A Literature Review on Neuroanatomical Correlates in Hangul Agraphia

Right and left cortical lesions asymmetrically alter cerebrovascular permeability in the rat

Objective. To examine the relationship between the volume of the middle cerebral artery stroke lesion and functional status in the subacute phase of stroke. Methods. Infarctvolumes of 94 patients with a 1st middle cerebral artery stroke assessed on conventional MRI scans obtained in the 2nd week poststroke were related to a clinical measure of stroke severity (National Institutes of Health Stroke Scale [NIHSS]) and to functional status: motor impairment (Motricity Index [MI]) and limitation in activities (Barthel Index [BI] and modified Rankin Scale). Separate correlations were computed for patients with large (>30 ml) and small (30 ml) lesions, and to investigate the influence of lesion location on the relationship between volume and functional status, correlations were computed for patients with left and right hemisphere lesions and for patients with cortical and subcortical lesions. Results. Lesion volume correlated strongly with NIHSS scores (R = 0.61) and moderately with the patient’s functional status (MI [R between -0.42 and - 0.49], BI [R = -0.43], and Modified Rankin Scale [R = 0.45]). Right hemisphere lesions and cortical lesions had a stronger correlation with functional status. In patients with small lesion volumes (0-30 ml), no relationship between lesion volumes and functional status was seen at all. Conclusions. Lesion volume is moderately to strongly related to the functional status in the 2nd week poststroke.

51 children with localized cerebral lesions were investigated with the British Ability Scales, Wechsler test, Porteus Mazes, Conners Teacher Rating Scale, and computerized tomography. The extent of the lesions was quantitatively determined. The IQ was 10 points lower in the left hemispheric lesions, although the right hemispheric lesions were larger. When corrected for size of lesions, the IQ is 17 points higher (p less than 0.05) in children with right than with left hemispheric early lesions. The children with left hemispheric lesions had also significantly more behavioural problems (Conners Scale). Children with bilateral lesions had 15 points lower IQ than those with unilateral lesions, although from the slightly larger extent one could expect only 3 points difference. There was no influence of hemiparesis or of epilepsy of the IQ independent of the extent of lesion. There was more plasticity of the hemisphere than of the lobes as shown by Wisconsin Card Sorting data. The higher density of mental capacities in the left cerebral hemisphere of man is explained by more efficient programs, and more dense packing of functions due to more training of the left cerebral hemisphere.

The capacity to reacquire motor skills lost after a stroke is crucial to promote upper-limb motor recovery, but the impact of lesion location on motor skill acquisition and the underlying neurophysiological mechanisms remain uncertain. Cortico-spinal excitability, measured with transcranial magnetic stimulation, provides information about the functional integrity of the cortico-spinal tract, a structure essential for upper-limb motor function and recovery post-stroke. Cortico-spinal excitability is a biomarker that has been used to predict upper-limb motor recovery and guide interventions post-stroke. We investigated associations between different cortico-spinal excitability measures of facilitation and inhibition and the capacity to improve the performance of a short-term visuomotor adaptation task that required accurate force modulation with the most affected hand in 103 individuals with either cortical (n = 34) or subcortical (n = 69) lesions. Cortico-spinal excitability measures included resting motor threshold, resting and active excitability derived from the amplitude of motor evoked potentials, cortical silent period, as well as intracortical facilitation and short intracortical inhibition. Both lesion groups showed similar rates of motor skill performance but individuals with subcortical lesions exhibited more impairment in the most affected hand and lower excitability in the ipsilesional hemisphere inferred from a reduced amplitude of motor evoked potentials elicited during an active muscle contraction. Exploratory analyses revealed that upper-limb impairments and reductions in active and resting excitability in the ipsilesional hemisphere were exacerbated in individuals with subcortical lesions affecting the cortico-spinal tract. In individuals with cortical lesions, better motor skill performance was associated with lower motor thresholds (β = −0.25, 95% CI [−0.47, −0.03]; P = 0.024) and higher intracortical inhibition (β = −3.93, 95% CI [−6.89, −0.98]; P = 0.011) in the ipsilesional hemisphere. In contrast, in individuals with subcortical lesions motor skill performance was associated with smaller motor evoked potentials (β = −4.46, 95% CI [−8.54, −0.38]; P = 0.033), less intracortical inhibition (β = 3.45, 95% CI [0.34,6.56]; P = 0.030) and higher facilitation (β = 1.34, 95% CI [0.15,2.54]; P = 0.028) in the ipsilesional hemisphere. Associations with intracortical inhibition and facilitation in the subcortical group were driven primarily by observations from individuals with lesions affecting the cortico-spinal tract. Importantly, no associations were found in the contralesional hemisphere. Reinforcing the existence of lesion-specific neurophysiological reorganization patterns, individuals with cortical and subcortical lesions show divergent associations between cortico-spinal excitability and the capacity to improve the performance of a short-term visuomotor adaptation task. The use of cortico-spinal excitability as a biomarker to guide motor recovery interventions such as non-invasive brain stimulation or to predict upper-limb recovery post-stroke should consider lesion location.

Mental training appears to be an attractive tool in stroke rehabilitation. The objective of this study was to investigate whether any differences in the processing of action observation and imagery might exist between patients with left and right hemisphere subcortical strokes. Eighteen patients with strictly subcortical stroke (nine right-hemispheric) underwent a functional magnetic resonance imaging (fMRI) study with an experimental paradigm in which motor acts had to be observed and/or imagined from a first person perspective. Changes in hemodynamic activity were measured using fMRI. The activity level was found to be higher in the non-lesioned compared to the lesioned hemisphere. Patients with lesions in the left hemisphere had a higher activation level in visual (fusiform and lingual gyri), superior temporal areas and dorsal premotor regions across all performed comparisons than those with right hemisphere lesions. Furthermore they had more vivid imagery experiences and lower scores on the Stroke Impact Scale. Patients with left hemisphere subcortical lesions recruit more cortical regions in the processing of action pictures and videos. This recruitment was further enhanced during imagery. This is most likely related to the fact that the lesion touched the dominant hemisphere.

Correlation between lesion location and dysphagia characteristics in post-stroke patients

A number of cortical and subcortical areas are involved in the control of saccades and smooth pursuit, and lesions affecting these areas result in various ocular motor syndromes. Most of these syndromes are relatively subtle and have to be ascertained using recordings, because other brain areas may largely take over the function of a damaged area. Anterior cortical, posterior cortical, large and bilateral cortical, subcortical and degenerative cerebral lesions are successively reviewed. In the anterior part of the cerebral hemisphere, the frontal eye field (FEF), supplementary eye field (SEF) and prefrontal cortex (PFC), i.e. area 46 of Brodmann, control eye movements. The FEF appears to be principally involved in the control of intentional saccades, in particular those made with a retinotopic reference system, and in smooth pursuit. The SEF could control saccades made with a spatiotopic reference system, and sequences of saccades (requiring a temporal working memory). The PFC could control the inhibition of unwanted reflexive saccades, and be involved in spatial memory used for programming all types of memory-guided saccades. In the posterior part of the cerebral hemisphere, the parietal eye field (PEF) is involved in the triggering of reflexive visually guided saccades, and the middle temporal (MT) and medial superior temporal (MST) areas in smooth pursuit. Acute and large unilateral lesions usually result in transitory ipsilateral conjugate eye deviation. Bilateral lesions affecting both the FEF and the PEF result in severe saccade and smooth-pursuit paresis, whereas bilateral posterior temporoparietal lesions result in Balint's syndrome, consisting of both eye movement and visual-attention abnormalities. Subcortical lesions also result in various eye movement abnormalities, which have been little documented to date. Lastly, degenerative cerebral diseases, such as Alzheimer's disease, Parkinson's disease, Huntington's disease, progressive supranuclear palsy and corticobasal degeneration result in more or less severe eye movement disturbances. Eye movement recordings may contribute to early differential diagnosis of some of these degenerative diseases.

Background: A great deal of research suggests that both the left hemisphere (LH) and right hemisphere (RH) contribute to the resolution of lexically ambiguous words. If this is indeed the case, then patients with left (LHD) or right hemisphere brain damage (RHD) should exhibit deficits in ambiguity resolution. Although several studies have explored this issue, there is still little consensus regarding the exact nature of the patients' deficits. Moreover, the focus of most studies has been on ambiguity resolution in short, single-sentence contexts, so less is known about the impact of LH and RH damage on ambiguity resolution in larger contexts. Aims: The goal of the present study was to investigate sensitivity to a global (i.e., two-sentence) context during lexical ambiguity resolution in LHD and RHD patients relative to a group of control participants with no neurological impairment. Control participants were expected to activate only contextually appropriate meanings. In contrast, LHD patients were expected to have difficulty activating ambiguous word meanings or selecting contextually appropriate meanings. RHD patients were expected to have difficulty using context or suppressing contextually inappropriate meanings. Methods & Procedures: Three groups of participants took part in this study: 10 LHD patients with nonfluent aphasia, 8 RHD patients, and 9 age-matched control participants. A cross-modal sentence priming task was employed where participants first listened to a biased two-sentence passage ending in an ambiguous word. After each passage a visual target word, related to either the first or second meaning of the ambiguous word, was presented for lexical decision. Reaction time data were analysed using a repeated-measures ANOVA. Priming effects were tested by way of planned comparisons. Outcomes & Results: The performance of both patient groups differed markedly from that of the control group, who only showed priming for contextually appropriate meanings. The LHD patients did not exhibit any significant priming of ambiguous word meanings, whereas the RHD patients only showed priming for the most frequent or dominant meaning of ambiguous words (e.g., the “animal” meaning as opposed to the “emblem” meaning of seal) regardless of context. Conclusions: Both LH and RH damage can disrupt the process of ambiguity resolution in a global context. Specifically, LH damage is argued to impair the degree of activation of ambiguous word meanings or the time course of meaning activation, while RH damage seems to impair the use of context, leading to frequency-based meaning activation.

Impaired ability to shift weight onto the non-paretic leg in right-cortical brain-damaged patients

Background: Recent research suggests that damage to right hemisphere regions homotopic to the left hemisphere language network affects language abilities to a greater extent than previously thought. However, few studies have investigated acute disruption of language after lesion to the right hemisphere. Here, we examined lesion correlates of acute speech deficits following left and right hemisphere ischemic stroke to clarify the neural architecture underlying early language dysfunction. Methods: We retrospectively analyzed 410 patients (225 left, 185 right hemisphere lesions) from the Stroke Outcome Optimization Project dataset. Presence and severity of speech deficits was measured using the National Institute of Health Stroke Scale Best Language subscore within 48 h of onset. Manual lesion masks were derived from clinical MRI scans and normalized to MNI space. Lesion-symptom mapping was conducted using voxelwise and region-of-interest analyses with permutation correction (5000 iterations; p < 0.05), controlling for total lesion volume. Results: Speech deficits were observed in 53.7% of the cohort (58.2% left, 48.1% right hemisphere lesions). In the full sample, the presence of speech deficits was associated with bilateral subcortical and perisylvian damage, including the external and internal capsules, insula, putamen, and superior fronto-occipital fasciculus. Severity of speech deficits localized predominantly to left hemisphere structures, with peak associations in the external capsule (Z = 6.39), posterior insula (Z = 5.64), and inferior fronto-occipital fasciculus (Z = 5.43). In the right hemisphere cohort, the presence and severity of speech deficits were linked to homologous regions, including the posterior insula (Z = 3.70) and external capsule (Z = 3.63), although with smaller effect sizes relative to the left hemisphere cohort. Right hemisphere lesions resulted in milder deficits despite larger lesion volumes compared with left hemisphere lesions. Conclusions: Acute speech impairment following right hemisphere stroke is associated with damage to a homotopic network encompassing perisylvian cortical and subcortical regions analogous to the dominant left hemisphere language network. These findings demonstrate that damage to the right hemisphere consistently results in acute speech deficits, challenging the traditional left-centric view of post-stroke speech impairment. These results have important implications for models of bilateral language representation and the neuroplastic mechanisms supporting language recovery.

Manic-depressive and pure manic states after brain lesions

MRI has superior capabilities for the detection of cerebral infarcts compared with CT. CT was used to locate infarcts in most previous studies of atherothrombotic middle cerebral artery (MCA) territory infarcts. Thus, there was a possibility of missing concomitant small infarcts. More accurate identification of topographic lesions in MCA territory with MRI may help to establish the pathogenesis of stroke. The present study determines topographic patterns, distribution of vascular lesions, and probable mechanisms. Forty-two patients with MCA territory infarcts on routine MRI and no major cause of cardioembolism were studied with conventional angiography or MR angiography. The topographic patterns seen on MRI were subdivided into 4 groups: cortical border-zone infarcts (n=6), pial territory infarcts without insular infarct (n=3), pial territory infarcts with insular infarct (n=14), and large subcortical infarcts (n=19). Of 6 patients with cortical border-zone infarcts, 4 had concomitant small cortical or subcortical multiple lesions. Angiography showed intrinsic MCA disease in 4 patients. Of 3 patients with pial territory infarcts without insular infarct, 2 also had small multiple centrum ovale lesions. All had intrinsic MCA disease. Pial territory infarcts with partial or whole insular lesions were present in 10 and 4 patients, respectively. Five patients had additional multiple cortical or subcortical lesions. Ten patients had intrinsic MCA disease. Of the 19 patients with large subcortical infarcts, 12 had centrum ovale infarcts, and 4 had both basal ganglia and centrum ovale lesions. Ten had concomitant small cortical or subcortical lesions. Six patients had intrinsic MCA disease. Similar vascular lesions induce different topographic patterns in MCA territory infarction, which are related to individual vascular variability, degree of primary and secondary collateralization, and pathogenesis of infarcts. Our study indicates that concomitant small cortical or subcortical lesions are also commonly associated findings in diverse patterns of MCA territory infarction, which can mostly be explained by probable embolic mechanism.

Background and Purpose: Preliminary reports suggest that central stimulation may enhance the effect of conventional physical therapies after stroke. This pilot study examines the safety and methodology of using transcranial direct stimulation (tDCS) with robot-assisted arm training (AT), to inform planning a larger randomised controlled trial. Subjects: Ten patients, after an ischaemic stroke 4–8 weeks before study onset, no history of epilepsy, participated. Eight had a cortical lesion and 2 had subcortical lesions: all had severe arm paresis and, co-incidentally, 5 had severe aphasia. Methods: Over six weeks, they received thirty 20 min-sessions of AT. During the first 7 minutes, 1.5mA of tDCS was applied, with the anode over the lesioned hemisphere and the cathode above the contralateral orbit. Arm and language impairment were assessed with the Fugl-Meyer motor score (FM, full range 0–66) and the Aachener Aphasie Test. Results: No major side effects occurred. Arm function of three patients (two with a subcortical lesion) improved significantly, with FM scores increasing from 6 to 28, 10 to 49 and 11 to 48. In the remaining seven patients, all with cortical lesions, arm function changed little, FM scores did not increase more than 5 points. Unexpectedly, aphasia improved in 4 patients. Conclusions: These procedures are safe, and easy to use in a clinical setting. In future studies, patients should be stratified by degree of arm weakness and lesion site, also the unexpected aphasia improvement warrants following-up.

Revisiting Lenneberg’s Hypotheses About Early Developmental Plasticity: Language Organization After Left-Hemisphere Perinatal Stroke

Laryngeal Closure during Swallowing in Stroke Survivors with Cortical or Subcortical Lesion