Şizofreni hastalarında optik koherens tomografi bulgularının bilişsel işlevler, psikotik belirtiler ve inflamatuar biyobelirteçler ile ilişkisi / The relation of optical coherence tomography findings with psychotic symptoms, cognitive functions and inflammatory biomarkers in patients with schizophrenia

Abstract

Introduction: Neuroimaging studies have revealed that there are some structural changes such as gray matter volume reduction, ventriculer enlargement in patients with schizophrenia, which support the neurodegenerative hypothesis of the disease, and some studies indicating that these changes are correlated with the level of cognitive impairment. Optical Coherence Tomography (OCT) is a noninvasive imaging technique and psychiatric use of OCT is relatively new. Decreased thickness of retinal sublayers has been reported in patients with schizophrenia and it has been tought that these changes might be a sign of CNS neurodegeneration. The aim of our study is to investigate the relation of OCT findings with cognitive functions and inflammatory biomarkers which is thought to play a role in pathopyshiology of schizophrenia. Methods: Fifty patients who were diagnosed with schizophrenia according to DSM-5 and age and sex-matched 40 healthy controls were recruited in the study. Wisconsin Card Sorting Test (WCST), Stroop Test, Trail Making Test (TMT), Oktem Verbal Memory Process Test and Reading the mind in the eyes test were applied to evaluate cognitive functions in subjects. Symptom severity was assessed with Positive and Negative Syndrome Scale (PANSS). Retinal nerve fiber layer (RNFL), ganglion cell layer (GCL), inner plexiform layer (IPL), choroid and macular thickness were measured and recorded automatically by a spectral OCT device. IL-1β, IL-6 and TNF- levels were measured by enzyme-linked immunosorbent assay (ELISA) in plasma samples. Fasting glucose, triglycerides, HDL cholesterol and CRP levels were also measured in all subjects. Results: The levels of all three cytokines were significantly higher in the patient group compared to the control group (p <0.001). In the patient group, IL-1 levels were reversely correlated with the time to perform TMT-B (p = 0.03) and positively correlated with the immediate memory scores (p = 0.05). There was a positive correlation between IL-6 and Stroop 5th card number of correction (p = 0.03), and a reverse correlation between IL-6 and WCST number of categories (p = 0.04). IPL was found to be significantly thinner in patients than the controls (p = 0.04), and the other OCT parameters did not show any significant difference between the groups. In patients; choroidal thickness was reversely correlated with Stroop 2nd card time scores (p = 0.05) and positively correlated with immediate memory scores (p = 0.002) and WCST non-perseverative error count (p = 0.02) There was also a positive correlation between RNFL thickness and immediate memory scores (p = 0.04). GCL thickness was also positively correlated with WCST number of trials to complete the first category scores (p = 0.03). There was no relationship between OCT parameters and cytokine levels in the patient group. Conclusion: In our study, IPT thickness was significantly decreased in patients with schizophrenia. Retinal layer thicknesses were also correlated with various cognitive tests. These findings support the hyphothesis that OCT parameters might reflect central neurodegeneration. For this reason, further studies are needed to be done with large sample groups.On the other hand, our findings support the hypothesis of abnormal immunity in schizophrenia, and it is observed that various cognitive subtests are related to cytokine levels. Identification of the role of inflammatory processes in the pathophysiology of the disease and its relation with disease symptoms in clinical practice will help to develop treatment options for schizophrenia.