Crossed aphasia in an illiterate dextral

An 83 year old illiterate, right-handed woman developed a persistent nonfluent aphasia following a right cerebral infarction (crossed aphasia). Computerized axial tomography localized the lesion to the right posterior frontal lobe.It is suggested that the neural mechanisms involved in learning to read and write may be critical for the complete establishment and maintenance of language dominance in the left hemisphere, and that, in this case, the patient's failure to acquire reading and writing skills altered the normal evolution of language lateralization and resulted in the right hemisphere assuming the dominant role.     

A different form of agraphia: Syntactic writing errors in patients with motor speech and movement disorders

Three patients are described who displayed syntactic writing errors in combination with a motor speech disturbance and impaired motor limb function. Two of the patients had bulbar amyotrophic lateral sclerosis (ALS). Agraphia appeared when verbal communication was no longer possible. Autopsy in one patient disclosed only lesions consistent with ALS. The third patient had palilalia and chorea and, although not aphasic, his written language showed persistent syntactic errors. We hypothesize that the agraphia in these patients occurred because of the combination of disordered feedback from the motor speech apparatus and limbs.     

Selective impairment of phonation: A case study

A 47-year-old right-handed man underwent craniotomy for clipping of an aneurism at the trifurcation of the left middle cerebral artery. Subsequently, he suffered a left hemisphere CVA after which his speech and language resembled that of Broca's aphasia with accompanying apraxia of speech. Medical, behavioral, and acoustical data amassed over a period of several months indicated numerous contraindications to traditional diagnoses of Broca's aphasia, apraxia of speech, and dysarthria. Ultimately, it was determined that the patient had a selective impairement of phonation or laryngeal apraxia. This was illustrated dramatically when he was taught to use an electrolarynx which allowed him to bypass his disrupted phonatory system. Speaking with the electrolarynx, the patient communicated normally. Any semblance of Broca's aphasia disappeared. Supralaryngeal articulation was normal; apraxia of speech behaviors were absent. This case report indicates that dissociation of oral and laryngeal gestures due to brain injury is possible. Mechanisms underlying such a dissociation for this case are reviewed. The possibility of discrete center lesions in the frontal motor association area causing different types of apraxia of speech is discussed.     

Neuropsychological analysis of a case of crossed dysphasia verified at postmortem

A case is reported of crossed dysphasia in a right-handed monolingual patient, where neuropathological verification of the unilateral site of the lesion was obtained within a year of detailed neuropsychological assessment. The patient's pattern of language impairment was characterized by agrammatic speech and relatively preserved naming ability. In addition, the patient had good repetition, poor comprehension, and marked impairment on visuospatial tasks. Neuropathological investigations showed a large area of infarction affecting cortex, white matter, and subcortical structures in the right hemisphere. The possibility is discussed of a distinction between two types of crossed dysphasia with either dissociated or simultaneous language and visuospatial deficits due to reversed representation of hemispheric specific functions or transfer of most cognitive functions to the right hemisphere.     

Writing with the right hemisphere

We studied writing abilities in a strongly right-handed man following a massive stroke that resulted in virtually complete destruction of the language-dominant left hemisphere. Writing was characterized by sensitivity to lexical-semantic variables (i.e., word frequency, imageability, and part of speech), semantic errors in writing to dictation and written naming, total inability to use the nonlexical phonological spelling route, and agrammatism in spontaneous writing. The reliance on a lexical-semantic strategy in spelling, semantic errors, and impaired phonology and syntax were all highly consistent with the general characteristics of right hemisphere language, as revealed by studies of split-brain patients and adults with dominant hemispherectomy. In addition, this pattern of writing closely resembled the syndrome of deep agraphia. These observations provide strong support for the hypothesis that deep agraphia reflects right hemisphere writing.     

Does the right hemisphere take over after damage to Broca's area? the Barlow case of 1877 and its history

In 1877 Thomas Barlow, a London physician, published a remarkable case of functional recovery of speech following brain damage. It involved a 10-year-old boy who had lost his speech, regained it, and lost it again before he died from a disorder that affected his heart and produced embolisms that subsequently affected other organs, including his brain. Examination of the boy's brain revealed two focal regions of softening; one that affected Broca's area and the left facial-motor area, and another, which occurred weeks later, in the homologous regions of the right hemisphere. Although Barlow was most concerned with motor deficits, others at the turn of the century began to cite this case as strong evidence that the corresponding region of the right hemisphere can take over speech functions for Broca's area on the left. Whether this case really provides good support for functional takeover or vicariation theory is critically evaluated in the light of contemporary research, including PET scan studies involving damage to Broca's speech region.     

Dissociations of writing and praxis: Two cases in point

For normal writing it is essential that both motoric and linguistic competence be present; disruption of one or the other of these faculties may result in qualitatively different types of agraphia. Two right-handed patients became agraphic after left hemisphere lesions; pure apraxic agraphia in the absence of limb apraxia developed in one patient and pure linguistic agraphia in association with severe ideomotor limb apraxia in the other. The performance of these patients not only serves to illustrate the dissociation between the motoric and linguistic faculties that underlie writing but also confirms that ideomotor limb apraxia and apraxic agraphia are distinct and dissociable entities.     

Left non-dominant hand mirror writing

A 38-year-old right-handed woman, who had suffered a left cerebral hemisphere infarction, was studied. She developed right hemiparesis, motor and sensory aphasia, and left hand mirror writing. All possible brain mechanisms involved in writing, either perceptual or motor, were investigated in search of the one responsible for her mirror writing; however, no abnormality was detected. On examination of the left handwriting, in the directionality of writing tracings as related to the body midline, we detected a lack of inversion of the right handwriting motor patterns--at the moment they are transmitted from the left to the right cerebral hemisphere--implicating a motor rather than a perceptual mechanism.     

Selective loss of complex-pitch or speech discrimination after unilateral lesion

Twenty-eight right-handed patients who suffered a single cerebrovascular accident in the distribution of either the left or right middle cerebral artery were tested on their ability to discriminate complex-pitch and speech stimuli presented dichotically. Whereas the left hemisphere lesion group was impaired in dichotic speech but not in dichotic complex-pitch discrimination, the right hemisphere lesion group was impaired in dichotic complex pitch but not in dichotic speech discrimination. Complex-pitch phenomena may provide a useful model for the study of auditory function in the nondominant hemisphere.     

Spelling dyslexia: A form of cross-cuing

A patient with spelling dyslexia maintained the ability to write, spell, and pronounce spelled nonsense words and words that require knowledge of orthographic rules of language. He was unable to perform grapheme-phoneme conversions except after naming the letter involved. We propose that he uses a letter-naming strategy to circumvent the disconnection of visual areas from the area of visual word images and that his letter-naming strategy represents a compensatory cross-cuing strategy.     

Alexia and agraphia with spared spelling and letter recognition abilities

A patient with alexia and agraphia had intact spelling and comprehension of spelled words and used a letter-naming strategy to read and write. We propose that there is a graphemic area important for distinguishing graphemic features and for programming movements used in writing. In this patient this area was not functioning or did not have access to the area of visual word imagés. Therefore, he used an ideographic letter-naming strategy to verbally circumvent his disability and gain access to the area of visual word images.     

Toward a theory of apractic syndromes

Theoretical development on human motor behavior has occurred largely independently of data on pathological movement disorders. This paper represents an initial attempt to interface findings from studies of apraxia and those of normal motor behavior with a view to formulating a common theoretical framework. Such an integration may ultimately aid in understanding the nature of skill acquisition and provide insights into the organization of motor systems. Three putative theoretical models of movement control are discussed with reference to apractic syndromes. The most commonly accepted view—the hierarchy—possesses properties such as linear transitivity and unidirectionality of information flow that render it inadequate in explaining functional plasticity in the central nervous system. The heterarchy, which incorporates reciprocity of function and circular transitivity, is a more likely candidate but suffers from an inability to regulate the degrees of freedom of the system. Our favored candidate is the coalition model which embodies heterarchical principles, but in addition, offers a solution to the problems of degrees of freedom and context for motor systems. Evidence is reviewed from apraxia of speech and limbs in terms of a coalitional style of control and an experimental approach, consonant with coalitional organization, is developed. We promote the claim that an understanding of apractic behavior—and perhaps motor systems in general—will benefit when clinicians and experimenters embrace a theory of context and constraints rather than a theory of commands as is currently in vogue.     

Multiple component agraphia in a patient with atypical cerebral dominance: an error analysis

A 52-year-old man with atypical cerebral dominance (left-handed for writing but mixed handedness for other tasks) suffered an extensive right hemisphere stroke, resulting in a combination of deficits that has not been previously reported. There were profound visual constructive and visual perceptual disturbances and a spatial agraphia, which were consistent with a nondominant hemisphere lesion. There was also a severe apraxic agraphia, which is typically associated with a dominant hemisphere lesion, but no other signs of dominant hemisphere dysfunction such as linguistic disturbance or limb-motor apraxia were present. This case serves to highlight the functional and anatomical relationship between handwriting and other forms of praxis; the various sources of error in letter formation; the need to be specific in labeling and describing agraphias ; and the role of a detailed analysis of writing errors in delineating the neuropsychological processes involved in handwriting.     

Apraxia in a patient with atypical cerebral dominance

Liepmann postulated that the left hemisphere of right-handed persons contains the "movement formulas" that control purposeful skilled movements of the limbs on both sides of the body. Accordingly, in right-handers apraxia should follow damage to the left hemisphere, whereas right hemisphere damage should not lead to apraxia. Although this is generally true, we recently examined a right-handed man who after a right hemispheric stroke became aphasic and apraxic with his nonparalyzed right hand. Our observations suggest that the right hemisphere of this right-handed man made a critical contribution to the planning and execution of skilled movements. This case provides evidence that right-handers should not be considered a homogeneous group in terms of cerebral motor dominance and that contrary to Liepmann's postulate, hemispheric dominance for the control of skilled movements does not entirely determine handedness.     

Structural complexity of motor patterns: A study on reaction times and movement times of handwritten letters

This study investigates the effects of psychomotor complexity on latencies for beginning to write single letters and numerals, and on times taken to complete the first strokes of letters and numerals. An experiment measured simple and choice reaction times for writing homogeneous graphemes (i.e., letters or numerals made up of similar strokes) and for writing heterogeneous graphemes (i.e., characters made up of dissimilar strokes). It was assumed that the motor programme for writing a letter is retrieved from long-term memory and briefly held, until it is used, in a short-term buffer store. The experiment examined the hypothesis that it is more difficult to read out homogeneous than heterogeneous stroke-structures from this store. For three out of four allographic grapheme pairs, homogeneous graphemes required longer initiation times or longer movement times for completion of the first stroke than did heterogeneous graphemes. These results are discussed in relation to recent findings on motor programming based on the use of reaction-time paradigms.     

Three variant forms of subcortical aphasia in Chinese stroke patients

Five right-handed patients with subcortical aphasia that involved the left hemisphere subcortical lesion sites were subjected to CT scans. Given their etiology, two cases were infarctions and the other three were hemorrhages. Two of the patients presented an involvement of the anterior limb of the internal capsule and of the basal ganglia and an anterior superior white-matter lesion extension. In both cases slow scanty dysarthric speech was noted; one had markedly impaired auditory comprehension, and the others were only partially impaired. The third patient presented an involvement of the posterior limb of the internal capsule and of the thalamus and a posterior paraventricular white-matter lesion extension. He had poor auditory comprehension, echolalia, and fluent speech. The last two patients presented an involvement of the internal capsule, the basal ganglia, and the thalamus and an anterior posterior paraventricular white-matter lesion extension. The latter two showed poor auditory comprehension with nonfluent and scanty spontaneous speech. The speech sounds were nonsensical monosyllabic words with a pattern similar to that of global aphasia. All patients had lasting right hemiplegia.     

Directional apraxia: A unitary account of mirror writing following brain injury or as found in normal young children

Mirror writing refers to the production of individual letters, whole words or sentences in reverse direction. Unintentional mirror writing has been observed in young children and brain‐damaged people and interpreted as the manifestation of different cognitive impairments. We report on a mirror writing patient following left hemisphere stroke and the mirror writing phenomena in one sample of children learning to write. We propose a unitary account of mirror writing as the unavailability of the appropriate movement direction representation, either because the right configuration has yet to be specified fully (children learning to write) or because of its damage (acquired brain injury). For this reason, we propose that the lack of directional information relevant to writing be labelled ‘directional apraxia’.     

大脑半球损害病人的汉字抄写研究

对３７例左、右半球病变者进行汉字抄写等测查。结果发现：１．大脑半球病变影响汉字抄写,但左和右半球病变者、皮层和皮层下病变者、失语和非失语病人的汉字抄写成绩无明显差异;２．无论有无失语,抄写与听写都无相关;与画图的关系取决于文化背景,即文化水平低者（无读写能力）汉字抄写与临摹画图高度相关,并受半测空间疏忽影响,而有读写能力者汉字抄写不受以上因素影响。由此推测：不同的汉字书写方式有着不同的神经机制;无汉字读写能力者抄写过程主要与右脑有关,而有读写能力者汉字抄写时双脑并用。     

Hemiplegic writing in severe aphasia

Three patients with severe aphasia and right hemiplegia are described who could write to dictation with the right arm using a limb prosthesis though agraphic with the "intact" left hand. The phenomenon of "hemiplegic writing" is explained as an access to submerged or preprocessing levels in language and action structure, through the use of older proximal motor systems. This interpretation has implications for our understanding of language and brain function, as well as for approaches to the treatment of patients with severe language disorders.