Abstract
Limb apraxia is a disorder of skilled movement characterized by the inability to use tools and pantomime or imitate gestures. Apraxia most often results from left hemisphere lesions and is frequently accompanied by aphasia. Here we present the case of an 82 year old, left-handed man seen one month after an ischemic stroke affecting the right frontal lobe and basal ganglia. Assessment revealed a marked limb apraxia, including impairments to pantomime, imitation, and conceptual praxis tasks. Language testing revealed a minor anomic aphasia with relatively preserved speech production and comprehension, but a marked agraphia and alexia. The patient also demonstrated difficulty with working memory and constructing drawings of common objects from memory. We argue that this is a case of "crossed apraxia" in which lateralization for praxis control, typically involving the left hemisphere, is controlled by the right hemisphere. Despite crossed praxis, this patient's preserved verbal comprehension and speech implies these functions are controlled by the intact left hemisphere. The deficits observed on conceptual praxis tasks suggest that unlike verbal comprehension action comprehension like praxis is subserved by the right hemisphere. Although relatively rare, other cases of "crossed-apraxia" have been reported in the literature, and provide insight into the potential dissociation among the neural representations underlying praxis, language, reading and writing.Acknowledgments: Funded by Heart and Stroke Foundation of Ontario (EAR and SEB)