A new method for measuring cranial cavity volume and its application to the assessment of cerebral atrophy at autopsy Cranial cavity volume has been measured at autopsy by occupying the cranial cavity completely with a lubricated balloon filled with water while the calvarium was held in place by a rigid metal coronet. The pressure in the balloon was raised to 150 mm Hg and the water‐filled balloon removed and weighed. Brain volume has been measured by an accurate displacement method. Repeat measurements showed a difference of no more than 8 ml and usually less than 5 ml. The ratio between the brain volume and the cranial cavity volume has been found to be constant in young adults 20–55 years old (92.2±SEM 1.6%). Cerebral atrophy has been measured by observing the deviation from this relationship. We have found a striking decrease in brain volume in normal old people. This is not due to water loss as brain density change with age was found to be slight.

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