Apraxia due to a pathologically documented thalamic infarction

We report a pathologically documented case of infarction of the dominant thalamus with extensive involvement of the ventral lateral, ventral posterolateral, and lateral posterior nuclei and some involvement of the pulvinar. This patient exhibited linguistic impairment with features fairly typical for thalamic lesions. He also demonstrated a severe ideomotor apraxia. The preservation of repetition, syntax, and implicit memory despite severe naming deficits in patients with thalamic lesions suggests the possibility that thalamic involvement in cognitive function involves processes underlying declarative as opposed to nondeclarative (eg, implicit or procedural) memory. The occurrence of apraxia with thalamic lesions may be consistent with this hypothesis if it is accepted that only actual tool use approaches a pure skill that involves only nondeclarative memory, while other aspects of praxis implicate declarative memories.