Factors behind poor cognitive outcome following a thalamic stroke

Objective Thalamic strokes produce a range of neurological, cognitive, and behavioral symptoms depending on the thalamic nuclei involved. While thalamic strokes are traditionally associated with severe cognitive deficits, recent studies suggest more modest impairments. This study aims to identify the factors that influence the severity of cognitive impairment following thalamic stroke. Methods We recruited 40 patients (median age 51) with chronic isolated thalamic stroke and 45 healthy subjects. All subjects underwent neuroimaging and neuropsychological testing. Cluster and principal component analyses were used to discriminate patients from healthy subjects based on cognitive performance. Disconnectome maps and cortical thickness were analyzed to understand the distant impact of thalamic strokes. Results Two cognitive profiles emerged. Cluster 1 included mostly healthy subjects (n = 43) and patients with no or minor deficits (n = 20); Cluster 2 included patients (n = 19) and 2 healthy subjects with severe deficits of verbal memory, executive functions, and attention. Cluster 1 included all patients with right thalamic stroke. Cluster 2 included all patients with bilateral stroke or mammillothalamic tract disruption. Patients with left-sided stroke were equally divided between Cluster 1 and 2. Other significant differences included age, education, interthalamic adhesion disruption, lesion volume, and location. Disconnectome maps showed larger disruptions of the anterior thalamic projection in patients with left-sided stroke of Cluster 2. Interpretation Contrary to common expectations, our findings indicate that many patients with thalamic stroke have relatively good cognitive outcomes. In contrast, we identified some of the factors behind poor outcomes that may help clinicians.