[The normal range of cerebral atrophy during aging: statistical analysis of 500 normal subjects].

We previously reported the newly developed quantitative measurement of the cerebral atrophy (pixel count method), and advocated the value CCR (CSF-cranial ratio) as the index of the volumetric measurement of the cerebral atrophy. As the pixel count method is somewhat troublesome, we tried to compare the various linear measurement methods with pixel count method by means of multivariant analysis, and reported a single formula to calculate CCR from the linear measurement methods. Now we studied 500 normal subjects using the pixel count method and examined the normal range of the cerebral atrophy during aging by means of the maximum likelihood method. The normal range was estimated as follows; 0.32 less than y less than 5.78 (t less than 48), 0.068 t--2.944 less than y less than 0.368 t--11.884 (t greater than 48). Using these formula and this newly reported normal range, we can easily predict whether the cerebral atrophy is pathological or not.