Constructional apraxia as a function of lesion locus and size in patients with focal brain damage

Patients with penetrating missile wounds confined to one of the four brain quadrants were evaluated to determine the incidence and severity of constructional apraxia. The visual constructive tasks used were the WAIS Block Designs subtest and the Bender Gestalt (reproduction) Test. Estimates of lesion size were used to investigate the effect of this factor on constructional ability. Patients with right posterior lesion tended to perform least adequately in general, although significant differences were obtained only for the Bender Gestalt Test. The effect for lesion laterality was greater than that for caudality , although neither analysis reached statistical significance. Lesion size made a relatively minor contribution to the visual constructional deficits in this sample. Only in the left posterior sample did lesion size correlate significantly with measures of constructional impairment. The lack of consistent findings may have been due to the restricted lesion size in these patients and to the absence of significant cognitive deficits in most subjects. The results support either a regional interpretation of the mass action theory or the possible role of deficient verbal mediation in the constructional performance of patients with left hemisphere lesions. This study emphasizes the importance in neurobehavioral research of controlling potentially confounding variables (e.g., lesion size and type of associated cognitive deficits) when studying any specific aspect of neuropsychological functioning.