The reduction in brain tissue volume, accompanied by the enlargement of the ventricles and subarachnoid space, is referred to as brain atrophy. Most elderly individuals experience mild diffuse brain atrophy, while a minority may exhibit moderate levels.

Brain atrophy cannot be diagnosed through standard X-ray examinations; it typically requires a cranial CT scan or MRI. A CT scan can reveal mild enlargement of the ventricles and cisterns, as well as slight widening of the cerebral sulci, usually exceeding 5 millimeters in width, with bilateral symmetry.

This is particularly noticeable in the frontal lobes and the parasagittal parietal regions, often accompanied by the enlargement of the subarachnoid space around the anterior part of the interhemispheric fissure and the cerebellar tonsils. The enlargement of the ventricles is most prominent in the anterior and inferior horns of the lateral ventricles and the third ventricle.