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Page 4 of 7 Guan et al. Neuroimmunol Neuroinflammation 2018;5:4 I http://dx.doi.org/10.20517/2347-8659.2017.52

by neutrophil pleocytosis or a mixed cellular response with neutrophils and lymphocytes. In later stages of
tuberculous meningitis, lymphocytic inflammation predominates while neutrophils remain present until
ful clinical remission. The cytological picture of CNS viral infection predominantly shows a lymphocytic
response. However, neutrophil pleocytosis may present in necrotizing cerebral processes of acute viral
infections (e.g. herpes simplex virus-1 encephalitis or CNS vasculitis). Eosinophilic pleocytosis in the CSF is
a hint at a parasitic infection, such as neurocysticercosis, a relatively common type of parasitic infection in
North China. A cytological picture of eosinophil predominance in CSF, so called “eosinophilic meningitis”,
indicates either a special type of neurocysticercosis (e.g. meningeal type of cysticercosis) or Angiostrongylus
[7]
cantonesis, mostly in Southeastern China [Figure 2].

The presence of plasma cells, the antibody-synthetic cells transformed from B-lymphocyte, in CSF indicates
a chronic infection (e.g. tuberculosis, syphilis or borreliosis) or intrathecal humoral immunological response.
Some infections lead to a higher content of atypical lymphoid or lymphoblastic cells in the CSF, which makes
the differential diagnosis from lymphoma very difficult.

CSF CYTOLOGY OF AUTOIMMUNE CNS DISEASE
Autoimmune CNS disorders include primary neuroimmune disorders [e.g. multiple sclerosis (MS),
neuromyelitis optica spectrum disorders (NMOSD) and autoimmune encephalitis] and those secondary to
systemic autoimmune disease.

Inflammatory reactions in CSF are observed in about half of AQP4-IgG positive NMOSD patients. The
main inflammatory type is lymphocytic inflammation, while neutrophils and eosinophils are also seen in a
few patients. Activated lymphocytes, activated mononuclear cells, and plasma cells can be detected in some
patients’ CSF. The positive rate of the specific oligoclonal bands in AQP4-IgG positive NMOSD is lower than
that in multiple sclerosis. These CSF characteristics may contribute to the diagnosis of NMOSD. A mildly
increased percentage of eosinophils is common in autoimmune CNS demyelination including NMOSD,
acute disseminated encephalomyelitis and transverse myelitis. The demonstration of plasma cells in CSF of
[8]
patients with MS is significantly correlated with pleocytosis and intrathecal IgG synthesis .

Anti-NMDAR encephalitis is a major type of autoimmune encephalitis associated with autoantibodies
against neuronal surface proteins. Intrathecal synthesis of autoantibodies is a pathological mechanism of
this disease. CSF cytology findings include lymphacytic inflammation, occasionally with a mild increased
percentage of neutrophils. Plasma cells are common in CSF of anti-NMDAR encephalitis which indicates
[9]
intrathecal immunoglobulin synthesis . For other type of autoimmune encephalitis without the mechanism
of intrathecal immunoglobulin synthesis (e.g. anti-LGI1 encephalitis and anti-GABAbR encephalitis), the
[10]
CSF cytology findings are normal or less reactive .
Neuro-Behçet Syndrome (NBS) may present with various clinical manifestations. The most common
neuroimaging finding is CNS midline structure involvement including brainstem, basal ganglion and
thalamus. The CSF cytological findings, typically the presence of neutrophils, indicate the nature of
neutrophilic vasculitic of NBS and are important clues in the diagnosis of NBS.

Neuropsychiatric systemic lupus erythematosus (SLE) is the CNS involvement of SLE. According to
our observation, he CSF cytology was abnormal in 32.9% of SLE patients, which showed lymphocytic
inflammatory reactions or lymphocyte - neutrophil inflammation. Among these cases with positive CSF
cytological findings, activated lymphocytes, plasma cells and activated monocytes were frequently present.
Abnormal endocytosis of monocytes, which presented as monocytes phagocytosing lymphocytes or plasma
[11]
cells, was shown in some cases .