Neuropsychological characteristics of mild vascular cognitive impairment and dementia after stroke

Hydrogen Proton Magnetic Resonance Spectroscopy in Multidomain Amnestic Mild Cognitive Impairment and Vascular Cognitive Impairment Without Dementia

To investigate the value of hydrogen proton magnet resonance spectroscopy ((1)H-MRS) in the differential diagnosis of multiple-domain amnestic mild cognitive impairment (M-aMCI) and vascular cognitive impairment with no dementia (VCIND); (1)H-MRS was performed in patients with M-aMCI and VCIND. The level was determined for N-acetylaspartate (NAA), glutamate (Glu), inositol (mI), choline (Cho), and creatine (Cr). Compared with the normal control group, the NAA-Cr ratio in all regions studied was significantly lower in the M-aMCI and VCIND groups. The Glu-Cr ratio in the posterior cingulate gyrus of the M-aMCI group was significantly lower than in the VCIND. The mI-Cr ratio in the frontal white matter of the VCIND was significantly higher than in the M-aMCI group. In the white matter adjacent to the lateral ventricles, the Cho-Cr ratio was significantly higher in the VCIND than the M-aMCI. Our results suggested (1)H-MRS is an effective method in the differential diagnosis of M-aMCI and VCIND.

Regional Coherence Alterations Revealed by Resting-State fMRI in Post-Stroke Patients with Cognitive Dysfunction

Objectives

Post-stroke cognitive dysfunction greatly influences patients’ quality of life after stroke. However, its neurophysiological basis remains unknown. This study utilized resting-state functional magnetic resonance imaging (fMRI) to investigate the alterations in regional coherence in patients after subcortical stroke.

Methods

Resting-state fMRI measurements were acquired from 16 post-stroke patients with poor cognitive function (PSPC), 16 post-stroke patients with good cognitive function (PSGC) and 30 well-matched healthy controls (HC). Regional homogeneity (ReHo) was used to detect alterations in regional coherence. Abnormalities in regional coherence correlated with scores on neuropsychological scales.

Results

Compared to the HC and the PSGC, the PSPC showed remarkably decreased ReHo in the bilateral anterior cingulate cortex and the left posterior cingulate cortex/precuneus. ReHo in the bilateral anterior cingulate cortex positively correlated with the scores on the Symbol Digit Modalities Test (r = 0.399, P = 0.036) and the Complex Figure Test-delayed recall subtest (r = 0.397, P = 0.036) in all post-stroke patients. Moreover, ReHo in the left posterior cingulate cortex/precuneus positively correlated with the scores on the Forward Digit Span Test (r = 0.485, P = 0.009) in all post-stroke patients.

Conclusions

Aberrant regional coherence was observed in the anterior and posterior cingulate cortices in post-stroke patients with cognitive dysfunction. ReHo could represent a promising indicator of neurobiological deficiencies in post-stroke patients.

Alpha-linolenic acid given as enteral or parenteral nutritional intervention against sensorimotor and cognitive deficits in a mouse model of ischemic stroke

Stroke is a leading cause of disability and death worldwide. Numerous therapeutics applied acutely after stroke have failed to improve long-term clinical outcomes. An emerging direction is nutritional intervention with omega-3 polyunsaturated fatty acids acting as disease-modifying factors and targeting post-stroke disabilities. Our previous studies demonstrated that the omega-3 precursor, alpha-linolenic acid (ALA) administrated by injections or dietary supplementation reduces stroke damage by direct neuroprotection, and triggering brain artery vasodilatation and neuroplasticity. Successful translation of putative therapies will depend on demonstration of robust efficacy on common deficits resulting from stroke like loss of motor control and memory/learning. This study evaluated the value of ALA as adjunctive therapy for stroke recovery by comparing whether oral or intravenous supplementation of ALA best support recovery from ischemia. Motor and cognitive deficits were assessed using rotarod, pole and Morris water maze tests. ALA supplementation in diet was better than intravenous treatment in improving motor coordination, but this improvement was not due to a neuroprotective effect since infarct size was not reduced. Both types of ALA supplementation improved spatial learning and memory after stroke. This cognitive improvement correlated with higher survival of hippocampal neurons. These results support clinical investigation establishing therapeutic plans using ALA supplementation.

Impaired Arm Function and Finger Dexterity in a Nonhuman Primate Model of Stroke

Background and Purpose—

Ischemic stroke is the leading cause of upper extremity motor impairments. Although several well-characterized experimental stroke models exist, modeling of upper extremity motor impairments, which are unique to primates, is not well established. Cortical representation of dexterous movements in nonhuman primates is functionally and topographically similar to that in humans. In this study, we characterize the African green monkey model of focal ischemia reperfusion with a defined syndrome, impaired dexterous movements.

Methods—

Cerebral ischemia was induced by transient occlusion of the M3 segment of the left middle cerebral artery. Motor and cognitive functions after stroke were evaluated using the object retrieval task with barrier-detour. Postmortem magnetic resonance imaging and histopathology were performed to map and characterize the infarct.

Results—

The middle cerebral artery occlusion consistently produced a necrotic infarct localized in the sensorimotor cortex in the middle cerebral artery territory. The infarction was reproducible and resulted in significant loss of fine motor function characterized by impaired dexterity. No significant cognitive impairment was detected. Magnetic resonance imaging and histopathology demonstrated consistent and significant loss of tissue on the left parietal cortex by the central sulcus covering the sensorimotor area. The results suggest that this species has less collateralization, which closely resembles humans.

Conclusions—

The reported nonhuman primate model produces a defined and reproducible syndrome relevant to our understanding of ischemic stroke, cortical representation, and sensorimotor integration controlling dexterous movements. This model will be useful in basic and translational research addressing loss of arm function and dexterity.

Stroke injury, cognitive impairment and vascular dementia

The global burden of ischaemic strokes is almost 4-fold greater than haemorrhagic strokes. Current evidence suggests that 25–30% of ischaemic stroke survivors develop immediate or delayed vascular cognitive impairment (VCI) or vascular dementia (VaD). Dementia after stroke injury may encompass all types of cognitive disorders. States of cognitive dysfunction before the index stroke are described under the umbrella of pre-stroke dementia, which may entail vascular changes as well as insidious neurodegenerative processes. Risk factors for cognitive impairment and dementia after stroke are multifactorial including older age, family history, genetic variants, low educational status, vascular comorbidities, prior transient ischaemic attack or recurrent stroke and depressive illness. Neuroimaging determinants of dementia after stroke comprise silent brain infarcts, white matter changes, lacunar infarcts and medial temporal lobe atrophy. Until recently, the neuropathology of dementia after stroke was poorly defined. Most of post-stroke dementia is consistent with VaD involving multiple substrates. Microinfarction, microvascular changes related to blood–brain barrier damage, focal neuronal atrophy and low burden of co-existing neurodegenerative pathology appear key substrates of dementia after stroke injury. The elucidation of mechanisms of dementia after stroke injury will enable establishment of effective strategy for symptomatic relief and prevention. Controlling vascular disease risk factors is essential to reduce the burden of cognitive dysfunction after stroke. This article is part of a Special Issue entitled: Vascular Contributions to Cognitive Impairment and Dementia edited by M. Paul Murphy, Roderick A. Corriveau and Donna M. Wilcock.

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Ischaemic injury is common among long-term stroke survivors

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About 25% stroke survivors develop dementia with a much greater proportion developing cognitive impairment

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Risk factors of dementia after stroke include older age, vascular comorbidities, prior stroke and pre-stroke impairment

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Current imaging and pathological studies suggest 70% of dementia after stroke is vascular dementia

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Severe white matter changes and medial temporal lobe atrophy as sequelae after ischaemic injury are substrates of dementia

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Controlling vascular risk factors and prevention strategies related to lifestyle factors would reduce dementia after stroke

Impact of repetitive transcranial magnetic stimulation on post-stroke dysmnesia and the role of BDNF Val66Met SNP

Background

Little is known about the effects of low-frequency repetitive transcranial magnetic stimulation (rTMS) on dysmnesia and the impact of brain nucleotide neurotrophic factor (BDNF) Val66Met single-nucleotide polymorphism (SNP). This study investigated the impact of low-frequency rTMS on post-stroke dysmnesia and the impact of BDNF Val66Met SNP.

Material/Methods

Forty patients with post-stroke dysmnesia were prospectively randomized into the rTMS and sham groups. BDNF Val66Met SNP was determined using restriction fragment length polymorphism. Montreal Cognitive Assessment (MoCA), Loewenstein Occupational Therapy of Cognitive Assessment (LOTCA), and Rivermead Behavior Memory Test (RBMT) scores, as well as plasma BDNF concentrations, were measured at baseline and at 3 days and 2 months post-treatment.

Results

MoCA, LOTCA, and RBMT scores were higher after rTMS. Three days after treatment, BDNF decreased in the rTMS group but it increased in the sham group (P<0.05). Two months after treatment, RMBT scores in the rTMS group were higher than in the sham group, but not MoCA and LOTCA scores.

Conclusions

Low-frequency rTMS may improve after-stoke memory through various pathways, which may involve polymorphisms and several neural genes, but not through an increase in BDNF levels.

Practice effects and test-re-test reliability of the Five Digit Test in patients with stroke over four serial assessments

OBJECTIVES

To investigate practice effect and test-re-test reliability of the Five Digit Test (FDT) over four serial assessments in patients with stroke.

DESIGN

Single-group repeated measures design.

METHODS

Twenty-five patients with stroke were administered the FDT in four consecutive assessments every 2 weeks. The FDT contains four parts with five indices: 'basic measures of attention and processing speed', 'selective attention', 'alternating attention', 'ability of inhibition' and 'ability of switching'.

RESULTS

The five indices of the FDT showed trivial-to-small practice effects (Cohen's d = 0.03-0.47) and moderate-to-excellent test-re-test reliability (intra-class correlation coefficient = 0.59-0.97). Practice effects of the five indices all appeared cumulative, but one index, 'basic measures of attention and processing speed', reached a plateau after the second assessment. The minimum and maximum values of the 90% confidence interval (CI) of reliable change index modified for practice (RCIp) for this index were [-17.6, 11.2].

CONCLUSIONS

One of five indices of the FDT reached a plateau, whose minimum and maximum values of the 90% CI RCIp are useful to determine whether the change in an individual's score is real. However, clinicians and researchers should be cautious when interpreting the test results of these four indices over repeated assessments.

Profile and determinants of vascular cognitive impairment in African stroke survivors: the CogFAST Nigeria Study

OBJECTIVE

Sub-Saharan Africa faces a potential epidemic of non-communicable diseases including stroke and dementia but little is known about the burden of stroke-related cognitive dysfunction. We assessed the baseline profile and factors associated with vascular cognitive impairment (VCI) in stroke survivors participating in the Cognitive Function After STroke (CogFAST) Nigeria Study.

METHODS

We recruited 217 subjects (>45 years old) comprising 143 stroke survivors and 74 demographically matched stroke-free healthy controls. We obtained demographic, clinical and lifestyle information and assessed the cognitive status of the subjects at baseline three months after stroke. Standard neuropsychological tests included the Vascular Neuropsychological Battery, which assessed executive function/mental speed, memory, language, and visuospatial/visuoconstructive functioning. Cognitive impairment and dementia were defined based on the AHA/ASA VCI guidelines and the DSM IV criteria.

RESULTS

Among the stroke survivors (mean ag e= 60.4+9.5 years, 43.4% female, mean number of years of education = 9.4+5.6 years, median modified Rankin score = 2), 57 (39.9%) had cognitive impairment no dementia while 12 (8.4%) were demented at baseline. Multivariate analysis revealed that older age [OR = 1.05 (1.00-1.09)], low education [OR = 5.09 (2.17-11.95)], pre-stroke cognitive decline [OR = 4.51 (1.20-16.88)] and medial temporal lobe atrophy [OR = 2.25 (1.16-4.35)] were independently associated with cognitive dysfunction whereas pre-stroke daily intake of fish [p = 0.022, OR = 0.39 (0.15-0.89)] was inversely associated.

CONCLUSIONS

These results suggest a high frequency of early VCI in older Nigerian stroke survivors. Apart from aging, associated neurodegeneration and cognitive decline, educational level and pre-stroke diet particularly fish consumption were identified as modifiable factors. This emphasizes the vital role of education and healthy nutrition in building reserves to ameliorate cognitive dysfunction after stroke.

Understanding and preventing the development of post-stroke dementia

Post-stroke dementia (PSD) is a clinical entity but it now appears that most of PSD may be categorized as vascular dementia. The well-established relationship between vascular factors and dementia provides a rationale for the implementation of intervention and prevention efforts. Larger primary prevention trials related to lifestyle factors are warranted in association with dementia. Published clinical trials have not been promising and there is meager information on whether PSD can be prevented through the use of pharmacological agents. Control of vascular disease risk and prevention of recurrent strokes are obviously key to reducing the burden of cognitive decline and dementia after stroke. However, modern imaging and analysis techniques will help to elucidate the mechanism of PSD and establish better treatment.

Rehabilitation for post-stroke cognitive impairment: an overview of recommendations arising from systematic reviews of current evidence

BACKGROUND

Although cognitive impairments are common following stroke, there is considerable uncertainty about the types of interventions that can reduce activity restrictions and improve quality of life. Indeed, a recent project to identify priorities for research into life after stroke determined that the top priority for patients, carers and health professionals was how to improve cognitive impairments.

OBJECTIVE

To provide an overview of the evidence for the effectiveness of cognitive rehabilitation for patients with stroke and to determine the main gaps in the current evidence base.

METHODS

Evidence was synthesised for the six Cochrane reviews relating to rehabilitation for post-stroke cognitive impairment and any subsequently published randomized controlled trials to February 2012.

RESULTS

Data arising from 44 trials involving over 1500 patients was identified. Though there was support for the effectiveness of cognitive rehabilitation for some cognitive impairments, significant gaps were found in the current evidence base. All of the Cochrane reviews identified major limitations within the evidence they identified.

CONCLUSIONS

There is currently insufficient research evidence, or evidence of insufficient quality, to support clear recommendations for clinical practice. Recommendations are made as to the research required to strengthen the evidence base, and so facilitate the delivery of effective interventions to individuals with cognitive impairment after stroke.

TMS follow-up study in patients with vascular cognitive impairment-no dementia

Vascular cognitive impairment-no dementia (VCI-ND) is a condition at risk for future dementia and should be the target of preventive strategies. Recently, an enhanced intracortical facilitation observed in VCI-ND patients was proposed as a candidate neurophysiological marker of the disease process. The aim of this study was to monitor the excitability of the motor cortex and the functioning of excitatory/inhibitory intracortical circuits in patients with VCI-ND after a follow-up period of approximately 2 years, in order to pick out early markers of disease progression into dementia. Nine patients and 9 age-matched controls were re-evaluated for single and paired pulse TMS measures of cortical excitability, as well as for neuropsycological and functional assessment. Compared to the first evaluation, patients showed a decrease of the median resting motor threshold (rMT). Patients exhibited a significant worsening at Stroop Color-Word Test Interference scores without substantial functional impairment. Our study represents the first evidence of a decrease of rMT in VCI-ND patients during the progression of cognitive impairment. This result might be considered an index of motor cortex plasticity and interpreted as a compensatory mechanism for the loss of motor cortex neurons.

The effects of a rhythm and music-based therapy program and therapeutic riding in late recovery phase following stroke: a study protocol for a three-armed randomized controlled trial

BACKGROUND

Stroke represents one of the most costly and long-term disabling conditions in adulthood worldwide and there is a need to determine the effectiveness of rehabilitation programs in the late phase after stroke. Limited scientific support exists for training incorporating rhythm and music as well as therapeutic riding and well-designed trials to determine the effectiveness of these treatment modalities are warranted.

METHODS/DESIGN

A single blinded three-armed randomized controlled trial is described with the aim to evaluate whether it is possible to improve the overall health status and functioning of individuals in the late phase of stroke (1-5 years after stroke) through a rhythm and music-based therapy program or therapeutic riding. About 120 individuals will be consecutively and randomly allocated to one of three groups: (T1) rhythm and music-based therapy program; (T2) therapeutic riding; or (T3) control group receiving the T1 training program a year later. Evaluation is conducted prior to and after the 12-week long intervention as well as three and six months later. The evaluation comprises a comprehensive functional and cognitive assessment (both qualitative and quantitative), and questionnaires. Based on the International classification of functioning, disability, and health (ICF), the outcome measures are classified into six comprehensive domains, with participation as the primary outcome measure assessed by the Stroke Impact Scale (SIS, version 2.0.). The secondary outcome measures are grouped within the following domains: body function, activity, environmental factors and personal factors. Life satisfaction and health related quality of life constitute an additional domain.

CURRENT STATUS

A total of 84 participants were randomised and have completed the intervention. Recruitment proceeds and follow-up is on-going, trial results are expected in early 2014.

DISCUSSION

This study will ascertain whether any of the two intervention programs can improve overall health status and functioning in the late phase of stroke. A positive outcome would increase the scientific basis for the use of such interventions in the late phase after stroke.

TRIAL REGISTRATION

Clinical Trials.gov Identifier: NCT01372059.

Randomized controlled trial of home rehabilitation for patients with ischemic stroke: impact upon disability and elderly depression

BACKGROUND

Patients with major stroke are often left with disability and may have depression and dementia during the recovery phase. Rehabilitation programmes have been shown to improve short-term physical outcome, but their long-term effectiveness and impact on dementia and depression are uncertain.

METHODS

We performed a 6-month randomized controlled trial of a home rehabilitation programme and compared it with the standard care patients with recent ischemic stroke receive. The intervention group received home-based physical therapy once a month for 6 months, along with educational support, counselling and audiovisual materials. The control group received rehabilitation as prescribed by a physician and educational materials upon discharge from hospital. The primary measurement was a change in Barthel Index. Secondary measurements were the Hospital Anxiety and Depression Scale (HADS) and Thai Mini-Mental State Examination.

RESULTS

Of the 68 screened patients, 60 patients were enrolled. At baseline, there was no significant difference in patient characteristics between the two groups. Over 2 years, the mean Barthel Index and Hospital Anxiety and Depression Scale were significantly improved in the intervention group compared to the control group (Barthel Index mean: from 31.7 ± 5.9 to 97.2 ± 2.8 vs from 33.2 ± 4.8 to 76.4 ± 9.4, P < 0.001; Hospital Anxiety and Depression Scale mean: from 16.1 ± 7.6 to 9.1 ± 0.3 vs 16.4 ± 4.9 to 9.1 ± 0.3, P= 0.003). Depression was strongly associated with being dependent on others. However, the Thai Mini-Mental State Examination in both groups did not significantly differ (Thai Mini-Mental State Examination mean: from 24.4 ± 2.0 to 24.6 vs 23.8 ± 1.9 to 24.1 ± 0.3, P= 0.068). There was no significant interaction between baseline characteristics and treatment outcome.

CONCLUSIONS

At 2 years follow-up, it was evident that a 6-month home rehabilitation programme after ischemic stroke improved functional outcome and reduced incidence of depression, but not dementia.

Neuropsychological performance in patients with subcortical stroke

Vascular cognitive impairment (VCI) is characterized by cognitive compromise predominantly of executive dysfunction. OBJECTIVES: To assess cognitive functions in VCI, focusing on executive functions, to observe functional losses in relation to activities of daily living (ADLs) and to detect early symptoms prior to the onset of dementia. METHODS: We evaluated healthy subjects matched for gender, education and age to patients with diagnosis of subcortical vascular disease who had a stroke classified into three groups: 1) vascular lesions and no impairment; 2) vascular cognitive impairment with no dementia (VCIND); 3) vascular dementia (VaD). RESULTS AND DISCUSSION: The performance on neuropsychological tests differed among groups, worsening with increased impairment level. The probable VaD group demonstrated impaired performance in memory, processing speed and verbal production, while the VCIND group showed attention deficits. CONCLUSION: Impairment in executive functions and difficulties in ADLs allow us to differentiate levels of impairment in groups of subcortical vascular disease.

Concurrent Validity of the Executive Function Performance Test in People with Mild Stroke

Introduction:

Studies have shown that executive dysfunction is common in adults after stroke. Occupational therapists working in acute care assess the performance of activities of daily living; most instruments focus on personal care. However, the assessment of instrumental activities of daily living has been shown to discriminate executive dysfunction more effectively. An instrument for assessing executive dysfunction in more complex activities that is easy to handle in acute care is consequently required for clinical use. The Executive Function Performance Test (EFPT) was recently introduced into Sweden. The purpose of this study was to evaluate the concurrent validity of the EFPT in acute care for patients with mild stroke.

Method:

Twenty-three patients from an acute stroke unit were assessed with both the EFPT and the Assessment of Motor and Process Skills (AMPS).

Results:

The correlation between the EFPT and the AMPS assessments was highly significant (p = 0.003) and the concurrent validity was rho = 0.61.

Conclusion:

Since there is a risk that adult patients with mild stroke are discharged without rehabilitation, and there is a lack of a relevant instrument for occupational therapists that discriminates executive dysfunction in acute stroke care, the EFPT may be a suitable instrument to use with these patients.

Cognitive impairment in acquired brain injury: a predictor of rehabilitation outcomes and an opportunity for novel interventions

Cognitive impairment is a common sequela in acquired brain injury and one that predicts rehabilitation outcomes. There is emerging evidence that impairments in cognitive functions can be manipulated by both pharmacologic and nonpharmacologic interventions to improve rehabilitation outcomes. By using stroke as a model for acquired brain injury, we review the evidence that links cognitive impairment to poor rehabilitation outcomes and discuss possible mechanisms to explain this association. Furthermore, we examine nascent promising research that suggests that interventions that target cognitive impairments can lead to better rehabilitation outcomes.

The neuropsychological characteristics and regional cerebral blood flow of vascular cognitive impairment-no dementia

OBJECTIVE

To investigate the neuropsychological characteristics of VCI-ND and to analyze the relationship between deficit pattern and regional cerebral blood flow (rCBF) in various VCI-ND subtypes defined by cognitive features.

METHODS

69 subjects diagnosed with VCI-ND were recruited, then further classified into four subtypes: amnestic VCI-ND with single memory impairment (subtype I, n = 19), amnestic VCI-ND with multi-domain impairment (subtype II, n = 27), non-amnestic VCI-ND with single domain impairment (subtype III, n = 16), and non-amnestic VCI-ND with multi-domain impairment (subtype IV, n = 7) according to their cognitive profile. Xenon-CT scan was administered to 31 VCI-ND patients (11 of subtype I, 12 of subtype II and 8 of subtype III) and 10 normal controls (NC) to evaluate rCBF.

RESULTS

The rate of different cognitive domains impairment in VCI-ND group ranged from 17 to 66%, lowest in clock drawing test and highest in time of modified version of trails making test A and maze tracing compared with NC, significant reduced rCBF was found in bilateral temporal lobe and thalamus, left periventricular white matter and caudate of subtype I, and in left temporal lobe and lenticular nucleus, bilateral periventricular white matter, white matter adjacent to left posterior horn of lateral ventricular and right caudate of subtype III, while significant reduced rCBF of subtype II was found in left subfrontal white matter, bilateral subtemporoparietal white matter, right lenticular nucleus, and in both regions of subtype I and III.

CONCLUSIONS

The manifestation of rCBF in VCI-ND subtypes was consistent with performance of neuropsychological assessment.

Utility of the Neuropsychological Assessment Battery in detecting cognitive impairment after unilateral stroke

This study evaluated the clinical utility of the Neuropsychological Assessment Battery (NAB) in a stroke sample by examining the NAB's ability to differentiate a chronic stroke group with radiologically confirmed unilateral damage (n = 42) and a demographically matched healthy control (HC) group (n = 36). The stroke group performed more poorly than the control group across NAB Total score and all five Domain scores. Receiver operator curves (ROC) were derived and area under the curve (AUC) showed moderate diagnostic effectiveness (AUC .70 to .90) for NAB Total score, all five Domain scores, a motor composite, and a Global Deficit Score (GDS) that has been shown to closely approximate clinical ratings of neuropsychological impairment. The NAB Total, GDS, and motor composite had comparable clinical utility, whereas the Attention and Executive domain scores demonstrated better classification utility compared with the Memory domain. Because 90.5% of our stroke sample had middle cerebral artery territory strokes, the comparison of motor and cognitive classification utility may be biased. However, follow-up analyses showed that the NAB accounted for additional variance even when motor composite was included in the model. Sensitivity, specificity, and odds ratios at various clinical cutoffs are provided. These results suggest that the NAB is a useful clinical tool for detection of cognitive deficits in individuals with chronic unilateral stroke, although lenient clinical cutoffs appear warranted to maximize sensitivity.

A screen for cognitive assessments for patients with vascular cognitive impairment no dementia

OBJECTIVE

To screen for cognitive assessment for patients with vascular cognitive impairment (VCI) no dementia (V-CIND) from a set of cognitive measures.

METHODS

Extensive neuropsychological tests covering five cognitive domains were performed on 80 V-CIND patients and 80 normal controls. The impaired domains in V-CIND were determined and the most discriminating tests were selected to form a comprehensive assessment. The discriminating validity of the individual tests and the comprehensive assessment were explored.

RESULTS

Compared with the control group, five cognitive domains were all impaired in V-CIND group. World Health Organization-University of California-Los Angeles Auditory Verbal Learning Test (WHO-UCLA AVLT) immediate recall, Semantic Category Verbal Fluency Test (animal), Chinese version of the Wechsler Adult Intelligence Test (WAIS-RC) Digit Symbol Subtest, and Block Design Subtest were finally selected to form a comprehensive assessment tool, which achieved a sensitivity of 92.5% and a specificity of 98.8% in differentiating V-CIND patients from normal controls. Even in the subjects with Mini-Mental State Examination (MMSE) scores of 28 or above, high discriminative validity was also obtained.

CONCLUSIONS

Our study revealed a multiple domain cognitive deficit in V-CIND patients. The comprehensive assessment tapping memory, executive functions, mental processing speed, and visuoconstructive skill may be potentially useful for an overall cognitive evaluation for V-CIND.

Effectiveness of home rehabilitation for ischemic stroke

The objective of this study was to develop and examine the effectiveness of an individual home rehabilitation program for patients with ischemic stroke. This was a randomized controlled trial in 60 patients with recent middle cerebral artery infarction. After hospital discharge for acute stroke care, they were randomly assigned to receive either a home rehabilitation program for three months (intervention group) or usual care (control group). We collected outcome data over three months after their discharge from the hospital. The Barthel Index (BI), the Modified Rankin Scale (MRS), the health-related quality-of-life index (EQ-5D), the Hospital Anxiety and Depression score (HADs), and the Thai Mental State Examination (TMSE) were used to analyze the outcomes. In the intervention group, all outcomes were significantly better (p<0.05) than in the control group, except in the case of TMSE. A favorable outcome, which was defined as minimal or no disability as measured by BI (score 95-100), was achieved by 93.33% of patients in the intervention group, and 90% had favorable scores (0 or 1) on the MRS. This showed a benefit in reducing disability, with two being the number of patients considered as needed-to-treat (NNT) (95% CI, 1.0-1.2). All dimensions of EQ-5D in the intervention group were significantly better for quality of life and generic health status than in the control group (p=0.001). Depression was found in one patient (3.33%) in the intervention group and in two patients (6.67%) in the control group. Dementia was found in three patients (10%) in the intervention group and in four patients (13.33%) in the control group. We concluded that an early home rehabilitation program for patients with ischemic stroke in the first three-month period provides significantly better outcomes in improving function, reducing disability, increasing quality of life, and reducing depression than a program of usual care does.

Heterogeneity in mild cognitive impairment: differences in neuropsychological profile and associated white matter lesion pathology

This study examined whether distinct neuropsychological profiles could be delineated in a sample with Mild Cognitive Impairment (MCI) and whether white matter lesion (WML) burden contributed to MCI group differences. A heterogeneous, clinical sample of 70 older adults diagnosed with MCI was assessed using cognitive scores, and WML was quantified using a semi-automated, volumetric approach on T2-weighted fluid-attenuated inversion recovery (FLAIR) images. Using cluster and discriminant analyses, three distinct groups (Memory/Language, Executive/Processing Speed, and Pure Memory) were empirically derived based on cognitive scores. Results also showed a dose dependent relationship of WML burden to MCI subgroup, with the Executive/Processing Speed subgroup demonstrating significantly higher levels of WML pathology when compared to the other subgroups. In addition, there was a dissociation of lesion type by the two most impaired subgroups (Memory/Language and Executive/Processing Speed) such that the Memory/Language subgroup showed higher periventricular lesion (PVL) and lower deep white matter lesion (DWML) volumes, whereas the Executive/Processing Speed demonstrated higher DWML and lower PVL volumes. Results demonstrate that distinct MCI subgroups can be empirically derived and reliably differentiated from a heterogeneous MCI sample, and that these profiles differ according to WML burden. Overall, findings suggest different underlying pathologies within MCI and contribute to our understanding of MCI subtypes.

Executive functioning: a comparison of the Tower of London(DX) and the D-KEFS Tower Test

This study compared the Delis-Kaplan Executive Function System (D-KEFS) Tower Test to the Tower of London (TOL)(DX) in assessing executive functioning (EF) during a psycho-educational assessment by examining students' performances on both tests. Forty-two university students were administered both tests in a counterbalanced order. Findings indicate that students did not perform significantly differently on the D-KEFS Tower Test than on the TOL(DX), but that the tests only shared 22% of their variance. Although the moderate correlation found between overall achievement scores indicates that the D-KEFS Tower Test assesses some similar EF abilities as the TOL(DX), the different problem spaces between these tests may be tapping into different constructs and may account for the non-shared variance.

Subclinical cerebrovascular disease in mild cognitive impairment

BACKGROUND

Cerebrovascular disease (CVD) may contribute to mild cognitive impairment (MCI). We sought to determine the relation of white matter hyperintensity (WMH) volume and infarcts in brain MRI to MCI in a community-based sample.

METHODS

A total of 679 elderly persons without dementia underwent brain MRI. WMH and infarcts were quantified using research methods. WMH was adjusted for total cranial volume. The Petersen criteria were used to define MCI. MCI was further subclassified into amnestic and non-amnestic. We used logistic regression to relate WMH and infarcts to prevalent MCI.

RESULTS

WMH were associated with amnestic MCI (odds ratio [OR] = 1.9; 95% confidence interval [CI] 1.1, 3.4) but not non-amnestic MCI (OR = 1.2; 95% CI 0.4, 1.6) after adjusting for age, gender, ethnic group, education, and APOE-epsilon4. Infarcts were more strongly associated with non-amnestic MCI (OR = 2.7; 95% CI 1.5, 4.8) than amnestic MCI (OR = 1.4; 95% CI 0.9, 2.3). In secondary analyses using continuous cognitive scores as outcomes, WMH, but not infarcts, were related to memory, while infarcts were more strongly related with non-amnestic domains.

CONCLUSION

White matter hyperintensity (WMH) is more strongly related to amnestic mild cognitive impairment (MCI). Infarcts are more strongly related to non-amnestic MCI. The nature of WMH in amnestic MCI requires further study.

Current Concepts in Vascular Cognitive Impairment and Pharmacotherapeutic Implications

Objective:

To review evolution of the vascular cognitive impairment (VCI) construct, including diagnosis, pharmacotherapeutic implications, and address challenges that will shape future developments.

Data Sources:

Literature retrieval was accessed through PubMed, from 1966 to December 2008, using the terms vascular cognitive impairment, vascular dementia, post-stroke dementia, vascular cognitive disorder, mild cognitive impairment, criteria, disease progression, outcomes, treatment, prevention, biomarkers, and neuroimaging.

Study Selection and Data Extraction:

All articles in published English identified from the data sources were evaluated for inclusion. Regarding pharmacotherapy, prospective double-blind, placebo-controlled studies were included as well as extensions or relevant post hoc analyses.

Data Synthesis:

In the 1970s, “senile dementia due to hardening of the arteries” was used to describe dementia due to vascular causes. This was a narrow view of what is now known to be a common form of cognitive impairment in older people. Multiple infarct dementia (MID) was first proposed to describe dementia attributable to multiple cerebral infarcts, followed by the vascular dementia (VaD) construct, itself meant to be an improvement over MID. The VaD construct had limitations, not the least of which was that, by the time a patient was diagnosed with VaD, the opportunity for prevention was lost. Thus arose the concept of VCI, representing a group of heterogeneous disorders that share presumed vascular causes. The importance of VCI is centered on the fact that vascular risk factors are treatable, and thus should lead to a reduction in the incidence of cognitive impairment due to vascular causes. There is evidence that treatment of hypertension can lead to a reduction in the incidence of cognitive impairment and dementia, and that treatment of VaD with acetylcholinesterase inhibitors may be beneficial.

Conclusions:

Careful attention needs to be given to controlling vascular risk factors in at-risk patients. Pharmacists should play an active role in this important area of geriatric pharmacotherapy.

Relationship between executive functions and productivity outcomes following stroke

PURPOSE

Stroke occurs in many individuals of working age and can considerably disrupt their capacity for employment and other productive activities. Few studies have examined the relationship between loss of productivity and cognitive impairment, particularly deficits in executive function. The present study examined whether performance on tests of executive function is related to employment and productivity at 12-months follow-up.

METHOD

Twenty-seven individuals (mean age = 47.3 years, SD = 10.7) on average 2.1 years (SD = 1.6) post-stroke were recruited from hospital and community rehabilitation services and administered a theory-driven battery of executive function tests (i.e. Health and Safety sub-test, FAS Test, Five-Point test, Key Search Test and Tinkertoy Test). A 12-month follow-up assessment of employment outcome ('employed' or 'unemployed') and productivity (measured by the Sydney Psychosocial Reintegration Scale) was conducted.

RESULTS

A series of between-group comparisons identified that a measure of purposive behaviour and self-regulation (i.e. the Tinkertoy Test) best distinguished between the employed and unemployed groups (p < 0.01) irrespective of time since injury and neglect. Level of post-stroke productivity was significantly correlated with measures of planning (p < 0.05), self-monitoring (p < 0.01) and self-regulation (p < 0.05), as well as time since injury (p < 0.05) and functional status (p < 0.01).

CONCLUSIONS

These findings highlight the importance of routinely assessing executive functions to guide cognitive rehabilitation interventions following stroke.

Aerobic exercise improves cognition and motor function poststroke

BACKGROUND

Cognitive deficits impede stroke recovery. Aerobic exercise (AEX) improves cognitive executive function (EF) processes in healthy individuals, although the learning benefits after stroke are unknown.

OBJECTIVE

To understand AEX-induced improvements in EF, motor learning, and mobility poststroke.

METHODS

Following cardiorespiratory testing, 38 chronic stroke survivors were randomized to 2 different groups that exercised 3 times a week (45-minute sessions) for 8 weeks. The AEX group (n = 19; 9 women; 10 men; 64.10 +/- 12.30 years) performed progressive resistive stationary bicycle training at 70% maximal heart rate, whereas the Stretching Exercise (SE) group (n = 19; 12 women; 7 men; 58.96 +/- 14.68 years) performed stretches at home. Between-group comparisons were performed on the change in performance at "Post" and "Retention" (8 weeks later) for neuropsychological and motor function measures.

RESULTS

VO(2)max significantly improved at Post with AEX (P = .04). AEX also improved motor learning in the less-affected hand, with large effect sizes (Cohen's d calculation). Specifically, AEX significantly improved information processing speed on the serial reaction time task (SRTT; ie, "procedural motor learning") compared with the SE group at Post (P = .024), but not at Retention. Also, at Post (P = .038), AEX significantly improved predictive force accuracy for a precision grip task requiring attention and conditional motor learning of visual cues. Ambulation and sit-to-stand transfers were significantly faster in the AEX group at Post (P = .038), with balance control significantly improved at Retention (P = .041). EF measurements were not significantly different for the AEX group.

CONCLUSION

AEX improved mobility and selected cognitive domains related to motor learning, which enhances sensorimotor control after stroke.

Relationship between lesion location and cognitive domains in acute ischemic stroke patients

Localization of brain lesions in acute ischemic stroke has a significant effect on performance in various cognitive domains. The aim of the study was to determine whether there is association between different locations of ischemic brain lesions and different cognitive domains. The study included 40 acute ischemic stroke patients (26 male and 14 female, aged 45-78 years, with 8-16 years of education). Lesion location was visualized using brain computerized tomography, whereas performance in different cognitive domains was assessed using an extensive neuropsychological test battery. The following domains were evaluated: executive function, language, immediate recall, delayed recall, attention, divergent reasoning, and visual-constructive performance in two dimensions. A series of categorical regression analyses were applied. The results showed a significant association between the domains of executive function and language and a set of predictors related to lesion location. Global brain atrophy was found to be a significant partial predictor of performance in all cognitive domains, with higher degrees of global brain atrophy correlating with poorer performance in each of the studied domains. Combined (cortical-subcortical) lesions and unilateral lesions were both found to be significant partial predictors for language, with a higher lesion load being associated with poorer language performance. Combined lesions were also a significant partial predictor for delayed recall, with a higher lesion load correlating with poorer performance in the delayed recall domain.

Vascular cognitive impairment: current concepts and clinical developments

Vascular cognitive impairment (VCI) comprises a range of cognitive disorders related to cerebral vessel disease and has generally replaced the term multi-infarct dementia. Despite the heterogeneity of the VCI construct, some clinical patterns can be discerned, which enable subtypes, such as mixed dementia and VCI-no dementia, to be recognised. Diagnostic criteria for vascular dementia do not encompass the full range of the VCI construct, and clinical investigators now recognise the need for harmonised standards to study the many manifestations of VCI seen in daily practice and to inform the development of diagnostic criteria. Although executive dysfunction is a recognised feature of VCI, some data suggest a less exclusive role than was previously proposed. VCI might be preventable, although the evidence for this is not as complete as it is for the prevention of stroke. Future studies into specific therapies for VCI will need to consider the clinical features and outcomes carefully.

The value of the clock drawing test and the mini-mental state examination for identifying vascular cognitive impairment no dementia

OBJECTIVE

To determine the validity of the Clock Drawing Test (CDT) and the Mini-Mental State Examination (MMSE) respectively or in combination for differentiating Vascular Cognitive Impairment No Dementia (V-CIND) from normal subjects.

METHODS

Eighty V-CIND patients and 80 healthy control subjects were blindly evaluated with MMSE, CDT, and additional neuropsychological tests. CDT was scored according to the Rouleau method and AD Cooperative Study method. Sensitivities and specificities of the two CDT measures and MMSE for identifying V-CIND patients were determined. The Areas Under the Receiver Operating Characteristic Curve (AUCs) were compared, and the sensitivity of the combination of CDT with MMSE calculated.

RESULTS

V-CIND group performed worse than controls on both MMSE (p < 0.0001) and the two CDTs (p < 0.0001). In differentiating V-CIND patients from normal subjects, the two CDT measures provided sensitivities of 68.7% and 65.0%, and specificities of 78.7% and 86.2% respectively at optimal cutoff scores, which did no better than MMSE (sensitivity 80%, specificity 70%) (comparison of the AUCs, p = 0.992 and 0.428). The sensitivity of MMSE was marginally higher than that of CDT scored with AD Cooperative Study method (p = 0.053). By combining the two CDT measures with MMSE, the sensitivity was improved to 93.7% and 92.5% respectively.

CONCLUSIONS

Compared with MMSE, CDT is of only similar or even weaker ability for identifying V-CIND. MMSE at a cutoff of 28 may be of some value in detecting V-CIND patients. CDT and MMSE in combination provide a valid instrument for V-CIND screening.

Construct Validity of the Wisconsin Card Sorting Test-64 in Patients with Stroke

This study examined the factor structure and contrasted-group validity of the Wisconsin Card Sorting Test-64 (WCST-64) in a stroke sample (n = 112). Confirmatory factor analyses were used to compare five different models suggested by prior factor analyses. The results indicated that the WCST-64 was best represented by a three-dimensional model comprising response inflexibility (factor 1), ineffective hypothesis-testing strategy (factor 2), and set maintenance (factor 3). A significant overall multivariate effect for group (F = 2.87, df = 18,495.46, p <.001) was found in a multivariate analysis of covariance with WCST scores as dependent variables and four different groups (three stroke subgroups with different levels of cognitive function and a normal control group) as independent variable, after controlling for gender. The results of discriminant analysis supported the use of the WCST-64 in stroke patients with cognitive impairment.

Clinical presentation of prodromal frontotemporal dementia

BACKGROUND

Misrecognition of symptoms in the early stages of frontotemporal dementia (FTD) frequently contributes to diagnostic delay. Three frameworks have been proposed for the clinical identification of prodromal FTD: (1) cognitive profiling, (2) the presence of behavioral/psychiatric symptoms in the absence of memory complaints, and (3) a combined approach of cognitive, behavioral, and neuroimaging features.

OBJECTIVE

To evaluate current conceptual frameworks for the clinical recognition of prodromal FTD with current empirical evidence.

METHOD

We performed a comprehensive PsychINFO and MEDLINE database search to identify articles investigating the prodromal symptoms of FTD.

CONCLUSIONS

The 3 frameworks capture important aspects of the clinical picture of prodromal FTD but require further refinement. The prodromal stage of FTD is characterized by both cognitive and behavioral features. Diagnostic accuracy will likely be improved by considering a combination of cognitive and behavioral features, because some features overlap with prodromes for Alzheimer's disease and vascular dementia.

Clinically silent cerebral ischemic events after cardiac surgery: their incidence, regional vascular occurrence, and procedural dependence

BACKGROUND

The reported frequency of stroke after coronary artery bypass grafting varies between 1.5% and 6%, approaches 10% after aortic valve replacement, and may occur in between 40 to 70% in high-risk groups. Clinically silent infarction may be far more frequent and could contribute to long-term cognitive dysfunction in patients after cardiac procedures. Using diffusion-weighted magnetic resonance imaging we document the occurrence, vascular distribution, and procedural dependence of silent infarction after cardiac surgery with cardiopulmonary bypass. We also document the association of preexisting white matter lesions with new postoperative ischemic lesions.

METHODS

Thirty-four patients underwent T2-weighted fluid attenuated inversion recovery and diffusion-weighted magnetic resonance imaging before and after cardiac surgery with cardiopulmonary bypass for coronary artery bypass grafting, aortic valve replacement, and mitral valve repair or replacement surgery. Images were evaluated by experienced neuroradiologists for number, size, and vascular distribution of lesions.

RESULTS

Mean age of participants was 67 +/- 15 years. Imaging occurred before and 6 +/- 2 days after surgery. New cerebral infarctions were evident in 6 of 34 patients (18%), were often multiple, and in 67% of patients were clinically silent. The occurrence of new infarctions by surgical procedure was as follows: aortic valve replacement (2 of 6), coronary artery bypass grafting and aortic valve replacement (3 of 8), aortic valve replacement with root replacement (1 of 1), coronary artery bypass grafting and mitral valve repair or replacement (0 of 4), mitral valve repair or replacement (0 of 2), and isolated coronary artery bypass grafting (0 of 13). New infarction occurred in 6 of 15 (40%) of all procedures involving aortic valve replacement. The severity of preexisting white matter lesions trended toward predicting the occurrence of new lesions (p = 0.055).

CONCLUSIONS

Diffusion-weighted imaging reveals new cerebral infarctions in nearly 40% of patients after aortic valve replacement.

Conceptualizing Functional Cognition in Stroke

Background. Up to 65% of individuals demonstrate poststroke cognitive impairments, which may increase hospital stay and caregiver burden. Randomized stroke clinical trials have emphasized physical recovery over cognition. Neuropsychological assessments have had limited utility in randomized clinical trials. These issues accentuate the need for a measure of functional cognition (the ability to accomplish everyday activities that rely on cognitive abilities, such as locating keys, conveying information, or planning activities). Objective. The aim of the study was to present the process used to establish domains of functional cognition for development of computer adaptive measure of functional cognition for stroke. Methods. Functional cognitive domains involved in identifying relevant neuropsychological constructs from the literature were conceptualized and finalized after advisory panel feedback from experts in neurology, neuropsychology, aphasiology, clinical trials, and epidemiology. Results. The following 17 domains were proposed: receptive aphasia, expressive aphasia, agraphia, alexia, calculation, visuospatial, visuoperceptual, visuoconstruction, attention, language usage, executive functions, orientation, processing speed, memory, working memory, mood, awareness and abstract reasoning. The advisory panel recommended retaining the first 12 domains. Recommended changes included: to address only encoding and retrieval of recent information in the memory domain; to add domains for limb apraxia and poststroke depression; and to keep orientation as a separate domain or reclassify it under memory or attention. The final 10 domains included: language, reading and writing, numeric/calculation, limb praxis, visuospatial function, social use of language, emotional function, attention, executive function, and memory. Conclusion. Conceptualizing domains of functional cognition is the first step in developing a computer adaptive measure of functional cognition for stroke. Additional steps include developing, refining, and field-testing items, psychometric analysis, and computer adaptive test programming.

Executive Function Deficits in Acute Stroke

OBJECTIVES

To establish the frequency of executive dysfunction during acute hospitalization for stroke and to examine the relationship of that dysfunction to stroke severity and premorbid characteristics.

DESIGN

Inception cohort study.

SETTING

Inpatient wards at a Veterans Affairs hospital.

PARTICIPANTS

Consecutive sample of inpatients with radiologically or neurologically confirmed stroke. Final sample included 47 patients screened for aphasia and capable of neuropsychologic testing. Two nonstroke inpatient control samples (n=10 each) with either transient ischemic attack (TIA) or multiple stroke risk factors were administered the same research procedure and tests.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Composite cognitive impairment ratio (CIR), calculated from 8 scores indicative of executive function on 6 neuropsychologic tests by dividing number of tests completed into the number of scores falling below cutoff point, defined as 1.5 standard deviations below normative population mean.

RESULTS

Stroke patients had a mean CIR of .61, compared with .48 for TIAs and .44 for stroke-risk-only. Analysis of variance revealed that CIRs of stroke-risk-only patients but not TIAs were lower than those of the stroke patients (P=.02). Impairment frequencies were at least 50% for stroke patients on most test scores. The Symbol Digit Modalities Test (75% impairment) and a design fluency measure distinguished stroke from nonstroke patients. CIR was not related to stroke severity in the stroke patient sample, but was related to estimated premorbid intelligence.

CONCLUSIONS

Executive function deficits are common in stroke patients. The data suggest that limitations in information processing due to these deficits may require environmental and procedural accommodations to increase rehabilitation benefit.

Poststroke memory function in nondemented patients: a systematic review on frequency and neuroimaging correlates

BACKGROUND AND PURPOSE

Poststroke memory dysfunction is a prerequisite for the diagnosis of poststroke dementia. This diagnosis is made within months after a stroke, apparently assuming a relatively stable course of the poststroke memory function. Clinical experience added to anecdotal evidence from the literature suggests that poststroke memory function may be reversible. The aim of the present study was to systematically review the available data on the time course of poststroke memory function in nondemented stroke survivors. In addition, we wanted to investigate the role of (pre-)stroke characteristics on poststroke memory function.

METHODS

We performed systematic literature search of PubMed with the following medical subject heading terms: memory and stroke. The search strategy yielded 798 articles of which 65 fulfilled our inclusion criteria and went on to the data extraction stage.

RESULTS

Five studies reported the prevalence of poststroke memory dysfunction at different poststroke intervals. The prevalence of poststroke memory dysfunction varied from 23% to 55% 3 months poststroke, which declined from 11% to 31% 1 year poststroke. Larger stroke volume, prestroke medial temporal lobe atrophy, and white matter lesions were related with decreased poststroke memory function.

CONCLUSIONS

Not all patients with poststroke memory dysfunction 3 months after a stroke had memory dysfunction 1 year poststroke. Consequently, not all criteria for the dementia diagnosis were fulfilled any more. This may indicate that poststroke dementia may be reversible in a substantial proportion of patients with stroke. Preferably, standardized reassessment of cognitive function should be performed in each patient diagnosed with poststroke dementia.

Vascular cognitive impairment

Cerebrovascular disease is increasingly recognized as a common cause of cognitive impairment and dementia in later life either alone or in conjunction with other pathologies, most often Alzheimer disease (AD). Progress in the field has been limited by difficulties in terminology; for example, use of the term dementia necessitates the presence of memory impairment, which is the norm in AD, but not in cognitive disorders associated with cerebrovascular disease. The term vascular cognitive impairment (VCI) has been proposed as an umbrella term to recognize the broad spectrum of cognitive, and indeed behavioral, changes associated with vascular pathology. It is characterized by a specific cognitive profile with predominantly attentional and executive impairments together with particular noncognitive features (especially depression) and a relatively stable course, at least in clinical trial populations. Subtypes of VCI have been proposed based on clinical and pathologic differences, including cortical, subcortical, strategic infarct, hypoperfusion, hemorrhagic, and mixed (with AD) type. Diagnostic criteria are emerging but require refinement and validation, especially for mixed dementias. There remain fundamental gaps in our understanding of pathophysiology, predicting prognosis and outcome, and in therapeutics. Clinical trials to date, mainly in populations selected using currently accepted criteria for vascular dementia, have generally been disappointing. A relatively modest cognitive benefit of agents such as nimodipine, memantine, and cholinesterase inhibitors has been reported, although the clinical significance of these improvements remains to be established. Further studies, focusing on particular subtypes of VCI and involving subjects at earlier stages of the disease, are required. The aim of this article is to review the concept of VCI in terms of the evidence base surrounding diagnosis, clinical features, pathophysiology, and management and to make some recommendations regarding further research in the area. It begins with a discussion on the historical background, which is important to understand the different and somewhat confusing terminology that currently exists in the field.