Assess brain volume by assessing volume of the CSF spaces
Age must be taken into account when assessing brain volume
Brain volume is assessed by subjectively estimating relative volume of the cerebrospinal fluid spaces (CSF spaces). However, the age of the patient must be taken into account. The ventricles may be very small in young adults and very large in the elderly and still be considered normal.
Brain volume decreases throughout adulthood and with certain disease processes such as dementia or alcoholism.
There are no agreed measurements to quantify brain volume. An estimation of brain volume can be made by subjective assessment of volume of the CSF spaces (sulci, fissures, ventricles and basal cisterns).
Assessment of the size of the sulci is often easiest near the vertex of the brain
Both these patients are in their 60s
The image on the right shows loss of volume with corresponding enlargement of the sulci in an alcoholic individual
Hydrocephalus
Hydrocephalus is the result of increased production or decreased absorption of cerebrospinal fluid (CSF). Hydrocephalus can result in massive enlargement of the ventricles. Acute hydrocephalus may cause damage to the ependyma (the lining of the ventricles) which results in oedema of the periventricular white matter. This is known as transependymal oedema.
The periventricular white matter appears of low density due to transependymal oedema
The sulci are not enlarged
Alzheimer's disease
Although Alzheimer's disease, the commonest cause of dementia, cannot be diagnosed on the basis of imaging findings alone, there are certain features which are characteristic. The typical pattern in Alzheimer's is of volume loss predominantly affecting the medial side of the temporal lobes.
The temporal lobes are much reduced in volume - particularly on their medial side
Enlargement of the temporal horns of the lateral ventricles - as shown in this image - is a specific sign of volume loss of the temporal lobes
Increased brain volume - cerebral oedema
Generalised cerebral oedema can cause the brain to swell so that there is generalised reduction of the CSF space volume and loss of differentiation between the grey and white matter.
