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January 1998

Functional Brain Imaging in Apraxia

Author Affiliations

From the Departments of Neurology (Drs Kareken and Farlow), Psychiatry (Drs Kareken and Unverzagt), and Radiology (Drs Caldemeyer and Hutchins), Indiana University School of Medicine, and the Richard L. Roudebush Veterans Affairs Medical Center (Dr Kareken), Indianapolis.

Arch Neurol. 1998;55(1):107-113. doi:10.1001/archneur.55.1.107

Background  An extensive literature describes structural lesions in apraxia, but few studies have used functional neuroimaging. We used positron emission tomography (PET) to characterize relative cerebral glucose metabolism in a 65-year-old, right-handed woman with progressive decline in ability to manipulate objects, write, and articulate speech.

Objective  To characterize functional brain organization in apraxia.

Design and Methods  The patient underwent a neurological examination, neuropsychological testing, magnetic resonance imaging, and fludeoxyglucose 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-handed, healthy controls. Hemispheric regions of interest were normalized by calcrine cortex.

Results  Except for apraxia and mild grip weakness, results of the neurological examination were normal. There was ideomotor apraxia of both hands (command, imitation, and object) and buccofacial apraxia. The patient could recognize meaningful gestures performed by the examiner and discriminate between his accurate and awkward 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 than the right. Focal metabolic deficit was present in the angular gyrus, an area hypothesized to store conceptual knowledge of skilled movement.

Conclusions  Greater parietal than frontal physiological dysfunction and preserved gesture recognition are not consistent with the theory that knowledge of limb praxis is stored in the dominant parietal cortex. Gesture comprehension may be more diffusely distributed.