecting the involvement of several adjacent structures. Microangiopathy was the most frequent etiology. (3) Posterolateral territory (8 patients [11%]), involving inferolateral and posterior territories, with hemihypesthesia as the most frequent manifestation, followed by hemiataxia, executive dysfunction, and aphasia in left-sided lesions. Artery-to-artery embolism and microangiopathy were the main stroke mechanisms.

CONCLUSIONS

We describe 3 variant topographic patterns of thalamic infarction with distinct manifestations and etiologies. We postulate that these infarcts are the result of a variation in thalamic arterial supply or reflect borderzone ischemia.

Thalamic atrophy in Huntington's disease co-varies with cognitive performance: a morphometric MRI analysis

The pattern of motor, behavioral and cognitive symptoms in Huntington's disease (HD) implicates dysfunction of basal-ganglia-thalamo-cortical circuits. This study explored if cognitive performance in HD is correlated with localized cerebral changes. Psychomotor functions were investigated by verbal fluency, Stroop color word and Digit Symbol tests in 44 HD patients and 22 controls. Three-dimensional magnetic resonance imaging (MRI) data were analyzed with regard to regional gray matter changes by use of the observer-independent whole-brain-based approach of voxel-based morphometry (VBM). Using statistical parametric mapping, the MRI data of the HD patients were analyzed in an ANCOVA including the individual results of the neuropsychological tests. Besides striatal areas, symmetrical regional atrophy of the thalamus was found to co-vary significantly with cognitive performance (P < 0.001, corrected for multiple comparisons). In particular, thalamic subnuclei projecting to prefrontal areas (dorsomedial subnucleus) and connected to the striatum (centromedian/parafascicular and ventrolateral nuclear complex) displayed volume loss, in agreement with neuropathological studies. These results suggest that thalamic degeneration contributes in an important way to the impairment of executive function in early HD. Patients who are impaired in executive tests display structural double lesions of the basal-ganglia-thalamo-cortical circuitry both at the striatal and at the thalamic level.