Preserved repetition in thalamic afasia. A pathophysiological hypothesis

Area of Science:

• Neuroscience
• Neurology
• Neuroimaging

Background:

• Thalamic aphasia is characterized by language deficits, with word repetition typically spared.
• The underlying mechanisms of thalamic aphasia and the preservation of repetition remain unclear.

Observation:

• A case study of severe aphasia with preserved repetition following a left thalamic hemorrhage.
• MRI revealed a left thalamic lesion and reduced fractional anisotropy in the centrum semiovale.
• FDG-PET demonstrated significant hypometabolism in the left cerebral hemisphere, sparing certain areas like the superior and transverse temporal gyri.

Findings:

• Extensive cortical hypometabolism, attributed to diaschisis, likely contributed to the severe aphasia.
• Relatively preserved metabolism in the superior and transverse temporal gyri, and Broca's area, may explain the preserved ability to repeat words.

Implications:

• Primary sensory functions might be less reliant on thalamic connections compared to heteromodal and paralimbic regions.
• Understanding these patterns can refine our comprehension of language processing and recovery after thalamic stroke.