Aphasia or Neglect after Thalamic Stroke: The Various Ways They may be Related to Cortical Hypoperfusion.

Although aphasia and hemispatial neglect are classically labeled as cortical deficits, language deficits or hemispatial neglect following lesions to subcortical regions have been reported in many studies. However, whether or not aphasia and hemispatial neglect can be caused by subcortical lesions alone has been a matter of controversy. It has been previously shown that most cases of aphasia or hemispatial neglect due to acute non-thalamic subcortical infarcts can be accounted for by concurrent cortical hypoperfusion due to arterial stenosis or occlusion, reversible by restoring blood flow to the cortex.

Longitudinal Imaging and Deterioration in Word Comprehension in Primary Progressive Aphasia: Potential Clinical Significance.

Background: Three variants of primary progressive aphasia (PPA), distinguished by language performance and supportive patterns of atrophy on imaging, have different clinical courses and the prognoses for specific functions. For example, semantic variant PPA alone is distinguished by impaired word comprehension. However, sometimes individuals with high education show normal performance on word comprehension tests early on, making classification difficult.

The roles of occipitotemporal cortex in reading, spelling, and naming.

We evaluated the hypothesis that Brodmann's area (BA) 37 within left occipitotemporal cortex has at least two important functions in lexical processing. One role is the computation of case-, font-, location-, and orientation-independent grapheme descriptions for written word recognition and production (reading and spelling). This role may depend on the medial part of BA 37, in left midfusiform gyrus.

Motor extinction in distinct reference frames: a double dissociation.

Objective: Test the hypothesis that right hemisphere stroke can cause extinction of left hand movements or movements of either hand held in left space, when both are used simultaneously, possibly depending on lesion site.

Methods: 93 non-hemiplegic patients with acute right hemisphere stroke were tested for motor extinction by pressing a counter rapidly for one minute with the right hand, left hand, or both simultaneously with their hands held at their sides, or crossed over midline.

Results: We identified two distinct types of motor extinction in separate patients; 20 patients extinguished left hand movements held in left or right space (left canonical body extinction); the most significantly associated voxel cluster of ischemic tissue was in the right temporal white matter.

Patterns of dysgraphia in primary progressive aphasia compared to post-stroke aphasia.

We report patterns of dysgraphia in participants with primary progressive aphasia that can be explained by assuming disruption of one or more cognitive processes or representations in the complex process of spelling. These patterns are compared to those described in participants with focal lesions (stroke). Using structural imaging techniques, we found that damage to the left extrasylvian regions, including the uncinate, inferior fronto-occipital fasciculus, and sagittal stratum (including geniculostriate pathway and inferior longitudinal fasciculus), as well as other deep white and grey matter structures, was significantly associated with impairments in access to orthographic word forms and semantics (with reliance on phonology-to-orthography to produce a plausible spelling in the spelling to dictation task).

Disentangling the neuroanatomical correlates of perseveration from unilateral spatial neglect.

Perseverative behavior, manifest as re-cancelling or re-visiting targets, is distinct from spatial neglect. Perseveration is thought to reflect frontal or parietal lobe dysfunction, but the neuroanatomical correlates remain poorly defined and the interplay between neglect and perseveration is incompletely understood. We enrolled 87 consecutive patients with diffusion-weighted, perfusion-weighted imaging, and spatial neglect testing within 24 hours of right hemisphere ischemic stroke.

Asyntactic comprehension, working memory, and acute ischemia in Broca's area versus angular gyrus.

We evaluated sentence comprehension of variety of sentence constructions and components of short-term memory (STM) in 53 individuals with acute ischemic stroke, to test some current hypotheses about the role of Broca's area in these tasks. We found that some patients show structure-specific, task-independent deficits in sentence comprehension, with chance level of accuracy on passive reversible sentences, more impaired comprehension of object-cleft than subject-cleft sentences, and more impaired comprehension of reversible than irreversible sentences in both sentence-picture matching and enactment tasks. In a dichotomous analysis, this pattern of "asyntactic comprehension" was associated with dysfunctional tissue in left angular gyrus, rather than dysfunctional tissue in Broca's area as previously proposed.

Formal education, socioeconomic status, and the severity of aphasia after stroke.

Objective: To determine the role of education and socioeconomic status on the severity of aphasia after stroke.

Design: Cross-sectional study.

Setting: Stroke units of 2 affiliated medical centers.

Reperfusion of specific cortical areas is associated with improvement in distinct forms of hemispatial neglect.

Objective: To test the hypothesis that restoring blood flow to specific right cortical regions in acute stroke results in improvement in distinct forms of hemispatial neglect distinguished by reference frame: viewer-centered versus stimulus-centered neglect.

Methods: Twenty five patients with acute right stroke were evaluated at Day 1 and Day 3-5 with a battery of neglect tests and Diffusion- and Perfusion-Weighted MR Imaging. Multivariate linear regression analysis revealed Brodmann areas (BAs) where reperfusion predicted degree of improvement in scores on each type of neglect, independently of reperfusion of other areas, total change in the volume of infarct or hypoperfusion, and age.

Neuroanatomical correlates of oral reading in acute left hemispheric stroke.

Oral reading is a complex skill involving the interaction of orthographic, phonological, and semantic processes. Functional imaging studies with nonimpaired adult readers have identified a widely distributed network of frontal, inferior parietal, posterior temporal, and occipital brain regions involved in the task. However, while functional imaging can identify cortical regions engaged in the process under examination, it cannot identify those brain regions essential for the task.

The nature of naming errors in primary progressive aphasia versus acute post-stroke aphasia.

Objective: To compare the distribution of error types across subgroups of primary progressive aphasia and poststroke aphasia in different vascular locations.

Method: We analyzed naming errors in 49 individuals with acute left hemisphere ischemic stroke and 55 individuals with three variants of primary progressive aphasia. Location of atrophy or ischemic stroke was characterized using MRI.

Patterns of breakdown in spelling in primary progressive aphasia.

Introduction: The objective of this study is to determine which cognitive processes underlying spelling are most affected in the three variants of primary progressive aphasia (PPA): Logopenic variant primary progressive aphasia (lvPPA), Semantic variant primary progressive aphasia (svPPA), and Nonfluent variant primary progressive aphasia (nfvPPA).

Methods: 23 PPA patients were administered The Johns Hopkins Dysgraphia Battery to assess spelling. Subtests evaluate for effects of word frequency, concreteness, word length, grammatical word class, lexicality (words vs pseudowords), and "regularity" by controlling for the other variables.

Ischemia in broca area is associated with broca aphasia more reliably in acute than in chronic stroke.

Background And Purpose: We aimed to determine if ischemia involving Broca area predicts Broca aphasia more reliably in acute or chronic stroke.

Methods: We included consecutive right-hand-dominant patients with left hemisphere ischemic stroke (<48 hours from onset for acute stroke or >6 months after stroke for chronic stroke). MRI scans were analyzed for ischemic lesions or hypoperfusion in Broca area (Brodmann areas 44 and 45).

Acute recovery of oral word production following stroke: patterns of performance as predictors of recovery.

Background: Impairments in oral word production are common at the onset of stroke. The identification of factors that predict early recovery has important implications for identifying those at greater risk of continued impaired functioning, and the management of the patient's care following discharge.

Aims: To identify patterns of performance that are predictors of acute recovery of oral word production abilities following stroke; to identify any association between early and more chronic recovery.

Severity of hypoperfusion in distinct brain regions predicts severity of hemispatial neglect in different reference frames.

Background And Purpose: Hemispatial neglect is among the most common and disabling consequences of right hemisphere stroke. A variety of variables have been associated with the presence or severity of neglect but have not evaluated the independent effects of location, severity, and volume of ischemia. Few have determined areas involved in different types of neglect.

A neural network critical for spelling.

We aimed to identify neuroanatomical regions associated with deficits to the graphemic buffer, a working memory component of the spelling system that holds the sequence of letter identities during production. We evaluated 331 patients with left hemisphere ischemic stroke with various spelling tests and magnetic resonance diffusion-weighted imaging and perfusion-weighted imaging, within 48 hours of stroke onset. A voxel-wise statistical map showed that ischemia in voxels in posterior and inferior frontal and parietal cortex, subcortical white matter underlying prefrontal cortex, lateral occipital gyrus, or caudate was associated with impairment in maintaining the sequence of letter identities while spelling.

Patterns of reading performance in acute stroke: A descriptive analysis.

Unlabelled: One of the main sources of information regarding the underlying processes involved in both normal and impaired reading has been the study of reading deficits that occur as a result of brain damage. However, patterns of reading deficits found acutely after brain injury have been little explored. The observed patterns of performance in chronic stroke patients might reflect reorganization of the cognitive processes underlying reading or development of compensatory strategies that are not normally used to read.

The NIHSS-plus: improving cognitive assessment with the NIHSS.

Background: The National Institutes of Health Stroke Scale (NIHSS) has been criticized for limited representation of cognitive dysfunction and bias towards dominant hemisphere functions. Patients may therefore receive a low NIHSS score despite a fairly large stroke. A broader scale including simple cognitive tests would improve the clinical and research utility of the NIHSS.

Where (in the brain) do semantic errors come from?

Background: Semantic errors result from the disruption of access either to semantics or to lexical representations. One way to determine the origins of these errors is to evaluate comprehension of words that elicit semantic errors in naming. We hypothesized that in acute stroke there are different brain regions where dysfunction results in semantic errors in both naming and comprehension versus those with semantic errors in oral naming alone.

Hemispherectomy sustained before adulthood does not cause persistent hemispatial neglect.

Introduction: Hemispatial neglect has been well established in adults following acute ischemic stroke, but has rarely been investigated in children and young adults following brain injury. It is known that young brains have a tremendous potential for reorganization; however, there is controversy as to whether functions are assumed by the opposite hemisphere, or perilesional areas in the same hemisphere. Patients with intractable epilepsy who undergo hemispherectomy for treatment are missing the entire cortex on one side following surgery.

Neural substrates of visuospatial processing in distinct reference frames: evidence from unilateral spatial neglect.

There is evidence for different levels of visuospatial processing with their own frames of reference: viewer-centered, stimulus-centered, and object-centered. The neural locus of these levels can be explored by examining lesion location in subjects with unilateral spatial neglect (USN) manifest in these reference frames. Most studies regarding the neural locus of USN have treated it as a homogenous syndrome, resulting in conflicting results.

Gender differences in unilateral spatial neglect within 24 hours of ischemic stroke.

Hemispatial neglect is a common and disabling consequence of stroke. Previous reports examining the relationship between gender and the incidence of unilateral spatial neglect (USN) have included either a large numbers of patients with few neglect tests or small numbers of patients with multiple tests. To determine if USN was more common and/or severe in men or women, we examined a large group of patients (312 right-handed) within 24 hours of acute right hemisphere ischemic stroke.

Speech and language functions that require a functioning Broca's area.

A number of previous studies have indicated that Broca's area has an important role in understanding and producing syntactically complex sentences and other language functions. If Broca's area is critical for these functions, then either infarction of Broca's area or temporary hypoperfusion within this region should cause impairment of these functions, at least while the neural tissue is dysfunctional. The opportunity to identify the language functions that depend on Broca's area in a particular individual was provided by a patient with hyperacute stroke who showed selective hypoperfusion, with minimal infarct, in Broca's area, and acutely impaired production of grammatical sentences, comprehension of semantically reversible (but not non-reversible) sentences, spelling, and motor planning of speech articulation.

Characteristics and reversibility of dementia in Normal Pressure Hydrocephalus.

Studies of the cognitive outcome after shunt insertion for treatment of Normal Pressure Hydrocephalus have reported widely mixed results. We prospectively studied performance of 60 patients with Normal Pressure Hydrocephalus on a comprehensive battery of neuropsychological tests before and after shunt surgery to determine which cognitive functions improve with shunt insertion. We also administered a subset of cognitive tests before and after temporary controlled drainage of cerebrospinal fluid to determine if change on this brief subset of tests after drainage could predict which patients would show cognitive improvement three to six months after shunt insertion.

Neural regions essential for reading and spelling of words and pseudowords.

Objective: To identify dysfunctional brain regions critical for impaired reading/spelling of words/pseudowords by evaluating acute stroke patients on lexical tests and magnetic resonance imaging, before recovery or reorganization of structure-function relationships.

Methods: A series of 106 consenting patients were administered oral reading and spelling tests within 24 hours of left supratentorial stroke onset. Patients underwent diffusion- and perfusion-weighted magnetic resonance examination the same day to identify regions of hypoperfusion/infarct of 16 Brodmann areas.