CSF Formulae in Meningitis and Encephalitis

CSF Formulae in Meningitis and Encephalitis

	Pyogenic	Viral	Tuberculous	Cryptococcal	Viral
Element	meningitis	meningitis	meningitis	meningitis	encephalitis
White cell count/mm³	>1000	<500	<500	<150	<250
Predominant cell type	Polymorphs	Lymphocytes	Lymphocytes	Lymphocytes	Lymphocytes
Protein concentration	>1.5	0.5–1.0	1.0–5.0	0.5–1.0	0.5–1.0
(g/L)
CSF: blood glucose	<50%	>50%	<50%	<50%	>50%

The values given are typical, but many exceptions occur.
Red cells may be seen in the CSF in herpes encephalitis, reflecting cerebral necrosis.
Antibiotic therapy substantially changes the CSF formula in pyogenic bacterial meningitis, leading to a fall in cell count, increased proportion of lymphocytes and fall in protein level. However, the low CSF glucose level usually persists.