Constancy of convexity air block on pneumoencephalography.

Twenty-two patients with dementia were examined by pneumoencephalography using special technic with the aim of filling the subarachnoid convexity space. Seven had no obvious hydrocephalus. All patients had convexity blocks which were more or less extensive. Ten had bilateral air block in the frontal, parietal and occipital regions. It was concluded that convexity air block is not a technical artifact and consequently seems to have an organic background.