Thalamic Aphasia Research Articles

Fronto-thalamic networks and the left ventral thalamic nuclei play a key role in aphasia after thalamic stroke

Thalamic aphasia results from focal thalamic lesions that cause dysfunction of remote but functionally connected cortical areas due to language network perturbation. However, specific local and network-level neural substrates of thalamic aphasia remain incompletely understood. Using lesion symptom mapping, we demonstrate that lesions in the left ventrolateral and ventral anterior thalamic nucleus are most strongly associated with aphasia in general and with impaired semantic and phonemic fluency and complex comprehension in particular. Lesion network mapping (using a normative connectome based on fMRI data from 1000 healthy individuals) reveals a Thalamic aphasia network encompassing widespread left-hemispheric cerebral connections, with Broca’s area showing the strongest associations, followed by the superior and middle frontal gyri, precentral and paracingulate gyri, and globus pallidus. Our results imply the critical involvement of the left ventrolateral and left ventral anterior thalamic nuclei in engaging left frontal cortical areas, especially Broca’s area, during language processing.

Thalamic aphasia and SARS-CoV-2 infection (COVID-19)

Damage to the thalamus that results in thalamic aphasia, a language disability, is typically associated with vascular events, tumours, or degenerative disorders. There is growing interest in examining the relationship between COVID-19 and thalamic aphasia due to its association with several neurological problems, including strokes and minor lesions that may affect the thalamus. The virus's ability to induce hypercoagulable states and systemic inflammation, which may result in thalamic ischemic strokes and interfere with language processing networks, has sparked this interest. In light of the COVID-19 pandemic's continuous nature, more investigation is necessary to fully comprehend the virus's neurological effects, particularly any potential connections to thalamic aphasia, in order to diagnose and treat thalamic aphasia, forecast language recovery, and customise rehabilitation plans for those affected, including those recuperating from COVID-19-related neurological complications.

Topographic Mapping of Isolated Thalamic Infarcts Using Vascular and Novel Probabilistic Functional Thalamic Landmarks

PurposeWe aimed to re-evaluate the relationship between thalamic infarct (TI) localization and clinical symptoms using a vascular (VTM) and a novel functional territorial thalamic map (FTM).MethodsMagnetic resonance imaging (MRI) and clinical data of 65 patients with isolated TI were evaluated (female n = 23, male n = 42, right n = 23, left n = 42). A VTM depicted the known seven thalamic vascular territories (VT: inferolateral, anterolateral, inferomedial, posterior, central, anteromedian, posterolateral). An FTM was generated from a probabilistic thalamic nuclei atlas to determine six functionally defined territories (FT: anterior: memory/emotions; ventral: motor/somatosensory/language; medial: behavior/emotions/nociception, oculomotor; intralaminar: arousal/pain; lateral: visuospatial/somatosensory/conceptual and analytic thinking; posterior: audiovisual/somatosensory). Four neuroradiologists independently assigned diffusion-weighted imaging (DWI) lesions to the territories mapped by the VTM and FTM. Findings were correlated with clinical features.ResultsThe most frequent symptom was a hemisensory syndrome (58%), which was not specific for any territory. A co-occurrence of hemisensory syndrome and hemiparesis had positive predictive values (PPV) of 76% and 82% for the involvement of the inferolateral VT and ventral FT, respectively. Thalamic aphasia had a PPV of 63% each for involvement of the anterolateral VT and ventral FT. Neglect was associated with involvement of the inferolateral VT/ventral FT. Interrater reliability for the assignment of DWI lesions to the VTM was fair (κ = 0.36), but good (κ = 0.73) for the FTM.ConclusionThe FTM revealed a greater reproducibility for the topographical assignment of TI than the VTM. Sensorimotor hemiparesis and neglect are predictive for a TI in the inferolateral VT/ventral FT. The hemisensory syndrome alone does not allow any topographical assignment.

Involvement of Thalamocortical Networks in Patients With Poststroke Thalamic Aphasia.

Theories assume that thalamic stroke may cause aphasia because of dysfunction in connected cortical networks. This takes into account that brain functions are organized in distributed networks, and in turn, localized damage may result in a network disorder such as thalamic aphasia. With this study, we investigate whether the integration of the thalamus into specific thalamocortical networks underlies symptoms after thalamic stroke. We hypothesize that thalamic lesions in patients with language impairments are functionally connected to cortical networks for language and cognition. We combined nonparametric lesion mapping methods in a retrospective cohort of patients with acute or subacute first-ever thalamic stroke. A relationship between lesion location and language impairments was assessed using nonparametric voxel-based lesion-symptom mapping. This method reveals regions more frequently damaged in patients with compared with those without a symptom of interest. To test whether these symptoms are linked to a common thalamocortical network, we additionally performed lesion-network-symptom mapping. This method uses normative connectome data from resting-state fMRI of healthy participants (n = 65) for functional connectivity analyses, with lesion sites serving as seeds. Resulting lesion-dependent network connectivity of patients with language impairments was compared with those with motor and sensory deficits as baseline. A total of 101 patients (mean [SD] age 64.1 [14.6] years, 57 left, 42 right, and 2 bilateral lesions) were included in the study. Voxel-based lesion-symptom mapping showed an association of language impairments with damage to left mediodorsal thalamic nucleus lesions. Lesion-network-symptom mapping revealed that language compared with sensory deficits were associated with higher normative lesion-dependent network connectivity to left frontotemporal language networks and bilateral prefrontal, insulo-opercular, midline cingular, and parietal domain-general networks. Lesions related to motor and sensory deficits showed higher lesion-dependent network connectivity within the sensorimotor network spanning prefrontal, precentral, and postcentral cortices. Thalamic aphasia relates to lesions in the left mediodorsal thalamic nucleus and to functionally connected left cortical language and bilateral cortical networks for cognitive control. This suggests that dysfunction in thalamocortical networks contributes to thalamic aphasia. We propose that inefficient integration between otherwise undamaged domain-general and language networks may cause thalamic aphasia.

Gli esiti dello stroke ischemico del bambino: afasia e talamo

Left thalamic stroke in adults commonly results in thalamic aphasia, which is characterized by defects in lexical and semantic abilities associated with fluency and comprehension disabilities and intact word repetition. Although few cases have been reported, aphasia with similar features can also be present as a consequence of left-brain hemisphere stroke in children, which has usually a poorer prognosis if compared with that of the adult population. The paper reports the case of a 20-month-old female child that developed aphasia after an ischemic stroke that involved the left anteromedial thalamus. In these cases it is necessary to initiate an early rehabilitation treatment, possibly supported by augmentative and alternative communication techniques.

Clinical, imaging spectrum and outcome of PRES

Background: Posterior reversible encephalopathy syndrome (PRES), also called the acute hypertensive encephalopathy and reversible leukoencephalopathy syndrome (RPLS), is a clinico-radiological syndrome presents with rapid onset of headache, seizures, loss of consciousness, visual loss and characterized by white matter vasogenic edema affecting parietal and occipital lobes of the brain predominantly. However, the imaging findings are variable and may occur in other locations such as the frontal lobes, thalami, basal ganglia and brainstem. Objective: To study the clinical, imaging spectrum and final disease outcome of PRES Materials And Methods: The study was conducted on 52 patients who presented with clinical features and radiological diagnosis of PRES The clinical, imaging features and outcome of each patient were analyzed Results: The study was conducted on 52 patients with age range from below 10yrs to 65 yrs. Patients presented with various symptoms of which seizures(84.6%) is most common followed by headache(59.6%), vomiting (36.5%), visual disturbances(32.7%), altered sensorium(15.3%), thalamic aphasia (5.7%), hemiparesis(3.8%), paresthesia(3.8%), ataxia(3.8%), Quadriparesis (3.8%) and facial numbness (1.9%) is the least. On MR imaging typical parieto-occipital lobe involvement(98%)is seen in most of the cases, however other atypical regions involved were frontal lobe(52%),temporal lobe (17.3%), cerebellum (27%),thalamus (15.3%), brainstem (13.4%), basal ganglia (9.6%) and corpus callosum (1.9%) Lesions in atypical locations also had lesions in typical locations in all cases except in one case of central PRES. Dominant parieto-occipital pattern was seen in 32%,superior frontal sulcus pattern in 27%,holohemispheric pattern in 34.6%,Partial or asymmetric expression of primary patterns in 5.2% cases Diffusion restriction and postcontrast enhancement was seen in less than 25% cases. Complete resolution of symptoms was seen in 90.5% cases,3.8% of them succumbed to death. On follow up 5.7% of cases showed persistence of symptoms. Conclusion: PRES is a clinico-radiological syndrome with varied clinical and imaging spectrum. Involvement of atypical regions is not uncommon. However lesions in atypical locations often have lesions in typical locations also.Atypical imaging features like restricted diffusion and contrast enhancement are also not uncommon. Knowledge of atypical lesion location, atypical imaging features is necessary for the clinicians and radiologists not to misdiagnose PRES in the appropriate clinical setting

Subcortical Aphasia.

Subcortical structures have long been thought to play a role in language processing. Increasingly spirited debates on language studies, arising from as early as the nineteenth century, grew remarkably sophisticated as the years pass. In the context of non-thalamic aphasia, a few theoretical frameworks have been laid out. The disconnection hypothesis postulates that basal ganglia insults result in aphasia due to a rupture of connectivity between Broca and Wernicke's areas. A second viewpoint conjectures that the basal ganglia would more directly partake in language processing, and a third stream proclaims that aphasia would stem from cortical deafferentation. On the other hand, thalamic aphasia is more predominantly deemed as a resultant of diaschisis. This article reviews the above topics with recent findings on deep brain stimulation, neurophysiology, and aphasiology. The more recent approach conceptualizes non-thalamic aphasias as the offspring of unpredictable cortical hypoperfusion. Regarding the thalamus, there is mounting evidence now pointing to leading contributions of the pulvinar/lateral posterior nucleus and the anterior/ventral anterior thalamus to language disturbances. While the former appears to relate to lexical-semantic indiscrimination, the latter seems to bring about a severe breakdown in word selection and/or spontaneous top-down lexical-semantic operations. The characterization of subcortical aphasias and the role of the basal ganglia and thalamus in language processing continues to pose a challenge. Neuroimaging studies have pointed a path forward, and we believe that more recent methods such as tractography and connectivity studies will significantly expand our knowledge in this particular area of aphasiology.

Isolated thalamic stroke \u2013 analysis of clinical characteristics and asymmetry of lesion distribution in a retrospective cohort study

BackgroundMore patients with left-hemispheric than right-hemispheric strokes are admitted to hospitals. This is due to the easier recognition of cortical symptoms of the dominant-hemisphere. The thalamus constitutes a “micro-model” of the brain cortex with structure-function relationships known to be asymmetric, especially for language, memory, and visuo-spatial neurocognitive functions. The goal of this study was to characterize clinical symptoms and lesion distribution patterns of patients with acute isolated thalamic stroke (ITS) and to evaluate whether left-sided lesions are overrepresented in the hospital.MethodsWe performed a radiological database search including all brain scans performed in the Center of Neurology and Neurosurgery of the University Hospital Frankfurt between 2010 and 2019. A total of 5733 patients presenting with acute ischemic stroke were screened for ITS. Based on the MRI data, a lesion-overlap map was then generated to visualize the ITS lesion distribution.ResultsFifty-eight patients with unilateral ITS were identified. A majority of 38 patients (65.5%) showed left-sided ITS, whereas only 20 patients (34.5%) had right-sided ITS (p = 0.012). A particular difference was found for ITS lesions in the anterior thalamus of the anterolateral (n = 10) and anteromedian (n = 3) vascular territory, which were located in the left thalamus in 85% of patients (p = 0.011). No distribution difference was found for ITS lesions in the inferomedial (n = 7), central (n = 8), inferolateral (n = 23) and posterior (n = 7) vascular territories. The neuropsychological symptoms of thalamic aphasia (n = 8), neurocognitive impairment (n = 6), behavioral changes (n = 2), neglect (n = 2) and memory deficits (n = 3) were described predominantly in patients with left-sided ITS (p < 0.01). In contrast, other stroke symptoms (e.g., sensorimotor hemi-syndromes) did not reveal a side preponderance.ConclusionsThe better recognizability of left anterior compared to right anterior thalamic stroke symptoms may have an impact on the frequency in which ITS patients are admitted to the hospital. Clinical characteristics of right anterior thalamic stroke should therefore be further investigated, and diagnostic instruments towards their detection be identified.

Frequency and phenotype of thalamic aphasia

BackgroundAphasia is a recognized presenting symptom of thalamic lesions. Little is known regarding its frequency and phenotype. We examined the frequency of thalamic aphasia following Isolated Acute unilateral ischemic Lesions in the Thalamus (IALT) with respect to lesion location. Furthermore, we characterized thalamic aphasia according to affected language domains and severity.MethodsFifty-two patients with IALT were analyzed [44% female, median age: 73 years (IQR: 60–79)]. Lesion location was determined using 3-Tesla magnetic resonance imaging and categorized as anterior, posterior, paramedian or inferolateral. Standardized language assessment was performed using the validated Aphasia checklist (ACL) directly after symptom onset. Aphasia was defined as an ACL sum score of < 135 (range: 0–148).ResultsOf 52 patients, 23 (44%) fulfilled the ACL diagnostic criteria for aphasia, including nearly all lesion locations and both sides. The average ACL sum score was 132 ± 11 (range: 98–147). Aphasia was characterized by deficits within domains of complex understanding of speech and verbal fluency. Patients with left anterior IALT were most severely affected, having significantly lower ACL scores than all other patients (117 ± 13 vs. 135 ± 8; p < 0.001). In particular, aphasia in patients with left anterior IALT was characterized by significantly worse performance in the rating of verbal communication, verbal fluency, and naming (all p ≤ 0.001).ConclusionAphasia occurs in almost half of patients with focal thalamic lesions. Thalamic aphasia is not confined to one predefined thalamic lesion location, but language deficits are particularly pronounced in patients with left anterior IALT presenting with a distinct pattern.

Cognitive and linguistic dysfunction after thalamic stroke and recovery process: possible mechanism.

Thalamic stroke may result in cognitive and linguistic problems, but the underlying mechanism remains unknown. Especially, it is still a matter of debate why thalamic aphasia occasionally occurs and then mostly recovers to some degree. We begin with a brief overview of the cognitive dysfunction and aphasia, and then review previous hypotheses of the underlying mechanism. We introduced a unique characteristic of relatively transient “word retrieval difficulty” of patients in acute phase of thalamic stroke. Word retrieval ability involves both executive function and speech production. Furthermore, SMA aphasia and thalamic aphasia may resemble in terms of the rapid recovery, thus suggesting a shared neural system. This ability is attributable to the supplementary motor area (SMA) and inferior frontal cortex (IFG) via the frontal aslant tract (FAT). To explore the possible mechanism, we applied unique hybrid neuroimaging techniques: single-photon emission computed tomography (SPECT) and functional near-infrared spectroscopy (f-NIRS). SPECT can visualize the brain distribution associated with word retrieval difficulty, cognitive disability or aphasia after thalamic stroke, and f-NIRS focuses on SMA and monitors long-term changes in hemodynamic SMA responses during phonemic verbal task. SPECT yielded common perfusion abnormalities not only in the fronto–parieto–cerebellar–thalamic loop, but also in bilateral brain regions such as SMA, IFG and language-relevant regions. f-NIRS demonstrated that thalamic stroke developed significant word retrieval decline, which was intimately linked to posterior SMA responses. Word retrieval difficulty was rapidly recovered with increased bilateral SMA responses at follow-up NIRS. Together, we propose that the cognitive domain affected by thalamic stroke may be related to the fronto–parieto–cerebellar–thalamic loop, while the linguistic region may be attributable to SMA, IFG and language-related brain areas. Especially, bilateral SMA may play a crucial role in the recovery of word retrieval, and right language-related region, including IFG, angular gyrus and supramarginal gyrus may determine recovery from thalamic aphasia.

視床失語とは何か─無関連錯語から背景に迫る─

視床失語とは何か─無関連錯語から背景に迫る─

Transcranial Direct Current Stimulation in the Treatment of Subacute Post-Stroke Thalamic Aphasia.

Although many studies have demonstrated the effectiveness of transcranial direct current stimulation (tDCS) in improving speech recovery in post-stroke aphasia, as far as we know patients affected by thalamic aphasia have never been investigated. A 65-year-old man with severe non-fluent aphasia due to a left thalamic haemorrhagic stroke underwent intensive daily speech therapy combined with tDCS. The patient showed progressive improvement with almost complete recovery of his speech disorder, behavioural disinhibition and apathy. Our findings suggest that tDCS with concurrent speech therapy can be useful in patients with subcortical stroke lesions. The thalamus has a central role in the development of the higher functions, such as memory, regulation of behaviour and emotions, and language elaboration.Transcranial direct current stimulation (tDCS) applied to the cerebral cortex is a promising tool for improving language recovery in patients with post-stroke aphasia.Combined treatment with tDCS and speech and language therapy (SLT) was effective in a patient with subacute thalamic aphasia, who showed improvement in all aspects of linguistic and behavioural communication.

The Supplementary Motor Area Responsible for Word Retrieval Decline After Acute Thalamic Stroke Revealed by Coupled SPECT and Near-Infrared Spectroscopy.

Damage to the thalamus may affect cognition and language, but the underlying mechanism remains unknown. In particular, it remains a riddle why thalamic aphasia occasionally occurs and then mostly recovers to some degree. To explore the mechanism of the affected cognition and language, we used two neuroimaging techniques—single-photon emission computed tomography (SPECT), suitable for viewing the affected brain distribution after acute thalamic stroke, and functional near-infrared spectroscopy (f-NIRS), focusing on hemodynamic responses of the supplementary motor area (SMA) responsible for speech production in conjunction with the frontal aslant tract (FAT) pathway. SPECT yielded common perfusion abnormalities not only in the fronto–parieto–cerebellar loop, but also in the SMA, IFG and surrounding language-relevant regions. In NIRS sessions during a phonemic verbal fluency task, we found significant word retrieval decline in acute thalamic patients relative to age-matched healthy volunteers. Further, NIRS showed strong correlation between word retrieval and posterior SMA responses. In addition, follow-up NIRS exhibited increased bilateral SMA responses linked to improving word retrieval ability. The findings suggest that cognitive dysfunction may be related to the fronto–parieto–cerebellar loop, while language dysfunction is attributed to the SMA, IFG and language-related brain areas. SMA may contribute to the recovery of word retrieval difficulty and aphasia after thalamic stroke.

Wzgórze w świetle afazji podkorowych

The article is devoted to the specific nature of subcortical aphasia, with particular emphasis on thalamic aphasia. It describes the features of subcortical aphasias which make it possible to differentiate them from cortical aphasias and defines the characteristics of thalamic aphasia which are indicated by researchers seeking its constitutive features. The article also discusses the anatomic aspects of the thalamus and the latest reports on the functions it performs in the language processing process through thalamocortical networks.

"Thalamic aphasia" after stroke is associated with left anterior lesion location.

Aphasic symptoms are typically associated with lesions of the left fronto-temporal cortex. Interestingly, aphasic symptoms have also been described in patients with thalamic strokes in anterior, paramedian or posterolateral location. So far, systematic analyses are missing. We conducted a retrospective analysis of consecutive patients admitted to our tertiary stroke care center between January 2016 and July 2017 with image-based (MRI) proven ischemic stroke. We evaluated stroke lesion location, using 3-T MRI, and presence of aphasic symptoms. Out of 1064 patients, 104 (9.8%) presented with a thalamic stroke, 52 of which (4.9%) had an isolated lesion in the thalamus (ILT). In patients with ILT, 6/52 had aphasic symptoms. Aphasic symptoms after ILT were only present in patients with left anterior lesion location (n = 6, 100% left anterior vs. 0% other thalamic location, p < 0.001). Aphasic symptoms in thalamic stroke are strongly associated with left anterior lesion location. In thalamo-cortical language networks, specifically the nuclei in the left anterior thalamus could play an important role in integration of left cortical information with disconnection leading to aphasic symptoms.

Thalamic Lesions and Aphasia or Neglect

When the thalamus is damaged, not only are there neurological symptoms such as sensory impairment, hemianopia, or motor control disorders, but there are also various neuropsychological symptoms. We discuss the basic anatomy and function of the thalamus followed by a discussion of thalamic aphasia and hemineglect. Subcortical lesions in patients with hemineglect involved the anatomical network directly linked to the superior temporal gyrus. Furthermore, the pulvinar, part of the thalamus, may be associated with hemineglect. General linguistic tasks activated the thalami, depending on the difficulty, as well as the frontal and temporal lobes. The thalamus may play a role in language and be involved in the activation of cortical language areas, and in the linguistic integration function via verbal memory and semantic mechanisms. Thalamic lesions are associated with aphasia and hemineglect. It is possible the mechanisms and such neuropsychological may be different depending on the size and site of the thalamic lesion.

Unusual Presentation of Childhood Reversible Angiopathy: Aphasia due to Acute Bilateral Paramedian Thalamic Infarct

AbstractAn 8-year-old right-handed girl manifested aphasia after bilateral thalamic infarcts. The features of thalamic aphasia are similar to that of previously reported patients with thalamic lesions. Paucity of speech, reduced voice volume, some paraphasia, and severe dysgraphia were present, but comprehension and repetition were preserved. Thalamic aphasia is usually associated with left thalamic lesions. Our patient also had spatial neglect and anosognosia probably due to right thalamic infarction. She had recovered near-normal speech after rehabilitation.

The Implication of the Thalamus in Speech Disturbance in a Boy with Rolandic Epilepsy

Transient oromotor deficits in children with rolandic epilepsy (RE) have been described in literature. It has been reported that thalamic aphasia can be caused by thalamic infarction or hemorrhage; however, it has never been reported that thalamic aphasia can be caused by epileptic disorders. Here, we describe a 6-year-old right-handed boy who showed transient oromotor deficits and speech disturbance with worsening of both epileptic seizure and paroxysmal discharges on electroencephalogram. He had paucity of spontaneous speech, feeble speech, arrest of speech, and anomia, but his repetition skills were intact. A single-photon emission computed tomography (SPECT) scan using technetium-99m hexamethyl propylene amine oxime (99mTc-HMPAO) to measure regional cerebral blood flow showed a reduction in flow in the left thalamus and ipsilateral frontotemporal areas, which appeared concurrently with the speech dysfunction. We suggest that speech disturbance such as thalamic aphasia, which is similar to the symptoms of Landau-Kleffner syndrome, may occur due to epileptic disorders such as RE. It may be possible to miss speech disturbance implicated in the thalamus in cases complicated by oromotor dysfunction. It is important that speech disturbance implicated in the thalamus is not overlooked in patients with RE showing an atypical course.

Dominant Thalamus and Aphasia

Many studies have shown that lesions of the dominant thalamus precipitate language disorders in a similar manner to transcortical aphasias, in a phenomenon known as "thalamic aphasia." In some cases, however, aphasia may not occur or may appear transiently following thalamic lesions. Furthermore, dominant thalamic lesions can produce changes in character, as observed in patients with amnesic disorder. Previous work has explored the utility of thalamic aphasia as a discriminative feature for classification of aphasia. Although the thalamus may be involved in the function of the brainstem reticular activating system and play a role in attentional network and in memory of Papez circuit or Yakovlev circuit, the mechanism by which thalamic lesion leads to the emergence of aphasic disorders is unclear. In this review, we we survey historical and recent literature on thalamic aphasia in an attempt to understand the neural processes affected by thalamic lesions.

Teaching Neuro Images : Thalamic aphasia syndrome

An 83-year-old right-handed woman presented with sudden right-sided hemiparesis, somnolence, and loss of normal speech. Speech was nonfluent with semantic paraphasias and word-finding difficulties. Word repetition and comprehension were normal. MRI brain showed an area of restricted diffusion in the left thalamus consistent with acute infarction (figure 1). Speech fluency returned to normal after 2 days with occasional dysnomia and paraphasias.