Functional Brain Imaging in Apraxia

Abstract

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, re-sults 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.

Upper and Lower Face and Ideomotor Apraxia in Patients with Alzheimer’s Disease

“…Foster et al [26] reported evidence of right parietal lobe activation detected in AD patients when performing a limb apraxia imitation task. Further evidence of a largely distributed network is provided by the PET findings in a patient with left fronto-parietal dysfunction who showed preserved gesture comprehension [31].…”

Brain activation during ideomotor praxis: imitation and movements executed by verbal command

“…A functional neuroimaging study of a patient with apraxia using fludeoxyglucose F 18 positron emission tomography (PET) reported focal reductions of glucose metabolism in the left angular gyrus and left supramarginal gyrus. 27 Heilman and colleagues proposed a model of ideomotor apraxia in which the movement formulae for ideomotor praxis are stored in the left inferior parietal lobule based on lesion data. 13 Our finding fits well with a recent lesion study using computed tomography (CT) and MRI by Haaland and colleagues, who found maximal overlap of lesions in patients with ideomotor apraxia in the left intraparietal sulcus.…”

“…Twenty two (20 men and two women) young, right handed, healthy subjects were examined (mean age, 22.9 years; SD, 3.70; range, [19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37]. Handedness was assessed by the Edinburgh inventory (mean, 97; SD, 4.8; range, 84-100).…”

Update on apraxia

“…Moll et al [33] reported that functional MRI during gesture performance in neurologically intact individuals revealed activation in left frontal and parietal regions, including the dorsolateral frontal and intraparietal cortex [33]. Kareken et al [41] performed a positron emission tomography (PET) study of a 65-year-old woman with progressive neurologic deficits including apraxia and showed reduced uptake in left frontal (supplementary motor area) and parietal (angular gyrus, supramarginal gyrus) regions [41]. …”

“…Support for this anterior-posterior dissociation has come from lesion studies showing impaired gesture recognition after posterior, but not anterior, left hemispheric injury [22]. Imaging studies have less consistently shown such a relationship [15,41,47]. …”