FUNCTIONAL BRAIN IMAGING IN APRAXIA

Background: An extensive literature describes structural lesions in ap raxia, but few studies have used functional neuroimaging. We used posi tron emission tomography (PET) to characterize relative cerebral gluco se metabolism in a GS-year-old, right-handed woman with progressive de cline in ability to manipulate objects, write, and articulate speech. Objective: To characterize functional brain organization in apraxia. D esign and Methods: The patient underwent a neurological examination, n europsychological testing, magnetic resonance imaging, and fludeoxyglu cose F 18 PET. The patient's magnetic resonance image was coregistered to her PET image, which was compared with the PET images of 7 right-h anded, healthy controls. Hemispheric regions of interest were normaliz ed by calcrine cortex. Results: Except for apraxia and mild grip weakn ess, results of the neurological examination were normal. There was id eomotor apraxia of both hands (command, imitation, and object) and buc cofacial apraxia. The patient could recognize meaningful gestures perf ormed by the examiner and discriminate between his accurate and awkwar d pantomime. The magnetic resonance image showed moderate generalized atrophy and mild ischemic changes. Positron emission tomographic scans showed abnormal fludeoxyglucose F 18 uptake in the posterior frontal, supplementary motor, and parietal regions, the left affected more tha n the right. Focal metabolic deficit was present in the angular gyrus, an area hypothesized to store conceptual knowledge of skilled movemen t. Conclusions: Greater parietal than frontal physiological dysfunctio n and preserved gesture recognition are not consistent with the theory that knowledge of limb praxis is stored in the dominant parietal cort ex. Gesture comprehension may be more diffusely distributed.