The diagnostic value of the examination of the cerebrospinal fluid.

Normal Cerebrospinal Fluid Before turning to the findings in various diseases it is necessary to be certain of the normal range and of the alterations that may occur naturally, for example as a result of increasing age. Table i gives the ranges that are commonly accepted for most of the substances examined. The exact figure for chlorides may depend to some extent on the blood chloride level, but the sugar level does not vary greatly from one time of the day to another as raised blood sugar levels following a carbohydrate meal are hardly reflected at all in the fluid, and when they are there is a considerable time lag. Even so it is best to try to take C.S.F. at about the same time if one patient is being followed from day to day. Age affects the findings particularly in relation to protein content. Subjects of 6o or over very frequently show figures of up to 55 or 6o mg./ioo ml., whereas children under io frequently have only 15 mg./ioo ml. in the fluid and there is a corresponding variation between these ages. Prolonged immobility in bed also tends to raise the protein content. The other substances commonly examined show little variation due to these causes.