Serum Neurofilament Polypeptide Level in Patients with Bipolar Disorder and its Effect on Cognitive Functioning.

Background: Elevated neurofilaments in serum are thought to be an indicator of neurodegeneration in bipolar disorder (BD). In our study, we evaluated serum neurofilament light chain (NF-L), medium chain (NF-M) and heavy chain (NF-H) levels in manic, depressive and euthymic phases of BD by ELISA method and investigated the relationship of these levels with neuropsychological functions by CNSVS (Central Nervous System Vital Signs).

Method: Patients with manic, depressive and remission periods, aged between 18 and 50, diagnosed with BD according to DSM-5, and healthy volunteers were included in the study. The sociodemographic-clinical data form, clinical scales and CNSVS tests were applied to the participants. Serum values of NF-L, NF-M and NF-H were measured by ELISA method.

Results: Mean NF-L, NF-M and NF-H levels showed significant differences between the patient and control groups (p < 0.001). When neurofilament levels and neurocognitive domains were evaluated in bipolar patients; NF-M and NF-H levels showed a negative correlation with NCI, composite memory, verbal and visual memory, cognitive flexibility, executive functions, psychomotor speed.

Conclusion: Elevated neurofilament polypeptide levels during all stages of BD compared to controls may be an indicator of inflammatory-mediated axonal damage in bipolar patients and might be used as a biomarker for neurodegeneration in BD. CNSVS neuropsychological test battery has an important place in determining the neurocognitive dysfunctions in individuals with BD. Negative correlation detected between serum NF-M and NF-H levels and cognitive test performance might reflect the neurodegeneration related poor cognitive performance.