Pathologic correlates of apraxia in Alzheimer disease

To examine the neuroanatomical correlates of apraxia in Alzheimer disease.

Twenty-three patients with clinically overt Alzheimer disease.

Anterograde study and neuropathologic case series. Clinical severity was assessed using the Global Deterioration Scale. Ideomotor praxis was examined on transitive and intransitive movements and meaningless gestures, and dressing ability was evaluated clinically. Constructive praxis was tested using a 3-dimensional figure copying task. Correlations between neurofibrillary tangle and senile plaque densities and praxis test performance were studied using stepwise logistic regression models.

Studies were conducted at the Psychiatric and Geriatric Hospitals of the University of Geneva School of Medicine, Geneva, Switzerland.

Odds ratios to estimate the associations between neurofibrillary tangle and senile plaque densities in each neocortical area and the presence of ideomotor, dressing, and constructional apraxia.

Statistically significant relationships were found between neurofibrillary tangle densities in the anterior cingulate cortex and ideomotor and dressing apraxia and between neurofibrillary tangle densities in the superior parietal, posterior cingulate, and occipital cortex and constructional apraxia. Senile plaque counts did not correlate with praxic performance.

These results suggest that ideomotor and dressing apraxia are associated with mild damage of the anterior cingulate cortex, whereas constructional apraxia is related to the disruption of cortical pathways mediating visuospatial cognition in Alzheimer disease. Senile plaque densities do not represent a valuable pathologic correlate of apraxia in this disorder.