In normal spinal fluid from an adult, 60% of cells are lymphocytes and up to 30% are monocytes. Up to 2% neutrophils is also considered within normal limits when a cytospin smear is used for the differential.
In children, normal CSF cells are 70% monocytes, up to 20% lymphocytes and up to 4% neutrophils.
When any of these normal cell abundances are increased, the term pleocytosis is used. Neutrophil pleocytosis is an increase in neutrophils and usually indicates the presence of a bacterial infection.
