Serum Biomarkers in Neuro-Ophthalmology: When to Test

Serum and Cerebrospinal Fluid Testing in Optic Neuropathy Patients with Malignant Tumors

Purpose. To evaluate the value of serum and cerebrospinal fluid (CSF) testing in optic neuropathy (ON) patients with malignant tumors. Methods. Fourteen patients clinically diagnosed as ON with malignant tumors but without intracranial or orbital mass in MRI were included in this study. Detailed medical records including medical history, complete ophthalmic examination, colour fundus photography, visual field test, orbital MRI examination, serum and CSF testing data were collected and analyzed. The diagnosis of paraneoplastic optic neuropathy (PON) based on the 2004 recommended criteria of the paraneoplastic syndrome- Euronetwork consortium for paraneoplastic neurological disorders, and current adaption for neuropathies. All patients underwent serum tests for pathogens and autoantibodies including antinuclear antibodies, anticardiolipin antibodies, antineutrophil cytoplasmic antibodies, AQP4-Ab and MOG-Ab, as well as CSF tests for malignant cells under microscope. Serum paraneoplastic antibodies were detected in PON patients. Monkey cerebellar tissue-based assay was used to detect unknown serum anti-neuron antibodies in PON patients with negative paraneoplastic antibody testing results. Results. Fourteen ON patients were classified as four groups based on their clinical and MRI characteristics, as well as serum and CSF testing results: [1] definite PON, 6 cases (11 eyes); [2] possible PON, 3 case (5 eyes); [3] meningeal carcinomatosis-associated optic neuropathy (MCON), 4 cases (6 eyes); [4] infiltrative optic neuropathy (ION), 2 cases (2 eyes). Malignant cells were found under microscope in CSF samples from MCON and ION patients, contrast to no malignant cells in CSF samples from PON cases. All 14 ON patients with malignant tumors showed negative results in serum tests for pathogens and autoantibodies. Serum paraneoplastic antibodies were tested in PON patients, anti- CV2, anti-Yo, and anti- amphiphysin were detected positive in 2, 1, and 1 case, respectively, in definite PON group, whereas no serum paraneoplastic antibody detected in possible PON group. Two unknown serum antineuronal antibodies (an anti- Purkinje cell antibody and an anti-granular cell antibody) were detected using monkey cerebellar tissue-based assay in 2 of 5 PON patients with negative paraneoplastic antibody test results. Conclusions. Serum and CSF tests are of great importance in differentiating different subtypes of ON with malignant tumors. Current diagnosis of PON still depends on combination of clinical and MRI manifestations, as well as serum and CSF tests. Tissue-based assay may help to detect new biomarkers for ON etiology and diagnosis.