Thalamic Aphasia: a Review

Abstract

Purpose of Review Thalamic aphasia is a rare language disorder resulting from lesions to the thalamus. While most patients exhibit mild symptoms with a predominance of lexical-semantic difficulties, variations in phenotype have been described. Overall, the exact mechanisms of thalamic aphasia await empirical research. The article reviews recent findings regarding phenotypes and possible underlying mechanisms of thalamic aphasia. Recent Findings Variations in phenotype of thalamic aphasia may be related to different lesion locations. Overall, the thalamus’ role in language is thought to be due to its involvement in cortico-thalamic language networks with lesioning of certain nuclei resulting in the diachisis of otherwise interconnected areas. Its possible monitoring function in such a network might be due to its different cellular firing modes. However, no specific evidence has been collected to date. Summary While recent findings show a more distinct understanding of thalamic aphasia phenotypes and possible underlying mechanisms, further research is needed. Additionally, as standard language testing might oftentimes not pick up on its subtle symptoms, thalamic aphasia might be underdiagnosed.

A modified neural circuit framework for semantic memory retrieval with implications for circuit modulation to treat verbal retrieval deficits

“…In particular, lesions in the pulvinar and anterior/ventrolateral thalamic nuclei have been associated with deficits in lexical‐semantic retrieval (as reported in thalamic aphasia; Fritsch et al., 2022 ; Radanovic & Almeida, 2021 ; Segal et al., 2003 ). Pathophysiologically, the deficits may be the result of more direct interference with thalamic function (Crosson, 2013 , 2021 ; Wang et al., 2021 ) or indirect impact via diaschisis mediated by cortical hypoperfusion/hypometabolism (e.g., pre‐SMA hypoperfusion in Fritsch et al., 2022 ; Obayashi, 2020 ). These thalamic nuclei are central for relaying and integrating information streams between multiple cortical regions, as well as selecting and engaging relevant on‐line lexico‐semantic information for word production (see Crosson, 2013 , 2021 ).…”

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