Vascular aphasias: main characteristics of patients hospitalized in acute stroke units

BACKGROUND AND PURPOSE

Aphasia is frequent in stroke patients and is associated with poor prognosis. However, characteristics and determinants of vascular aphasias remain controversial. The aim of this study was to evaluate aphasia characteristics at the acute stage in patients admitted to a stroke unit.

METHODS

The study was performed in 308 patients consecutively assessed with a standardized aphasia battery.

RESULTS

Aphasia was observed in 207 patients; global and nonclassified aphasias accounted for 50% of aphasic syndromes at the acute stage, whereas classic aphasias (Wernicke's, Broca's, transcortical, and subcortical aphasias) were less frequent. Age differed across aphasic syndromes in ischemic stroke patients only; patients with conduction aphasia were younger, and patients with subcortical aphasia were older. Sex did not significantly differ across aphasic syndromes. The presence of a previous stroke was more frequent in nonclassified aphasia.

CONCLUSIONS

This study shows (1) that vascular aphasias are frequently severe or nonclassic at the acute stage, a finding explained in part by the presence of a previous stroke; (2) that the age effect is due mainly to its influence on infarct location; and (3) that the main determinant of aphasia characteristics is lesion location.

Recovery of semantic word processing in transcortical sensory aphasia: a functional magnetic resonance imaging study

In a previous functional magnetic resonance imaging (fMRI) study with normal subjects, we demonstrated regions related to conceptual-semantic word processing around the first frontal sulcus (BA 9) and the posterior parietal lobe (BA 7/40) in agreement with several previous reports. We had the possibility, using the same fMRI paradigm, to study two consecutive cases with left middle cerebral artery (MCA) infarction (RC and HP) and lesions affecting either solely the pre-frontal (HP) or both the pre-frontal and posterior parietal part of the network activated in normal subjects (RC). Both patients showed transcortical sensory aphasia (TSA) on acute assessment. This contradicts classical disconnection accounts of the syndrome stating intact conceptual representations in TSA. Their recovery of language comprehension was associated with activation of a left hemispheric network. Mainly activations of left perilesional pre-frontal regions (RC), left Wernicke's area (RC and HP) or the left posterior middle and inferior temporal cortex (HP) were demonstrated in the TSA patients. The latter findings suggest that in our cases of TSA functional take-over has occurred in regions with related functions ('redundancy recovery') rather than in previously unrelated areas ('vicarious functioning'). Our data support distributed models of conceptual-semantic word processing and multiple left hemispheric representations of closely related functions.

Hypoperfusion of Wernicke's area predicts severity of semantic deficit in acute stroke

Based on earlier findings that the presence of word comprehension impairment (a deficit in the meaning of words, or lexical semantics) in acute stroke was strongly associated with the presence of hypoperfusion or infarct in Wernicke's area, we tested the hypothesis that the severity of word comprehension impairment was correlated with the magnitude of delay in perfusion of Wernicke's area on magnetic resonance perfusion-weighted imaging. Eighty patients were prospectively studied within 24 hours of onset or progression of acute left hemisphere stroke symptoms, with diffusion-weighted imaging, perfusion-weighted imaging, and detailed language tests. For 50 patients without infarct in Wernicke's area, we found a strong Pearson correlation between the rate of errors on a word comprehension test and the mean number of seconds of delay in time-to-peak concentration of contrast in Wernicke's area, relative to the homologous region on the right. These results add further evidence for the crucial role of Wernicke's area (Brodmann's area 22) in word comprehension and indicate that the magnitude of delay on PWI may be a gross indicator of tissue dysfunction.

Language deficits, localization, and grammar: evidence for a distributive model of language breakdown in aphasic patients and neurologically intact individuals

Selective deficits in aphasic patients' grammatical production and comprehension are often cited as evidence that syntactic processing is modular and localizable in discrete areas of the brain (e.g., Y. Grodzinsky, 2000). The authors review a large body of experimental evidence suggesting that morpho-syntactic deficits can be observed in a number of aphasic and neurologically intact populations. They present new data showing that receptive agrammatism is found not only over a range of aphasic groups, but is also observed in neurologically intact individuals processing under stressful conditions. The authors suggest that these data are most compatible with a domain-general account of language, one that emphasizes the interaction of linguistic distributions with the properties of an associative processor working under normal or suboptimal conditions.

The influence of phonological context on the sound errors of a speaker with Wernicke's aphasia

A corpus of phonological errors produced in narrative speech by a Wernicke's aphasic speaker (R.W.B.) was tested for context effects using two new methods for establishing chance baselines. A reliable anticipatory effect was found using the second method, which estimated chance from the distance between phoneme repeats in the speech sample containing the errors. Relative to this baseline, error-source distances were shorter than expected for anticipations, but not perseverations. R.W.B.'s anticipation/perseveration ratio measured intermediate between a nonaphasic error corpus and that of a more severe aphasic speaker (both reported in Schwartz et al., 1994), supporting the view that the anticipatory bias correlates to severity. Finally, R.W.B's anticipations favored word-initial segments, although errors and sources did not consistently share word or syllable position.

Verbal and design fluency in patients with frontal lobe lesions

The ability to generate items belonging to categories in verbal fluency tasks has been attributed to frontal cortex. Nonverbal fluency (e.g., design fluency) has been assessed separately and found to rely on the right hemisphere or right frontal cortex. The current study assessed both verbal and nonverbal fluency in a single group of patients with focal, frontal lobe lesions and age- and education-matched control participants. In the verbal fluency task, participants generated items belonging to both letter cues (F, A, and S) and category cues (animals and boys' names). In the design fluency task, participants generated novel designs by connecting dot arrays with 4 straight lines. A switching condition was included in both verbal and design fluency tasks and required participants to switch back and forth between different sets (e.g., between naming fruits and furniture). As a group, patients with frontal lobe lesions were impaired, compared to control participants, on both verbal and design fluency tasks. Patients with left frontal lesions performed worse than patients with right frontal lesions on the verbal fluency task, but the 2 groups performed comparably on the design fluency task. Both patients and control participants were impacted similarly by the switching conditions. These results suggest that verbal fluency is more dependent on left frontal cortex, while nonverbal fluency tasks, such as design fluency, recruit both right and left frontal processes.

Differences between conduction aphasia and Wernicke's aphasia

Conduction aphasia and Wernike's aphasia have been differentiated by the degree of auditory language comprehension. We quantitatively compared the speech sound errors of two conduction aphasia patients and three Wernicke's aphasia patients on various language modality tests. All of the patients were Japanese. The two conduction aphasia patients had "conduites d'approche" errors and phonological paraphasia. The patient with mild Wernicke's aphasia made various errors. In the patient with severe Wernicke's aphasia, neologism was observed. Phonological paraphasia in the two conduction aphasia patients seemed to occur when the examinee searched for the target word. They made more errors in vowels than in consonants of target words on the naming and repetition tests. They seemed to search the target word by the correct consonant phoneme and incorrect vocalic phoneme in the table of the Japanese alphabet. The Wernicke's aphasia patients who had severe impairment of auditory comprehension, made more errors in consonants than in vowels of target words. In conclusion, utterance of conduction aphasia and that of Wernicke's aphasia are qualitatively distinct.

[Effect of traumatic brain injury on control and suppression of inhibition processes]

Recent hypotheses have renewed discussion on the mechanisms linking executive functions and working memory in patients with traumatic brain injury. In this context, we studied the control and suppression functions of inhibition processes. Results obtained with a suppression paradigm showed that the traumatic brain injury patient makes a number of suppression errors and that suppression responses imply an important temporal loss in this population.

Disorder in sequential speech perception: a case study on pure word deafness

We described disorders of a patient which were uniquely restricted to speech perception of syllable sequences after brain damage. The results of series of experiments using syllable sequences showed "negative recency effect," in which the subject's repetition performance at the latter syllable position was remarkably poor. Experimental analyses suggested that the "negative recency effect" could be due to dual factors: the lower rate of processing of speech sounds and the memory load of holding processes of preceding syllables imposed on the succeeding phonological processing. The results also suggested that the holding processes which imposed the memory load on the succeeding auditory phonological coding processing were modality nonspecific.

Dissociation of semantic and phonological errors in naming

We report the naming performance of a fluent aphasic, DP, who shows a striking dissociation between semantic and phonological (nonword) errors: he produced numerous semantic errors but virtually no phonological errors. DP's pattern of performance is the reverse of that reported for patient DM (Caramazza, Papagno, & Ruml, 2000), who only made phonological errors in a naming task. These patterns of performance are inconsistent with the proposal by Dell, Schwartz, Martin, Saffran, and Gagnon (1997) that the naming deficit in fluent aphasia is the result of global damage to all levels of the lexical access system and support instead the hypothesis that brain damage can selectively disrupt distinct subcomponents of the lexical processing system.

The selective impairment of phonological processing in speech production

We report the naming performance of a patient (DM) with a fluent progressive aphasia who made phonological errors in all language production tasks. The pattern of errors in naming was strikingly clear: DM made very many phonological errors that resulted almost always in nonword responses. The complete absence of semantic errors and the very low ratio of formal errors relative to nonword errors (1.6:30.3) in DM's performance are discussed in the context of recent claims about the nature of naming deficits in fluent aphasics. We argue that DM's performance makes highly improbable the claim that fluent aphasia results from global lesions affecting all levels of the lexical access system equally.

Diffusion- and perfusion-weighted MRI in a patient with a prolonged reversible ischaemic neurological deficit

We report acute and follow-up diffusion- and perfusion-weighted MRI (DWI, PWI) findings in a patient with a prolonged reversible ischaemic neurological deficit. PWI 12 h after the patient was last seen to be without symptoms revealed a large perfusion deficit in the left posterior MCA territory with a relatively inconspicuous and much smaller abnormality on DWI. Follow-up showed resolution of abnormalities on both DWI and PWI, and conventional MRI was normal, apart from a very slight abnormality, visible only on FLAIR images, at the centre of the initially DWI-positive region. These findings demonstrate the utility of PWI when be used in combination with DWI to investigate the pathophysiology of transient ischemic syndromes.

A model-driven analysis of severity, response characteristics, and partial recovery in aphasics' picture naming

Dell, Schwartz, Martin, Saffran, and Gagnon (DSMSG; 1997) presented a computational analysis of aphasic naming that, among other things, purports to explain why some error types correlate with naming severity while others do not. It does so in terms of chance response opportunities, which differ among error types and which come into play particularly when activation levels are small. The present study looks at error frequencies in relation to severity at two points in time: at study entry and after a period of partial recovery. Results support the model's distinction between severity-sensitive errors (nonwords. formal paraphasias, and unrelated errors) and those that are severity insensitive (semantic; mixed). Additionally, we show that the degree of target overlap in nonwords is sensitive to severity but various measures of monitoring and error correction are not. While these results generally support DSMSG, effects at the level of individual patients underscore the difficulties that their model encounters in explaining some pure error dissociations.

Chronological progression of a language deficit appearing to be postictally reversible in a patient with symptomatic localization-related epilepsy

A language deficit occurring interictally, with chronological progression, and postictally in a patient with symptomatic localization-related epilepsy, which began at 1.6 years of age, is reported. The patient was a 30-year-old right-handed man whose seizures seemed to originate from the left frontal lobe and to involve the left temporal lobe. The deficit in oral language consisted mainly of features of motor aphasia, including delayed initiation of speech with great effort, echolalic and palilalic tendencies, and word-finding difficulty, but he also showed features of sensory aphasia. Written language had agraphia observed in sensory aphasia, including well-formed letters, paraphasias, neologisms, and paragrammatism. Postictally, the language deficit appeared to be superficially reversible, and evolved from mutism through non-fluent jargon to the interictal level of language. Analysis of the patient's diaries from 10 to 26 years of age disclosed chronologically progressive deterioration of language with paragrammatism, showing an increase of grammatical errors, neologismus, literal and verbal paraphasias and misconstruction of sentences. The results suggest that localization-related epilepsy of presumably left frontal lobe origin causes not only a postictal language deficit but also a slowly progressive deficit of language function.

The role of speech production in auditory-verbal short-term memory: evidence from progressive fluent aphasia

We report investigations of auditory-verbal short-term memory (AVSTM) in a patient with progressive fluent anomic aphasia. Despite having apparently normal AVSTM as measured by digital span, FM was significantly impaired in immediate serial recall of short sequences of familiar words, and even in reproducing a single word after a filled delay of just a few seconds. In both tasks, unlike normal subjects, she produced numerous phonological errors, often consisting of phonological segments from the intended target word concatenated with segments from other words in the stimulus sequence. Her success in these tasks was modulated (i) consistently by word frequency (high > low), (ii) inconsistently by word imageability (high > low), and (iii) most dramatically by 'nameability': that is, FM was much more likely to reproduce a word correctly in AVSTM if it was a word that she could also produce successfully in picture-naming tasks. On the basis of these and additional experiments designed to exclude other interpretations, we conclude that AVSTM may be crucially supported by activation of the lexical phonological representations responsible for production of content words in speech.

Transcortical sensory aphasia in a right-handed patient following watershed infarcts in the right cerebral hemisphere: a 15-month evaluation of another case of crossed aphasia

Well-documented cases of crossed (transcortical sensory) aphasia, especially those with longitudinal evaluation, are rare. We report a case of crossed transcortical sensory aphasia following watershed infarcts in the right hemisphere, from the moment of the accident until 15 months afterward. The aphasia type, and the course of recovery, is a "mirror" representation of that seen in cases of uncrossed aphasia. Unfortunately, the data do not permit strong conclusions regarding the lateralization of language in association with praxis and visuospatial abilities. This underlines the need for more well-documented (case) studies to come to a better understanding of the mechanisms through which lateralization occurs.

Transcortical sensory aphasia due to a left frontal subcortical haemorrhage

A case of transcortical sensory aphasia caused by a cerebral haemorrhage in the left frontal lobe is presented. A 72-year-old right-handed woman was admitted to the hospital, with a history of acute onset of speech disturbance and headache. On initial assessment, her spontaneous speech was fluent. She had no difficulty initiating speech, articulated normally, and did not exhibit logorrhea. Her ability to repeat phonemes and short sentences (5-6 words) was fully preserved, however she had severe difficulty with visual recognition of words, and with aural comprehension at the word level, although she was able to read words aloud. Computed tomography and magnetic resonance imaging showed cerebral haemorrhage in the left frontal lobe, involving the superior and middle frontal gyrus. Single photon emission CT revealed a wider area of low perfusion over the entire left frontal lobe, including the superior, middle and inferior frontal gyrus. The aphasia symptoms, mainly poor comprehension, disappeared quickly several weeks after the event. This may have been due to a reduction in the size of the haematoma and a resolution of the oedema around the haematoma. Clinically, the transcortical sensory aphasia in this case was indistinguishable from that caused by damage to the posterior language areas. Further case reports of transcortical sensory aphasia associated with frontal lobe lesions would help to confirm whether a relatively rapid recovery is characteristic in cases such as this.

Brain plasticity in poststroke aphasia: what is the contribution of the right hemisphere?

The brain may use two strategies to recover from poststroke aphasia: the structural repair of primarily speech-relevant regions or the activation of compensatory areas. We studied the cortical metabolic recovery in aphasic stroke patients with positron emission tomography (PET) at rest and during word repetition. The left supplementary motor area (SMA) showed the most prominent compensatory activation in the subacute state of stroke. The restitution of the left superior temporal cortex determined the long-term prognosis of aphasia. The brain recruited right-hemispheric regions for speech processing, when the left-hemispheric centers were permanently impaired. This strategy, however, was significantly less effective than the repair of the original speech-relevant network.

Klüver-Bucy syndrome after bilateral selective damage of amygdala and its cortical connections

Isolated symmetric damage to the amygdala and their cortical connections occurred in an individual following cancer treatment. The lesions were imaged after reversal of hyponatremia. The patient displayed marked behavioral changes including visual agnosia, hypersexuality, hyperorality, a tendency to react to every visual stimulus, and memory deficits. The cluster of neurobehavioral symptoms is similar to previously reported accounts of Klüver-Bucy syndrome and suggests the importance of bilateral amygdala involvement in these behavioral changes.

Some relationships between skills in word-category recall and factors in adults' aphasia

It has long been recognized that a basic dimension to the lexical organization of the brain is semantic, and some brain mapping studies have indicated that the brain fields are distinctly different from some grammatical classes. Findings from the present investigation showed consistent relationships between 29 aphasic adults' performances on tasks involving graphic and gestural skills and those involving sequential recall of spoken words from different word categories. Each adult received the Porch Index of Communication Abilities which relies upon the physical manipulation of objects to assess verbal, gestural, and graphic abilities. Scores on a test requiring recall of word strings of nouns, verbs, adverbs, adjectives, or prepositions were used to predict the subscale scores from the Graphic and Gestural factors of the index. Recall scores for verb and preposition were predictive of the aphasic subjects' performances on the Graphic subscale, and noun and preposition scores were predictors of subjects' scores on the Gestural subscale. The results are related to other research showing that verb and preposition skills are predictive of fine motor abilities of children with communication disorders and brain-mapping studies. Some discussion centers on possible overlapping functions of brain activity involving word categories, language, and fine motor skills.

Primary progressive semantic aphasia: a case study

A longitudinal case study of a patient with a progressive loss of meaning of objects with preserved phonology and syntax is presented. Repeated measures of language, praxis, visual cognition, and semantic processing were carried out. The patient still has preserved conversational speech, social skills, and orientation in her 8th year of her illness, but shows severe anomia and comprehension deficit in all modalities of stimulus presentation. In addition to standardized tests of language, cognition, and memory, specific experiments of categorization, modalities of word access, item consistency, category specificity, and definition of words were carried out. Results indicate a frequency dependent loss of meaning that was consistent in all modalities and throughout all object categories. However, the relative preservation of visual categorization of all categories tested and the language based categorization of animals suggested some fractionation of semantic memory. Relative preservation of autobiographical and personal memories versus semantic memory was a striking observation. Evidence for selective impairment of central semantic processing was obtained from experiments indicating item consistency of loss and the lack of semantic cuing. Neuroimaging evidence of left temporal lobe atrophy and the classical picture is compatible with similar cases published under the term semantic dementia or "transcortical sensory aphasia with visual agnosia" and suggest the diagnosis of Pick's disease.

Consonant and vowel production of right hemisphere patients

Recent reports of subclinical phonetic deficits in posterior and most particularly in Wernicke's aphasics have challenged the traditional dichotomy which characterized speech deficits in aphasia as anterior/phonetic and posterior/phonological. It is unclear whether the basis of the phonetic deficit in posterior aphasics reflects the fact that the speech production system extends to more posterior regions of the left hemisphere than previously thought or alternatively is the result of generalized brain damage effects. The present study explores the latter possibility by investigating the patterns of speech production in right hemisphere brain-damaged, non-aphasic patients with anterior and posterior lesions. Acoustic analyses conducted on a range of consonant and vowel parameters showed differences between the speech patterns of both anterior and posterior right hemisphere patients and that of Wernicke's aphasics. These findings suggest that the subclinical deficit of Wernicke's aphasics can not simply be ascribed to a generalized brain-damage effect and raise the possibility that the right hemisphere also plays some role, if only a minor one, in the phonetic implementation of speech.