Vergleichende MR-volumetrische Untersuchung des dorsolateralen präfrontalen Kortex bei Schizophrenie, Bipolarer Störung, Zwangserkrankung und gesunden Kontrollpersonen

Abstract

The presented doctoral thesis deals with the MR-volumetric measurement of the dorsolateral prefrontal cortex (DLPFC) of patients suffering from different psychiatric diseases. In schizophrenia patients several neuropsychological studies demonstrated cognitive deficits in executive functioning. Working memory is seen as a essential part of executive functions. The function of working memory is characterised by the temporarily storing and handling of information which is often disturbed in schizophrenia patients. The MR sample consists of 35 first-episode schizophrenia patients, 39 bipolar patients, 27 patients with obsessive-compulsive disorder and 37 healthy control subjects. With this study the issue was addressed if there is a volumetric difference of the DLPFC between first-episode schizophrenia patients and healthy subjects. Further we explored if possible volumetric differences can also be shown in schizophrenia patients compared to bipolar patients and patients with obsessive-compulsive disorder. The DLPFC volumes have been measured on both sides to discover asymmetries. The volumetric measurements were performed by using the program MRIcroN with the volume of interest approach (manually tracing DLPFC) on T1-weighted MR scans (1,5 Tesla, 1cmm voxel). The repeated measurements of 10 MR scans (10 subjects) provided high retest and interrater reliability showing an intraclass correlation of more than 0.95. Statistical analysis showed significant differences between the groups regarding the relative grey matter DLPFC volume (DLPFC volume in relation to the grey matter prefrontal cortex volume (PFC). Relative DLPFC volume was increased in first-episode patients compared to healthy controls. Bipolar patients and patients with obsessive-compulsive disorder demonstrated no differences compared to healthy controls. In conclusion, with our volumetric approach in this study no disease-related DLPFC volume reduction could be observed in schizophrenia patients, as it has been reported several times in the literature. This may be related to the characteristics of our study sample and the used morphometric methods. Volume reduction in schizophrenia may occur during the later course due to the disease progression but not already in first-episode schizophrenia. Furthermore a change in prefrontal cortex shape (compression of anterior frontal cortex parts) could be responsible for our result of increased DLPFC with consecutive volume reduction in other prefrontal areas.