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

Background More 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. Methods We 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. Results Fifty-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. Conclusions The 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

Background Aphasia 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. Methods Fifty-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). Results Of 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). Conclusion Aphasia 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

<abstract> <p>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.</p> </abstract>

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

Background: 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. Patient and method: 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. Results: The patient showed progressive improvement with almost complete recovery of his speech disorder, behavioural disinhibition and apathy. Conclusions: Our findings suggest that tDCS with concurrent speech therapy can be useful in patients with subcortical stroke lesions.

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.

Preserved repetition in thalamic afasia. A pathophysiological hypothesis

ABSTRACT. The ability to repeat words is almost always preserved in thalamic aphasia. The pathophysiology of both thalamic aphasia and preservation of repetition are not fully understood. In a case of severe aphasia with preserved repetition after a left thalamic hemorrhage, MRI disclosed left thalamic lesion and loss of fractional anisotropy in the left centrum semiovale. FDG-PET showed severe hypometabolism in the left cerebral hemisphere, except for superior and transverse temporal gyri, calcarine fissure and frontopolar regions. Primary sensory function may be less functionally dependent on thalamic connections than heteromodal and paralimbic areas, which have connections with several thalamic nuclei. The extensive cortical hypometabolism due to diaschisis may have been responsible for the severity of the aphasia, whereas the less severe reduction of metabolism in the superior and transverse temporal gyri, and also, albeit less evident, in Broca’s area, might explain the preservation of repetition.

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

An 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.