A dysexecutive syndrome of the medial thalamus

Abstract

Thalamic stroke is associated with neurological and cognitive sequelae. Resulting neuropsychological deficits vary with the vascular territory involved. Whereas sensory, motor and memory deficits following thalamic stroke are comparatively well characterized, the exact relationship between executive dysfunction and thalamic damage remains more ambiguous.To assess the pattern of executive-cognitive deficits following thalamic stroke and its possible association with distinct thalamic nuclei, 19 patients with focal thalamic lesions were examined with high-resolution structural imaging and neuropsychological testing. Twenty healthy individuals served as controls. Patient MRIs were co-registered to an atlas of the human thalamus. Lesion overlap and subtraction analyses were used for lesion-to-symptom mapping.In eight patients (42.1%), neuropsychological assessment demonstrated a disproportionate deficit in the Wisconsin Card Sorting Test (WCST), while other executive and memory functions were much less affected. Subtraction analysis revealed an area in the left medial thalamus, mainly consisting of the centromedian and parafascicular nuclei (CM–Pf complex) that was damaged in these patients and spared in patients with normal WCST performance. Thus, damage to the CM–Pf complex may yield a distinct dysexecutive syndrome in which deficient maintenance and shifting between cognitive sets predominates. We hypothesize that the CM–Pf complex may contribute to maintenance and shifting of cognitive sets by virtue of its dense connections with the striatum. The pattern of executive dysfunction following thalamic stroke may vary considerably with lesion location.