The thalamus and behavior: effects of anatomically distinct strokes.

Data on behavioral changes after thalamic lesion are sparse and largely based on isolated reports of patients with thalamic strokes. However, recent findings suggest that behavioral patterns can be delineated on the basis of the four main arterial thalamic territories. The anterior pattern consists mainly of perseverations and superimposition of unrelated information, apathy, and amnesia. After paramedian infarct, the most frequent features are disinhibition syndromes, with personality changes, loss of self-activation, amnesia, and, in the case of extensive lesions, thalamic "dementia"; this pattern may often be difficult to distinguish from primary psychiatric disorders, especially when neurologic dysfunction is lacking. After inferolateral lesion, executive dysfunction may develop but is often overlooked, although it may occasionally lead to severe long-term disability. After posterior lesion, whereas cognitive dysfunction with neglect and aphasia are well known, no specific behavioral syndrome has been reported. In the future, perfusion CT, functional MRI, and tractography using diffusion imaging in stroke patients may provide a better understanding of the role of the corticothalamic relationship in behavioral changes associated with thalamic stroke.