Relation of serum level of tumor necrosis factor-alpha to cognitive functions in patients with Parkinson's disease

Background: Inflammation is suggested to play a role in the development of non-motor Parkinson's disease (PD) symptoms. We aimed to investigate the association between serum tumor necrosis factor-alpha (TNF-alpha) levels and cognition in PD patients. Thirty patients with PD and 30 healthy controls were included. Evaluation and staging of PD were done using Unified PD Rating Scale. Cognitive assessment was done using Addenbrooke's Cognitive Examination (ACE-III) and trail making B tests. Measurement of serum levels of TNF-alpha was done. Results: Patients had significantly worser cognitive scores than controls except for language subclass of ACE score. Mean serum TNF-alpha level was significantly greater in PD patients as compared to controls. TNF-alpha serum level was significantly negatively correlated with ACE visuospatial function. Sensitivity and specificity of TNF-alpha to detect cognitive dysfunction in PD using ACE III and trail making B tests were (73.1, 75%), (57.1, 56.2%), respectively, whereas sensitivity and specificity of TNF-alpha to detect severity of PD using H&Y staging in PD were 50%. Conclusion: Patients with PD frequently have cognitive impairment. Elevated serum TNF-alpha levels in patients with PD, and association of this cytokine to visuospatial impairment, implicate this pro-inflammatory cytokine in the neurobiology of cognitive impairment in PD.