Walsh & Hoyt: Laboratory and Neuroimaging Findings

During the active stage of neuromyelitis optica, the CSF usually shows evidence of an inflammatory process. There is often a mild lymphocytic pleocytosis, although polymorphonuclear leukocytes (PMNs) may also be present. Cell counts may vary widely. Walsh reported a case in which there were 1000 white blood cells/mm3; however, although cell counts may be more than 50/mm3 in up to one-third of patients, such elevated cell counts are sufficiently unusual that they should prompt consideration of alternative diagnoses.