Cognitive Dysfunction in Type 1 Diabetes Mellitus

CONTEXT

We have summarized key studies assessing the epidemiology, mechanisms, and consequences of cognitive dysfunction (CD) in type 1 diabetes.

EVIDENCE SYNTHESIS

In a number of studies, the severity of CD in type 1 diabetes was affected by the age of onset and duration, and the presence of proliferative retinopathy and autonomic neuropathy. Diabetes-related CD has been observed, not only in adults, but also in children and adolescents. Most neuroimaging studies of patients with type 1 diabetes did not show any differences in whole brain volumes; however, they did reveal selective deficits in gray matter volume or density within the frontal, posterior, and temporal cortex and subcortical gray matter. Studies of middle-age adults with long-standing type 1 diabetes using diffusion tensor imaging have demonstrated partial lesions in the white matter and decreased fractional anisotropy in posterior brain regions. The mechanisms underlying diabetes-related CD are very complex and include factors related to diabetes per se and to diabetes-related cardiovascular disease and microvascular dysfunction, including chronic hyperglycemia, hypoglycemia, macro- and microvascular disease, and increased inflammatory cytokine expression. These mechanisms might contribute to the development and progression of both vascular dementia and Alzheimer disease.

CONCLUSIONS

Higher rates of CD and faster progression in type 1 diabetes can be explained by both the direct effects of altered glucose metabolism on the brain and diabetes-related cardiovascular disease. Because the presence and progression of CD significantly worsens the quality of life of patients with diabetes, further multidisciplinary studies incorporating the recent progress in both neuroimaging and type 1 diabetes management are warranted to investigate this problem.

10Kin1day: A Bottom-Up Neuroimaging Initiative

We organized 10Kin1day, a pop-up scientific event with the goal to bring together neuroimaging groups from around the world to jointly analyze 10,000+ existing MRI connectivity datasets during a 3-day workshop. In this report, we describe the motivation and principles of 10Kin1day, together with a public release of 8,000+ MRI connectome maps of the human brain.

Aging and Hypertension - Independent or Intertwined White Matter Impairing Factors? Insights From the Quantitative Diffusion Tensor Imaging

Aging disrupts white matter integrity, and so does continuous elevated blood pressure that accompanies hypertension (HTN). Yet, our understanding of the interrelationship between these factors is still limited. The study aimed at evaluating patterns of changes in diffusion parameters (as assessed by quantitative diffusion fiber tracking - qDTI) following both aging, and hypertension, as well as the nature of their linkage. 146 participants took part in the study: the control group (N = 61) and the patients with hypertension (N = 85), and were divided into three age subgroups (25-47, 48-56, 57-71 years). qDTI was used to calculate the values of fractional anisotropy, mean, radial and axial diffusivity in 20 main tracts of the brain. The effects of factors (aging and hypertension) on diffusion parameters of tracts were tested with a two-way ANOVA. In the right hemisphere there was no clear effect of the HTN, nor an interaction between the factors, though some age-related effects were observed. Contrary, in the left hemisphere both aging and hypertension contributed to the white matter decline, following a functional pattern. In the projection pathways and the fornix, HTN and aging played part independent of each other, whereas in association fibers and the corpus callosum if the hypertension effect was significant, an interaction was observed. HTN patients manifested faster decline of diffusion parameters but also reached a plateau earlier, with highest between-group differences noted in the middle-aged subgroup. Healthy and hypertensive participants have different brain aging patterns. The HTN is associated with acceleration of white matter integrity decline, observed mainly in association fibers of the left hemisphere.

Understanding the Physiopathology Behind Axial and Radial Diffusivity Changes-What Do We Know?

The use of the diffusion tensor imaging (DTI) is rapidly growing in the neuroimaging field. Nevertheless, rigorously performed quantitative validation of DTI pathologic metrics remains very limited owing to the difficulty in co-registering quantitative histology findings with magnetic resonance imaging. The aim of this review is to summarize the existing state-of-the-art knowledge with respect to axial (λ_║) and radial (λ_┴) diffusivity as DTI markers of axonal and myelin damage, respectively. First, we provide technical background for DTI and briefly discuss the specific organization of white matter in bundles of axonal fibers running in parallel; this is the natural target for imaging based on diffusion anisotropy. Second, we discuss the four seminal studies that paved the way for considering axial (λ_║) and radial (λ_┴) diffusivity as potential in vivo surrogate markers of axonal and myelin damage, respectively. Then, we present difficulties in interpreting axial (λ_║) and radial (λ_┴) diffusivity in clinical conditions associated with inflammation, edema, and white matter fiber crossing. Finally, future directions are highlighted. In summary, DTI can reveal strategic information with respect to white matter tracts, disconnection mechanisms, and related symptoms. Axial (λ_║) and radial (λ_┴) diffusivity seem to provide quite consistent information in healthy subjects, and in pathological conditions with limited edema and inflammatory changes. DTI remains one of the most promising non-invasive diagnostic tools in medicine.

Cognitive Predictors of Cortical Thickness in Healthy Aging

This study seeks to define the role of predictive values of the motor speed, inhibition control, and fluid and crystallized intelligence in estimating the cortical thickness in healthy elderly. Forty-six older healthy subjects (37 women, 9 men) over 60 years of age were included in the study. The participants were examined on 3.0 T MRI scanners. The protocol included standard anatomical sequences, to exclude brain pathology, and a high-resolution T1-weighted sequence used to estimate the cortical thickness. The neuropsychological protocol included fluid intelligence assessment (Raven Progressive Matrices), crystalized intelligence assessment (information or vocabulary subtest of the Wechsler Adult Intelligence Scale-Revised (WAIS-R)), and executive functioning (Color Traits Test). The findings unraveled several interdependencies. The higher the intelligence, the thicker was the grey matter in nine regions of both hemispheres, but also some paradoxical reversed associations were found in four areas; all of them were localized along different sections of the cingulate gyrus in both hemispheres. An inverse association was found between crystallized intelligence and the thickness of the pars opecularis of the right hemisphere. The better the executive functioning, the thicker was the grey matter of a given region. The better the motor performance, the thicker was the grey matter of the rostral middle frontal area of the left hemisphere and the lingual gyrus of both hemispheres. In conclusion, the associations unraveled demonstrate that the neural mechanisms underlying healthy aging are complex and heterogenic across different cognitive domains and neuroanatomical regions. No brain aging theory seems to provide a suitable interpretative framework for all the results. A novel, more integrative approach to the brain aging should be considered.

Wisconsin card sorting test as a measure of executive function impairments in stroke patients

The Wisconsin Card Sorting Test (WCST) is among the most frequently administered neuropsychological tests. It is assumed that successful completion of this test requires engagement of executive functions (EF). One of the most common origins of EF impairments is ischemic stroke. The present study intends to evaluate the diagnostic use of the WCST as a measure of these impairments in poststroke patients. Forty-four patients (8 women and 36 men) who had recent unilateral stroke (22 left hemisphere, 22 right hemisphere) participated in the study. The overall accuracy of the WCST in classifying stroke survivors as having executive disorders was poor. Nevertheless, statistical analysis revealed its negative predictive power to be greater than positive predictive power (i.e., normal scores on the WCST reliably indicated the absence of executive disorders in 8 or more out of 10). Performance on the WCST is clearly influenced by severity of the executive disorders. Namely, patients with severe impairment of EF (as measured by go/no-go, fluency, and other EF tests) performed more poorly on the WCST than patients with lesser impairment or those with no impairment at all, the latter group's results being indistinguishable. In addition, this study highlights a three-factor solution to the WCST, which accounted for 90.3% of the variance. The scores that most strongly loaded on Factors 1 to 3 were, in order: percentage of conceptual-level responses, number of trials to complete the first category, and failures to maintain the set of responses. Finally, an analysis using multivariate analysis of variance, with the anterior versus posterior site and left versus right side of the lesion as independent variables, revealed a relatively weak effect of lesion location on the WCST performance. In particular, with respect to all test scores, there is only one significant interaction between the site and side of lesion was obtained (F(₁(,)₂₄) = 4.12; p < .05; i.e., the number of categories achieved was significantly smaller after damage to the frontal lobe on the left than on the right side, whereas the laterality effect was not significant after nonfrontal lesions). In conclusion, to ascertain the cerebral substrates of poststroke executive dysfunction, there is a need to apply more accurate tests than the WCST. The study highlights the importance of a multicomponent approach to executive functioning in stroke patients.

Selectivity of lexical-semantic disorders in Polish-speaking patients with aphasia: evidence from single-word comprehension

Several neuropsychological studies have shown that patients with brain damage may demonstrate selective category-specific deficits of auditory comprehension. The present paper reports on an investigation of aphasic patients' preserved ability to perform a semantic task on spoken words despite severe impairment in auditory comprehension, as shown by failure in matching spoken words to pictured objects. Twenty-six aphasic patients (11 women and 15 men) with impaired speech comprehension due to a left-hemisphere ischaemic stroke were examined; all were right-handed and native speakers of Polish. Six narrowly defined semantic categories for which dissociations have been reported are colors, body parts, animals, food, objects (mostly tools), and means of transportation. An analysis using one-way ANOVA with repeated measures in conjunction with the Lambda-Wilks Test revealed significant discrepancies among these categories in aphasic patients, who had much more difficulty comprehending names of colors than they did comprehending names of other objects (F((5,21))=13.15; p<.001). Animals were most often the easiest category to understand. The possibility of a simple explanation in terms of word frequency and/or visual complexity was ruled out. Evidence from the present study support the position that so called "global" aphasia is an imprecise term and should be redefined. These results are discussed within the connectionist and modular perspectives on category-specific deficits in aphasia.

The contribution of the left and right hemispheres to early recovery from aphasia: A SPECT prospective study

This prospective study examined the relationship between post-stroke recovery of aphasia and changes in cerebral blood flow (CBF). To address the question of right hemisphere (RH) involvement in restitution of language, we tested the hypothesis that the increase in perfusion of the RH is crucial for early recovery from aphasia. Twenty-four right-handed patients with acute aphasia following left hemisphere (LH) ischaemic stroke were examined twice with a six-month interval. At each session CBF and language scores were measured on the same stroke patients. Language was measured by selected tasks derived from the Boston Diagnostic Aphasia Examination (BDAE). The SPECT scans were obtained using (99m)Tc-ECD on a triple-head gamma camera Multispect-3. Although initial CBF measured for the whole group of aphasic patients was not a predictor for future language recovery for either hemisphere, increased perfusion of the RH during a six-month interval was found to parallel the recovery of aphasic disorders. There was a correlation between the change in the right parietal CBF (but not the left) and a change in numerous language abilities. Nevertheless, only CBF values on the left predicted performance on the language tests at initial and follow-up examinations. When the area damaged on structural imaging was excluded from perfusion analysis, only subcortical CBF change on the left showed a positive correlation with language improvement. Thus, the cerebral mechanism associated with early recovery from aphasia is a dynamic and complex process that may involve both hemispheres. Probably this mechanism involves functional reorganisation in the speech-dominant (damaged) hemisphere and regression of haemodynamic disturbances in the non-dominant (structurally intact) hemisphere.

Defective comprehension of emotional faces and prosody as a result of right hemisphere stroke: modality versus emotion-type specificity

Studies of patients with brain damage, as well as studies with normal subjects have revealed that the right hemisphere is important for recognizing emotions expressed by faces and prosody. It is unclear, however, if the knowledge needed to perform recognition of emotional stimuli is organized by modality or by the type of emotion. Thus, the purpose of this study is to assess these alternative a priori hypotheses. The participants of this study were 30 stroke patients with right hemisphere damage (RHD) and 31 normal controls (NC). Subjects were assessed with the Polish adaptation of the Right Hemisphere Language Battery of Bryan and the Facial Affect Recognition Test based on work of Ekman and Friesen. RHD participants were significantly impaired on both emotional tasks. Whereas on the visual-faces task the RHD subjects recognized happiness better than anger or sadness, the reverse dissociation was found in the auditory-prosody test. These results confirm prior studies demonstrating the role of the right hemisphere in understanding facial and prosodic emotional expressions. These results also suggest that the representations needed to recognize these emotional stimuli are organized by modality (prosodic-echoic and facial-eidetic) and that some modality specific features are more impaired than others.

Neuropsychological differences between frontotemporal dementia and Alzheimer's disease: a review

This paper surveys the similarities and differences between frontotemporal dementia (FTD) and Alzheimer's disease (AD). The review covers findings primarily from neuropsychological studies on memory, language, attention/executive function, and visuospatial abilities. However, neuropsychiatric and neuroimaging data are also briefly discussed. Distinguishing features of both FTD and AD are described in order to present a comprehensive clinical picture of these dementing diseases, which is essential for the process of differential diagnosis. The cause of specific cognitive deficits is also considered. Our comprehensive review of the empirical literature reveals that AD is characterized by early memory loss and visuospatial problems, while among the main features of FTD are behavioral abnormalities and executive dysfunctions.

[Cerebral blood flow in patients with various symptoms of hemispatial neglect following ischemic stroke]

BACKGROUND AND PURPOSE

The most common cause of hemispatial neglect (HN) is cerebral infarction. It can be induced by lesions in many different regions of the right hemisphere. The purpose of this article was to determine the prevalence of post-stroke HN, its clinical picture, and neuroanatomical correlates.

MATERIAL AND METHODS

Forty-six stroke patients with a focal right-hemisphere lesion were studied. Neglect in visual domain, assessed with a battery of drawing, line bisection and shape cancellation tests, was observed in 20 cases. The single-photon emission-computed tomography (SPECT) images of the brain were obtained with 740 MBq (20 mCi) of Tc-99m-labeled ECD on a triple-headed gamma camera.

RESULTS

The most sensitive measure of HN was the cancellation test, which all neglect patients performed poorly. Twelve patients, classified as mildly impaired, showed no significant rightward deviation on line bisection, but they showed left visual neglect on the cancellation test. Reverse dissociation was not noted. Performance on a clock-drawing test revealed HN only in two patients, who showed also evidence of HN on other tests. Thereby, some of the tests seem to be more difficult or more sensitive to impairment. The critical area of perfusion abnormalities in all neglect patients were frontal lobe and striatum on the right. In severe HN, SPECT images evidenced the most extensive hypoperfusion throughout the perisylvian region and subcortical structures of the right hemisphere. Although parietal cortex was affected in patients with moderate to severe HN, it was spared in the rest.

CONCLUSIONS

HN was a relatively common symptom of vascular right-hemisphere damage (43% of the patient population). HN was a complex disturbance in terms of its clinical manifestation and neuroimaging correlates. Our findings challenge the classical notion that damage to the parietal cortex is critically associated with HN. Instead, our results support the model attributing hemispatial neglect to a defect in a cortico-striato-thalamo-cortical loop. Also, the present study highlights the usefulness of cerebral blood flow SPECT imaging as a diagnostic aid in the post-stroke deficits of cognition following right-hemisphere damage.

Neuroanatomical correlates of the post-stroke aphasias studied with cerebral blood flow SPECT scanning

BACKGROUND

Researchers are not in complete agreement over the extent to which specific language functions are subserved by certain brain areas. The purpose of this article was to determine neuroanatomical correlates of aphasia following cerebrovascular accident.

MATERIAL/METHODS

The participants included 50 stroke patients with a single left-hemisphere lesion and residual mild to severe aphasia. Language, assessed by the Boston Diagnostic Aphasia Examination (BDAE), was affected to various degrees by a wide range of pathologies. Single-photon emission computed tomography (SPECT) images of the brain were acquired with 740 MBq (20 mCi) of Tc-99m-labeled ECD on a triple-headed gamma camera equipped with low-energy, high-resolution collimator. Correlation between reduced cerebral perfusion and the BDAE score was analyzed.

RESULTS

The most prominent perfusion abnormalities in Broca's aphasia, as determined by the laterality index, were found in the frontal lobe, and to a lesser degree, the parietal lobe and striatum, whereas the most prominent deficits in Wernicke's aphasia were found in the left temporal and parietal areas. In global aphasia, SPECT images evidenced the most extensive damage throughout the perisylvian region of the left hemisphere.

CONCLUSIONS

There is need for reinterpretation of the anatomical correlation of selected aphasic syndromes, especially classic Broca's and Wernicke's aphasias. The present study highlights the integrative role of some subcortical structures in language and speech functions. The results support the usefulness of regional cerebral blood flow SPECT imaging as a diagnostic aid in the post-stroke aphasias.

Cerebral blood flow SPECT imaging in right hemisphere-damaged patients with hemispatial neglect. A pilot study

BACKGROUND

Hemispatial neglect is characterised as a failure by a brain-damaged patient to attend to contralesional space. It is hypothesised to be a result of damage to a network involving the frontal, parietal and cingulated cortices, basal ganglia and thalamus.

MATERIAL AND METHODS

The aim of this preliminary study was to verify this model of neglect in 22 right hemisphere-damaged acute stroke patients, using single photon emission-computed tomography (SPECT). The presence of a single right-sided vascular brain lesion was confirmed on CT and/or MRI. Hemispatial neglect, assessed with a battery of drawings, line bisection and line and shape cancellation tests, was observed in 12 cases.

RESULTS

Patients with neglect (compared with those without neglect) had more extensive hypoperfusion in the frontal and parietal cortex, as well as striatum and thalamus. Left-sided hypoperfusion in the parietal cortex and the thalamus was also significantly associated with neglect on SPECT imaging. Performance in three out of five psychological tasks commonly used to detect the presence of hemispatial neglect, such as drawing tests and line bisection test, was exclusively linked with damage to the parietal cortex of the right hemisphere, while the line cancellation test might be attributable to the lesion of the right striatum.

CONCLUSIONS

These findings support the model attributing hemispatial neglect to a unilateral defect in a cortico-striatothalamo-cortical loop. CBF SPECT imaging may provide a reliable description of the brain pathology associated with hemispatial neglect.

[Objective complaints and results of memory tests in depression and diffuse brain damage]

Memory complaints are a common symptom among hospitalized depressed and brain damaged patients. In present work we attempted to identify factors that affected the severity and character of these complaints. 21 hospitalized psychiatric patients with diagnosis of major depressive disorder, and 21 patients with diffuse brain damage, participated in the study. They completed self-reported memory questionnaire, mood questionnaire and performed on neuropsychological memory tests. There were lower performance results on several memory tests in results the brain damaged group but no between-groups difference was found the in self-reported memory questionnaire. The results suggest that different factors contributed to subjectively experienced memory problems in each group. Current mood state and immediate memory deficit were the most important predictors in the depressed group. In brain damaged patients, memory complaints the were associated with delayed story recall problems and learning deficit.

[Level of depression in outpatients with low back pain syndromes]

There was significantly higher level of depression in chronic low-back pain patients than revealed in healthy subjects.

[Neuropsychological description of memory impairment following cortical and subcortical brain injuries]

This article, basing on experimental analysis and clinical observations, focuses on the role of subcortical structures in memory processes. It explained terminological problems and defined terms of memory: immediate, delayed, recent, remote, declarative and procedural. The present article pointed out functional hemispheric specialization as a predicator of material-specific forms of memory. Neuroanatomical basis was revealed, especially limbic system with its connections to prefrontal, cortical and brain stem regions. Amnesic Korsakoff and Wernicke syndromes, transient global amnesia, memory loss after bilateral damage of temporal lobes and after anterior communicating artery aneurysm rupture, were also discussed. Next part exhibited current knowledge about definition of dementia which may be caused by many multi-focal brain diseases like multiinfarct (vascular) dementia, Parkinson disease, Huntington disease, and sclerosis multiplex, and compared to Alzheimer disease. Term of dementia was defined, according to Cummings and Benson, as syndrome of acquired intellectual dysfunction when three of the following mental functions are impaired: language, memory, visuospatial skills, emotion, and cognition (abstraction, calculation, judgement). There is little doubt that various subcortical diseases are characterised by similar, no specific dysfunctions of cognitive processes including: disturbed attention and concentration, slowness of mental processing, forgetfulness, personality alterations and mood disturbances as well as motivational impairment, visuospatial disturbances, absence of symptoms of cortical dysfunction such as aphasia, agnosia and apraxia and associated motor disorder. Review of the literature suggests that rapid forgetting and retrieval deficits are most often symptoms of memory deficits observed after subcortical brain injuries.

[Personality changes of neurotic patients as outcome of the treatment]

The present article attempted to assess the importance of outcomes which appeared during the treatment of 30 neurotic patients. This study specially concentrates on measures of emotional empathy, self-confidence and introspection. There were two surveys in the clinical group: before and after the treatment was completed. Data were compared with a control group, also consisting of 30 persons (15 male and 15 female) matched for age and education. All patients attending group psychotherapy were also treated by pharmacotherapy. As it appeared from the analysis before treatment high empathy in patients was found, but this declined after therapy, however it was still significantly higher than in the control group. The first survey revealed also that patients demonstrated lower levels of self-confidence and introspection. After treatment there were no important differences between the groups. Relationships between the studied qualities were not statistically significant.