Skull asymmetries bear no relation to the occurrence of apraxia. A clinical and CT-scan study in patients with unilateral brain damage

This study aimed at assessing whether there was a relation between presence or absence of apraxia following a parietal and/or frontal left hemisphere lesion and "typical" skull asymmetries, evidenced by CT scan (prevalence of the left over the right occipital length and width and of the right over the left frontal length and width). Skull asymmetries were measured in a sample of 160 brain-damaged patients and their prevalence was found to agree with those reported by the literature in normal subjects. A subgroup of 72 patients with lesions restricted to the parietal and/or frontal lobe were given a movement imitation test and diagnosed as apraxic, borderline or normal making reference to the performance of 150 control subjects. The incidence in these three groups of typical or atypical occipital and frontal asymmetries was assessed and found not to differ significantly. It is concluded that no consistent relation between hemisphere dominance for praxis and skull asymmetry can be asserted. The study also investigated the relation of idemotor apraxia to the locus of left hemisphere damage and confirmed that both the incidence and the severity of the disorder are much greater following parietal than frontal lesions.